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April 6

Boredom

Is it possible, either biologically or psychologically, to be literally bored to the point of death? I don't mean brought to the point of suicide, but sort of losing the will to live without being taken by any specific other cause. —Akrabbim^talk 01:28, 6 April 2009 (UTC)[reply]

It seems unlikely. We know that there are people have been kept in solitary confinement for many years (Richard Wurmbrand, for example - suffered extremes of this horrible torture for 14 years) - they suffer mental symptoms - but they don't die (at least, not from boredom). SteveBaker (talk) 03:18, 6 April 2009 (UTC)[reply]

Lightweight! These guys did 36 years of solitary in lovely Angola Prison. --Sean 14:02, 6 April 2009 (UTC)[reply]

According to this book and other places, it is believed that babies in orphanages die when they are not given any tactile stimulation. However, I haven't been able to find anything more concrete. I vaguely recall reading somewhere about the investigation of two orphanages in Victorian England; the one that was better financed supposedly had a 100% death rate because the caregivers were trained in the latest Victorian theories (i.e. no touching), while in the other, the adults received little or no instruction and interacted more with the babies, so some of the kids survived. I have no idea if this is true or just a story. Clarityfiend (talk) 06:00, 6 April 2009 (UTC)[reply]

You might find Atul Gawande's recent article in the New Yorker about solitary confinement enlightening on this point. --98.217.14.211 (talk) 14:16, 6 April 2009 (UTC)[reply]

Interesting, thank you. The defining factor here seems to be interpersonal interaction, rather than mere lack of activity. —Akrabbim^talk 15:53, 6 April 2009 (UTC)[reply]

RNA polymerase

How does RNA polymerase selects the DNA strand for transcription? —Preceding unsigned comment added by Mmpdsetti (talk • contribs) 03:13, 6 April 2009 (UTC)[reply]

You want to read Transcription_(genetics)#Initiation. Basically, the RNA polymerase recognizes a promotor that is bound on a specific part of the RNA. Perhaps the 5'and 3'ends of the RNA fooled you into thinking the RNA strands were palindromic? = Mgm|^(talk) 08:04, 6 April 2009 (UTC)[reply]

since shorelines are fractal, how are they really (IN FACT) calculated, when we read figures about x miles of shoreline?

We often hear that shorelines are "fractal" -- which makes sense, since what would make them straight? But how then are the data for x miles of shoreline in FACT calculated? Do you just go inland until you CAN get a straight line, and just cut off many many many factors of jutting edges or what? THank you. —Preceding unsigned comment added by 94.27.225.22 (talk) 08:26, 6 April 2009 (UTC)[reply]

One possible method (which I believe is used) is to approximate the shoreline by a polygonal curve with each side about the same length. Of course, the result you get from this depends strongly on the length you choose for the sides, which is why different authorities often give wildly different figures for the lengths of coastlines and other non-straight borders. Algebraist 08:50, 6 April 2009 (UTC)[reply]

(after ec): Dr_Dima hypothesis number n+1: People who understand what a fractal is, and people who assign "shoreline length" a definite numerical value, form two non-empty disjoint (non-intersecting) sets. Seriously now, this reference explains how shoreline length is "measured" in practice. As expected, the word "fractal" is never mentioned, and neither is the systematic increase of the result with map resolution. --Dr Dima (talk) 09:00, 6 April 2009 (UTC)[reply]

Shorelines aren't truly fractal anyway. People like to imagine "shore line" as a fractal that is coherent all the way down to individual grains of sand. But really, even if you're standing on a beach, you'd be hard-pressed to draw a line in the sand at the "Shoreline". Not because of the infinite precision needed to describe a fractal, but because the ocean and even the beach itself are constantly in motion. Beyond a certain point there isn't any more precision to measure.

I'd wager that nowadays, It's entirely possible to define the length of a coastline with enough precision that the "fractal nature" of the coast doesn't make any difference.

How often this is done, I don't know. APL (talk) 13:40, 6 April 2009 (UTC)[reply]

That could introduce new problems, as the length of the shoreline changes when the tides goes out, and also after every storm (if a sandbar is connected or disconnected from the shore, does that change the length of the shoreline ?). StuRat (talk) 17:07, 6 April 2009 (UTC)[reply]

Exactly, what you're dealing with is an average. It doesn't make sense to talk about the fractal nature of an average. APL (talk) 20:26, 6 April 2009 (UTC)[reply]

I think it does. There's one fractal when the tide is out and another when it's in, and we'd average those. StuRat (talk) 19:42, 7 April 2009 (UTC)[reply]

well you know what people OUGHT TO DO? Just DRIVE DOWN THE SHORE, there is ALWAYS an easy way to drive along the shoreline, and just measure the difference the odometer shows at the end! 94.27.194.165 (talk) 15:45, 6 April 2009 (UTC)[reply]

That wouldn't work for fjords. I blame Slartibartfast. Gandalf61 (talk) 15:50, 6 April 2009 (UTC)[reply]

See Coastline paradox. --Heron (talk) 18:25, 6 April 2009 (UTC)[reply]

Easily solved. You drive an infinitesimally small car. Confusing Manifestation(Say hi!) 23:15, 6 April 2009 (UTC)[reply]

But wouldn't it take you an infinite amount of time to drive it around the coast? All of those tedious detours around sand grains...I bet you'd cheat and take shortcuts. SteveBaker (talk) 01:58, 7 April 2009 (UTC)[reply]

How about using the shortest path between the low-tide and high-tide lines? —Tamfang (talk) 05:20, 7 April 2009 (UTC)[reply]

Comorbidity of pulmonary and liver diseases

Hello. I'm trying to help out a friend who's studying Medicine to solve a medical case. I'm not going to give all the details of the case that's been assigned to her (lest you believe I am looking for medical advice), only those I believe are the most important. The pacient has rales, coughs and other pulmonary symptoms. The pacient also has abnormal liver test results, such as high GGT and alkaline phosphatase levels.

As I said, I am not going to ask for a specific diagnosis, but I would greatly appreciate if someone can give us a little push in the right direction, since we have been unable to find any disease which would cause both pulmonary and liver symptoms. Thanks a lot. Leptictidium (mt) 09:41, 6 April 2009 (UTC)[reply]

Chronic liver disease can present with numerous respiratory symptoms, see hepatopulmonary syndrome, though I'm not sure if that's mentioned in your case. In addition, in can result in elevated GGT levels, but I'm not sue about alkaline phosphatase levels. I'm not saying this is your answer, I'm not a doctor, but this is a logical option to consider. Cyclonenim : Chat 10:43, 6 April 2009 (UTC)[reply]

Have you considered alcoholism? I mean, for your test case; not personally. Perhaps an alcoholic cardiomyopathy resulting in cor pulmonale to produce the respiratory symptoms; and alcoholic liver disease to cause GTT elevation. ALD and heart disease can both cause elevated ALP, as can many other things. The heart disease can also cause hepatic venous congestion and contribute to the deranged LFTs, particulary GGT as its a sign of hepatobiliary pathology moreso than pure hepatic pathology. You don't mention whether or not there's any other biochemical abnormalities, for example hypoalbuminemia, elevation of transaminases, hyperbilirubinemia (conjugated or not) - these would be useful to know. Also consider anything else that causes congestive heart failure, as the same physiology applies. Mattopaedia ^{Have a yarn} 02:59, 8 April 2009 (UTC)[reply]

Royal Society of Canada

Does the FRS(Canada) enjoy the same prestige as Memberships of American Academy of Arts and Sciences,French Academy of Sciences,Royal Society Of London,Royal Swedish Academy of Sciences,National Academy of Sciences and Pontificial Academy of Sciences(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 11:13, 6 April 2009 (UTC)[reply]

I don't have an answer about the FRS(Canada), but wanted to point out that the American Academy of Arts and Sciences may not be as prestigious as you think it is. Perhaps you're thinking of the United States National Academy of Sciences? --Scray (talk) 02:03, 7 April 2009 (UTC)[reply]

I must say I am surprised!According to the site American Academy of Arts and Sciences has more than 160 Nobel Laureates and 70 Pulitzer Prize winners amongst its membership and looking at the membership anybody who is anybody in US is a member!Surely that makes it perhaps one of the most sought after learned societies in the world apart from being the oldest learned society in the US!I was not so sure about the Royal Society of Canada.(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 09:35, 8 April 2009 (UTC)[reply]

Reference material for doctors

What materials do doctors use/refer to for diagnostic/differential purposes. In other words, for psychology/psychiatry you use the DSM-IV--this gives you criteria you must meet for certain disorders, possible treatment plans, etc. My question is, is there something comparable for the medical field? Thanks in advance for your help! Dimblethum (talk) 12:27, 6 April 2009 (UTC)[reply]

I'm just a layman but the last time I went to my NHS doctor in the UK, she used her computer after examining me. I realised later that she was looking up the recommended course of treatment. This is available publically online somewhere as I had a look at it, but sorry I've forgotten what it is called. In Britain patient records have been computerised, and apparantly this involves a classification system of some kind. I understand there are different classification systems used in the US. 78.147.28.51 (talk) 12:43, 6 April 2009 (UTC)[reply]

The ICD-10 from the WHO is what's used for general medical classification (and also used outside the US for psychiatry, rather tan the DSM-IV).Fribbler (talk) 15:33, 6 April 2009 (UTC)[reply]

Also see PubMed for which you can use Medical Subject Headings. For prescription drugs there's a pharmacological tome. Had the title when I started posting and now can't find it again, sorry. 76.97.245.5 (talk) 15:57, 6 April 2009 (UTC)[reply]

Depending on the doctor - and I suspect, the nature of the disorder you're being treated for - some doctors use Google. No, this is not a joke. However, upon re-reading your question, I feel that this probably doesn't address exactly what you're after. <.< 90.193.232.106 (talk) 17:59, 6 April 2009 (UTC)[reply]

Doctors use a variety of books, medical journals and internet resources. The Oxford Textbook series is widely used for reference, and all hospital libraries (in the UK) will have a copy of the Oxford Textbook of Medicine. I prefer Harrison's Principles of Internal Medicine; it is a little easier to read, and not just for reference. Again, Harrison's Principles is available everywhere. More recently, Uptodate.com has become a widely used web-based resource. In the UK, the British National Formulary is the definitive manual for drug dosing. [Declaration of conflict of interest: I am a pulmonologist and internist. I don't often read outside my areas of specialism.] Axl ¤ [Talk] 18:59, 6 April 2009 (UTC)[reply]

I agree with Axl. A great deal of medical training is learning to look things up and evaluate evidence. The list of reference sources is legion, as evidenced by the huge market for reference books and (increasingly) electronic media. While it's true that physicians use Google, it's often an indirect search for a specific reliable source or fact. Skills vary, of course, but good clinicians are very good at information retrieval. --Scray (talk) 19:51, 6 April 2009 (UTC)[reply]

@78.147.28.51. In Canada, the drug tome to which you were referring is called the CPS. // BL \\ (talk) 01:37, 7 April 2009 (UTC)[reply]

And in NZ, New Ethicals (randomly enough). Gwinva (talk) 03:49, 8 April 2009 (UTC)[reply]

If Sulforaphane is good for you, is sulphur dioxide beneficial also?

Sulforaphane is found in broccoli, cabbage and so on. Suplhur dioxide is used to preserve dried fruit etc. I make my own muesli using dried fruit, and I have been wary of sulphur dioxide. How likely would it be that if sulphoraphane is good for you, then suphur dioxide may be also? Would the metabolic pathways or the reasons for the benefit of the first chemical be similar to those of the second? Can this inference be made? 78.147.28.51 (talk) 12:50, 6 April 2009 (UTC)[reply]

If you really want to get into the details of this, you'll need to consult a doctor or some other appropriate professional. However, our sulfur dioxide article says that "[s]ulfur dioxide is an allergen to which some consumers are sensitive" and includes an EPA reference which notes that "SO₂ is associated with increased respiratory symptoms and disease, difficulty in breathing, and premature death."[1] — Lomn 13:06, 6 April 2009 (UTC)[reply]

I had already read both the articles thanks. I'm hoping for an answer from someone with knowledge of metabolic chemistry or physiology. It is not a medical question. 78.147.28.51 (talk) 13:29, 6 April 2009 (UTC)[reply]

I don't think we need any specialist knowledge here. Sulforaphane (C₆H₁₁NOS₂) has a completely different chemical formula from sulfur dioxide (SO₂) and has a much more complex molecular structure. There is no reason to expect their metabolic effects be at all similar. Our sulfur dioxide article says "Sulfur dioxide has no role in mammalian biology". Gandalf61 (talk) 13:32, 6 April 2009 (UTC)[reply]

The common mistake here is thinking that molecules which contain the same element must be similar. This is not true, at all. The most basic example is table salt, sodium chloride, which is composed of a metal, sodium, which bursts into flame when it gets wet, and a poisonous gas, chlorine. Obviously salt isn't much like either of those. StuRat (talk) 17:01, 6 April 2009 (UTC)[reply]

Magnetic flux

I have a doubt regarding magnetic flux, and i would appreciate if someone bothers to explain me this concept.

Basically, there is no such thing as a magnetic monopole right, so the most basic thing we can analyze is a dipole. And the dipole has to be a point dipole, it can't be two monopoles separated by a distance, for that would mean monopoles exist. So the most basic entity, corresponding to a point electric charge, is a point magnetic dipole. And i can regard the dipole as two monopoles, very close to each other( the monopoles have to be very strong, or the dipole moment will be zero, so consider both the pole strength and the distance as limits , one tending to infinity and the other to zero). Magnetic flux is a count of the no. of field lines emanating through a surface. But whatever the surface i consider (even if it is open), i can say that the positive flux caused by the positive point pole will exactly cancel the negative flux of the negative pole, as they are very close to each other, so the net flux has to be zero! So the magnetic flux through any surface is zero!

I know i am making a mistake somewhere in the argument, and i would be happy if someone would point it out to me. Thanks in advance (going through this would have caused some effort). —Preceding unsigned comment added by Rkr1991 (talk • contribs) 13:26, 6 April 2009 (UTC)[reply]

I believe you are exactly correct, the net magnetic flux through any closed surface is indeed zero. See http://en.wikipedia.org/wiki/Gauss%27s_law_for_magnetism It states "The left-hand side of this equation is called the net flux of the magnetic field out of the surface, and Gauss's law for magnetism states that it is always zero." —Preceding unsigned comment added by 81.11.162.104 (talk) 13:50, 6 April 2009 (UTC)[reply]

Indeed! In a world without magnetic monopoles any closed surface you construct will have zero net flux. There are still surfaces with net magnetic flux through them: unclosed ones.

You can prove this from Maxwell's equations if you don't mind some vector calculus: you start with

{\vec {\nabla }}\cdot {\vec {B}}=0

try integrating it over a general volume and then use the divergence theorem to see that the boundary surface has a zero flux.

But do we live in a world without magnetic monopoles? Maxwell's equations are pleasingly symmetric if we include them and Dirac showed that if magnetic monopoles exist electric charge is quantized. Pretty tantalizing... 163.1.176.253 (talk) 14:27, 6 April 2009 (UTC)[reply]

I just noticed that you had mentioned open surfaces and you're not correct in thinking they would lead to zero flux. It's not correct to think of our ideal dipole as two point magnetic charges separated by zero distance. If it were then the two fields, generated by each monopole, would cancel perfectly (and therefore there wouldn't be any field lines at all).

So, if you want to think about it in terms of two separated points we need to have two monopoles separated by some non-zero distance. This then leads to fluxes for open surfaces and zero-fluxes for closed ones. (Although, as magnetic monopoles don't exist we should probably not give too much importance to the microscopic structure of a dipole constructed with them. We should really be using either the dipole as the fundamental generator of magnetic field or current loops, which have a magnetic moment and the advantage of existing.) 163.1.176.253 (talk) 16:25, 6 April 2009 (UTC)[reply]

Pah! A "point dipole" is an oxymoron -- it is nothing. Two opposite moments at the same location give a net sum of zero. The principle that there is no magnetic monopole only means that any positive magnetic moment must be associated with an equal negative moment in the vicinity. Looie496 (talk) 01:54, 7 April 2009 (UTC)[reply]

Well let me put forth my question more directly. This is a question which was handled in my class. There is a cylinder of radius r and height 2L. A point dipole m is placed at its center. Find the magnetic flux through the top surface, the axis of the cylinder being vertical. My teacher did this using the formula of the field due to a point dipole... but i want to know what's wrong with my logic. Since it is a point dipole, i have to bring the 2 monopoles(imaginary) very close to each other, which means they should cancel out each other's field lines, so there should be no flux. What's wrong with my logic? —Preceding unsigned comment added by Rkr1991 (talk • contribs) 05:38, 7 April 2009 (UTC)[reply]

You can indeed get a magnetic dipole by taking 2 magnetic monopoles of opposite magnetic charge, and let the distance between the monopoles go to zero while you let their charge go to infinity. If the magnetic charges remained finite, the fields would cancel out, but the magnetic charges go to infinity. The field in the limit is not zero. It's like finding x*(1/x) in the limit for x goes to 0 : the limit is 1, even though you seem to multiply by 0.

The monopoles are very close to each other, but they are also very strong. Surely you derived the formula for the field due to a point dipole by calculating the limit for the field of 2 monopoles whose magnetic charge goes to infinity and whose separation goes to zero? If not, try to do so mathematically. You'll see the field does not become 0. —Preceding unsigned comment added by 81.11.162.104 (talk) 07:39, 7 April 2009 (UTC) Ok thanks--Rkr1991 (talk) 13:27, 7 April 2009 (UTC)[reply]

Earthquake radius

I guess I know the basic answer to this question, but I am wondering if I can get more detail.

The terrible earthquake that occurred in Italy seems to have an exceedingly small radius in which it was felt. Is there a reason for this? Is my perception incorrect?

The related larger question is, why is an earthquake in St Louis felt in Boston, while an earthquake in LA is felt perhaps as far as San Diego (if even that far), while an earthquake in Italy is felt for barely 40 miles? Apollo58 (talk) 15:25, 6 April 2009 (UTC)[reply]

Fault (geology), Earthquake are worth a look. For Boston particularly Earthquake#Earthquakes away from plate boundaries. 76.97.245.5 (talk) 15:37, 6 April 2009 (UTC)[reply]

It's also worth noting that the Richter scale is logarithmic. Italy's quake is being estimated between 5.8 and 6.3 (a factor of five, give or take, so there's a lot of uncertainty). The 1812 New Madrid earthquake, which originated near St. Louis and rang church bells in Boston, was an 8.0 or higher -- approximately 100 times more powerful. — Lomn 15:49, 6 April 2009 (UTC)[reply]

Also, this USGS source suggests that the Italy quake was perceptible at least 200 km from the epicenter, significantly more than the 40 miles you first note. — Lomn 16:15, 6 April 2009 (UTC)[reply]

There are two aspects to this Q:

1) How severe a quake is at it's epicenter. This has to do with the magnitude on the Richter scale, of course, but also the population in that location, the building codes, and the local geology.

2) How well it travels. This depends on the geology between the source and measurement location as well as the local geology at the measurement site. A deeper quake will also tend to be felt more evenly over a wider area, while a shallow quake will be much stronger in the local area. StuRat (talk) 16:53, 6 April 2009 (UTC)[reply]

Indeed. An interesting comparison puts this week's Italian earthquake magnitude 6.3 M_w, depth 10km against the 2007 Gisborne earthquake, of 6.8 M_L and depth of 35.6 km. The Gisborne earthquake was felt in Christchurch, well over 700km away, yet there was little damage in Gisborne itself, and only 1 related death. (Of course, the depth is not the only contributor to damage: a medieval city will sustain more damage than a modern town built to exacting earthquake building codes. Gwinva (talk) 04:11, 8 April 2009 (UTC)[reply]

However, if an earthquake is say, over 100 km deep, then it would be felt over a wider area, but almost no major damage is likely to occur, because deeper quakes generally do less damage for a given area than a shallow one. ~A H 1^(TCU) 02:08, 10 April 2009 (UTC)[reply]

Article: Science and technology in the United States

The article I mentioned above has almost no references or sources. For the article's quality, that's a problem that should be addressed elsewhere, but I'm looking for a good place to find some reliable sources on that topic. Thanks! Randnotell (talk) 16:12, 6 April 2009 (UTC)[reply]

While that article itself doesn't have references it's peppered with internal links. See if the linked articles have relevant information and whether that is referenced there. If it is you could either copy that ref. or leave things be as it is. (Latter option will almost guarantee the next "improve quality" editor stumbling over that article will scream murder. :-) 76.97.245.5 (talk) 17:26, 6 April 2009 (UTC)[reply]

Internal links cannot by themselves be used as references unless the fact in question is pretty obvious. It is also worth noting that there are long, synthetic paragraphs with almost no internal linking—which smacks of OR. There are also some major misconceptions. German scientists didn't leave Germany because Einstein urged them to, they left because the Nazis passed the Law for the Restoration of the Professional Civil Service that made them lose all their jobs. (Einstein didn't even flee Germany in the wake of Hitler—he had already left for a temporary position in the US, and after Hitler took power he announced that he wouldn't be coming back. That's not the same thing as fleeing.) (It also manages to totally omit any discussion of biology but that's another question.) It is... problematic to say the least. --140.247.242.83 (talk) 19:26, 6 April 2009 (UTC)[reply]

You can try my reliable sources search engine: [2] A Quest For Knowledge (talk) 19:28, 6 April 2009 (UTC)[reply]

A hypermiling question

I recently listened to a podcast about hypermiling and various fuel economy-maximizing behaviors. I drive an automatic Toyota Celica and have been hypermiling it for one fill-up so far; however, I'm wondering if constantly shifting into neutral is bad for my transmission? Presumably there's some general wear-and-tear, but is doing more harm than good in the long-run? -- MacAddct1984 ^{(talk  contribs)} 16:14, 6 April 2009 (UTC)[reply]

Yes, it will do more harm than good unless you happen to drive down some very long hills (miles long), where the gas savings will be more significant. StuRat (talk) 16:39, 6 April 2009 (UTC)[reply]

Well, this last fill-up I went from averaging about 27 MPG (based on 9 data points, varying between 26-28 MPG) to 32.5 MPG, a 20% increase. As this was my first attempt, I suspect there may be improvement next time. I shift into neutral whenever suspect I won't need to accelerate for maybe 15+ seconds. How about shifting into neutral when stopped for at a traffic light? I have a feeling that the engine is working about the same fighting the brake in drive and spinning around incessantly in neutral. -- MacAddct1984 ^{(talk  contribs)} 17:21, 6 April 2009 (UTC)[reply]

I read a report on the BBC website earlier this year, that shifting into neutral does not help fuel consumption; rather, it makes the car use more fuel because the engine thinks it should be doing something and starts eating fuel. The economical way they recommended was to keep the car in gear but to take your foot off the accelerator and drive it as long as possible without touching the pedals. --TammyMoet (talk) 18:35, 6 April 2009 (UTC)[reply]

In my above response, I definitely noticed an increase in MPG, granted it's only one data point so far. I can say that with my car, in neutral, the revs stay at about 700-800 RPM, in drive with my foot off the gas, it's about 1300 RPM. The problem with coasting in drive is that the car slows down much faster than when it is in neutral. -- MacAddct1984 ^{(talk  contribs)} 19:37, 6 April 2009 (UTC)[reply]

But your fuel consumption is not proportional to RPM. If you have a car like mine with an instantaneous MPG meter - you'll see that you can have the tachometer wrapped around the end-stop

It's also very dangerous to let your car roll in neutral down long hills - you can't use engine braking (in a hurry) if you need to - and if you slow the car using the brakes, they may overheat, boil the brake fluid and then you'll have no brakes! If you want to do hypermiling - you're going to need a stick-shift car. Moreover, your 20% increase is much more likely from being acutely aware of your driving style than it is to do with rolling in neutral.

I did a proper scientific test (actually, as the result of a bet) in my first MINI Cooper'S (back when those cars only got 25-ish mpg when you drove them moderately agressively, as I usually do). What I did was:

Turned off the A/C.
Kept the tires slightly over-pressurized.
(most important) Never let the RPM get over 3,000 or under 2,000 (no easy feat!).
Kept my top speed down to 55mph.
Planned a route with the fewest stop-signs and traffic lights - even though it was ~10% longer than my usual commute.

By taking only those measures, I was able to squeeze 40mpg out of my 25mpg car...woohooo!

I love driving...but it was the most boring two weeks of my life!

Then I did some math...by driving like this, it was taking me 10 minutes longer to get to work each day - and 10 minutes longer to get home again. (People say that agressive driving doesn't get you there any quicker - but the science says "Bullshit"). Over the 560 miles I drove (56 miles per day) I used 14 gallons of gas - rather than the 22 gallons I usually used over that time. So at the cost of 200 minutes (3.3 hours) of my life, I saved 8 gallons of gas. At the time, gas was at it's most expensive - $4 a gallon...so I saved a princely $32. So - I was 'earning' about $10 per hour. Unfortunately, I earn $50 per hour - and at the time I was being paid for overtime work - so this represented a net loss of $150. Since I happen to enjoy being at work rather than creeping along the highway at 55mph - feeling uncomfortable because of the lack of A/C...it was actually a lot worse than that. But now - with gas under $2 per gallon, I'd only be saving $5 per hour - which means that I'd be paying myself less than minimum wage. So all of this nonsense doesn't make economic sense. If you are doing it - you're doing it for the greenhouse gas savings.

So now, I have the newest MINI Cooper'S - which does close to 40mpg with the A/C turned on and with my usual style of driving. This means that if I tried the experiment again - even if I got the same percentage mpg improvement - I'd be down to about $3 per hour.

My proper scientific conclusion is - don't drive a gas guzzler - get something with a 6 second 0-60 time and 140mph top speed - floor it at every red light if the car next to you is a VW Bug turbo, any kind of Scion or anything that says "Hemi" on the back. See if you can take cloverleafs at 80mph by following a proper racing line (um...you probably shouldn't try that in a Celica). Drive happy. SteveBaker (talk) 19:39, 6 April 2009 (UTC)[reply]

Your analysis avoids such things as time lost to more frequent refueling, possibly more frequent maintenance, and the occasional traffic accident ;-). --Stephan Schulz (talk) 20:12, 6 April 2009 (UTC)[reply]

Thanks for the lengthy reply, as always, Steve. Yes, the fact that I changed a bunch of variables at the start wasn't very scientific, so it is very possible that the change in driving style had more to do with it. Maybe I'll stop doing the neutral bit and see how much that actually changes things. Why keep the RPM over 2,000?

My commute to work is only about 10 minutes; however, I do a decent amount of highway driving a month (~800 miles) for work, visiting clients. For the record, I think those who turn their engines off completely while driving are insane. -- MacAddct1984 ^{(talk  contribs)} 20:27, 6 April 2009 (UTC)[reply]

Well, 2000 rpm is what's recommended for my car - yours may be different. But in general - if the rpm is too low (and presuming it's doing work) - then the engine will be 'lugging' - which is when the sides of the piston to slap against the walls of the cylinder...it is extremely damaging to the cylinder walls. The car can safely idle at those low revs - but as soon as it has work to do - it needs more revs. Hmmm - oddly, we don't have an article about that...just a one-liner in a disambiguation page. It's not generally a problem in automatic cars because the transmission keeps the revs in the efficient range - but when you start messing around shifting it yourself - you get the worst of the stick shift and automatic approaches. Note: The cost of replacing your engine will make any amount of marginal gas savings irrelevent - so be careful. SteveBaker (talk) 00:30, 7 April 2009 (UTC)[reply]

Just for the record you should NEVER turn your engine off in a modern car while it's in motion. The steering may lock and you'll lose power assistance for the brakes and steering - extremely dangerous. Exxolon (talk) 21:06, 6 April 2009 (UTC)[reply]

Driving habits make a huge difference, but I agree with those above- there's no plausible explanation on why shifting into neutral would improve your mileage. Turning the engine off entirely would plausibly improve mileage, but it's dangerous, as pointed out above. Friday (talk) 21:15, 6 April 2009 (UTC)[reply]

You're talking automatic transmissions only, right? I can get a substantial improvement in "coast time" by dropping my manual Camry out of gear, because I'm no longer in compression. At one point in my commute, I crest one bridge over a crossroad, shift into neutral (which drops the engine speed from 2100 to 900 rpm), and can coast 7/10 of a mile to my exit, still hitting the cloverleaf at about 40mph. There's no plausible explanation for that? --DaHorsesMouth (talk) 22:33, 6 April 2009 (UTC)[reply]

Check the engine braking article. Exxolon (talk) 22:49, 6 April 2009 (UTC)[reply]

Sure, maintaining speed so you have it later can improve your mileage. What I mean specifically was, you're not using more gas in engine braking than you are just idling. Friday (talk) 14:57, 7 April 2009 (UTC)[reply]

I strongly disagree with DaHorsesMouth - doesn't matter whether it's stick or automatic. The "Gas pedal" is called that for a reason...it (essentially) controls how much gasoline is going into the cylinders. If your foot is not on the gas pedal, then it doesn't matter a damn whether you're in neutral at 900 rpm or in 4th gear at 3000 rpm...you're not using significant amounts of gas in either situation. If you have a car (like my '09 MINI Cooper'S) that has an instantaneous MPG gauge, you can prove this for yourself. If you take your foot off the gas pedal, then the reading goes to 99mpg (it's a two digit display) and then about half a second later, flips to flashing '-- mpg' irrespective of the RPM because the amount of fuel that's being used is zero and your MPG is infinite (or at least off the charts). Sliding into neutral doesn't do much (if anything)...and it's potentially dangerous. SteveBaker (talk) 15:23, 7 April 2009 (UTC)[reply]

I think all he was saying is that he slows down more when in gear, not that coasting in gear uses more gas than coasting in neutral. If you slow down when you didn't want to, and then have to give it some gas later, that uses more gas than not accidentally slowing down in the first place. Is the gas consumption really zero? I assumed the engine was still getting the same amount of gas it would get when idling, but I suppose I have no particular reason for having assumed that. I suppose a sufficiently-smart engine wouldn't bother injecting any gas at all, if it's not needed. But I don't know whether engines are commonly that smart. Friday (talk) 17:28, 7 April 2009 (UTC)[reply]

I would expect most modern engines to completely stop injecting fuel when the throttle is closed and the engine speed is sufficiently high (above 1,000 rpm or so). My 1994 Honda Civic del Sol did, and so does my 2006 MINI Cooper S (as documented by their service manuals), so I think it's a pretty well-established engine management feature. -- Coneslayer (talk) 13:14, 10 April 2009 (UTC)[reply]

Leave the car in gear and coast. This is engine braking, all modern fuel injected cars will completely shut off the injectors when you are engine braking, using no fuel. Also driving habits make a big difference, the harder you press the gas, the worse the MPG will be. That's about it.Extide (talk) 20:51, 7 April 2009 (UTC)[reply]

Centre of gravity

Hi! Where is the centre of gravity of the bow (weapon)when it is in passive state? Thanks! —Preceding unsigned comment added by 84.52.162.94 (talk) 18:04, 6 April 2009 (UTC)[reply]

That would depend on the bow. They come in all sorts of shapes and designs. It would also depend on whether you mean strung or unstrung when you say 'passive'. Algebraist 18:08, 6 April 2009 (UTC)[reply]

If you call the grip the front of the bow, then the center of gravity for a strung bow is going to be behind the grip. The center will move further back once it is drawn because the ends of the bow are pulled further from the grip. I am ignoring the contributions of the arrow in this case. Sifaka ^talk 18:37, 6 April 2009 (UTC)[reply]

But your first claim does not necessarily hold for a recurve bow. --Stephan Schulz (talk) 19:01, 6 April 2009 (UTC)[reply]

Composite bows sometimes have a weight out the front so that when drawn the centre of gravity is pretty much at the grip. Polypipe Wrangler (talk) 22:21, 12 April 2009 (UTC)[reply]

Violet scent

Is there any simple chemical (ester, perhaps?), that makes the characteristic scent of violets? Thanks, --Dendre (talk) 18:48, 6 April 2009 (UTC)[reply]

Perhaps Ionone per this website (see entry for 1905). Our article claims that ionone is a rose smell though. Rmhermen (talk) 19:01, 6 April 2009 (UTC)[reply]

Actually, our article on Ionones claims that one variety of Ionone is responsible for the rose smell. It seems entriely reasonable that a different Ionone or mixture thereof could be responsible for the violet smell as well... --Jayron32.talk.contribs 19:43, 6 April 2009 (UTC)[reply]

Another probe to Uranus?

Will we eventually send another probe to Uranus and Neptune? If so when? 2020? 2030? So far on Voyager 2 have been there.--69.228.146.223 (talk) 19:02, 6 April 2009 (UTC)[reply]

According to exploration of Uranus and exploration of Neptune, there are no current planned missions. I should think someone will send something eventually, if civilization survives long enough. Algebraist 19:14, 6 April 2009 (UTC)[reply]

We don't provide medical advice here. ;-) Axl ¤ [Talk] 22:27, 6 April 2009 (UTC)[reply]

I really don't want to make the obvious joke here. It's killing me not to... URGH... Probing Uranus? Did he at least buy you a nice dinner first? Too late... --Jayron32.talk.contribs 00:04, 7 April 2009 (UTC)[reply]

If Uranus was named in 1781, when was the first off-color joke published about its name? (Perhaps something like "Gosh, with my new telescope, I believe I can see Uranus!"). Understandably, with the correct pronunciation there is no humorous effect in such observations as 1902 "one with good eyesight can easily see Uranus without artificial help" or from 1914 "A remarkable thing about Uranus is that it is enveloped in a dense atmosphere of enormous extent." Edison (talk) 21:40, 7 April 2009 (UTC)[reply]

Garrison Dam

If Garrison Dam on the Missouri river in North Dakota failed catastrophically, how long would it take for the flood to reach the next dam down? Is it likely that this would cause a failure of the second dam as well? 65.121.141.34 (talk) 19:03, 6 April 2009 (UTC)[reply]

There are simply too many unknown variables to answer that. Some things that would influence the outcome is whether most of the water ends up going downriver or whether it can spread out; how fast the dam fails, how much debris it will carry, whether the other dams have been softened by rains; ice flow; etc.. The engineers probably allowed for some margin of error, but thing can always go wrong. 76.97.245.5 (talk) 11:04, 7 April 2009 (UTC)[reply]

Just curious, are there any examples of this kind of sequential dam failure? Rmhermen (talk) 16:13, 7 April 2009 (UTC)[reply]

I do not know of any, which is why I am thinking of using something like this for a disaster type book. 65.121.141.34 (talk) 16:55, 7 April 2009 (UTC)[reply]

See Banqiao Dam. -Arch dude (talk) 17:46, 7 April 2009 (UTC)[reply]

Fear of Abandoment

First - should psychology be under the Science Reference Desk? Second - What are the treatments for Fear of Abandoment? Has one treatment been more successful than other? --Reticuli88 (talk) 19:27, 6 April 2009 (UTC)[reply]

If we recommended treatments to you for any medical condition, that could be construed as advice. It would be irresponsible to make any statement which would encourage you to take a course of action which could end up being wrong. The best advice we could give you is to seek the advice of a qualified medical professional. --Jayron32.talk.contribs 19:40, 6 April 2009 (UTC)[reply]

Not seeking treatment for myself nor anyone. Just an objective question. --Reticuli88 (talk) 19:44, 6 April 2009 (UTC)[reply]

Perhaps our articles on Obsessive Love, Delusion or Anxiety may have some sources to help you out. We are not qualified to give you any advice, as psycological illnesses are extremely complex and treatments of any sort may vary greatly. Livewireo (talk) 20:15, 6 April 2009 (UTC)[reply]

The main treatments would be tranquilizers, cognitive behavioral therapy, or psychoanalysis, probably. Looie496 (talk) 02:07, 7 April 2009 (UTC)[reply]

Hammer Striking a Nail

Quick/dumb question: Why is it when you strike a nail (or any metal) with a hammer really hard there are sparks? —Preceding unsigned comment added by 24.171.145.63 (talk) 21:29, 6 April 2009 (UTC)[reply]

As a result of the impact, small pieces of iron or steel are shaved off and frictionally heated; so much so that they ignite and burn in air. Surface to volume ratio increases as the particle size decreases, therefore these particles burn much more readily than any "macroscopic" iron or steel objects. --Dr Dima (talk) 21:46, 6 April 2009 (UTC)[reply]

It is interesting to note that sufficiently small, unoxidized iron particles ignite spontaneously in air. So, frictional heating may not even be required (although it certainly helps). See pyrophoricity. --Dr Dima (talk) 21:56, 6 April 2009 (UTC)[reply]

I wouldn't say it's friction at all. If small bits of metal stick up on the nail when it is first struck, there will be an enormous pressure applied to those bits, causing them to heat enough to glow or even melt and splatter out. They then rapidly cool and solidify in the air. StuRat (talk) 19:05, 7 April 2009 (UTC)[reply]

Thanks! —Preceding unsigned comment added by 24.171.145.63 (talk) 22:05, 6 April 2009 (UTC)[reply]

Sparking is mostly true for steel hammers, a brass hammer will spark far less, or not at all, which is why they are used in emergencies when flammable gasses are in the area. 65.121.141.34 (talk) 13:39, 7 April 2009 (UTC)[reply]

Self-induced synesthesia?

I've recently been reading a lot about synesthesia as well as self-hypnosis. I found a study (http://www.medindia.net/news/Hypnosis-can-Induce-Synesthesia-Study-43347-1.htm) in which researchers claim to have induced Grapheme-> color synesthesia in their test subjects and I was wondering if the same would be possible via self-hypnosis. Further, would it by possible to induce sound->color synesthesia, assuming one has perfect pitch? Thank you! 128.252.254.7 (talk) 22:02, 6 April 2009 (UTC)[reply]

There are certain non-prescription medications which have been shown to induce synesthesia, but use of these is against the law in most jurisdictions... --Jayron32.talk.contribs 00:02, 7 April 2009 (UTC)[reply]

Thank you for answering; however, I was wondering if it was possible to induce grapheme->color synesthesia via self-hypnosis. Thank you! —Preceding unsigned comment added by 128.252.254.7 (talk) 00:54, 7 April 2009 (UTC)[reply]

The paper in question, PMID 19175754, was only published last month, which isn't really enough time for people to have weighed it and evaluated its implications. Looie496 (talk) 02:14, 7 April 2009 (UTC)[reply]

I remember reading about that study. The popular reportings suggest that the study considered grapheme-colour synaesthetes to be unable to see a black grapheme printed on a background of the related colour. I found this baffling based on my own experience of and readings about synaesthesia. No doubt there is some group of people for which this is true, but I don't think it's representative of synaesthesia in general. Is the actual study more nuanced on this? 80.41.115.101 (talk) 19:33, 7 April 2009 (UTC)[reply]

Global warming

Rather than we're destroying the planet couldn't global warming just be the sun going through what a star does when it becomes middle aged, i.e. become warmer and expand and bring its heat closer to the earth. I know we dont help but the idea of the sun being closer to us seems so much more viable to me. —Preceding unsigned comment added by 92.232.184.222 (talk) 23:09, 6 April 2009 (UTC)[reply]

See Stellar evolution. The kind of aging of the sun you describe takes place on the magnitude of 1,000,000,000's of years. Global warming is taking place on the order of 10's of years. Demonstrably unrelated events. Now, the sun does show small fluctuations in energy output, both increases and decreases, and sometimes on short-time periods, but the current trend in global warming has not been correlated to any such changes. It has, however, been nicely correlated to an increase in carbon dioxide levels in the atmosphere, AND to increases in industrialization... --Jayron32.talk.contribs 23:28, 6 April 2009 (UTC)[reply]

Yeah - the timescale of the present change is vastly too quick to be a 'natural' thing. Also, if you plot a graph of temperature gain versus CO2 levels - they track each other very closely. The correlation is close to perfect. Correlation doesn't mean causation - but we have plenty of reasons to show causation too. There is really no doubt left - none whatever - not a shred. We're beyond the "Is this really happening?" and "Is it a natural event?" thing...now it's down to "Can we fix it?", "How bad will it be before we do fix it?", "How much will it cost?" and "How can we pursuade China and India to do their part?"...sadly, we still get a dozen questions of this kind for every one of the latter - and that's a sad, sad measure of the success of the evil corporations who are trying to bury the facts under a whelter of FUD. SteveBaker (talk) 00:07, 7 April 2009 (UTC)[reply]

Well, there are natural events which can cause climate change on the time scales we're seeing now, such as giant meteors and supervolcanoes. However, we haven't had either of those events recently, so we know that's not the issue. StuRat (talk) 15:44, 7 April 2009 (UTC)[reply]

Yes, it's possible that changes in the Sun are the primary cause of global warming. Mars is getting warmer [3], Jupiter is getting warmer [4], Triton (Neptune's largest moon) is getting warmer [5] and even Pluto is getting warmer [6]. Meteorologist John Coleman, founder of the Weather Channel, states that global warming is primarily the cause of the Sun getting hotter [7]. This topic was discussed on Penn and Teller's Bullshit! program [8]. Although they stopped short of claiming that the idea that mankind is responsible for global warming is bullshit, they did say that it smells like bullshit (watch all 3 parts of the episode and the extra's for Penn and Teller's complete take on this issue). A Quest For Knowledge (talk) 03:34, 7 April 2009 (UTC)[reply]

I'm pretty sure he meant the effect of the sun getting hotter, not the cause. Global warming couldn't possibly cause the sun to get hotter.--KageTora (talk) 18:49, 7 April 2009 (UTC)[reply]

Dear OP: The previous respondent prefers to take the word of two comedians and a TV weather show anchor over hundreds and hundreds of qualified climatologists and scientists of all kind who are essentially unanimous on this point. You may judge his/her ability to answer questions of this kind accordingly. Sadly, I'm not allowed to use the phrase "total idiot" at this point (oops!). (Actually - it's just one comedian - the other one doesn't say much.) 14:55, 7 April 2009 (UTC)

I watched that episode of BS!, and it should be noted that it was made some time ago, before all the evidence was in. What they essentially said on the show was that global warming may or may not be occurring due to human activities, and that all the evidence was not in (at that point). Now it is, and it is pretty much clear to every scientist not on the payroll of a major polluter that global warming is a real problem. StuRat (talk) 18:43, 7 April 2009 (UTC)[reply]

According to a column Penn wrote last year [9], his position is "I don't know". A Quest For Knowledge (talk) 20:24, 8 April 2009 (UTC)[reply]

There is also some theory I saw on some science channel about the temperature of the galaxy being warmer in the spiral arms than in between (obvious, warmer near stars and colder away from them) and how that affects the overall temperature of the solar system as it passes through denser and less dense areas of the galaxy. That would mean that it could be a warm spot in the galaxy, not necessarily the sun getting warmer. Since I really have no interest in this theory, I didn't reserve any brain cells to remember what program it was or who was stating the theory. I vaguely remember that they had rather nice graphics (which is why I watched it). -- kainaw ™ 03:56, 7 April 2009 (UTC)[reply]

"Planetary warming" is a myth promulgated by certain so-called sceptics. Of course, on average about half of all bodies in the solar system will get warmer at any one time due to orbital dynamics (elliptical orbits will move them towards and away from the sun). We do not have reasonable climate estimates for any of the farther solar system bodies. We only know about Pluto for 1/3rd of a Plutonian orbital period ("year"). The "warming" on Pluto, for example, is an extremely indirect measurement of atmospheric density during two occlusion events of stars -the atmosphere was thicker the second time, which may mean that more of it had thawed from the frozen state, which may mean that Pluto was warmer (or not). But Pluto, at that time was (and still is) fairly close to the sun, so of course it's expected to warm. Mars is not significantly warming - does anyone ever look at the second page of that NatGeo article? Jupiter is not getting significantly warmer, it very likely goes through a periodic event of wind system reorganization that makes some parts of it much warmer (and others cooler). And you might want to read the Triton article for yourself - there is no hint about increased solar output, but the warming is driven by atmospheric and albedo changes as the the moon goes through an unusual orbital alignment. We cover most of this with sources in the global warming FAQ. --Stephan Schulz (talk) 06:26, 7 April 2009 (UTC)[reply]

As Stephan said, the "warming" of other planets are due to measurement errors, or factors unrelated to the sun. To warm Pluto by 1C as a result of the sun warming is to warm Earth past the boiling point, so that's pretty much out of the question, although the Sun is expected to make Earth too hot for life in about 500 million years. ~A H 1^(TCU) 02:03, 10 April 2009 (UTC)[reply]

April 7

Toads and warts

Is it true that handling certain species of toad will cause an outbreak of warts in a human? I was told this as a child and it has stuck with me. I have never, ever touched a toad (or frog, just in case) in my life up to this point because of it. It's not that I feel that I've missed out on anything important growing up, but I'm wondering now if I have been misled. :) When I say warts, I mean the typical warts that humans suffer from, not a reaction to toxins in the toad's skin that causes something that looks a bit like warts to come up. --84.71.174.88 (talk) 01:09, 7 April 2009 (UTC)[reply]

No. Toads cannot cause warts in humans. This is an urban legend. Warts are caused by a variety of viruses. The relevant viruses are not carried by toads. JoshuaZ (talk) 01:42, 7 April 2009 (UTC)[reply]

It's more like sympathetic magic: toads have warts, therefore toads cause warts. Looie496 (talk) 02:16, 7 April 2009 (UTC)[reply]

No. See List_of_common_misconceptions#Biology. Axl ¤ [Talk] 09:21, 7 April 2009 (UTC)[reply]

It should be noted that this particular item is currently unsourced. Me and several other editors are attempting to find reliable sources for this article, but this item may be removed shortly. A Quest For Knowledge (talk) 12:31, 8 April 2009 (UTC)[reply]

The problem is that the term "warts" is used to refer to different things. The warts on a frog are more like what we call moles, which are not usually caused by a virus and therefore can't be passed on to others. StuRat (talk) 15:39, 7 April 2009 (UTC)[reply]

When you say "frog" do you mean "toad"? In these parts, our frogs are pretty smooooth. --Scray (talk) 21:03, 7 April 2009 (UTC)[reply]

Yes, I meant toads. StuRat (talk) 14:58, 8 April 2009 (UTC)[reply]

hearing

I went to a rock concert about a year ago and had tinnitus for 3-4 days after that. I want to go to another concert in a couple months and was wondering if there was a way that I would not get that ringing in the ears, or to keep the duration of the ringing shorter, and still enjoy the concert without muffling the music. 12.216.168.198 (talk) 02:48, 7 April 2009 (UTC)[reply]

I find that earplugs do an excellent job of reducing volume to enjoyable levels without muffling the music -- in fact, I tend to find the audio quality better once so filtered. Plus, no ringing! I prefer the cheap disposable foam variety for this sort of thing. — Lomn 03:02, 7 April 2009 (UTC)[reply]

I know a lot of professional audio people (I work in the video games business). They value their hearing above all else (One guy calls his ears his "golden moneymakers" because without them he has no career!) - yet they also enjoy listening to and playing music more than any people I know. They each have reusable ear plugs that are created especially for each individual by an audiologist who measures their ear canals. These earplugs attenuate the volume of the sound to a huge degree - but do so in a way that's completely uniform across the entire audio spectrum. This means that they still hear all of the nuances of the sound - and can ascertain the timbre, etc precisely as well as someone with unprotected ears. It also allows them to wind their audio systems up to higher volume levels so they get the satisfying 'gut feel' of the bass notes (and the all-important neighbours calling the police to complain about the noise)...without wrecking their hearing. They point out that every time you expose your ears to loud music, you erode your hearing a little bit more - and if it's loud enough to cause temporary deafness or tinnitus - then you have certainly damaged your hearing in a way from which it will never fully recover. So there is a STRONG recommendation that if you go to concerts or play instruments - to wear earplugs every single time - and that you should buy the best ones you can afford. SteveBaker (talk) 14:48, 7 April 2009 (UTC)[reply]

I agree with the earplug recommendation. If you're worried about looking uncool, get some earplugs which are skin-colored and put them in right before the music starts (say during a trip to the bathroom). If you put them in too early everyone will wonder why you can't hear. You don't have to worry about taking them out immediately afterwards, though, as people will attribute any lack of hearing acuity on your part as being due to damage to your hearing from the concert.

Another suggestion is to not sit right in front of any speakers. Obviously, this doesn't work if the concert enforces assigned seating, unless you know where the speakers will be when you choose your seats. However, avoiding speakers will only reduce the hearing damage, not eliminate it. You still need earplugs for that. StuRat (talk) 15:25, 7 April 2009 (UTC)[reply]

Certainly the inverse-square law applies here! If you can double your distance from the nearest speaker - the sound energy will be one quarter as much - but because our ears are logarithmic devices, it won't seem four times quieter. However, this doesn't really change the answer - if you like music and would like to be able to continue to enjoy it - wear earplugs. With decent earplugs - and hearing that hasn't already been fried by going to too many Motörhead concerts - you can easily hear normal conversation with the earplugs in...that's also a consequence of the logarithmic nature of our hearing. With good earplugs, things don't really sound that much quieter. SteveBaker (talk) 16:19, 7 April 2009 (UTC)[reply]

Distance from speakers certainly matters, but not only distance, as most speakers are highly directional. Therefore, sitting an equal distance to the side of a speaker isn't nearly as bad as in front of it. Intervening objects, such as a post or the heads of other concert-goers, may also block some of the sound. StuRat (talk) 19:34, 7 April 2009 (UTC)[reply]

As for why there aren't regulations which limit the volume at concerts to levels that won't damage hearing, there I am baffled. StuRat (talk) 15:31, 7 April 2009 (UTC)[reply]

There are such regulations in (for example) the UK - but the levels aren't set low enough to be 100% effective. SteveBaker (talk) 16:19, 7 April 2009 (UTC)[reply]

Plus what would be a safe level of noise for1 minute may not be safe if you have 3 hours of that noise level. 65.121.141.34 (talk) 16:53, 7 April 2009 (UTC)[reply]

Some musicians use "high fidelity" earplugs by Etymotic Research [10]. The frequency response is preserved while lowering the dB level. We cannot give medical advice, and specifying "safe" noise levels seems to fall in that category. For general information, you might check OSHA for the noise levels employees can be exposed to for varying durations under U.S. regulations. This regulation does not guarantee complete safety for persons exposed to noise levels under the curve. But they are an improvement over the old days when every construction worker, person who fired guns, soldier, or especially boiler maker was deafened to varying extents. Did you plan to carry a calibrated dbA slow response meter with you? Else, how would you know the sound pressure level? Edison (talk) 20:59, 7 April 2009 (UTC)[reply]

Why do massive objects in space don't look like they are moving?

Small objects in space look like they are moving, while massive objects don't. Why is this? 98.221.85.188 (talk) 04:36, 7 April 2009 (UTC)[reply]

I'm not sure what you mean. They look that way to whom? —Tamfang (talk) 05:15, 7 April 2009 (UTC)[reply]

I think that the OP means that when you travel, small things such as trees move when you look at it while larger (and probably distant) objects such as landmarks and the Moon doesn't appear to move even if you are travelling by car.--Lenticel ^(talk) 06:28, 7 April 2009 (UTC)[reply]

The appearance of moving results from the object appearing at a different angle at different times. So for a distant object to appear to move it will have to move a significant fraction of its distance away, so for something like the moon, you would have to move hundreds of kilometers to notice the change in its angle compared to say the stars. For distant stars there is even less movement in the sky, Astronomers can use parallax to find out how far away stars are. Graeme Bartlett (talk) 06:40, 7 April 2009 (UTC)[reply]

It's especially noticable with large aircraft. When you look at an airliner slowly drifting across the sky - it's hard to imagine that it's belting along at 400 mph! Partly that's because perspective has reduced the angular rate of speed relative to your eyepoint - the other part is that being such a large object, it takes more time to travel it's own length than a little cessna or something - which is going maybe a quarter the speed but is ten times shorter in length. Another problem with anything high in the air or in space is that there are typically no nearby, stationary objects for you to compare against. This is a problem that plagues science fiction movies and TV shows - even when the Starship Enterprise is zipping along at several times lightspeed - the stars in the background ought to appear dead still for hours at a time...but they don't - they move and even have parallax! That's totally unrealistic (even in a 'classical universe' with no relativity and no speed-of-light limit) - but that's the only way they have to convey speed. There is often a similar problem with size - you see spacecraft disappearing behind planets and moons - when in reality, even a gigantic craft would have shrunken to an invisible dot long before it could be far enough away to get around a planet that's thousands of miles in diameter. SteveBaker (talk) 14:36, 7 April 2009 (UTC)[reply]

In Star Trek, they use "warp factors", which apparently are not just the number of times the speed of light they are going. If this was the case, then, traveling at say Warp Factor 5 would still take them years to get anywhere (although it might not seem so to them, due to time dilation, but they just ignore that). It seems to have been a logarithmic scale of some type, with Warp Factor 1 being the speed of light and Warp Factor 10 being infinitely fast. They did violate this principle and go over Warp Factor 10, on at least one occasion, though. They could typically travel to the nearby stars (let's say 10-100 light years away) in a matter of hours (again, ignoring time dilation). If we assume the typical trip to take 1/1000th of a year, that would give us speeds in the range of 10 thousand to 100 thousand times the speed of light. In at least one episode, they did go all the way to the edge of our galaxy, though, which implies speeds well into tens of millions of times the speed of light. At such speeds, you should notice some apparent movement of the nearby stars, but perhaps not as much as is shown. StuRat (talk) 15:05, 7 April 2009 (UTC)[reply]

They use at least two sets of warp factors in star trek (geek warning, but I'm sure I'll be beat). In Voyager, Warp 10 = infinite velocity. In other series, I think they've gone to at least warp 16-17, which, of course, wasn't anywhere near infinite velocity. -- Aeluwas (talk) 15:43, 7 April 2009 (UTC)[reply]

All Next Generation era series use the new system, the Original series and Enterprise use the old one. There is no clear rule for the old system, but the fan-devised rule of them is that warp factor W means a speed of c*W³. --Tango (talk) 17:37, 7 April 2009 (UTC)[reply]

In space, it's the distance to the objects that determine how fast they appear to be moving, as explained previously. But you asked about the size of the objects. It just works out that small objects we can see are close and large objects are far away. If the Moon was as far away as a star, we couldn't see it. If a star was as close as the Moon, we would all be dead. StuRat (talk) 15:18, 7 April 2009 (UTC)[reply]

Star Trek - Science or fiction?

While looking at this image, it occurred to me that the "lettering" of the quadrants was rather strange. Instead of going either clockwise or counter-clockwise, the quadrants are put in order from right to left, then criss-cross, and then go right to left again. Since Star Trek often tries to keep some slight grasp on science (theoretical or not), I'm left wondering where they got this mapping scheme. Is this based on anything in the real world or is this just a oversight on the part of the writers? Dismas|^(talk) 05:21, 7 April 2009 (UTC)[reply]

I'm not sure why this particular arrangement was chosen, but there are sometimes good reasons to eschew traditional ordering (obligatory xkcd). Also, why would a clockwise (or counterclockwise) arrangement be any more sensible? – 74 05:46, 7 April 2009 (UTC)[reply]

A counterclockwise arrangement would follow along the lines of the quadrants of a coordinate plane. Dismas|^(talk) 10:17, 7 April 2009 (UTC)[reply]

Certainly; but there is no scientific basis for that arrangement either—it is used by convention (i.e. because it has been used before) and because it roughly corresponds to polar coordinates (another arbitrarily-chosen system). Tellingly, only one octant is commonly labeled: the first octant (+,+,+). – 74 11:21, 7 April 2009 (UTC)[reply]

If you're looking for an explanation that would be plausible 'in-universe', the order of labelling follows the chronological order of exploration (by human beings); it also sorts the quadrants by increasing (mean) distance from Earth. I don't know of any explicit canonical reference which describes the labelling system, but you might try poking around over at Memory Alpha. TenOfAllTrades(talk) 12:30, 7 April 2009 (UTC)[reply]

Entertainment Desk answer:

I've seen every episode of every Star Trek show (except the animated series) and all the movies, and I do not believe they ever mentioned the physical layout of the quadrants. I always assumed that consecutive letters were in order around the galaxy and therefore it was gamma that was opposite alpha, and I would have noticed if they said something that meant it was different. The image is only sourced to a web site and it might well have been created by a fan or writer who just made an assumption about what the labeling was. The fact that it relates to both Deep Space Nine and Voyager suggests that it is non-canonical.

Science Desk answer:

Nothing in astronomy labels quadrants with letters. Where the details of an object are known well enough to talk about locations within it or on its surface, numerically expressed coordinate systems such as latitude and longitude are used.
--Anonymous, 20:10 UTC, April 7, 2009.

Not to sound like a total nerd, but in one of the episodes (in Voyager I think) where a prop map of the galaxy has the quadrants labeled. I don't recall the exact episode, but I bet that Memory Alpha would know where it is. 65.121.141.34 (talk) 20:46, 7 April 2009 (UTC)[reply]

I don't think there's any scientific basis at all. Basically, the original series took place in what's canonically now called the Alpha quadrant, and Deep Space Nine established the Gamma quadrant as a "far away" place to go to. But when Voyager came out, they wanted it set somewhere "farther away" so they had to establish the Delta quadrant as somehow even more remote than the Gamma quadrant. I'd say this is an issue of sense being thrown out the window in favor of suiting the show's theme. — The Hand That Feeds You:^Bite 14:35, 13 April 2009 (UTC)[reply]

Or just a different far-away place. --Anonymous, 00:56 UTC, April 14, 2009.

Vacuum flask

I was reading the Vacuum flask article and I came across this line:

A typical domestic vacuum flask will keep liquid cool for about 24 hours, and warm for up to 8.

Assuming the cool liquid has the same temperature difference from ambient temperature as the warm liquid does, how does this make sense?

This statement makes less sense if you think about common temperatures. Take ambient to be 20ºC, the cool liquid to be ice water (0ºC) and the warm liquid to be boiling water (100ºC) then surely it would take longer for the hot liquid to equilibrate than the cool liquid. Am I missing some thing here? —Preceding unsigned comment added by 130.194.164.217 (talk) 06:10, 7 April 2009 (UTC)[reply]

"Cold" doesn't flow; heat does. Take a point source located in a vacuum—all radiation produced will travel outwards radially and be lost. Now, take a point sink inside a vacuum—any radiation produced outside the vacuum is quite unlikely to strike the point sink. In real life, the interior dimensions are significantly larger than a point, but I'd suspect the principle still stands. – 74 06:33, 7 April 2009 (UTC)[reply]

If it's convenient to talk about cold flowing - we can. The math still works. Just as we talk about electricity flowing in the opposite direction than which the electrons are actually moving...it doesn't matter. Rigid thinking in science is not good. Very often, profound insights can be gained by kinda tipping your head sideways and squinting a bit! SteveBaker (talk) 14:26, 7 April 2009 (UTC)[reply]

"Lax" thinking is the kind of thing that generally leads to profound errors, not insights. In situations where the directionality of flow is irrelevant then you can use "cold" flow somewhat interchangeably (but with dubious benefit). However, in cases like this where directionality is important "cold" flow only confuses the issue. Science is all about precise (or "rigid") exploration of the world, and I am quite surprised by your dismissal of valid scientific principles in the interest of "convenience". – 74 21:17, 7 April 2009 (UTC)[reply]

It's only lax thinking if you don't understand the underlying mechanism. Low level atomic vibration/motion is what we call "heat". That vibration spreads to other atoms that are moving less quickly - and we talk about heat moving from hot to cold. However, when those fast moving atoms pass on their energy to the slow ones - they are slowed down in the process so talking about the reduction in motion spreading from the slow moving atoms into the fast moving atoms is no more or less valid than the "conventional" description of heat travelling from hot to cold. So long as you understand this, you can just as validly talk about the 'coolness' flowing into the hotter material as the other way around. This isn't "lax thinking" - it's unconventional thinking - looking at the problem in another way and possibly gaining some insights. It's truly just a matter of convenience to decide to talk about flow in one direction or the other. As I pointed out (and you've carefully ignored) we do this all the time when we talk about electricity flowing from + to - rather than from - to + as is "really" happening if you watch the electrons. However, we're quite happy to talk about the motion of "Electron holes" in the conventional direction as a way of making sense of the 'reversed' direction. Same deal with heat and cool. Far from "dismissal of valid scientific principles" I'm using those very principles in a way that might well make the explanation clearer. I should probably say something about being "quite surprised by your rigid thinking and lack of comprehension of underlying scientific principles"...but I'll let your imagination fill in the details (if you have an imagination that is). SteveBaker (talk) 13:18, 8 April 2009 (UTC)[reply]

It most certainly *is* less valid in the case of radiation, where a second material is not necessarily located in close proximity (and needn't exist at all). The "fact" that "electron holes" may be used to make some explanations of circuits simpler (personally, I've found it only adds confusion) has little to no bearing on heat transfer; an (equally pointless) counter-example would be darkness/light. But, if you insist on confusing the issue, I apparently cannot stop you. – 74 16:38, 8 April 2009 (UTC)[reply]

"Close that refrigerator door, you're letting all the coolth out !". StuRat (talk) 14:31, 7 April 2009 (UTC) [reply]

Yes, you are missing some physics. Radiative thermal losses (integrated over the entire spectrum) are proportional to temperature to the fourth power, see Stefan-Boltzmann law. Hot object in a warm environment loses energy faster than a cold object in the same environment gains energy, assuming the surface properties of the two objects are the same. Vacuum flask coating is not equally reflective at all infrared wavelengths, so the dE/dt ~ T₁⁴ - T₂⁴ approximation is not really accurate; but qualitatively it should work. --Dr Dima (talk) 07:28, 7 April 2009 (UTC)[reply]

You're also missing what people mean by keeping cool or hot. It would be considered cool if it is a bit cooler than ambient, but it would have stopped being hot and become warm or tepid in between getting to ambient temperature - and it would do that quicker because of the bigger temperature difference. Dmcq (talk) 09:58, 7 April 2009 (UTC)[reply]

I agree with all of our previous answers. The deal is that the vacuum inside the flask only stops losses due to conduction & convection (and even that, not completely since it's not a hard vacuum and there is a connection between interior and exterior at the neck of the vessel). It does little to prevent loss due to radiation (although they do apply a mirror coating to the glass of the inside vessel and use shiney metal for the exterior). But because the radiation from the warmer outside of the flask into the interior is happening at a lower temperature than the radiation from a hot liquid inside to that exact same exterior temperature - then the losses are faster. That taken with the undoubted truth that 'hot' liquids have a bigger temperature delta to the outside than the outside does to a cold liquid inside - so any conduction paths (which depend on temperature DIFFERENCE not absolute temperature) will be less significant in the cold case. Add to that that we care more about how hot our coffee is than how cold our soda is...this easily explains the factor of 3x difference. I'm actually rather surprised it's not more than that.

SteveBaker (talk) 14:26, 7 April 2009 (UTC)[reply]

Some Stanley "vacuum flasks" in recent years had finely powdered carbon in the "vacuum" space. A pinhole leak in the outer liner caused the fine carbon dust to spew out, reducing visibility if it happened in a moving auto. If it had lower than atmospheric pressure, why wouldn't air leak in instead of the carbon powder leaking out? Dewer's first vacuum flask in 1892 had a silvery mercury coating. In a vacuum flask without a silvery coating, a liquified gas evaporated 1/5 as fast as in open air; with the mercury coating, the evaporation was reduced to 1/33 the free rate. There should be a small hole in the lid of the inner container to avoid any pressure buildup. The flask allowed Dewar to transport liquified air on a rail trip from London to Cambridge to show it off. The outer of the flask was packed in dry ice to liquify the mercury and reduce the mercury vapor pressure. Edison (talk) 20:37, 7 April 2009 (UTC)[reply]

True area of a country

Hello, fellow Wikipedians. It has for a long time bugged me that it seems, when we measure the area of an... area, country rather, that we take the flattest approach. In truth, every hole and rise will result in a greater area, and so a 500km^2 country that is completely flat will have less area than a 500km^2 country that has, say, a mountain on it.

Afghanistan for instance, to point to a place where we know the intricate shapes and forms of their mountains, has a much higher area than is stated in its proper article, likewise Norway, whereas Western Sahara's real area isn't too far from its measured area - not off by as much as in other cases, at least. Are anyone able to measure area in this way, "real" area as it might be called? Thank you for your help. 62.128.252.85 (talk) 11:19, 7 April 2009 (UTC)[reply]

You may be interested in How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension. While that concerns the length of a coastline, the problem is analogous. -- Coneslayer (talk) 12:00, 7 April 2009 (UTC)[reply]

"True" or "real" area of a country is an interresting concept. Did the September 11 attacks reduce the real area of Manhatten? Cuddlyable3 (talk) 13:49, 7 April 2009 (UTC)[reply]

This is emphatically NOT the same as the 'coastline' problem. When we talk of the 'area' of a city or a country or whatever - we're not talking about the total area of everything contained inside of it - we're talking about the area of the city when it's projected downwards onto an idealized spheroid at mean sea level. Where my house is built, I have 1.2 acres of land - most of it slopes steeply at about (let's say) 45 degrees - which means that the ACTUAL area is about 1.4 times bigger which is close to 1.7 acres. But I'm taxed on 1.2 acres, the law regarding the amount of land I needed to build a 2 storey house said I had to have 1.2 acres...everyone talks about it being 1.2 acres. So taking the more reasonable definition of 'projected area' - even though the "coastline" of that area might be fractal in nature and it's length is therefore indeterminate, the area bounded by that fractal has a well-defined value that lies between limits that can be determined to arbitary precision by examining a more and more detailed coastline. That's the opposite of the coastline problem - where the more closely you look at the coastline, the longer it becomes and the less accurately you can determine the answer. Now, if you ARE talking about the area of everything inside the city - then indeed you are looking at a fractal-type of problem which is kinda similar to the the coastline problem in that you ultimately need to sum the areas of each blade of grass - and so forth...however, that's a fairly bizarre interpretation of the word for any practical purpose. SteveBaker (talk) 14:04, 7 April 2009 (UTC)[reply]

It seemed to me that the "bizarre interpretation" was the exact point of the question, which is why I brought it up. As you add up all the extra area due to terrain, your area gets bigger and bigger as you go to smaller scales (cracks in the mountain, etc.). BTW, are surveyed areas really projected to MSL? So a flat parcel surveyed at 1 acre in Denver is really slightly bigger than 1 acre? -- Coneslayer (talk) 14:14, 7 April 2009 (UTC)[reply]

Technically - yes - but the error is so spectacularly microscopic for a flat piece of land that the errors in measurement completely dwarf that. SteveBaker (talk) 15:43, 7 April 2009 (UTC)[reply]

I agree that the approach the original poster was asking about would lead to both the fractal issue and the problem of the area changing due to strip mining, landscaping, etc., so isn't practical. Whether the current measures are taken the way SteveBaker said is an interesting question. I suspect that in many cases the area of a plot of land is simply determined by measuring the distance along the edges (straight-line distance, through the air, not measured along the ground). I doubt if any adjustment for elevation is used. StuRat (talk) 14:29, 7 April 2009 (UTC)[reply]

When they surveyed the plot for my house, they determined the latitude/longitude for each corner of the lot and stuffed that into a piece of software that calculated the area. The altitude wasn't taken into account - and they certainly don't use tape-measures to just measure the straight-line distances between the corner markers...at least not in Texas. SteveBaker (talk) 15:43, 7 April 2009 (UTC)[reply]

Of course they don't use tape measures. I believe modern surveyors have a device which uses the speed of light to measure the distance (do we have an article on this ?). I can't see them using a GPS device to measure the latitude and longitude, as they just aren't accurate enough. Being within a few feet is fine for driving directions, but lousy when marking property lines. StuRat (talk) 19:24, 7 April 2009 (UTC)[reply]

Actually - they did use GPS - but not the regular satellite-only kind. They plant a special 'base station' at a known location and use 'differential GPS' which is accurate down to a millimeter or so to accurately measure the position relative to that base. In the case of a plot of land, they don't care much where it is (at least not to great precision) - but they do care how big it is...because that's what determines the taxes you pay, etc. What they actually did at my house was to check the position of a big steel spike that's driven into the ground at one corner of the lot using some kind of conventional measurement system with theodolites and such measured from a nearby road. Then they positioned the GPS base-station onto that spike then walked off to the other corners of the property with their differential GPS and got accurate numbers relative to the base station and hammered in more spikes. Then they hooked up the GPS widget to their laptop and got a number for the area. No elevation data. There is no way they could have used lasers or whatever - the terrain is WAY too rugged for that. You'd have to take down at least a hundred trees to get a line of site, even over the flatter parts! (Then my neighbour dug up one of the spikes because he claimed it was 20' away from where it should be...he ended up paying a $1000 fine and came close to going to jail when he argued with the police...don't do that!) SteveBaker (talk) 01:17, 8 April 2009 (UTC)[reply]

I didn't say they use light, but rather the "speed of light", which, of course, applies to the entire spectrum. I suspect that the "differential GPS" device you mentioned uses that method, with radio waves or some other frequency. I would have thought they would need to take differential elevation into account, as well, when determining the area of a piece of land. For example, if you have a 240 foot long lot which is 70 feet lower at one end, that will give a distance of 250 feet between the two points when measured at those different elevations. That's enough error that they might be rather concerned. StuRat (talk) 14:54, 8 April 2009 (UTC)[reply]

You do not get more hectares or acres of land by digging a hole and piling up the resulting dirt. See the 1902 "Manual of instructions for the survey of public lands... which included the oath to be taken by assistant surveyors:"...we will level the chain upon even and uneven ground, and plumb the tally pins..." U.S. Supreme Court Reports from 1901 says "...the mode of measuring will be to level the chain, as is usually done with chain carriers when measuring up and down mountain sides, or over other steep acclivities or depressions, so as to approximate, to a reasonable extent, horizontal measurement, this being the general practice of surveying wild lands in Tennessee." "Leveling the chain" can be done by physically keeping the chain horizontal, or by trigonometry on cliffs and steep river banks based on use of transits or other optical instruments. Only informal measurement, like a farmer dividing by his own efforts a 40 acre field into 2 twenty acre fields, might be done up hill and down. In such informal measurements, the farmer might cut a "pole" 16.5 feet long and walk along flipping it end over end to measure off "poles" or he could level it. "A "Gunter's chain was 66 feet long, equalling 4 "poles" or "rods." A British surveying book from 1881 compares the "levelled chain" and the theodolite for measuring slopes, and notes how hard it is in practice to perfectly "level the chain". Edison (talk) 19:54, 7 April 2009 (UTC)[reply]

Surveying and Aerial survey may have the info Stu was looking for. While it might be of statistical interest (or bragging rights) to measure surfaces at an angle, for most practical purposes the more level the area the more usable. (OR we have an brook in back with a slope of about 60 degr. You'd have to either dig things up or fill it in to do anything with the lot but admire the view.) 76.97.245.5 (talk) 20:18, 7 April 2009 (UTC)[reply]

I just wanted to add to Coneslayer's comment that even when 911 happened, the area of Manhattan stayed the same as long as the volume of the towers were still situated in Mahattan, therefore, even though the shape changed, the volume stayed the same. Buɡboy52.4 (talk) 04:37, 12 April 2009 (UTC)[reply]

Relationship between Thermodynamic Entropy and Cosmic Dark Energy?

What is the relationship (if any) between Entropy and Dark Energy The temperature-dependent term for Entropy is an important thermodynamic determinant in most bio/chemical reactions. Yet astrophysicists rarely discuss or estimate its role in determining the balance of cohesive/dispersive forces at work in the cosmos. Why is this? Is Entropy Dark Energy by another name? Has the dispersive effect of an Entropy increase in the cosmos (but outside a black hole!) been quantified -- I assume that it cannot be just ignored? 19Grumpah42 (talk) 13:08, 7 April 2009 (UTC)[reply]

Have you read our articles on entropy and dark energy? They should not be considered analogous. As dark energy is presently theorized to be doing work (accelerating the expansion of the universe), it is specifically not "the unavailability of energy to do work". — Lomn 13:28, 7 April 2009 (UTC)[reply]

temperature goes up as you dig down.

The temperature goes up as you dig down, like with the Kola borehole. If one was to dig a straight level tunnel starting at 1,000 ft under a 12,000 ft tall mountain, would the tunnel be far warmer in the middle then on the outside ends, or does the temperature only start going up when your hole is below sea level? 65.121.141.34 (talk) 14:22, 7 April 2009 (UTC)[reply]

It depends entirely on where you dig. If you start digging on a 12,000ft volcanic mountain, it won't take long to hit hot rock. If you start digging on a 12,00ft pile of granite, it will take a long time to hit hot rock. The Earth's crust is not uniform and there are hot spots under it. -- kainaw ™ 14:26, 7 April 2009 (UTC)[reply]

If your mountain is made of a 'hot' granite, i.e. with a high concentration of radionuclides, it could be quite hot due to its internal heat production from radioactive decay. Whatever the actual value of the geothermal gradient beneath your mountain, it would get hotter along your horizontal tunnel, the only question is 'how much?'. Mikenorton (talk) 14:41, 7 April 2009 (UTC)[reply]

Since most of the heat underground is either generated at the point where it's measured (by radioactivity and tidal forces) or underneath, the question is if the heat is kept where it is or allowed to radiate away on the surface. Therefore, the more insulation there is between a particular location and the surface, the hotter is should be. Horizontal distances would be the same as vertical distance, in this regard. However, solar heating means that the surface is sometimes hotter and sometimes cooler. On a hot day, it will be cooler underground or in a tunnel through a mountain. This effect will be much greater than the quite gradual effect of increasing temp with distance from the surface. StuRat (talk) 20:17, 7 April 2009 (UTC)[reply]

For a practical example, I have here a nice little book: the 2000 English translation Historical Tunnels in the Swiss Alps: Gotthard Simplon Lötschberg of the 1996 book Historische Alpendurchtische in der Schweiz by K. Kovári and R. Fechtig, published by the Gesellschaft für Ingenieurbaukunst (Society for the Art of Civil Engineering) there. This quotes a 1906 report saying that when constructing the original Simplon Tunnel, "the temperature of the rock rose rapidly from about 40 °C [that's 104°F] at distance 6340 m [3.94 miles] into the tunnel at the start of the period of observation to about 52 °C [125°F] at 7300 m [4.54 miles]. From there the increase in temperature was more gradual until at about 9100 m [5.65 miles] from the north portal it reached its highest value of 56 °C [132°F]" (that would be near the midpoint of the tunnel). From the accompanying diagram, the depth of rock above the tunnel at the three positions mentioned was roughly 1,200, 1,500, and 2,200 m respectively, or about 4,000, 5,000, and 7,200 feet.

The book does not mention the particular source of geothermal heat applicable to this tunnel, but a geological diagram shows that it is mostly in schist and gneiss, both of which are metamorphic rocks that may or may not be formed from granite. To deal with the heat, cold water was pumped into the tunnel and sprayed into the air. Many tunnel projects experience quantities of ground water flowing into the tunnel and in this case that water, which was at 12°C (55°F), was put to good use.

--Anonymous, 20:41 UTC, April 7, 2009.

Venusian thought experiment

Well, let's imagine our Solar System 4 billion years ago, with a little twist.

Let's say Venus and the Earth were pretty close to actually being twin planets 4 billion MyA. Same conditions, same [almost] everything. Time goes by, and eventually life evolves on Venus about 80 MyA before the same thing happens on Earth. Morphologically, you can imagine Venusian life to be as similar or as different from life on Earth as you wish, the only condition is that they must have the same vital requirements as we Earthlings.

Geological time speeds by, with both Earth and Venus having their share of diversity booms and extinction. Because Venus had a 80 MyA headstart, intelligent life evolves on Venus while the Earth is still in the Middle Cretaceous (ok, it doesn't have to be that way, but imagine it is).

While dinosaurs still rule the Earth, Venusians discover fire, erect buildings, create the movable print and eventually start burning fossil fuels. Like on Earth, they keep on pumping CO₂ and other greenhouse gases into the atmosphere for over a century. Even though they notice they've damaged the planet, it's too late to do nothing because they've already triggered the melting of permafrost methane, which in turn triggers a runaway heating. In the end, temperatures rise to the point that all life on Venus is scorched to death.

80 million years go by, and the weak but constant surface effects on Venus erase any trace of civilisation on that planet. Now, we only see a barren desert spreading everywhere. Even their spaceships won't be a witness before us, since either their orbit has decayed and they have been destroyed, or they are many lightyears away in interstellar space. Therefore, nothing remains to remind us of what happened to Venus and what may happen to us.

Okay then, end of the story. What is the scientific evidence for or against this possibility? What are the oversights I may have made when inventing this little tale? Or, on the contrary, is it possible that it might have happened? Leptictidium (mt) 14:30, 7 April 2009 (UTC)[reply]

I think the biggest flaw is the implausibility of "twin planets" as laid out at the open. Venus' surface atmospheric pressure is 90 times that of Earth and it's 97% CO₂. We colloquially refer to Venus as having a "runaway greenhouse effect", but there's no plausible way for humans to accidentally get from our global warming scenario to something akin to Venus. To be clear, Venus has over 200 thousand times more atmospheric CO₂ than Earth. We're speculating that Earth's change in CO₂ concentration peaks at give-or-take double present levels. Now, applying that much CO₂ to a Venusian atmosphere raises its concentration from 96.5% to 96.5004%. Clearly, the same mechanic could not apply. What is catastrophic for Earth isn't statistically measurable for Venus. — Lomn 14:56, 7 April 2009 (UTC)[reply]

But Earth's atmosphere had much more CO2 and was much much denser in the past, i.e. before those pesky cyanobacteria turned well-behaved CO2 into toxic oxygen and complex organic molecules. See Earth's_atmosphere#Evolution_of_Earth.27s_atmosphere and Oxygen Catastrophe. --Stephan Schulz (talk) 15:12, 7 April 2009 (UTC)[reply]

Did the Venusians develop any space travel technology? If so, is it possible that there might still be satellites in orbit after ~~4 billion years~~ 80 million years? I would think that they would have tried to leave some sort of record of their existence. Perhaps place satellites in orbit around all the major bodies in the Solar System (all the planets and the Sun). Actually, knowing that there's life on Earth, I would imagine they would send some probes down here as well as the Moon. In fact, why not move to the Earth? If the Earth's atomosphere isn't habitable for Venusians, perhaps Earth can be Venus-formed. A Quest For Knowledge (talk) 15:22, 7 April 2009 (UTC)[reply]

If you carefully construct a scenario in which there is no scientific evidence (as I think you tried to do) then there won't be any scientific evidence. If you don't do that - then there would be. It's kinda meaningless. If I had to specifically poke holes - I'd point out that if these Venusians were even a little ahead of where we are technologically - they'd be sure to have sent craft to the lagrange points of (at least) Venus - those locations are in principle accessible to our technology - and their equipment would still be sitting there pretty much intact even after millions of years because the lagrange points behave as if there were gravity pulling things towards that location (although that's not really what's going on) - so their positions would be stable and easily located. Of course you can just write that maybe the Venusian religion forbids sending things to the lagrange points and we're back with no evidence again...but that's true of anything we might come up with. SteveBaker (talk) 15:32, 7 April 2009 (UTC)[reply]

Or a large chunk of rock could have randomly flew through the Lagrange point taking the satellite with it. 65.121.141.34 (talk) 15:45, 7 April 2009 (UTC)[reply]

BTW, this is a pretty interesting premise for a science fiction story. If this is an original idea from you, you might want to run out to find a lawyer and see about getting a copyright on it. A Quest For Knowledge (talk) 15:37, 7 April 2009 (UTC)[reply]

You cannot get a copyright on an idea...--Stephan Schulz (talk) 15:40, 7 April 2009 (UTC)[reply]

And if you could, you'd have to fight my prior claim from years back. The basic idea is a fairly obvious one and I'm sure it's occurred to many people independently. Algebraist 15:47, 7 April 2009 (UTC)[reply]

Well, I'll try and clarify a few things.

When I said twin planets, I meant at the beginning. That means that Venus CO₂ would be 97%, but maybe as a result precisely of all the permafrost methane melting and triggering a positive feedback.
Yes, they did have space travel technology. But someone said above that they would be a little more advanced than we are now – no, in my thought experiment the 80-million-year old Venusians would be just as advanced as we are, only 80 million years earlier.
@ SteveBaker: I am not asking for evidence regarding the fact that this happened, but rather what information we have which may suggest it could have happened (or could not, for that matter).
Finally, a question: would it be likely that, with all meteors, comets, etc. flying around, artifficial satellites survived for so long in the Lagrangian point? Leptictidium (mt) 15:54, 7 April 2009 (UTC)[reply]

The Lagrangian point of what system? Earth-Moon, Sun-Venus, ...? —Tamfang (talk) 17:39, 7 April 2009 (UTC)[reply]

There ought to be atmospheric spectroscopic evidence. I would think at least some telltale organic molecules would remain even in the oxidizing atmospheric conditions. Also there would have been a lot of water on Venus to support life originally (assuming life on Venus operates on similar principles). Venus' atmosphere has a rather low water content (0.002% Water vapor compared to earth's ~ 1% water vapor). Venus' high temp would make liquid water on the surface unlikely. The article Venus says the best hypothesis as to what happened to the water Venus was hypothesized to have in the past is that the evaporated water "has dissociated, and with the lack of a planetary magnetic field, the hydrogen has been swept into interplanetary space by the solar wind." Is 80 million years enough time to get rid off an ocean's worth of water via that method? I'm not sure it is. According to Carbon, Earth has a total of about 40000 gigatons or 4 * 10¹³ kilograms of carbon dissolved in water, in the atmosphere, as coal and oil, and locked up in biosphere. That carbon would make about 1.5 * 10¹⁴ kilograms of carbon dioxide if I did my math right. There is 4.8 × 10²⁰ kg of atmosphere on Venus according to Atmosphere of Venus and around 95% (assuming by weight) of it (~4.6 × 10²⁰ kg) it is carbon dioxide. That amount of carbon dioxide is about 6 orders of magnitude greater than the amount of carbon dioxide that all the Earth's sources of carbon that I mentioned above would make. While I am not sure the Earth figure includes other sources of carbon like carbonate containing minerals (probably not), Venus has a ridiculously large amount or carbon dioxide nonetheless. That discrepancy makes me wonder if Venus' atmosphere could have ever not had a significant amount of carbon dioxide as there would had to have been a large amount of something that could have bound all of that up previously. If the rest of that carbon dioxide did come from carbonate minerals, again, is 80 million years enough to decarbonate enough of it to account for present day atmospheric concentrations? Also if that process was still going on, if you could get a spiffy probe to the surface to bore a deep hole, you might be able to tell. Sifaka ^talk 17:56, 7 April 2009 (UTC)[reply]

Sorry, but you're about a century too late with your sf scenario. Of course when Percival Lowell, H.G. Wells, and Edgar Rice Burroughs were at it, the conceit was that since Mars was further from the Sun than the Earth, it cooled and developed first, and had the old civilization, while Venus was still in its version of the Mesozoic.

Sorry to dash cold water on your idea, but there is utterly nothing that would support your scenario. At Venus' distance from the Sun, lower gravity than Earth, and long diurnal rotational period, liquid water could not naturally collect on its surface, without which life is not going to get a foothold.

B00P (talk) 00:54, 8 April 2009 (UTC)[reply]

Now it can be revealed: it was Venusian UFOs that abducted our dinosaurs. Cuddlyable3 (talk) 17:42, 8 April 2009 (UTC)[reply]

How common is runaway global warming?

Some people say that we will soon trigger, or already have triggered, runaway global warming, and once it happens it's nigh-impossible to stop. How often does this happen? How bad is it when it does? — DanielLC 16:42, 7 April 2009 (UTC)[reply]

I would say we have a severe deficiency of data considering we don't have an experimental control group, or a large enough population of planets with temperature data to get any kind of statistically relevant result. My WAG is that it is rare. 65.121.141.34 (talk) 16:48, 7 April 2009 (UTC)[reply]

Runaway global warming is, as far as I know, still something of a vague theory with several possible mechanisms - the Clathrate gun hypothesis being the most prominent I've seen, i'd recommend that article as a good starting point. There simply isn't enough data to make a solid answer to your question: past periods of large-scale warming can be as easily attributed to solar variations that we simply have no control over. ~ mazca ^t|c 17:18, 7 April 2009 (UTC)[reply]

see Interglacial. -Arch dude (talk) 17:22, 7 April 2009 (UTC)[reply]

Since the Earth's been hotter than this before and cooled down, obviously something must eventually kick in to bring temperatures back down. However, temps could get dangerously high until that happens. StuRat (talk) 19:57, 7 April 2009 (UTC)[reply]

And, while we don't have evidence of runaway global warming due to greenhouse gases, there is plenty of evidence of other dramatic climatic changes both in the Earth's past and on other planets. Mars, for example, appears to have once had quantities of liquid water. StuRat (talk) 20:07, 7 April 2009 (UTC)[reply]

Mars could certainly lose all its liquid water without high temperatures due to a dissipated atmosphere, even if the temp stayed around -20F, so I would like to see additional evidence before I would count Mars. 65.121.141.34 (talk) 20:39, 7 April 2009 (UTC)[reply]

I was using Mars as an example of "other dramatic climatic changes", not "runaway global warming". StuRat (talk) 14:22, 8 April 2009 (UTC)[reply]

There are certainly two parts to this - right now, we undoubtedly have global warming - far more rapidly than any of the 'nut-job' theories can explain. This much is established fact. What we don't know is precisely is whether it's reached the runaway stage yet - and if it hasn't, then by how much can we risk pushing it before it does? There is a small amount of legitimate doubt as to whether the runaway effect even exists - but the vast majority of serious experts claim that there is at the very least, a huge risk that the climate will run-away from our ability to control it by any means whatever.

There are a fair number of feedback mechanisms involved - things like that snow is white an shiney and reflects sunlight away from the earth - as the earth warms, the ice melts and is replaced by something darker (ocean or dirt) which ceases to reflect sunlight away and absorbs it instead. This extra absorption causes more temperature increase - which causes more ice to melt. Those kinds of mechanisms are what could kick us into 'runaway' global warming - a scary situation where even if we stopped all CO2 production instantly - the earth might continue to get warmer. But we don't really have a firm knowledge of which (if any) of those mechanisms are removing our ability to recover. It seems that the arctic ice sheet is melting far faster than we predicted - and that is perhaps evidence of a runaway effect at the North Pole. However, when all of that ice is gone - the effect will cease to run-away. Since the ice at the North Pole is floating, it doesn't make much difference to global sea levels when it melts - so aside from the ecological damage (say goodbye to polar bears, for example - they are going extinct within our lifetimes) - the net effect is limited.

The same effect happening at the South Pole would be VASTLY more dangerous - because there is a lot more ice locked up there - and it's sitting on land well above sea level - so when it melts, it pushes the ocean levels higher.

Then (as previously mentioned) we have the methane clathrate business - where (essentially) there are deep ocean deposits of frozen methane which will melt when the ocean temperatures rise - thereby releasing methane into the atmosphere - which is a MUCH nastier global warming agent than CO2 - causing more temperature rise - causing more clathrate to melt. A couple of ships have detected methane bubbles coming from areas where these deposits may be found...so there is a definite possibility that this has already started to run-away. That happened at the end of 2008 - so it's very possible that we're already too late.

Also, as temperatures climb - the warming of the ocean causes the water to expand - making the sea levels rise faster than you'd expect from ice melting alone. As the ocean inundates land, the darker water absorbs more heat than the land would - and (worse still) has a higher thermal inertia - so it locks the heat in so it doesn't radiate out into space again at night as much as it used to. This increases temperatures - which melts more ice, clathrates and increases the volume of the existing water still more.

At some point, the increase in water levels will start killing off green plants - which means less CO2 is absorbed and more gets into the atmosphere. This is somewhat tempered by the increase in green algea in the oceans - so maybe that's not a feedback mechanism - but we don't know that for sure.

The point is that there are MANY mechanisms - and they are all feeding back on each other. So the melting of the northern ice-cap might not be directly serious - but because it increases the absorption of sunlight - it may be enough to kick one of the other mechanisms into high gear. Estimating the consequences of such complex interactions is very tough. The consensus of opinion between serious researchers is that we'll see between 7 meters and 22 meters of water level increase over the next 100 years. Either of those would be extremely nasty for humans...and devastating for most non-human life.

As for what it would take to recover - it is indeed true that the planet has recovered from worst in the past - but that's always been at the price of mass extinction of plants and animals - and it's taken hundreds of thousands of years to do that. So this potential recovery in the future isn't something we have to care much about - it's unlikely that human civilisation could survive in anything like a recognisable form in the face of that kind of destruction.

SteveBaker (talk) 20:36, 7 April 2009 (UTC)[reply]

Let me clarify my question. I want to know how common sudden changes in climate are. I'm not asking about extremes in climate or about how sudden climate change can happen. If they all lead to Extinction events, there couldn't be much more than 20 in the last 540 million years, right? If so, we'd need to be changing the climate at hundreds of thousands of times its normal speed to have an appreciable chance of triggering it in the near future, right? If runaway climate change won't cause an Extinction event, don't we have more important things to worry about? — DanielLC 23:02, 7 April 2009 (UTC)[reply]

We ARE changing the mean temperature at hundreds of thousands of times it's normal speed - and that's pretty much exactly what the problem is! We've increased global temperatures by a couple of degrees over a hundred years. In the past, that's something that's taken a million years to happen 'normally'. So yeah - we're doing this 10,000 times faster than 'normal speed'. That high rate of change makes it impossible for evolution to keep up - so the polar bears don't have time to evolve to do without icebergs. Also, it means that any natural feedback (such as algea in the ocean evolving to consume more CO2 in warmer waters) cannot kick in. It's precisely because it's happening so fast that it's such a major problem. If we had 10,000 years to plan for this change, we could gradually move cities inland, breed crops that would thrive in higher temperatures and so on...but at the present rate of change, there simply isn't enough time. If we kick the climate into 'runaway' mode - then the rate of change (and the AMOUNT of change) will kick up into a higher gear and we'll truly be in deep doo-doo. SteveBaker (talk) 13:01, 8 April 2009 (UTC)[reply]

If current theories are correct, sudden climate change has happened many times in the past, leading to mass-extinction events. Though I think you are referring to a sudden (few hundreds to a few thousands of years) warming as opposed to a sudden cooling.

Right now it is a purely hypothetical phenomenon, though purely hypothetical doesn't mean wrong; it just means it's never happened before while us humans were around to see it and our computer modeling skill is insufficient to say how much CO₂ will lead to how much warming over how long a time with precision. Sudden runaway warming may have never happened before on this planet. Some people theorize that Venus was the victim of runaway global warming which occurred when its hypothetical oceans started boiling off (although I'm not sure how widespread that theory is accepted).

Steve already went over most of the mechanisms which can re-enforce the warming, but there are many important factors that could check or even reverse a speedy warming (forgetting all that The Day After Tomorrow BS). And most importantly (IMHO), there is the whole problem with clouds: no one is really sure whether clouds will increase, decrease, shift geologically or temporally, or stay the same with a warming planet. And daytime clouds cool the earth, while nighttime clouds warm the earth. What I'm trying to say in a very roundabout way is this: It could happen, and it may have happened in the past, but we just don't know. -Running On Brains 00:11, 8 April 2009 (UTC)[reply]

I'm referring to any climate change, even if temperature remains constant. You'd think there'd be some way to tell. It doesn't effect how glaciers freeze or anything like that? Anyway, is the idea that it would cause an extinction event a myth? If it would, it couldn't have happened very often. Is there at least a known lower limit on how recent the last runaway climate change was? — DanielLC 01:45, 8 April 2009 (UTC)[reply]

At high rates of change, (like over hundreds of years rather than millions), evolution can't keep up. Animals and plants will die rather than adapt. Hence a mass extinction event. Just as the giant meteor that killed the dinosaurs caused mass extinction - so will abrupt climate change. However, in a gradual change (gradual - over geological timescales, that is) - plants and animals will evolve to take advantage of the new conditions and although the warmer world would be a very different place, there would be no sudden kill-off of species. In either case, however, the 'new' world might not be a place where humans could thrive...and that's the ultimate concern here. SteveBaker (talk) 13:01, 8 April 2009 (UTC)[reply]

It should be said that while some plants and animals will die out in a changed climate, others will prosper, simply because the climate they like becomes more common. Tropical plants are already expanding their ranges into traditionally temperate zones, for example. People also don't need to evolve to adapt, we can either move or alter our environment with things like air conditioning. Of course, global warming will still cause enormous problems, and maybe kill off a substantial portion of the human race (many of those living in Bangladesh, due to flooding, for example), but extinction of the human race isn't the threat here.

Note that while "runaway global warming" may or may not occur, "global warming" (without the "runaway" part), is definitely already happening. The difference is that regular global warming would be reversible if we stopped adding greenhouse gases to the air. Unfortunately, I don't see that as ever happening, or at least not until we use up all the fossil fuels. StuRat (talk) 14:41, 8 April 2009 (UTC)[reply]

By "impossible to stop", do you mean it's impossible for human influences to stop, or impossible for any natural forcings to stop? With climatic change there are always negative feedbacks (factors that lessen the effects), so those could act to stop the warming over time. Truly runaway global warming would result in a climate like Venus, but events that have come rather close have triggered mass extinctions in the past to varying degrees. ~A H 1^(TCU) 01:55, 10 April 2009 (UTC)[reply]

It's worth saying that merely stopping adding CO2 to the atmosphere will only halt the increase - it won't cause a reversal. The half-life of CO2 in the atmosphere is of the order of 10,000 years. It's also worth stressing that we're not even CLOSE to talking about adding zero CO2 to the atmosphere - we're not even talking about reducing the amount we emit - the very best most countries are prepared to sign up to is not increasing the RATE at which we continue to add it. So reversing what we've already done is physically impossible - not making it worse is almost impossibly difficult - slowing down the rate of growth in order that we can buy ourselves time to find a proper fix is a distant dream - the best we can reasonably hope for is that the rate of increase won't get any steeper. SteveBaker (talk) 02:24, 10 April 2009 (UTC)[reply]

However, over the course of much less than 9 years, perhaps only days, we might be able to remove the excess CO₂ from the air by using plant life or some other method like windmills. StuRat (talk) 18:11, 10 April 2009 (UTC)[reply]

why is water transparent and ice white?

Mathityahu (talk) 17:53, 7 April 2009 (UTC)[reply]

From ice, "It can appear transparent or an opaque bluish-white color, depending on the presence of impurities such as air." Certainly from my experience, some ice is basically transparent, and some is quite opaque. Friday (talk) 17:58, 7 April 2009 (UTC)[reply]

Ice is pretty transparent when it doesn't have air cavity impurities in it. The reason why your ice cubes for instance don't look transparent all the time is that rather small air bubbles and other impurities get trapped in the structure of the ice which scatter the light making it appear opaque. I could be wrong, but I think that there are several neutrino telescopes which take advantage of Antartic ice being clear over long distances, like the IceCube and Radio Ice Cerenkov Experiment. Sifaka ^talk 18:13, 7 April 2009 (UTC)[reply]

In addition to air bubbles, there's also fractal planes which make ice look white. I believe that ice, if chopped up into tiny pieces, will look white even if this is done in a vacuum. StuRat (talk) 19:50, 7 April 2009 (UTC)[reply]

You might be interested in the Blue ice (glacial) article. --JGGardiner (talk) 22:10, 7 April 2009 (UTC)[reply]

Little cracks and air bubbles reflect light in random directions. White pigment reflects light in random directions. They look the same. — DanielLC 01:39, 8 April 2009 (UTC)[reply]

April 8

Make OH Hydroxide

Is there a way to create OH(hydroxide) with household or easy-to-get inexpensive materials?~~The Successor of Physics~~ 04:24, 8 April 2009 (UTC)[reply]

Yeah, dissolve Crystal Drano or Red Devil drain opener in water, and you get lots of it. (Disclaimer: if you create an explosion or burn yourself, you have only yourself to blame.) Looie496 (talk) 04:51, 8 April 2009 (UTC)[reply]

Indeed. In ordinary distilled water there are trace amounts of detectable hydroxides (about 1 x 10^-7 mol/liter on average). This is true in the purest of water, due to a reaction known as the autoionization of water. Drano will give you GOBS of the stuff, but is also highly caustic and toxic (you can get nasty chemical burns as it turns your skin into soap), and adding straight Drano to water is highly exothermic; it could heat the water to boiling, and it could spatter or splasg, at which point you could be covered with a highly caustic boiling solution. Not fun. Just about any high-pH substance will contain reasonable amounts of measurable hydroxide. Ammonia-water is basically a solution of ammonium hydroxide, and even simple soap, like say dishwasher liquid, will generate some hydroxide ions without being too dangerous. If you explained why you were interested in generating hydroxide, perhaps we could give you more direction... --Jayron32.talk.contribs 12:38, 8 April 2009 (UTC)[reply]

Well, I wanted OH because I read somewhere that shining light on OH could make the highly dangerous H2O2 hydrogen peroxide which I wanted to make a rocket fuel with.~~The Successor of Physics~~ 14:32, 10 April 2009 (UTC)[reply]

Well, actually all these responses seem to be about OH- . If TSoP really wants OH, as requested, that's a different kettle of fish. --Trovatore (talk) 00:23, 9 April 2009 (UTC)[reply]

Since he asked for hydroxide, we assumed he meant OH^-. The uncharged ·OH is the hydroxyl radical. TenOfAllTrades(talk) 00:38, 9 April 2009 (UTC)[reply]

If you want H2O2, go to any nearby pharmacy and buy a bottle of it. "All you have to do" is separate it from the water in which it's dissolved (or remove enough water that the H2O2 concentration is sufficient for your purposes). I think if you're intending to make rocket fuel using "something you heard somewhere" without knowing more about what you're dealing with, we probably shouldn't be providing more details about this. DMacks (talk) 15:02, 10 April 2009 (UTC)[reply]

So what I should do is goto a pharmacy and buy a bottle of hydrogen peroxide and separate it from the water it is dissolved in. Can I remove the water by evaporation(H2O2's boiling point is 150.2 °C but water's boiling point is 100 °C)?~~The Successor of Physics~~ 11:19, 12 April 2009 (UTC)[reply]

Why does accelerating a charged particle produce radiation?

What is the actual physical reason for this? —Preceding unsigned comment added by 118.139.4.222 (talk) 06:29, 8 April 2009 (UTC)[reply]

Acceleration in general (including linearly)? Or only circular? The latter is Cyclotron radiation or Synchrotron radiation, caused by the deflection or bending--centripetal acceleration--not just increasing speed. DMacks (talk) 06:58, 8 April 2009 (UTC)[reply]

Yes particularly circular acceleration. Why does bending the electron create radiation? 130.194.167.195 (talk) 07:31, 8 April 2009 (UTC)[reply]

The explanation is the same whether it's circular motion or accelerating linear motion. A radiating field consists of disturbances in both the E and H fields, perpendicular to each other. The H field is the time derivative of the E field, and the E field is minus the time derivative of the E field. This is a self-reinforcing relationship that causes an EM wave to propagate indefinitely through space. A charge moving at constant velocity won't create this relationship, because the E field is changing linearly and so the H field, which is the derivative of the E field, is constant. Changing E + static H --> no radiation. If you have an accelerating charge (whether that acceleration is linear or circular doesn't matter), then both the first and second derivatives of E are non-zero, so now you have changing E + changing H --> radiation.

Synchrotron radiation is just a special case of this. If the charge is going round in a circle then all the radiation comes from a finite area instead of being spread out in an infinite line. This makes it a more convenient source for experiments. --Heron (talk) 18:04, 8 April 2009 (UTC)[reply]

optical reflection distortion in tempered glass in automotive

dear sir,

I want to know which standards/methods has to follow to check optical reflection distortion in tempered glass. As per my information it is present in DIN standard , but i dont know it . I want to know the standard no. and why this occure during production of automotive glass and how to judge it. —Preceding unsigned comment added by Ravscapc (talk • contribs) 07:28, 8 April 2009 (UTC)[reply]

could a fast enough solar-powered car catch more sunlight?

Imagine if you had a raindrops powered car. It would make sense that if it were going very fast through raindrops it would be catching more of them. Is the same thing true of a solar-powered car going fast thorugh sunlight versus being stationary? 79.122.72.101 (talk) 08:01, 8 April 2009 (UTC)[reply]

Check out this derivation of the "simplified total wetness equation" by the BBC News. The answer is yes, but since the speed of (sun)light greatly exceeds that of your car (unless it's a really fast model), you'd only get an ultra teeny tiny improvement. Clarityfiend (talk)

No. Regardless of speed of your car, your car will measure speed of light to be same, and number of photons hitting the solar cells will be same and hence gathered solar energy will be same. In fact, if your call travels too fast (relativistic speed), your car will put on more mass, making it difficult to drive faster using the same quantity of solar energy. manya (talk) 09:13, 8 April 2009 (UTC)[reply]

Manya, I'm sorry to say that we're not discussing the change in the speed of light here and I think you have misunderstood the question, although what you mentioned about relativistic effects is true. My answer would be yes, and essentially the same as Clarityfiend's answer.~~The Successor of Physics~~ 09:45, 8 April 2009 (UTC)[reply]

(@Superwj5: I have un-struck Manya's answer that you so rudely struck-out. We do NOT go around striking out answers we don't agree with unless they flagrantly break the WP:RD rules. If you think a previous answer is wrong - you must explain why you think it's wrong - not just cross it out...after all - you could just as easily be wrong - and in this case (as it happens), I think you are entirely wrong. Please consider your knuckles firmly rapped!) SteveBaker (talk) 12:48, 8 April 2009 (UTC)[reply]

Actually - I believe Manya is correct and Superwj5 has not considered the matter carefully enough. The speed of light is constant in all reference frames - so the car sees the speed of light coming from the sun as being the same no matter what speed it's travelling at. However, there would be a 'blue-shift' in light coming from in front of the car and a red-shift from the rear - and I think that means that the light coming from the front has more energy (I'm not 100% sure about that - with relativistic stuff, it gets complicated). But that only applies when the car is driving towards the sun - whatever that effect was, it would cause you to lose energy when driving away from the sun. When the sun is vertically overhead or off to one side - there is no benefit either way. Photons are in no way like raindrops! However, it's pretty clear that whatever the effect is, it's entirely negligable at all 'reasonable' speeds. SteveBaker (talk) 12:48, 8 April 2009 (UTC)[reply]

The Michelson-Morley experiment indicates that a light source that is directly overhead remains overhead regardless of horizontal motion of our car. Hence there would be no change in the energy collected by a horizontal planar solar cell.Cuddlyable3 (talk) 16:57, 8 April 2009 (UTC)[reply]

I'm fairly certain that there's another effect that causes light moving perpendicular to the observer to blueshift. I think it also makes the light move in the opposite direction of the observer from their point of view, which is contradictory to what Cuddlyable3 said, so can someone double-check this? By the way, the OP was comparing this to hitting more raindrops, rather than hitting them harder, so maybe we should also think about how many photons hit. — DanielLC 17:21, 8 April 2009 (UTC)[reply]

DanielLC is confirmed with Relativistic aberration. Is anyone up to drawing some diagrams to illustrate this article? It could really do with picturesque adornment. Relativistic beaming talks about the variation in apparent intensity at different directions. Graeme Bartlett (talk) 21:51, 8 April 2009 (UTC)[reply]

If your rain collector is horizontal and sitting on the roof then it will collect the same amount of rain regardless of speed. Imagine a loop of identical rain-collecting cars on a closed track: they will collect the same amount of rain moving as they do stationary because both the total available rain and the total collecting area are unaffected by the speed. The reason this differs from the "wetness equation" that Clarityfiend linked is that they're also counting rain that hits your sides. If you have rain collectors on the sides/front/back of the car then you will collect more rain when you start moving (moving relative to the horizontal speed of the rain). Interestingly, the amount of rain you collect sideways has no direct dependence on speed or elapsed time, it's solely a function of the distance you travel. More precisely, it equals the rain density times the volume of the tube of space you occupy during your trip. So to minimize rain on your sides you want to head straight for the nearest shelter, and to minimize rain on your head you want to get there as fast as possible. (I'm assuming a cylindrical cow here, of course.)

With respect to the rest frame of the moving car there will be aberration: the rain/light will appear to be coming from in front of you if it was initially coming straight down. The rain/light will also have a higher energy per particle (Doppler shift in the light's case, I don't know if this has a name in the rain's case). Since the collected particle count is the same, you're getting more energy overall. This isn't as great as it sounds because it's kind of an artifact of the frame-dependent definition of energy. Since rain and light both carry momentum, they will also push you backward as they pummel you from the front, so you have to fight this by accelerating harder. You won't get a mixed redshift and blueshift in this situation because the light/rain is all going in the same direction. Everything will be blueshifted (if it was initially coming straight down).

When you add special relativity, with respect to the initial rest frame, Lorentz contraction means that the collecting area (on the top of the car) decreases by a factor of γ at high speeds, hence the count of collected particles per unit coordinate time goes down by the same factor. But the particle count per unit proper time gets another factor of γ, so it's independent of speed as in the nonrelativistic case. I don't think it's possible to push the relativistic analysis very far because too many of the problem's assumptions stop making sense (you can't accelerate to relativistic speeds using the friction of wheels against a road, for example). -- BenRG (talk) 10:41, 9 April 2009 (UTC)[reply]

Thanks, BenRG! That's my point, you have collectors all around(I didn't have time to point it out last few days)! Also, the front back sides don't face Lorentz contraction but the light will be blueshifted so the total collected energy will be higher, according to BenRG and my initial assumption that the energy collected on the top doesn't vary.~~The Successor of Physics~~ 06:55, 11 April 2009 (UTC)[reply]

why isn't the segway a unicycle?

i don't get why the segway isn't a unicycle, wouldnt it have to do the same job just with half the parts?

also why not sit over a ball (like an old mouseball) then it could roll in 2 dimensions instead of just 1 + turning? 79.122.72.101 (talk) 08:21, 8 April 2009 (UTC)[reply]

1 wheel would be less stable than 2 wheels. I know it does the gyroscope/whatever thing but it'd increase the workload on it. The ball would add more friction, making it require more 'effort' (power) to move it around. The wheel has a small amount of surface in contact with the path/road, whereas a ball would (I expect) have more. 194.221.133.226 (talk) 08:37, 8 April 2009 (UTC)[reply]

why would you expect it would have more contact? A plane is tangent to a wheel in only 1 point, and it is also tangent to a sphere in only 1 point. How much friction there is would just depend on what PSI you pump the wheel/sphere to, wouldn't it? (the more it sags the greater the actual touching surface area). Why would 1 wheel be less stable than 2 wheels? People are able to ride unicycles... 79.122.72.101 (talk) 08:42, 8 April 2009 (UTC)[reply]

Riding on a plane needs minimum 1 or 2 wheels. Riding on a sphere needs minimum 3 wheels (which you find inside an old mouse), that's 4 frictional contacts including ball-to-ground. Cuddlyable3 (talk) 16:43, 8 April 2009 (UTC)[reply]

But riding a bicycle is much easier than riding a unicycle, because balancing on a bike is much easier...Also it seems from reading the Segway article that it constantly rotates/moves both wheels to maintain its position - I suspect on 1 wheel that would be harder to achieve (and potentially much the same on a ball). 194.221.133.226 (talk) 09:18, 8 April 2009 (UTC) right|200px[reply]

The segway doesn't use a gyro to make it balance - it rotates the wheels forwards or backwards to keep them under the center of gravity of the segway+rider. That's why you lean forwards to make it accellerate and backwards to make it stop or reverse. If you watch a segway when it's just sitting there, perfectly balanced, you can see the wheels moving microscopically to keep the thing balanced. The gyro inside is just it's way to measure how it's moving. Hence, to make a unicycle segway with just one wheel would be impossible because the wheel can't rotate sideways to keep the unicycle vertical in the side-to-side direction. A human unicyclist has to supply lateral balance by leaning from side to side. A segway that rolled on a ball could possibly fix that - but now it would need two sets of motors and two sets of gyro's - one for forwards/backwards motion and another for lateral balance. This would make it considerably MORE complex - not less. It might also make it exceedingly difficult to ride because when you leaned a little sideways - the "ballway" would tend to roll in the direction you're leaning. Since you need to lean into corners in order to keep your balance - the ball would presumably rotate such as to keep you vertical - which would result in you failing to turn corners at all (I think...it's confusing!). Anyway - on complexity grounds alone, it's a bust. However - having said that - you might want to check out Uno (vehicle) - which is almost a unicycle "motorbike" that balances in the forward/backward direction using technology similar to the segway and uses a split center wheel to manage lateral balance...you need to read the article to understand it in more detail. SteveBaker (talk) 12:32, 8 April 2009 (UTC)[reply]

I think you're assuming that the Ballway would not change heading. (And perhaps it wouldn't, That would not be easy to build.) If you're leaning purely to the right you want the Ballway to sidestep to the right, but if you're leaning forward and to the right, then it's entirely acceptable to travel in an arc. That would keep you balanced.

Ideally the Segway's wheels do exactly what you would do with your own feet. When you walk, you lean forward a little, and then move your feet forward to keep them "under" you, the segway attempts to do the same thing with its wheel. (I rode one once. It's a weird feeling. It felt like the thing was reading my mind.) Since humans are perfectly capable of leaning into a turn I don't see why a Ballway couldn't do the same. APL (talk) 16:40, 8 April 2009 (UTC)[reply]

If it had a ball, it would have to be able to move forward/backward, left/right, and clockwise/counterclockwise. That's three degrees of freedom. You can only lean forward/backward and left/right, so you'd have to have another degree of freedom to control it. It's possible to make it so you can control it with just the two degrees of freedom, but you won't be able to do everything that it's mechanically capable of, for example: if you make it so you lean forward and to the side to make it turn, how do you make it go diagonal? It's mathematically possible to map three dimensions completely to two, but you'd up with a ridiculous control system (see space-filling curve). — DanielLC 17:13, 8 April 2009 (UTC)[reply]

That extra degree of freedom really isn't a problem though. The Segway only uses the balance/leaning thing to do acceleration and deceleration. For steering, you have a twist-grip thing. Because the same mechanism is used for controlling the gross motion of the segway as is used to make it balance - you really can't make leaning be the control for steering in our ballway. When you lean sideways - the machine MUST roll sideways (without turning) or you'll fall off! I imagine our ballway would have to have some kind of additional controller for rotation - just as the segway does. Hence, y concern is that when you use this additional controller to rotate the beast - you'll be forced to lean into the turn to counteract centrifugal force - and when you do that - the lateral balance system would roll you sideways - making your turn into a messy affair indeed! In fact, you'd have to take turns pretty gently because with the machine FORCING you to ride upright (because as fast as you try to lean, the machine counteracts that) - the centrifugal force in a turn would throw you off. SteveBaker (talk) 18:09, 8 April 2009 (UTC)[reply]

I'm unconvinced. Even if your analisys is correct, there's no reason the software couldn't compensate for this. Afterall, it's a 100% predictable effect. (If you lost the ability to go forward at high speed, change heading, and add an additional diagonal component all at once, then there's no great loss. I'm not confident I could do that with my own two feet. Let alone a computerized beach ball.)

But I'm not sure you are correct. Imagine if you used an accelerometer to measure your "levelness". The force from gravity as a result of your lean would be the same as the centripetal force from the turn, exactly balancing it out. That's why we do it.

Since the segway is designed to mimic the actions of our own two feet, I don't know why anyone in their right mind would program a 'lateral balance system' that would attempt to keep you strictly upright while you were cornering.

The logic of the Segway and other self-balancing systems has always been "Move the wheels towards the center of gravity." That would still work. The tricky part with the BallWay would be determining which way the user should be facing. I think some inteligent rules could catch most cases. APL (talk) 19:53, 8 April 2009 (UTC)[reply]

it seems you're thinking the ballway wouldn't have handlebars (which would define "which way the user should be facing") but why not? You think it should just be a platform? no way, that's why the segway isn't like a skateboard (no handelbars) but a scooter (has handlebars). shouldn't the ballway have some too? .... wait, do you mean determining which way the whole contraption should be facing? just face it whichever way is set by the handlebars then? i dont really get your point of concern... 79.122.72.101 (talk) 22:30, 8 April 2009 (UTC)[reply]

Of course it would have handlebars, but how does it know which way the handlebars should be facing?

(Does the user want to go diagonally forward and to the left? Or does he want to go forward and turn to the left? Both would keep him balanced if he's leaning forward&left. )There's some ambiguity that would have to be worked out with some sort of logic. APL (talk) 12:42, 9 April 2009 (UTC)[reply]

Maybe I'm not communicating it right, but my problem with SteveBaker's comment was that he seemed to be conflating "Staying Balanced" with "Staying upright". They're really only the same thing when you're stationary. APL (talk) 12:52, 9 April 2009 (UTC)[reply]

If you google for "electric unicycle" and take the first link found, there are instructions for making your very own. The site has some info about balancing. This is a proper unicycle too, unlike the Uno (vehicle). I can ride a unicycle and when I was learning, I never had any problems with side-to-side balance once I could get some forward motion. --80.176.225.249 (talk) 22:59, 8 April 2009 (UTC)[reply]

Quantum harmonic oscillator

what is the perfect defination of Quantum harmonic oscillator ?Supriyochowdhury (talk) 10:12, 8 April 2009 (UTC)[reply]

I don't really understand your question, but it might be answered by our article quantum harmonic oscillator. Algebraist 10:20, 8 April 2009 (UTC)[reply]

why the wave function corresponding to the E-nu for a simple harmoic oscillator are nondegenerate.Supriyochowdhury (talk) 10:23, 8 April 2009 (UTC)[reply]

why would they be degenerate? Degeneracy in a quantum-mechanical system is usually a consequence of a symmetry of some sort. Now, consider a quantum harmonic oscillator (a spinless particle in a one-dimensional parabolic potential). What kind of symmetry do you suspect here? Why would you expect any two or more states to be degenerate? If you are thinking about x => -x symmetry, it leads to no degeneracy as it produces no new states that are linearly independent from the "old" ones. Or do you mean something else? You can make the states degenerate if you ascribe your particle a nonzero spin, but that is just adding another dimension. Conversely, you can add another spatial dimension, that would also make your states degenerate. Is that what you want? Think about it. --Dr Dima (talk) 19:36, 8 April 2009 (UTC)[reply]

Mom's perception

Do mothers have a distorted perception of danger? Are they influenced by any hormone to watch carefully for danger?--217.12.16.53 (talk) 10:51, 8 April 2009 (UTC)[reply]

Due to maternal instincts, a mother may be more risk averse regarding the child's well-being than the child. So the negative implications of a factor that would increase the child's risk carries a higher "weight" than the positive implications of a factor that equally decreases the same risk. I'm not sure if that's a distorted perception. Regarding the hormone, oxytocin (which is released during labour and breastfeeding) is thought to influence the maternal bond. From the article:

"Rat females given oxytocin antagonists after giving birth do not exhibit typical maternal behavior. By contrast, virgin female sheep show maternal behavior towards foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise."

See the article for the refs. Zain Ebrahim (talk) 11:31, 8 April 2009 (UTC)[reply]

A squalling baby is incredibly irritating but a mother seems to have hearing uniquely sensitive to that sound combined with specific mental (protective) and neurophysical (lactation) responses. I observe that a cat mother seems to have very little idea of how many kittens she has, which may be a source of worry that one may be lost, but is content if she has sniffed them all. Cuddlyable3 (talk) 16:22, 8 April 2009 (UTC)[reply]

Is it possible to predict an unknown element's attributes?

I'm interested in creating believable fictional elements, sort of like how people create believable fictional worlds with defined orbital distance and such. The only problem is that there doesn't seem to be any information on this topic, anywhere.

So is there a reliable, or at least somewhat believable, method to determine which attributes an element could have? What, exactly, causes an element, or compound containing a certain element, to be more prone to acidity, magnetism, and other features? What about its appearance--thickness, weight, color? Can these kinds of properties be determined or assumed from basic knowledge such as atomic weight, number of electrons, placement on the periodic table or relation to other elements, etc.?

Basically I'm just looking for guidelines. What can one realistically expect from an unknown element? What are the possibilities? What defines the possibilities? Is the lack of information on this subject due to the fact that an element's properties cannot be predicted accurately, or just because nobody else cares? —Preceding unsigned comment added by 97.104.210.67 (talk) 13:09, 8 April 2009 (UTC)[reply]

At this point, the only unknown elements in this universe will be very unstable. Generally, an element will be somewhat similar to the elements in the same column on the periodic table. Noble gasses are pretty inert, Halogens are rather reactive etc. 65.121.141.34 (talk) 13:18, 8 April 2009 (UTC)[reply]

It's not certain that all super-heavy elements (and their isotopes) will be unstable - there may be an island of stability. Dog Day Today (talk) 13:32, 8 April 2009 (UTC)[reply]

I should note that when the periodic table of elements was created, it functioned very well at predicting elements' properties. Dmitri Mendeleev was able to predict some of the properties of ekasilicon (germanium), ekaaluminium (gallium), ekamanganese (technetium), and ekaboron (scandium) just from their positions in the periodic table. Once you knew where your new element fits on the periodic table, you can semi-convincingly determine its chemical properties. -- 128.104.112.117 (talk) 14:40, 8 April 2009 (UTC)[reply]

Yes and No. "Yes" because you can predict anything you like (and you would have to work hard to predict something that someone somewhere would not reject as unbelievable). "No" because fictional creations are speculations not predictions (if by luck they turn out to be true then they are no longer fictional). The believability of a fictional element is increased by incorporating some known physical chemistry. Example 1: Dilithium crystal in Star Trek is supposed to be an element with atomic weight 87 and remarkable properties in crystal form. There really is a dilithium molecule but the rest is believable fiction. Example 2: Superman has problems with Kryptonite which is a fanciful element with no more than a name similarity to Element no. 36. Example 3: Melange (fictional drug) is a substance that plays an role in Dune (novel) but is IMO the least believable example. If your aim is to invent an element for a story I suggest that its "entertainment value" is more important than its believability to chemists. Cuddlyable3 (talk) 16:05, 8 April 2009 (UTC)[reply]

Your question covers interesting areas of science. Scientists do care about predicting the properties of elements, particularly to test the abilities of computational chemistry and to search for possible allotropes and polymorphs not yet discovered experimentally. I imagine atomic physics does a great deal of computational and theoretical work trying to predict and understand the properties of atoms of as-yet-undiscovered elements.

One very important use of such interplay of theory and experiment is that it tells you if your theory is along the right lines. The fact that the periodic table allowed Mendeleev to accurately predict the existence and properties of undiscovered elements suggested it reflected something very fundamental about atoms. Science works on cycles of:

do an experiment
make a theory to explain the results
predict some new results with your theory
do experiments to see if the predict results actually happen
if yes, the theory is good (for now); if no, need to modify or abandon the theory.

If you want to create believable but fictional substances, you might be better off inventing fictional compounds rather than fictional elements - there's a lot more scope for undiscovered possibilities that would be stable - new compounds with unexpected properties are being discovered all the time.

Ben (talk) 17:07, 8 April 2009 (UTC)[reply]

The problem with inventing new elements is that the definition of an element basically revolves around the number of protons it has. Since that's a simple integer - and all of the elements up to well over a hundred are already 'known' - the only imaginary ones you can possibly have will need an ungodly number of protons. Sadly - it's all to easy to predict their properties...they fall apart in an alarmingly small number of milliseconds producing fairly boring elements and perhaps some stray radiation in the process! All of the very high numbered elements do that. There is some theoretical discussion of an 'island of stability' - a region where even an ungodly number of protons might hang together if the number of neutrons were just right. We don't yet have a way to make these high-atomic-weight elements right now - but the fact that we don't find them in nature is indicative that the island of stability either doesn't exist or is exceedingly hard to reach. This is really only theoretical - but I suppose you could use it as the basis of your fictional account. Personally, I agree with Benjah-bmm27 - you are better off thinking of imaginary compounds. There are (effectively) an infinite number of possible compounds - and we are only just learning of the near-magical properties of some of the weirder ones. Things like carbon nano-tubes, for example. Sadly - the prediction of their properties (especially the really weird ones like nano-tubes) is virtually impossible - which is what keeps chemistry from becoming a branch of physics! SteveBaker (talk) 18:02, 8 April 2009 (UTC)[reply]

Wow, what a reply. Thank you, everyone, this is all really helpful stuff. I should've thought to ask this here a long time ago! 97.104.210.67 (talk) 20:14, 8 April 2009 (UTC)[reply]

Alternative engine vehicles

I would like a list of all currently available hybrids, electrics, or PHEVs that can currently be ordered or will be available with the 2010 model year. —Preceding unsigned comment added by 198.176.41.2 (talk) 13:11, 8 April 2009 (UTC)[reply]

In what location? Some may even be sold in only one section of a single country (as was true of the GM EV1). The Category:Green vehicles looks like a good place to start but I doubt that we have a premade list of all current models anywhere. Rmhermen (talk) 13:46, 8 April 2009 (UTC)[reply]

Sorry - USA. Good point.

Effect of Centrifugal Force on Oceans

putting back in own heading again...Matt Deres (talk) 20:20, 8 April 2009 (UTC)[reply]
As the earth rotates, centrifugal force causes ocean water to be deeper at the equator than at latitudes farther north or south. Has the greater depth at the equator due to this been calculated? One result of this effect will be that as global warming increases, flooding of land areas will be worse near the equator and less in areas farther north or south. – GlowWorm. —Preceding unsigned comment added by 98.17.41.22 (talk) 15:23, 8 April 2009 (UTC)[reply]

What we call flooding is relative to the normal coastlines that already include effects of tides and centrifugal force. Holland is far from the equator but would be among the worst hit by a global rise in sea level. Cuddlyable3 (talk) 16:29, 8 April 2009 (UTC)[reply]

The Centrifugal force really does have an effect, but the effect is felt by the whole planet, not just by the oceans. The earth as a whole is not sufficiently rigid to hold its shape against centrifugal force. Yes, the ocean surface at the equator is farther from the center of the earth than is the ocean surface near toe poles, but this si also true of the ocean bottom. see geoid. -Arch dude (talk) 21:37, 8 April 2009 (UTC)[reply]

Yes; the interior of the Earth is fluid and the entire Earth can be thought of as a sphere of liquid rotating in space in hydrodynamic equilibrium, with a thin solid crust. The centrifugal force makes the radius at the equater bulge out 21.3 km (13.2 miles) greater than at the poles. Except for local features such as continental plates the crust follows this surface of equilibrium (geoid), so the oceans are no deeper on average at the equator than at the poles. --Chetvorno^TALK 06:15, 9 April 2009 (UTC)[reply]

OK, that's a good point about the earth itself bulging at the equator. But as more water is added to the oceans because of melting polar ice caps due to global warming, centrifugal force will bring more of the water to equatorial regions compared to areas farther north or south. And yes, Holland may still be severely affected. So will the city of New Orleans in the US. Bangladesh is closer to the equator, and a great deal of the country is at a very low level, so it may loose a significant part of its area. At least it will be slow flooding, so the people will be able to get out. – GlowWorm. —Preceding unsigned comment added by 98.17.41.22 (talk) 07:00, 9 April 2009 (UTC)[reply]

I wold say that, if anything, there would be a small effect due to the fact that as ice from the polar regions melt and move equatorward to fill the oceans, the earth 's Inertia moment changes slightly, slowing down erth's rotation and reducing the ocean's bulge. The solid earth's bulge would also respond, but much more slowly and (temporarily) there would be more floding at higher latitudes then around the equator. I haven't done the calculations but would not be surprised at all if the effect turns out to be completely negligible. Aside from that, I can't think of any reason why the floding would be any different at different places on earth. Dauto (talk) 22:23, 9 April 2009 (UTC)[reply]

You could also argue that, as the ice caps melt, isostatic rebound will be stronger in polar regions than in tropical regions, so therefore the tropical coasts would sink relative to the poles. However, this is likely to be cancelled out by other factors, for example a constant melting into the ocean from the poles could cause more water to "pile up" around the poles. ~A H 1^(TCU) 01:49, 10 April 2009 (UTC)[reply]

With regard to the earth's inertia moment changing as water moves away from the polar regions, that's a good thought. But I think that effect would be extremely small. The Greenland ice cap is about a mile deep. The radius of the earth is about 4,000 miles. So the melt water from the ice cap has a tiny mass compared to the mass of the earth. The mass of other ice around the north and south poles is similarly relatively tiny. Regarding isostatic rebound, that's another good thought. But the loss of 1 mile of ice and the resulting isostatic rebound would make the earth very, very, slightly more oblate than formerly. (The earth would not rise to the former height of the ice.) As a result, the centrifugal force at the equator would increase very, very slightly, making the ocean at the equator very, very, slightly deeper.. – GlowWorm. —Preceding unsigned comment added by 98.16.66.31 (talk) 04:52, 10 April 2009 (UTC)[reply]

Chemistry and lock, have any relation?

16:52, 8 April 2009 (UTC)bsm (=bimellahalrahmanalrahim) We must draw a plan for hacking door`s look that relate to chemistry any way, at least a little relation. we saw very ways but they are physically, completely. if there is any way or starting point?80.191.15.10 (talk) 16:52, 8 April 2009 (UTC)[reply]

Brute force! Destroy the lock with explosives, melt it, or dissolve it with Hg.

Ben (talk) 17:09, 8 April 2009 (UTC)[reply]

Freezing with liquid nitrogen could make the metal brittle and easy to fracture.Freezing could also inactivate the battery used for operating an electric lock, if it keeps a solenoid energized to hold it locked. Edison (talk) 17:30, 8 April 2009 (UTC)[reply]

Solids are solid and strong things are strong because of the bonds among their atoms. Take a solid, strong thing like a sledgehammer or crow-bar, for example. Or bones. Muscles contract because of chemical energy being released, so use those muscles to move those bones and kick down the door, swing a sledgehammer at it, or pry it open. DMacks (talk) 17:50, 8 April 2009 (UTC)[reply]

AKA MacGyver gets lazy? --Trovatore (talk) 22:19, 8 April 2009 (UTC)[reply]

On an utterly unrelated note: In Popular Culture DJ Clayworth (talk) 17:26, 9 April 2009 (UTC)[reply]

Make a replica of Humphrey Davy's 1808 vintage "Great Battery," which was constructed with 2000 pairs of zinc and copper plates in individual tanks of dilute acid. It could produce about 2000 volts and over an ampere, and an arc from it could vaporize all known substances. It operated by electrochemistry so it should fall within the assignment. Just (carefully! extreme hazards from electric shock, acid, and high heat, as well as likely damage to the corneas and retinas) use a couple of electrodes to create an arc and burn away the lock. Or use an oxyacetylene torch (again, chemistry) to do the same thing in a more modern way. Edison (talk) 22:39, 8 April 2009 (UTC)[reply]

Thank u, but these ways damge the lock. (writer) —Preceding unsigned comment added by 78.109.204.105 (talk) 20:54, 9 April 2009 (UTC)[reply]

I see, so you have to leave the lock and door in its original condition. I don't know much about locks, and I'm pretty sure it depends greatly on the type and age of the lock, but you might be able to make a camera out of optical fiber (a fiberscope), feed it into the lock hole, and find the shape and configuration of the lock from the inside. The "chemistry" part of it would be the fact that you're taking advantage of the refractive properties of the material used in the fiber. The hard part is creating a key to the shape that you decipher using the fiber optic camera. 124.154.253.25 (talk) 05:42, 10 April 2009 (UTC)[reply]

Pour rubber solution through the keyhole, wait for it to set, then pull out the solid rubber through the same hole. You now have a reverse mould of the lock mechanism. I don't know if there is any rubber that could withstand that much deformation, but you didn't say whether you wanted practicable ideas or not. --Heron (talk) 13:25, 10 April 2009 (UTC)[reply]

Go to the owner of the building and say "Hey - I'll give you this really nice chemistry set if you'll let me into your building for a couple of minutes." SteveBaker (talk) 22:49, 10 April 2009 (UTC)[reply]

HHH like Norwegian physician!

why don't we use the sun as a fusion generator?

i dont mean to be difficult but it seems that space is empty as you just have to fling something and then wait. so it's only a matter of waiting (and flinging in the exact correct trajectory) that separates something from earth orbit from the sun. so the sun is a huge fusion generator, and except for a bit of a wait after you've flung something at it, it is as easy to get to as earths orbit. so why dont we use it as close fusion generator? (sorry if i am misunderstanding something basic -- ive gotten a lot of flack elsewhere recently and have tried searching. thanks. 79.122.72.101 (talk) 22:12, 8 April 2009 (UTC)[reply]

The Sun already puts out as much energy as we actually want it to. If it put out more than it does, global warming would be an even worse problem than it is now. The difficulty is collecting that energy. --Trovatore (talk) 22:17, 8 April 2009 (UTC)[reply]

you don't see a difference between being as near to a huge fusion reaction as you want, 1 foot, 100 feet, 10000 feet, 100000 feet, etc, versus being able to build as large a solar panel as you want? i think there's a huge difference between having it in a few square meters and having it dispersed all over earth... 79.122.72.101 (talk) 22:34, 8 April 2009 (UTC)[reply]

That aside, it might be an interesting calculation to see how much energy would eventually be returned from 1 kg of hydrogen delivered to the Sun, versus the energy it takes to get it there. My intuition is that the return would be many orders of magnitude less than the investment, but I haven't actually run the numbers.

On another note, if you don't mind a bit of waiting, please send me a million US dollars. I'll pay you back one dollar a year, for a billion years. You get a 100000% ROI! --Trovatore (talk) 22:26, 8 April 2009 (UTC)[reply]

what? it doesn't take very long to get to the sun! also, you are discounting prevailing interest rates. 79.122.72.101 (talk) 22:34, 8 April 2009 (UTC)[reply]

In case we haven't yet been specific enough, solar energy is the term you're looking for. Anything we flung at the sun would return as such, and we've already got more sunlight than we can convert. This doesn't even get into the problems of getting something not just to the sun but to fusion depth (most of the hydrogen in the sun won't ever be fused) or of collecting the energy once it's created (the Earth receives less than one half of one billionth of the Sun's output). — Lomn 22:35, 8 April 2009 (UTC)[reply]

Follow-up fun. Burning one mole of hydrogen (w/ required oxygen) produces 242 kJ. Fusing that same one mole of hydrogen produces 2.7 billion kJ.[11] So fusion is better, right? Except that, as noted above, the Earth doesn't intercept all of the sun's output. Divide by the one part in 2.2 billion that we receive from the sun and that fusion nets us 1 kJ -- one half of one percent that of simple combustion on Earth (and well before we consider the point Trovatore raised regarding energy costs to move the hydrogen). No, sending stuff into the sun doesn't do anything to meet energy needs. — Lomn 22:45, 8 April 2009 (UTC)[reply]

Eh, the sun's already fusing; there's no need to fling *any* hydrogen. I believe the question here involves placing a satellite around the sun to harvest more of the generated energy and send it back to Earth. This concept has been explored in science fiction before (Asimov comes to mind – we even have an article), but I'm not aware of any practical research. A simpler implementation would involve Earth satellites transmitting power. Trovatore has it right though—any additional harvested energy sent to Earth would potentially cause an increase in global warming. – 74 01:08, 9 April 2009 (UTC) edited by 74 14:20, 9 April 2009 (UTC)[reply]

Oh, well, if you could somehow collect the energy up close, and then (perhaps even harder) transmit it back to Earth efficiently, you could power an awful lot of stuff without aggravating global warming. Most likely you'd actually alleviate global warming, because you could replace carbon-emitting sources.

What I thought the OP wanted to do was increase the total power coming out of the Sun, so as to be able to get more power out of the same area of photovoltaics or solar-thermal generators here on Earth. That would aggravate global warming.

But getting the power back to Earth in a usable form seems completely infeasible to me. It's not like you can string up a high-voltage line. There have been proposals, kind of blue-skyish but at least semi-serious, to put solar-power satellites in orbit and beam the energy back to Earth in some sort of microwave beam. But that's from very much closer. Trying to put a power satellite in low Sun orbit and from there put a microwave beam direct on the collection station, rather than (say) the entire county surrounding it, strikes me as outside the realm of engineering possibility. (But don't let that stop you, OP; if you can figure out how to do it you could be wealthy indeed....) --Trovatore (talk) 01:51, 9 April 2009 (UTC)[reply]

My favorite concept is to put antimatter factories in low solar orbit and bring the "batteries" down the Beanstalk. —Tamfang (talk) 03:33, 9 April 2009 (UTC)[reply]

my god, you people thought i wanted to hurl hydrogen at the sun??? it boggles the mind. the sun has more than enough fuel. MY QUESTION IS SINCE IT'S A WORKING FUSION GENERATOR WHY DON'T WE USE IT AS THOUGH IT WERE IN OUR BACKYARD? Because the only thing separating the sun from our back yard (ie Earth's orbit) is a bit of a WAIT while our gear hurtles, AT NO ADDITIONAL FUEL COST, through space.

Space is a near vacuum. You hurl something and it goes "forever" (if you avoid colliding with something). So the difference between GETTING RIGHT HERE and GETTING WAY OVER THERE is 0 grams of rocket fuel -- just a bit of a wait.

So the way I figure, if the Moon happened to have a continuing fusion reaction, we would damn well harness that. So since the Sun is just as close (minus the bit of a wait getting there -- but at 0 fuel cost, just a correct initial trajectory), why don't we harness THAT? Seriously. 94.27.175.226 (talk) 09:35, 9 April 2009 (UTC)[reply]

We thought you meant that, because that was our best guess as to what you were talking about. Now I have no idea what you are talking about. What exactly are you proposing? Algebraist 09:41, 9 April 2009 (UTC)[reply]

to clarify, if there were a working, large-scale, self-sustaining fusion reaction on the moon, you don't think we'd be using it? My question is, why not do the same with the sun, it's the same as getting to the moon except a longer wait... 94.27.175.226 (talk) 10:01, 9 April 2009 (UTC)[reply]

We are using the sun. What is your suggestion for how we should use it better? Algebraist 10:05, 9 April 2009 (UTC)[reply]

We're not using any of the sun's heat, but only a little bit of it's radiation from an average of one "astronomical unit" away -- that's 92,955,887 miles. Obviously we're not using the sun as a fusion reactor if we are doing it from 92 million miles away by means of collecting rays so weak you can just walk in them and at worst get sunburn. I mean 'fusion reactor' as 'fusion reactor' -- ie the thing scientists would build on Earth if they could! So why not use the one that's built already, and quite close and easy to get to? 94.27.175.226 (talk) 10:09, 9 April 2009 (UTC)[reply]

Speaking for myself, I don't want a sun-sized run-away fusion reactor in my back yard at all. Quite happy to put it in someone else's back yard and collect all the energy I need from a safe distance - say, oh, about 100 million miles away, give or take. Of course, what we really need is a Dyson sphere. Gandalf61 (talk) 11:21, 9 April 2009 (UTC)[reply]

Try looking up how fusion generators actually generate electricity. Then when you've found that out, look at different means of transporting electricity. Then come back here and tell us what you think.124.169.159.117 (talk) 11:39, 9 April 2009 (UTC)[reply]

I think the problem is that the OPer doesn't clearly understand how a fusion reactor would be, and how fission reactors already are, used on Earth.

What we get out of such reactors would be/is merely heat. This heat (often transferred via an intermediate medium such as molten sulpher) is usually used to boil water into steam, whose pressure is used to drive turbines that generate electricity, which is currently (pun intended) the most conveniently transmissable form of energy.

The fact that the Sun is 93 million miles away and transmits its heat energy via electromagnetic radiation through space, rather than directly via conduction as in reactors on Earth, makes no difference to this overall process. Intercepting and converting the Sun's e-m radiation - called "sunlight" - is the only feasible way of extracting and using its energy.

This is precisely what the various existing solar power systems do, whether they gently warm water in sunlight-exposed pipes, boil it or melt other materials by concentrating sunlight with mirrors, or convert it directly to electricity with solar cells. Wind turbines also utilize the Sun's energy indirectly, since wind is ultimately caused by the Sun's energy differentially warming the atmosphere: so do "renewable sources" such as the burning of wood from trees, or ethanol made from plants, since plants merely change atmospheric CO₂ into carbon-containing burnable molecules by photosynthesis, which is powered by the energy in sunlight.

"Fossil fuels" are merely another form of this, since they too (mostly or entirely) formed from plants which grew by photosythesizing sunlight. In fact, virtually all life on Earth is already entirely dependent on the radiation from the fusion-generated energy of the Sun. (The minor exceptions are bacteria in hot springs and various deep-sea creatures round geothermal vents - but we are already exploiting some geothermal energy as well.)

In short, the answer to the question "Why don't we use the Sun as a fusion generator?" is "We already are, and always have been."

So far, we're only tapping a small fraction of what we potentially could, and we should probably expand greatly our solar power generation from current levels. However, note that all of the sunlight we can currently intercept and use is already going to hit the Earth anyway and (neglecting what is immediately reflected) turn directly or indirectly into heat: by the above means we merely get a bit of work out of some of it it in a form we can easily use, and ultimately all that work itself also turns to heat.

We don't want to increase the Sun's heat imput to the Earth even more by, say, launching satellites to intercept more sunlight and transmitting the energy (perhaps via microwave beams) to us, because that would tend to raise the planet's overall temperature further - you may already have heard of Global Warming and the problems it is expected to cause. We certainly don't want to alter the Solar Flux unpredictably by tinkering with the Sun itself, but (perhaps fortunately) there is absolutely no way we currently know of by which we could do that.

Arguably, we shouldn't be be using any sources of energy that effectively create "new" heat (such as fission and fusion reactors) rather than converting what's already around, but the trade-offs in efficiency make the calculations very difficult - for example, it might use more resources/produce more waste heat building solar power systems to generate X kilowatt/hours than it would to build a fission/fusion plant to generate the same amount. But that's getting into a whole other argument when I've spouted on far too long about this one. 87.81.230.195 (talk) 12:54, 9 April 2009 (UTC)[reply]

Whilst what you say is technically true - the effect of heat from the energy we're using is entirely negligable. The sun slings about 1kW per square meter at the earth's surface - 1.7×10¹⁷ Watts altogether (at ground level) - we are consuming about 1.6x10¹³ Watts to drive our civilisation. So even if 100% of our energy needs were to come from solar collectors orbiting out far from the earth - this would only add to the natural heat arriving from the sun by about one hundredth of a percent. This is certainly not a concern - and if we could thereby avoid creating the worst of the greenhouse gasses, it would cut the absorption of sunlight by vastly more than one hundredth of a percent - so this would surely be a huge win. Unfortunately we really don't have the technology to build orbiting solar collectors with an area of around 10¹⁰ square meters (four thousand square kilometers - something in orbit that's the size of Rhode island!) - plus the technology to somehow beam that energy down to earth without frying everything for a hundred miles around. So, as attractive as that is, it's not really feasible yet. SteveBaker (talk) 00:29, 10 April 2009 (UTC)[reply]

Aye, Steve, but "mony a mickle maks a muckle," as my Scottish great-great granny might have said if I'd ever met her. There's a lot of things we do or did that we thought would have negligable effects, but have come back to bite us (or the environment), so I'd rather we played safe. As you say, the technology for large-scale space-based solar energy collection is a long way off, but meanwhile, our worldwide energy (= heat) generation/use is accellerating, and the developing nations (India, China etc) seem likely to exacerbate that (is there a single word for accellerating an accelleration?). On this present course the effects of that energy/heat itself (ignoring the decidedly non-negligable side-effects of its likely generation methods) may not remain negligable. Partly, therefore for the psychological effect of setting an example and partly for its actual impact, I prefer the current emphasis on reducing our energy consumption (or at least slowing down its increase) by developing methods of doing things more efficiently, using less energy. The promise of unlimited extra solar energy might have a detrimental psychological effect on that effort. 87.81.230.195 (talk) 13:15, 11 April 2009 (UTC)[reply]

OP, I'm not sure we're understanding you properly. Are you suggesting that we take a giant rechargeable battery, send it to do a close-pass to the sun, bring it back, and use the energy in the battery?

It's an interesting idea anyway, I'm going to suggest that we don't have the technology to capture and store enough energy to make the whole exercise worthwhile. APL (talk) 13:22, 9 April 2009 (UTC)[reply]

I agree. The number of batteries you'd need would be totally impracticable. Much better to put gigantic solar arrays in orbit...but we don't know how to do that either. SteveBaker (talk) 00:29, 10 April 2009 (UTC)[reply]

What? Build solar arrays? Put satellites in orbit? Or the unstated transfer of collected power? Just because we haven't doesn't mean we don't know how; see Space-based solar power. – 74 00:50, 10 April 2009 (UTC)[reply]

I think by 'we don't know how' SB meant we currently have no pratical way to do it for a price that would make it worth doing and with actually getting a net energy return. Sure there are a lot of theories about how we could do it, just as there a lot of theories about how we could colonise Mars or the Moon but we're still a long, long way from actually knowing how to do it pratically. Nil Einne (talk) 11:10, 10 April 2009 (UTC)[reply]

If you "fling" something at the sun to capture its energy, how are you going to get that device back to Earth? Once it gets close enough to the sun to touch its atmosphere (if that's what you meant), alongside with the solar flares and magnetic disturbances, the device would be caught by the Sun's gravity and fall into the sun. How are we supposed to harness that energy, then? ~A H 1^(TCU) 01:42, 10 April 2009 (UTC)[reply]

Also, you may be interested in this. ~A H 1^(TCU) 17:21, 10 April 2009 (UTC)[reply]

April 9

Ethanol Train

I took the family to a tiny nearby town for lunch, which just happened to be hosting some sort of event about an ethanol train sponsored by the EPA. I took my son (who loves trains) to walk around the engine and check it out, but nobody was there to talk to. I've been trying to find more information, but I can only find two things: articles calling ethanol a "train wreck" and articles about a train shipping ethanol that derailed. Can someone point me to some information on the EPA's ethanol train? -- kainaw ™ 03:57, 9 April 2009 (UTC)[reply]

Making the search more specific by searching for the phrase "ethanol-powered locomotive" avoids the sort of false hits you're talking about. I find one hit that might be relevant, which says a company called AHL-TECH is developing one. They have a web site at ahl-tech.com. --Anonymous, 4:07 UTC, April 9, 2009.

Or you can exclude terms which are in those false hits. I had good luck with "ethanol train -wreck -crash -derail": [12]. StuRat (talk) 05:50, 9 April 2009 (UTC)[reply]

Did you? The hits I looked at in that search all seem to be about ordinary trains shipping ethanol. --Anonymous, 8:28 UTC, April 9, 2009.

Hmm, your right. I guess that's a more common meaning of the phrase "ethanol train". StuRat (talk) 12:51, 9 April 2009 (UTC)[reply]

Don't confuse train and locomotive - try googling for "ethanol locomotive". Bazza (talk) 14:02, 9 April 2009 (UTC)[reply]

Thanks. Looking through AHL-TECH's site, I have found the train that I was looking at and a note that it will be brought to market in early 2009. Why it was being unveiled in a town with a population of about 400 people is a bit of a mystery, but not the one I was trying to solve. -- kainaw ™ 14:10, 9 April 2009 (UTC)[reply]

Weird example of relative size

I was reading a periodical piece on the new Planck craft when I came across this comparison:

Regions of the sky that today are separated by twice the apparent diameter of the full moon were once packed into a space much tinier than the diameter of a proton...

I've got no problem with the inflation theory itself, but I can figure out why they would choose to use "twice the apparent diameter of the full moon" when explaining relative size. I understand that angular diameter is usually used to describe the size of objects in space, but how is it any more useful/easier to understand than absolute measurements (e.g. the distance from the earth to the moon) in this case? Thanks! 124.154.253.25 (talk) 05:46, 9 April 2009 (UTC)[reply]

Is it any more useful? I personally don't think so. I'd chalk it up to bad writing. It's true that making sense of things is often done with relative sizes, but a poor choice of things to relate helps no one. --98.217.14.211 (talk) 12:23, 9 April 2009 (UTC)[reply]

We (using e.g. Planck) observe the temperature fluctuations of the microwave background (CMB) as a function of position on the sky and all the maps of the CMB are therefore presented in angular coordinates. Hence we compare the temperature distribution of the patch in one direction with that of a patch in another direction, some angle away from the first patch. The distance to the last scattering surface, where the CMB radiation originates, is the same for both patches and known, hence we can convert the observed angular separation to the absolute distance between those patches at the time of emission and compare that to the size of the horizon at the time (which we compute as an absolute size). Conclusion is that those two patches were not causally connected, yet the statistical properties of their temperature distributions are identical. (Inflation is a way to solve that problem.) The absolute distances are relevant for the physics, but angular distances are what we actually observe and are easier to appreciate. The diameter of the moon is just a unit of angular separation that everybody has a feeling for. --Wrongfilter (talk) 13:02, 9 April 2009 (UTC)[reply]

I'm not exactly sure what it is you're asking, but does it help to know that the diameter of the Moon is ½°? So twice that diameter is 1°,. B00P (talk) 07:13, 10 April 2009 (UTC)[reply]

ESP

Can we actually believe in ESP ? Has it been proven to exist ? Are feelings like Instinct and hunches scientifically backed? For example, can say a mother possibly know that perhaps an accident is going to happen to her child, who is say a thousand miles away ? What is Science's viewpoint on this ? Rkr1991 (talk) 07:16, 9 April 2009 (UTC)[reply]

You can believe in what you want, but this is the science desk and if you're talking from a scientific point of view, the answer is no. See extrasensory perception. The prize offered by James Randi may also be of interest. As to "How can a mother know", the answer is that she can't. People imagine things all the time and sometimes, by coincidence, they happen. --Anonymous, 08:34 UTC, April 9, 2009.

Note that not all "instinct" or "hunches" require ESP. For example, a mother who somehow knows her adult daughter is being beaten by her husband likely figured it out by their body language. StuRat (talk) 12:46, 9 April 2009 (UTC)[reply]

Many many people have been tested for ESP and no one ever comes up with a statistically significant "better than chance" score.

As for your mother question, about once a week my mom calls me to tell me she dreamed or was suddenly worried that some horrible accident had befallen me. She's always wrong, I'm always fine, and we forget about it moments later. At any given day the chance of my mother suddenly "knowing" that I've been in a horrible accident are about 20%. So if I ever really am hit by a car or something, There's a good chance that my mother will have "predicted it", But only because she predicts it every week. Still, it would seem very spooky and she'd probably tell all her friends about it. APL (talk) 13:12, 9 April 2009 (UTC)[reply]

Obligatory xkcd link. — Lomn 14:17, 9 April 2009 (UTC)[reply]

Well it all depends on what you mean by "ESP". Rupert Sheldrake has researched "the sense of being stared at", which might fall under this definition. He has also researched whether pets know when their owners are coming home.--TammyMoet (talk) 13:47, 9 April 2009 (UTC)[reply]

Pets knowing when their owners are coming home probably only requires hearing. If the owner keeps a regular schedule, sounds like church bells or a factory whistle might be clues. If the owner comes home at random times, there's still the sound of their car and maybe the garage door. StuRat (talk) 20:03, 9 April 2009 (UTC)[reply]

Smell may come into play as well. A Quest For Knowledge (talk) 20:24, 9 April 2009 (UTC)[reply]

...depending on how strongly their owners smell. :-) StuRat (talk) 00:38, 10 April 2009 (UTC)[reply]

See this article about confirmation bias. Looie496 (talk) 21:45, 9 April 2009 (UTC)[reply]

The answer is a clear "No" - there is no such thing as ESP. Since no experiment can reproduce it and no theory exists to suggest how it could exist without large swathes of science being overturned, we have to turn to Occam's razor and say that there is no point in even considering ESP any further until/unless some convincing evidence turns up. So no. It doesn't exist. Rupert Sheldrake's work is naive in the extreme. He doesn't consider (much less control-for) the super-subtle cues that we can pick up from tiny changes in interreflected lighting & shadowing, our sense of smell (which is better than we consciously think it is), small air currents and so forth. Any one of those things could be cuing us in to the presence of someone outside of our immediate gaze - and that's plenty enough for a brain that's evolved to be nervous of large predators sneaking up on us from behind. Hence we have zero experimental evidence (properly controlled experimental evidence, that is) for "the sense of being stared at" - and until we have, that too goes into the "nut job theories" pile along with perpetual motion, astrology and the flat earth theory. SteveBaker (talk) 22:31, 9 April 2009 (UTC)[reply]

If Occam's razor is so dominant, then why does physics come up with complicated and observationally unsupported theories about things like the Higgs boson, wormholes, singularity rings, parallel universes, gravitons, WIMPs and MACHOs, etc? This is almost analogous to putting a few final pieces into a jigsaw puzzle, finding a piece that fits the picture but has one of the convex-shape parts missing, but putting it there anyway because there are no other similar pieces to be found. Science doesn't want to change existing ideas, known as paradigms, but new observations tend to cause them to get changed anyway, for example the now-accepted theory of plate tectonics and continental drift took a whole 70 years before scientists abandoned work on the conventional theory and switched to the new one. ~A H 1^(TCU) 01:32, 10 April 2009 (UTC)[reply]

Well, science proceeds by making a hypothesis - then testing that by experiment - and depending on the result of the experiment, we either turn the hypothesis into a theory - or reject it. ESP (as a hypothesis) has been tested - it's failed and been rejected...many, many times. So it's done - gone - outta here. The Higgs Boson is still only a hypothesis - we truly do not know whether they exist or not. However, the existance of the Higgs would explain quite a lot - so Occam's razor does not apply. Remember Occams' razor warns us not to needlessly increase the number of unproven things we believe in. If we believe in ESP, we have to conclude that most of physics as we know it is wrong - and that's a MASSIVE increase in the number of unproven things we'd have to believe in. However, the Higgs would actually explain a lot of things and lead to a modest decrease in the number of unproven things we'd have to think about. But science does NOT say that the Higgs exists. Until we've actually gotten around to doing the experiment, it's just a hypothesis - nothing more. Wormholes, singularity rings, parallel universes and gravitons are all in pretty much the same category. Science does NOT have theories (in the sense of "Einsteins THEORY of Relativity") about any of those things - they are all just unproven hypotheses. So in a sense, we have a four-tiered scale of things:

Theories & Laws - which are things we believe to be true. Einsteins theory of relativity. The three laws of thermodynamics, etc.
Hypotheses - which are things that might be true. Things that don't violate any theories or laws - but which have not be proven either mathematically or by experiment. Good hypotheses explain things nicely and can (at least in theory) be either proven or disproven by experiment. The Higgs Boson, wormholes, etc, etc.
Unfalsifiables - which are things that might be true - but which are not proven and cannot possibly be disproven by any means imaginable. There are an infinite number of unfalsifiable things and we cannot reasonably distinguish between the good ones and the junk because there are no experiments we can do. We simply cannot continue to keep those things in our heads and Occam's razor encourages us to simply ignore them. The existance of a god (or gods) is a classic example of this. You can't ever disprove that - so this is an unfalsifiable hypothesis. If I claim that there are little green men on Mars - then that is falsifiable. We can (at least in principle) go to Mars, pull it apart, atom by atom if necessary, and if we don't find any little green men - then the hypothesis is busted. So that's a falsifiable hypothesis (although it's a pretty crappy hypothesis because it doesn't explain anything - so you may have a hard time getting anyone to do the experiment). But if I say that there are invisible, intangiable little green men on mars who couldn't be detected in that way - then that's an unfalsifiable. Parallel universes are another great example of an unfalsifiable.
Bullshit - which are things that may once have been reasonable hypotheses, but which have failed the 'experiment' stage. ESP is one of those - it seems like it might explain some odd coincidences - but we've done the experiments - and whenever we do them without cheating or accidentally biassing the results - the hypothesis is disproven. Things like N-Rays and Cold Fusion come into this category.

In less rigorous terms - we'd say that bullshit and unfalsifiables should be ignored. Good hypotheses (the ones that seem promising and which would explain something if shown to be true) demand work from scientists - we have to find ways to sort them into the theories and the bullshit - and that means math and experiments - which is what scientists mostly do when they aren't thinking up new hypotheses. The Big Bang is a great example of this. I remember when it was just one of three or four competing hypotheses for the formation of the universe. Then it gradually became more popular because it seemed to explain quite a few things - then we used a spacecraft to measure the cosmic background radiation - which turned out to be pretty much what the Big Bang hypothesis predicts...and now we talk about "The Big Bang Theory".

Another good way to think about this is in terms of "extraordinary claims require extraordinary evidence". If I claim that there is a mass-carrier particle that we'll call the Higgs Boson - then you are quite justified in demanding extraordinary evidence before you'll accept that hypothesis. So we go out and spend a few billions on a large hadron collider - and (when we get the bloody thing working) we do the experiment - and then we either put the Higgs hypothesis into the "Theory" pile or into the "Bullshit" pile depending on what emerges. On the other hand, if I claim that I have a dollar in my pocket - that's a very unextraordinary claim - and you might even be prepared to take my word for it - an unextraordinary claim really doesn't need much evidence in order for us to believe it. But ESP is an exceedingly extraordinary claim - it's far less likely to be true than the Higgs. But where is the evidence? We don't have a single experiment to prove it...and we've done hundreds of them. So it's firmly on the Bullshit pile.

SteveBaker (talk) 10:54, 10 April 2009 (UTC)[reply]

Coma

What are the reasons that doctors will sometimes deliberately/purposefully place a patient into a medically induced coma? What does this do? What is the benefit? What scenarios (health problems) would typically lead to this medical treatment? How do they induce the coma? Thanks. (Joseph A. Spadaro (talk) 08:24, 9 April 2009 (UTC))[reply]

The induced coma article is rather short, but did you read it? --Anonymous, 08:36 UTC, April 9, 2009.

This sounds like a homework question, of which most of the answers are in the induced coma article. --Mark PEA (talk) 11:48, 9 April 2009 (UTC)[reply]

One case where this process is used is when a patient suffers from severe burns. The reason is that the pain created by those burns would otherwise require massive doses of pain relievers for months, which would have negative consequences for the patient's health. StuRat (talk) 12:39, 9 April 2009 (UTC)[reply]

Powder coated steel

Could somebody tell me what "powder-coated steel" is. What advantages are there of using powder coated steel? Any help appreciated. —Preceding unsigned comment added by 87.115.64.1 (talk) 11:31, 9 April 2009 (UTC)[reply]

our article on Powder coating may help to answer your question. cheers, 10draftsdeep (talk) 13:44, 9 April 2009 (UTC)[reply]

Space and matter/observable vs actual

I was just thinking about the Big Crunch scenario. If gravity ends up being strong enough, and the universe starts contracting, all matter will end up forming a singularity. But what happens to space in this scenario? My intuition is that space is being destroyed as well, but I can't make a logical argument for it. While I'm here, is there a relationship between the observable universe and the actual one? I'm thinking they're the same but would like some reading material to confirm that. Cheers 124.169.159.117 (talk) 11:45, 9 April 2009 (UTC)[reply]

Our article on the observable universe may be useful. It is not synonymous with the universe. Dark flow, for instance, is theorized to be caused by the gravitational effects of something beyond our observable horizon. — Lomn 14:14, 9 April 2009 (UTC)[reply]

The source of dark flow within the observable universe, otherwise we'd have no way to detect it. We can't see the light coming from it because the light we'd be seeing was emitted when the universe was opaque. — DanielLC 18:01, 9 April 2009 (UTC)[reply]

Repairing damage to the vocal cords after the removal of a thyroid tumour

Is there a surgical or other method of repairing a gap in the vocal chords so that anything ingested does not trickle through into the lungs? Someone I know had a cancerous thyroid tumour that became sufficiently large as to put pressure on their vocal cords and ended up distorting them. He is now being fed through a PEG tube. The doctors have said that there is a chance they might heal, but they are from a rather provincial part of the world and there's a chance they are not aware of more advanced options. The ultimate goal is the ability to eat and drink independently. Any suggestions or advice would be most welcome. Referred many people here before, but never used it - quite keen on the experience. WLU (t) (c) Wikipedia's rules:^simple/_complex 12:23, 9 April 2009 (UTC)[reply]

Isn't that the job of the Epiglottis, not the vocal chords? Rmhermen (talk) 13:04, 9 April 2009 (UTC)[reply]

Not sure, I'll ask. The person I'm getting info from is a non-doctor. WLU (t) (c) Wikipedia's rules:^simple/_complex 14:49, 9 April 2009 (UTC)[reply]

Agreeing with Rmhermen, this is definitely the role of the epiglottis, not the vocal chords. —Cyclonenim | Chat 19:22, 9 April 2009 (UTC)[reply]

Keep in mind that difficulty in swallowing can arise not only from distortion of the anatomy, but also from any neurological problems (which in turn might be caused by local nerve damage). Speech pathologists are often consulted for such problems, and many hospitals have "swallowing teams" which assist in their evaluation and treatment. - Nunh-huh 23:24, 9 April 2009 (UTC)[reply]

I am assuming that he had a thyroidectomy to remove the tumor or they instead used Iodine-131 to kill off the cancerous cells. Is that right? These articles (http://www.nidcd.nih.gov/health/voice/vocalparal.htm) and (http://www.merck.com/mmpe/sec08/ch092/ch092g.html) say that a thyroid tumor or thyroidectomy itself can cause vocal cord paralysis; this can lead to dysphagia (difficulty swallowing), causing food to fall into the trachea. A thyroid tumor is capable of pressing on vocal cords (http://www.cancer.gov/cancertopics/pdq/treatment/thyroid/patient). Vocal cord paralysis can sometimes be treated with surgery or injections to fill in the gaps in the vocal cords. The thyroid gland can also compress the esophagus (http://www.chw.org/display/PPF/DocID/22801/router.asp). Do you know the term for the condition that he has? There are many different kinds of swallowing problems (see this Mayo Clinic article (http://www.mayoclinic.org/swallowing-problems/)). One scientific paper talked about dysphagia in thyroid tumor that was related to laryngeal edema (fluid accumulation) and was resolved with tracheotomy (http://jcem.endojournals.org/cgi/reprint/86/11/5148).71.31.105.213 (talk) 04:43, 10 April 2009 (UTC)[reply]

Major Histocompatibility Complex molecule

Hi all just a quick question: Is the Major Histocompatibility Complex molecule found on the surface of all cells in the human body? Am I right in thinking that the molecule is like a little flag of allegience which flags the cell as 'self' preventing the natural killer cells from attacking the cell? I did read the article on Major Histocompatibility Complex but I am still a little confused. Thanks —Preceding unsigned comment added by 139.222.240.209 (talk) 14:03, 9 April 2009 (UTC)[reply]

Hot dog as a representation of HLA molecule and peptide.

There is not just one Major Histocompatibility Complex (MHC) molecule. The human MCH molecules are called Human Leukocyte Antigen molecules, and there are two main groups of them, called HLA class I and HLA class II. The tissue distribution of class I and class II molecules is very different - class I molecules are found on most, but not all cells of the body. A notable exception - they are not found on red blood cells (or are found in trace amounts). This rather old paper gives some examples of the tissue distribution of class I molecules. Class II molecules are normally found only on the so-called professional Antigen presenting cells, i.e. B lymphocytes, Dendritic cells, Macrophages. We have three types of "classical" class I molecules, HLA A, HLA B and HLA C, and three types of class II molecules, HLA DR, HLA DQ and HLA DP. Most people are heterozygous for each of these molecules. HLA molecules show enormous allelic variation, the probability of two unrelated individuals being HLA identical is very small - that's why it's so difficult to find suitable bone marrow and organ donors. Class I and II MHC molecules share a common structural feature. On their surface are two alpha helices, and between them is a groove. In the groove sits a peptide, about 10 amino acids long. Think of it as a hot dog - the bread on each side is the alpha helices, and the sausage is the peptide.

Now for the second part of your question. Some NK cells act the way you describe, and HLA-C is the most important molecule for inhibiting an attack from NK cells. Such NK cells may attack cells that lack HLA molecules altogether, or that lack self HLA molecules (provided certain other molecules are present). Losing HLA expression is one way that cancer cells may escape an NK cell attack. For T cells, however, it works the other way around. T cells will ignore a cell that lacks HLA molecules. They also ignore cells with self HLA molecules containing self peptides (these peptides are breakdown products from intracellular proteins). However, they attack cells that have self HLA molecules containing foreign peptides (such as a virus peptide), or cells that have foreign HLA molecules (such as a poorly matched transplanted organ). --NorwegianBlue^talk 15:48, 9 April 2009 (UTC)[reply]

LIFE AND DEATH

What is Life and what is death ? Is is possible to give a precise definition of the two? Is it all just about electrical signals moving around, or is it something more? Like, does Science acknowledge the existence of the soul ? With all the modern theories floating around, is it possible to write an equation of life? Have we understood how life first came into existence, and perhaps come anywhere near creating it? What does SCIENCE say about all this? Is death something like an infinite sleep, or is it something more, or perhaps less? I have heard theories like Super string theory and Combined Quantum Gravity (pardon me if i am wrong) claim to explain everything. Does that include life and death? Are we any closer to solving that mystery of finding where we came from? Rkr1991 (talk) 14:46, 9 April 2009 (UTC)[reply]

From a scientific perspective, our articles on life and death should be more than sufficient. Note that there aren't good bright-line definitions, and much of what you ask is better suited to philosophical discussions. As for the last part, various "theories of everything" are concerned with unifying the three fundamental interactions, not solving all thought arguments and religious conundrums. — Lomn 14:53, 9 April 2009 (UTC)[reply]

I would say this is dodging the question. What the articles define are the characteristics of life, but not what it is! And while the aim of any theory is to explain every natural phenomena around us, why not that include life? Surely the concept of life is as natural as say stars or lightning, not philosophical! Just because the theories don't bother to worry about these phenomena, as one of the readers pointed out, doesn't mean they shouldn't or can't! Rkr1991 (talk) 15:01, 9 April 2009 (UTC) —Preceding unsigned comment added by Rkr1991 (talk • contribs) 15:01, 9 April 2009 (UTC)[reply]

If the question "what is life?" is not synonymous with "what are the defining characteristics of life, and how is it distinguised from non-life?", then you're not asking a scientific question. So yes: it is philosophical, and it's not within the realm of scientific theory. Fortunately, people have asked us about the meaning of life many many times. There should be more than enough opinions there to suit you, and if by some chance there are not, Google yet remains — Lomn 16:01, 9 April 2009 (UTC)[reply]

"Is death something like an infinite sleep, or is it something more, or perhaps less?" No, it's not like sleeping. I like the following quote: "I do not fear death, in view of the fact that I had been dead for billions and billions of years before I was born, and had not suffered the slightest inconvenience from it." which may or may not have been said by Mark Twain. [13] A Quest For Knowledge (talk) 18:06, 9 April 2009 (UTC)[reply]

Over 30 years ago, Lyall Watson wrote books on this subject. Two I can recommend are Supernature and The Romeo Error. Despite the passage of time, I don't think any modern discoveries have added to his work on the nature of life and death. --TammyMoet (talk) 18:18, 9 April 2009 (UTC)[reply]

What is Life and what is death ? - Sadly, this is one of those "I know it when I see it" kind of things. There are 'creatures' that are so unbelievably primitive that it's really tough to draw the line as what is merely chemistry and what crosses the invisible line into biology. The famous "tobacco mosaic virus" behaves much like a virus inside a tobacco plant - but can be extracted and made into rather beautiful crystals that behave just like any other crystal - until you dissolve them in water and feed them to a tobacco plant - and then they seem to be alive again. Similar problems exist with death. Drawing the line at when a human dies has proven exceedingly difficult and controversial. In the end, science has to say that there is no hard line - and just because the English language provides a sharp distinction - that's not necessarily how nature behaves.
Is is possible to give a precise definition of the two? - No.
Is it all just about electrical signals moving around, or is it something more? - No, the most primitive forms of life don't have neurons - and there is no electrical activity per-se...yet they are undoubtedly "alive".
Like, does Science acknowledge the existence of the soul ? - No science cannot find any reason to say that there is a soul. Hence Occam's razor says that we should simply ignore the possibility until/unless some actual evidence shows up.
With all the modern theories floating around, is it possible to write an equation of life? - Well, it wouldn't precisely be an "equation" - and as I've pointed out - it's not a bright line. But it's just like the stupid argument about whether Pluto is a planet or not. "Planet" is just a word - it doesn't have any solid scientific essence beyond what we choose to embue it with. So if we choose to define the word to exclude Pluto, then Pluto isn't a planet anymore. Nothing changed about Pluto - our understanding of it didn't change because of that name change. Similarly with "Life" - if we choose to say that virusses are not alive - then they aren't. If we say that they are - then they are. That doesn't affect anything other than the word we use when we talk about them.
Have we understood how life first came into existence, - Not conclusively. There are many theories surrounding 'abiogenesis'. The most probable (and certainly plausible) idea is that fairly complex carbon compounds (what we judgementally call "organic molecules") can form spontaneously in the air/water/ground of early earth. There are experiments that show that directly. Then, these molecules will react with each other - pretty much at random - and complicated molecules will come about purely by chance. If it is only a billion, billion, billion to one chance that one of those random molecules could spontaneously reproduce itself - then evolution can kick in and pretty soon after, we'd have recognisable life. The math to figure out the probability of that exceedingly unlikely event is tough to work out because we don't yet know what the simplest possible self-reproducing molecule might need to be. But because these reactions were occurring over trillions of cubic kilometers of water over a billion years - the odds can be exceedingly remote - and yet still add up to an almost certain chance of life appearing completely at random.
Have we...perhaps come anywhere near creating it? - Yes. There are at least two groups of scientists trying to do exactly that - and they are very close to success. They have made molecules that can self-reproduce when enclosed in a very simple droplet of oily lipids - and I would lay good odds of them having an entirely artificial lifeform within 5 years. Of course, that assumes that your definition of "life" has to include chemistry. Computer scientists have long been making synthetic lifeforms within the computer that can do pretty much everything that "real world" life does...including evolving into higher forms.
Is death something like an infinite sleep, or is it something more, or perhaps less? - The evidence is only that the brain stops working. No different from switching off a computer. How this must 'seem' to the person doing the dying is something of an unknown - but a gradual death seems that it might be a lot like falling asleep - a sudden one is just a sudden nothing. You can't ask what THAT feels like because the thing that's doing the feeling stopped working.
I have heard theories like Super string theory and Combined Quantum Gravity (pardon me if i am wrong) claim to explain everything. - Yes, but at a very very low level of explanation. Certainly there is the possibility that one of these theories might come to have the potential to explain everything down at the lowest possible level. But you would require an insane amount of time or computer power to go from a detailed description of how superstrings interact to get to the point where you could explain how a single DNA molecule does what it does. The potential to explain everything might be there - but that's not enough. To put it another way - you probably know all of the rules to the game of chess. Can you tell me then whether white will always win if he plays without making any mistakes? Well, theoretically - you have enough knowledge to answer that - but in practice, the number of possible games of chess exceeds the number of fundamental particles in the visible universe - so there is really no way to go from knowing all the rules to answering that kind of question. However, if I ask the same question about TicTacToe (Noughts-and-Crosses for us Brits) - a knowledge of the rules is all you need to say that if both players play a perfect game, then it'll always end in a draw. Well, superstring theory might MAYBE be able to tell us how something as simple as a hydrogen atom works in amazing detail - but it's still not going to answer the question of Life, The Universe And Everything. (Unless it really is 42).
Does that include life and death? - No - because those are just two words and until we decide what we want them to MEAN - we can't apply science to them.
Are we any closer to solving that mystery of finding where we came from? - Yes. Every day, we get a little bit closer. I would be surprised if we don't have a complete explanation in my lifetime (and I'm 54 years old). The largest piece of the puzzle is that 'abiogenesis' step - how did the very first most primitive thing that we'd say was "alive" (because it could reproduce - and therefore evolve) come about from a bunch of "chemicals". But "life" and "death" are really just words with poorly defined meanings. If we came up with two new words "squibbobble" and "anti-squibobble" and defined rigorously the meaning of squibobble as something like "an object which is capable of evolving" - then there would be no ambiguity (well, perhaps with that exact definition there still is...but you see what I mean). Sadly, people who are no longer capable of having children (eg women who are past menopause) would fall into the 'anti-squibobble' category - and just as with the definition of the word "planet", everyone would get very upset about it...even though it's "just a word".

SteveBaker (talk) 22:21, 9 April 2009 (UTC)[reply]

Have we come anywhere near creating it? If you include viruses as 'alive,' at least one has been made from scratch - kinda scary actually. --Bennybp (talk) 01:54, 10 April 2009 (UTC)[reply]

The first (and second) sentence says "A deadly virus has been made from scratch using standard laboratory equipment, an internet recipe and DNA freely available from mail-order companies", but if it's using pre-existing DNA, I'm not sure it's fair to say it was created from scratch. A Quest For Knowledge (talk) 10:38, 10 April 2009 (UTC)[reply]

No - the DNA is entirely synthetic. It came from companies who will take a list of A's, G's and T's in an email and for some amount of cash, send you back a bucket of DNA snippets that have that description. They start from scratch with Amino acids - so this is truly synthetic. They also inserted that DNA into an already functional organism - so they didn't have to make the other parts of the cell. What is also "cheating" is that they used the DNA code from a "natural" lifeform - they didn't design it from scratch. After a couple of generations, their "synthetic" virus would be utterly indistinguishable from the "natural" virus. However, there are also scientists out there who are trying to build a lifeform that's not just constructed synthetically - but also designed from scratch and placed into a cell-like structure that's also built from scratch. Such organisms would be entirely unlike anything else on the planet. SteveBaker (talk) 11:32, 10 April 2009 (UTC)[reply]

Oh, cool. Thanks! A Quest For Knowledge (talk) 13:09, 10 April 2009 (UTC)[reply]

Synthetic life may be of greater interest although sadly in a rather poor state Nil Einne (talk) 11:13, 10 April 2009 (UTC)[reply]

Colorado Bug ID

Alright, I'm a resident of Colorado Springs who's slightly concerned about these weird beetles/roaches I've been seeing around. There's a trail not far from where I live that I frequent, and there's this large mound about a yard across, dotted with holes roughly one inch in diameter. I believe this to be their burrow or nest, as they consistently retreat into said holes as I approach. These insects are roughly an inch and a half long, and fast as sin. I have literally never seen one up close, as they constantly are buzzing and darting quickly away when I get near. I'm sorry I can't give more information, these critters are just fantastic at hiding, and lord knows I'm not going to go poking around that nest. Thanks! 128.198.32.24 (talk) 22:31, 9 April 2009 (UTC)[reply]

I've never heard of a bug that fits that description -- seems to mix attributes of roaches, ants, and mice. Looie496 (talk) 23:02, 9 April 2009 (UTC)[reply]

Social insects in large colonies (about a yard or meter across) does somewhat limit the possibilities. Could they be termites ? What color are they ? Do they fly ? Do they have long antennae ? StuRat (talk) 00:32, 10 April 2009 (UTC)[reply]

Wrap a piece of duct tape around a small box sticky side up. Leave that near one of the holes. (Most bugs like sugar, so you might want to sprinkle a bit on your trap. Walk away for a while. If you managed to trap one of the critters take a picture and we might be able to help you identify them. Bring something to dispose of your trap in after you used it. You don't want to leave it as litter. 76.97.245.5 (talk) 07:12, 10 April 2009 (UTC)\[reply]

UPDATE: OP here. After consulting with some friends, I have discovered that these insects are most likely a breed of native Coloradoan Cicada. I took a listen to the recording on a cicada cry on the wiki page, and I'm quite sure we have a match! Thanks for your help, folks! These are some creepy little bugs! 75.148.127.194 (talk) 01:29, 11 April 2009 (UTC)[reply]

Noisy chalk holders

Why does the squeaking and skipping of chalk get worse with chalk holders (any that I've ever used, at least)? 124.154.253.25 (talk) 23:13, 9 April 2009 (UTC)[reply]

This is pure speculation - but the cause of the squeak is likely related to resonance in the chalk - and when you hold it in your fingers, that soft flesh is damping out the vibrations. The chalk holder may perhaps change the resonant frequency and perhaps make it worse. SteveBaker (talk) 23:30, 9 April 2009 (UTC)[reply]

Also maybe related is a change in the angle of the chalk on the board and how hard you are pressing. With the right combination of angle, pressure, and grip tightness, you can get enough resonance that the chalk skips off the board entirely and draws a clean dotted line. DMacks (talk) 06:50, 10 April 2009 (UTC)[reply]

Unfortunately I've never found an appropriate angle/pressure that will cancel out/dampen the vibration sufficiently with the holder on, unless I press so hard as to break the chalk (though it might still squeak while doing so) or hold it right on the tip, which usually nulls the benefit of using the holder in the first place. A change in the resonant frequency makes sense though, now that I think of it. The chalk is slightly longer and quite a bit fatter with the holder, and if the resonant frequency were lowered enough by the increase in size it might vibrate off the drawing surface. Normal chalk usually squeaks when you hold it too far up too; I would guess near the point of a resonance overtone and/or far enough away that the fingers aren't able to absorb so much of the vibration. Thanks for the responses! 124.154.253.25 (talk) 08:37, 10 April 2009 (UTC)[reply]

Cool! I think that pretty much clinches it then. Is it possible that you could install something soft between the chalk and the holder? I'm thinking of a thin strip of foam rubber - or perhaps even a strip of cloth might be enough...that might dampen out the vibration sufficiently to prevent it from building up into a squeak. If the chalk holder itself is resonating (which seems unlikely) then perhaps epoxy-gluing a chunk of lead to it would change the frequency enough to take it out of the range of human hearing? However, if the chalk squeaks when you hold it too far up - then that says that it's the chalk itself that's resonating - so messing with the holder's resonant frequency may not help at all. Failing, those things...white boards and marker pens! SteveBaker (talk) 10:06, 10 April 2009 (UTC)[reply]

April 10

can we get any "object" to anywhere near relativistic speeds?

can we get any "object" with significant mass (I don't really mean single particles, but it doesn't have to be a big object) to anywhere near relativistic speeds, either here or in space? 94.27.161.254 (talk) 09:55, 10 April 2009 (UTC)[reply]

Well, this is a somewhat vague question since there isn't any solid definition of "relativistic speed" or "significant mass" - but taking it in the spirit in which it's asked - no, we have never gotten anything weighing (say) at least a microgram up to (say) 90% of the speed of light. Single particles - yes, certainly. SteveBaker (talk) 10:18, 10 April 2009 (UTC)[reply]

I'm not expert on this subject so I'm prepared for one of our resident physists to blow this idea away, but I read somewhere that it takes between the MeV or TeV range of energy to accelerate one proton to a decent fraction of the speed of light, which is a lot of energy for just one particle. Add in a few more MeV/TeV for a neutron and another MeV or so for the electron, and for the most basic of atoms you're starting to rack up a decent amount of energy. Let's say, for example, it'd take 3.204 × 10^-7 joules to accelerate a hydrogen atom to near the speed of light. Not much? Except we have to remember to get a sense of scale, an atom is nothing in terms of an object. To get one mole of atoms to near the speed of light, by the previous figure which I'm not convinced is anywhere near accurate, we'd need 1.92 x 10^17 J, which is near about the amount of energy that strikes the Earth each second from the Sun... that's a lot of energy. —Cyclonenim | Chat 11:38, 10 April 2009 (UTC)[reply]

It looks like you just made those numbers up, am I right? We can calculate this, you know. In units in which the speed of light equals 1, the relativistic energy of an object of (rest) mass m at velocity v is

{\frac {m}{\sqrt {1-v^{2}}}}

, but m of that is its rest energy, so the extra energy to be supplied is

m\left({\frac {1}{\sqrt {1-v^{2}}}}-1\right)

. At v=0.9, the value Steve was considering, that's about 1.29m. For reference, the Hiroshima bomb liberated about one gram's worth of energy.

So for a bomb and a third you can get a one-gram object up to 90% of the speed of light, if you can figure out how to turn all that energy into KE of the object. That is a lot of energy, but it's about three orders of magnitude less than you came up with. --Trovatore (talk) 01:02, 11 April 2009 (UTC)[reply]

I believe that the fastest object created by man is the Voyager 1 spacecraft which is currently traveling at 38,350 mph. Light, by contrast, travels at about 11,176,943 mph. So Voyager 1 is at about 0.34% of the speed of light. You might be interested in Project Orion for some theoretical possibilities. A Quest For Knowledge (talk) 12:22, 10 April 2009 (UTC)[reply]

That should be 670,616,629 mph, which would put Voyager I at about .0057% that of light – equivalent to a true snail's pace (2 mm/s) on a superhighway (120 km/h). -- Tcncv (talk) 00:39, 11 April 2009 (UTC)[reply]

That would fit my def of "relativistic speeds", that is, speeds high enough that relativistic effects must be considered. At that velocity I imagine time dilation needed to be taken into account when using an on-board timer to tell it to come on and take pics of a passing planet or moon. StuRat (talk) 13:29, 10 April 2009 (UTC)[reply]

The LHC will be able to accelerate lead nuclei to just shy of the speed of light. I think that's pretty big. 163.1.176.253 (talk) 12:37, 10 April 2009 (UTC)[reply]

Accelerating a lead nucleus would still be in the order of a microjoule or so, and the LHC plans to use quite a few in order to achieve collisions (otherwise atoms will just miss each other), so the energy requirements soon add up. —Cyclonenim | Chat 12:42, 10 April 2009 (UTC)[reply]

While it certainly has not been done, I wouldn't be so quick to say it cannot be done. An orion ship ( http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) ) could reach 10% lightspeed. Beam-powered solar sails ( http://en.wikipedia.org/wiki/Solar_sail ) could reach "a significant fraction of the speed of light" —Preceding unsigned comment added by 81.11.182.18 (talk) 12:34, 10 April 2009 (UTC)[reply]

You might also be interested in NASA's antimatter spaceship.[14]. A Quest For Knowledge (talk) 13:13, 10 April 2009 (UTC)[reply]

If I remember correctly, astronauts aboard the space shuttle have been calculated to experience time about 1x10^-9 seconds faster than those on Earth. ~A H 1^(TCU) 17:14, 10 April 2009 (UTC)[reply]

Ornithosis agent

I ran across this article since it was uncategorized. I don't know anything about the topic, but as far as I can tell, ornithosis is any infection spread by birds. Orni- or Ornitho- is Greek for bird, and -osis is Greek for disease. So I assume an ornithosis agent is any pathogen present in birds. The article mentions Rickettsia. I'm unsure if the Ornithosis agent article should be deleted, redirected to Ornithosis (actually to Psittacosis since Ornithosis currently redirects there), or Chlamydophila pneumoniae, or Chlamydophila psittaci, or perhaps moved to Wiktionary. There are several hits for "ornithosis agent" on Google, Google Books, and Google Scholar. But maybe it's more suited to a medical dictionary? --Pixelface (talk) 11:19, 10 April 2009 (UTC)[reply]

This is more a matter for the WP:HELPDESK than for us. But in general, if there is more to be said on a subject than a mere definition of the term (and that seems likely in this case) - then if it's notable - then we should have an article about it. The word "Ornithosis" has 70,000+ google hits and "Ornithosis Agent" gets about 16,000 - so neither is something someone just made up. I guess the big question is whether it's just a synonym for some other more common term - in which case merging the articles together and turning the less commonly used into a REDIRECT page would make sense. SteveBaker (talk) 11:26, 10 April 2009 (UTC)[reply]

Thanks for your prompt reply. I considered asking at WT:MEDICINE, but the top of that page mentioned this page. --Pixelface (talk) 12:41, 10 April 2009 (UTC)[reply]

Merging the sentence from ornithosis agent into ornithosis would be the best plan, and then create a redirect to ornithosis from ornithosis agent. Regards. —Cyclonenim | Chat 12:45, 10 April 2009 (UTC)[reply]

I would not merge them just yet, as we have a bigger problem. The thing is, there is a microorganism Chlamydophila psittaci, which causes bacterial ornithosis (psittacosis), but it is not a Rickettsia. So, either ornithosis agent article is simply wrong, or it refers to a different microorganism. Would please someone who is either a MD or a certified vet sort this one out? To make things worse, there is also an ornithosis virus, which we do not currently have an article about; but we should. Any ideas? --Dr Dima (talk) 18:54, 10 April 2009 (UTC)[reply]

I replaced the contents of "Ornithosis agent" with a redirect to Chlamydophila psittaci. --NorwegianBlue^talk 11:50, 11 April 2009 (UTC)[reply]

Limits of curving a ball

In particular I have in mind the limits of curving a football (soccer ball), that is hitting it in such a way that it travels along a curve rather than a straight line (like this). To be honest, I don't really know the physics of the motion, but I believe it is possibly to do with high / low air pressure on one side? I believe the primary variables would be the speed the player strikes the ball, the point at which they strike the ball, and the size and shape of the area of the ball that their foot meets. What is the theoretical maximum curve a human could impart on a football assuming normal environmental conditions, a modern football and so on? To phrase the question more concretely, if a ball was positioned 25 metres from a vertical pole and a straight line is drawn between these positions, what is the maximum deviation from the straight line the ball could have when struck in an optimal way such that it still collides with the pole. --80.6.184.236 (talk) 13:48, 10 April 2009 (UTC)[reply]

The curve is due to spin, the Magnus effect. So you really need to figure out how rough a shoe one has (friction during the kick to spin the ball), how off-center you can kick it while still being able to control its direction, etc. There's another oddity from the video though...you're seeing a 2D projection of 3D motion, so there are all sorts of perspective problems (for example, parallax) that can make it hard to see the actual trajectory. DMacks (talk) 14:06, 10 April 2009 (UTC)[reply]

Footballers are capable of giving significant curl or dip to a ball with little or no spin. This is not a well understood area of science, due to the complex nature of the problem. There are factors which are often ignored (such as the non-rigid nature of the ball, and its non uniformly frictive surface) that are simplified out which are now believe to be major factors. I have been told (whether or not reliably I couldn't tell you) that oscillations in the shape of the ball caused by the initial impact of the players foot play a large part in curl. Elocute (talk) 21:53, 11 April 2009 (UTC)[reply]

I'd favor an experimental approach here (get a professional soccer player and have him give it as much spin as possible, then measure the results). Calculating it mathematically wouldn't work well because so many factors are unknown, like the amount of friction between the shoe and the ball. StuRat (talk) 15:48, 10 April 2009 (UTC)[reply]

Dashboards

Not to sure where to post this, feel free to move it (engineering? law?)... Does anyone know where I can find a precise list of the dashboard instruments (and tell-tales) required for a car to be road-legal in the U.K. ? A client wants a road-legal prototype ASAP, and I need to know what has to be finished, but I can't find this anywhere. I suppose the speedo is obligatory (in mph only or in kmh too?), but I'm not sure about the rest. If anyone has a Caterham or similar, could they tell me what they've got (I'm guessing it's pretty close to the minimum required)? Thanks! yandman 15:09, 10 April 2009 (UTC)[reply]

Most of the info you require is contained in ECE Regulation 121. The rest can be picked up from ECE R39 (speedometers) and R48 (installation of lighting and light-signalling devices). —Scheinwerfermann ^T·_C03:28, 12 April 2009 (UTC)[reply]

are flywheels any easier in space?

Note: flywheels are inherently mechanical devices akin to hard drives in the sense that they enclose spinning platters -- however in flywheels these platters spin in order to store energy -- thus the flywheel is a kind of "battery". This question concerns the design challenges of flywheels in space, namely whether designing flywheels becomes easier when they are to be in space. The question is purely theoretical and is not concerned with the economies of actually getting the (simplified?) design of the flywheel into space, or charging it with power! 79.122.65.253 (talk) 22:04, 10 April 2009 (UTC)[reply]

the question

Would a giant flywheel be much easier to implement in space for the following two reasons:

Space is a natural vacuum
The motor does not have to bear the weight of suspending the flywheel

I'm thinking: why not use two huge flywheels attached to your ship in a tandem rotor configuration (so your base isn't spinning wildly in the opposite direction)?

b. serial motors?

additionally what's wrong with this reasoning:

since you don't have to support any weight, couldn't you weakly couple (no load) a bunch of cheap, small motors serially to get the full rpm?
This insulates the base from the huge speeds of the flywheel and means you don't have to use such powerful motors or worry about:
- the problem of friction at high speed
- the problem of trying to couple electrically at high speed (in other cases the flywheels might not need any electricity, but in this case the rest of the motors do)
- the problems such as eddy currents that emerge at high speed

For example:

O------[ship]------O

(where the O's are your two flywheels and - are the weakly coupled [not load bearing] independent motors)

In this example here are the relative RPM's at each motor once the flywheels have fully powered up:

O5-5-5-5-5-5-[ship]-5-5-5-5-5-5O

But here are the RPM's relative to the ship:

O15625-3125-625-125-25-5-[ship]-5-25-125-625-3125-15625O

As you can see, you now have a huge RPM at the edge (that you slowly built up to) but each motor just has to turn a maximum of 5 rpm relative to the one below it -- that means each motor can turn with a huge torque, for example to turn flywheels that are really really massive.

This is how I imagine it would spin up:

First the innermost motors -[ship]-
start sloooooooooooowly turning the static rest of the motors+flywheel O----- and -----O
once the innermost have brought the rest up to 5 rpm (where they remain relative to it) ...
the second pair of motors --[ship]--
starts turning the static rest of the motors+flywheel O---- and ----O
etc etc

In this way any flywheel could be easily brought to the speed where it nearly shatters. It is also not hard to transfer electricity from one flywheel to the next, if it's only moving at 5 rpm! you could even use just a simple "brush" connector (not sure what to call it) it is a piece of cake.

I figure since friction is a function of speed, the relatively really small speeds between each section means the MAIN, main engineering challenge with flywheels (other than the load bearing part), ie reducing friction, becomes trivial. Also: you don't have to worry about trying to reduce the mass of the motors (making them lightweight), since they are also part of the flywheel and moving them isn't a "waste".

Are my logic, physics, and mechanics right, or am I missing something? 79.122.65.253 (talk) 16:03, 10 April 2009 (UTC)[reply]

We need to back up here first and figure out what your overall goal is. A flywheel is normally a device for storing mechanical energy. Is that really what you mean here ? If so, what is the source of the mechanical energy that you wish to store ? I'm thinking that perhaps you're talking about rotating part of the space station as a way of achieving artificial gravity. Is that what you mean ? StuRat (talk) 17:59, 10 April 2009 (UTC)[reply]

If you are talking about using flywheels to store energy, then bear in mind that moving large masses into space from Earth would be extremely expensive. If the flywheel could be made of something we already need to bring up, like maybe water tanks, then that would be another matter, although we then have the problem of how to access the contents while in motion. Another option might be to construct the flywheels of objects found in space. StuRat (talk) 18:03, 10 April 2009 (UTC)[reply]

The question is quite specific, as I gave in the title: "are flywheels any easier in space?" (ie easier to create under space conditions). As for uses, I believe that the flywheel article lists the uses for a flywheel, which all revolve around (heheh) storing energy. 79.122.65.253 (talk) 21:09, 10 April 2009 (UTC)[reply]

I've made this thread small and put a note at the top of the question explaining that a flywheel is for storing energy and that I was asking whether designing one is easier in space (given the reasoning in the rest of my original question). I hope you also feel the explanation now at top makes this change appropriate. 79.122.65.253 (talk) 22:01, 10 April 2009 (UTC)[reply]

Tether propulsion, Tether satellite Non-rocket spacelaunch There also was an idea in the eighties that looked somewhat like a shuriken and would have spun to catch and released metal balls like a space Jai alai game. Can't find the article anymore. (If someone knows what magazine it was in plse. let me know.) 76.97.245.5 (talk) 22:27, 10 April 2009 (UTC)[reply]

thank you for the links, which I looked at, but as near as I can tell none of them have anything to do with my question! 79.122.65.253 (talk) 23:12, 10 April 2009 (UTC)[reply]

Seeing as your ship is not anchored in space, by conservation of momentum it will gain rotational energy too. And since it is much closer to the axis centre, it will have to gain much much more rotational speed than your flywheels (Assuming it is of similar density). (left by 92.22.160.99)

maybe I didn't make it clear but like most tandem rotor configurations the two rotors would be spinning in opposite directions, for 0 net spin at the ship! 79.122.103.33 (talk) 22:15, 11 April 2009 (UTC)[reply]

There's a little problem with the math for your serial motors. If each motor is turning at 5 rpm relative to the one adjacent, there will be a linear progression (5 - 10 - 15 - 20 rpm) down the line, not geometric one (5 - 25 - 125 - 625).

Aside from that, there's no obvious reason why you couldn't stack motors in this fashion. Do bear in mind, however, that the same concerns regarding centrifugal force and dynamic instability apply to this set of chained, rapidly rotating motors as apply to a flywheel. The high-speed motor stages are going to be rotating very rapidly and have tremendous angular momentum, even if they're not moving very fast relative to the adjacent motors. From what I understand, constructing high-speed motors that will drive a flywheel isn't a major hurdle, even here on Earth. (Vacuum and zero gee do may make life a bit easier, though.) Our big problem is building flywheels with sufficient mechanical strength to handle really fast spins without exploding, not getting them up to speed in the first place. (Laboratory folk will be aware – hopefully through instruction, rather than personal experience – of the incredible destructive power of a failing ultracentrifuge rotor: [15].) TenOfAllTrades(talk) 22:30, 11 April 2009 (UTC)[reply]

[edit conflict] Your notion that serial motors would have multiplicative rotation rates is false; they would be additive (as Ten said). If you want to reduce the speeds of the motors to reduce friction, well-lubricated gearing systems could spin the flywheels much faster than the rotors; no serialization required. Certainly it would make things easier to not have to have bearings that were load-bearing. --Tardis (talk) 22:33, 11 April 2009 (UTC)[reply]

Name that UK bird! Orange chest, black head.

I live in the Midlands of the UK and I just saw a bird in the garden that I had never seen before. It had a black head and a vibrantly orange chest but with black tail feathers and darkish wings. It had a black beak which I couldn't tell the shape of (hardly distinguishable from the head, so I'm thinking small). It looked a lot like a parrot and was curling its head down in a way I'd call parrot-esque, size wise was smaller than a pigeon, much bigger than the robins and blue tits about. First impressions was of a small parrot, sadly no photos yet. Any ideas? MedicRoo (talk) 18:40, 10 April 2009 (UTC)[reply]

Turns out it was a bullfinch.MedicRoo (talk) 20:20, 10 April 2009 (UTC)[reply]

Early cyclotron-thing

Resolved

I can't seem to find a picture I know I've seen on Wikipedia of an early particle accelerator or isotope separator or something. It is roughly spherical, made of brass or copper, and looks a bit like the helmet at right. The photo has it sitting as a historical objet d'art in a courtyard at a place like CERN or Fermilab. I just can't seem to remember where. Anyone know? Thanks.

Is it possible that you're thinking of Henry Moore's Atomic Energy sculpture located at site where Enrico Fermi conducted the first self-sustaining nuclear chain reaction? A Quest For Knowledge (talk) 20:37, 10 April 2009 (UTC)[reply]

Nice try!, but no, it really was a bona fide scientific instrument that had been retired but not scrapped due to historical importance or its industrial beauty. --Sean 21:35, 10 April 2009 (UTC)[reply]

Wilson cloud chamber? They look sort of like that. Though not in the Wikipedia picture. --98.217.14.211 (talk) 23:29, 10 April 2009 (UTC)[reply]

A Van de Graaf generator? Or a Cockcroft-Walton voltage multiplier? Rmhermen (talk) 23:51, 10 April 2009 (UTC)[reply]

Got it, I think. See Microcosm (CERN), which has this image, a resonator from the Large Electron-Positron Collider. Mikenorton (talk) 10:47, 11 April 2009 (UTC)[reply]

YES! Thanks so much, that was driving me crazy! --Sean 13:47, 11 April 2009 (UTC)[reply]

Need WP:RS on a Common Misconception about Neutron Bombs

I'm currently working on our article List of common misconceptions. This article is/was horribly unsourced and I'm trying to add cites to some of the misconceptions. Although I've been able to find cites for all of the ones that I've worked on so far, I'm having difficulty regarding the one about neutron bombs.

Specifically, the article makes the following claim:

"*It is commonly believed ^{[by whom?]} that Neutron bombs are nuclear weapons whose blasts exclusively affect living tissue.^{[citation needed]} This is not true. There is still some heat and blast energy but at only a fraction of the intensity of a conventional thermonuclear warhead."

I believe that the claim that this is a popular misconception is essentially true: that people mistakenly believe that neutron bombs only kill people and leave all the buildings standing. But I can't seem to find a WP:RS that actually says such a thing.

The problem is compounded by the fact that the source needs to say that this is a common misconception (or words to that effect). A Quest For Knowledge (talk) 20:27, 10 April 2009 (UTC)[reply]

The trouble is that the misconception is somewhat backed up by the facts. As your article says "This is still some heat and blast energy but only at a fraction of the intensity..." - which means that providing you make an air burst at sufficient altitude that the heat and blast doesn't destroy buildings, it could well be that living beings are the only significant casualties - and the buildings remain intact. I have no clue to the degree to which that is true - but there is certainly room there for this not to be exactly a misconception. I mean, sure - if you do a ground-burst, it's going to level a lot of buildings and set fire to a bunch more - but it's not beyond the realms of possibility that it could be triggered such as to annihilate the populations and leave buildings and other infrastructure alone. SteveBaker (talk) 22:33, 10 April 2009 (UTC)[reply]

Well, it's not my article. I just started working on it a week or two ago. Anyway, the first part I think is the misconception "It is commonly believed [by whom?] that Neutron bombs are nuclear weapons whose blasts exclusively affect living tissue.". What follows is the correction: "This is not true. There is still some heat and blast energy but at only a fraction of the intensity of a conventional thermonuclear warhead.". To be honest, the second half may not be phrased the best. My understanding is that the blast is still larger than a conventional weapon, and I might rephrase it to say that. I think the point is that there is a false impression that that only people are killed and all building are left standing. But I see what you mean about if the blast is sufficiently high. If this item is factually incorrect, I can remove it from the article. A Quest For Knowledge (talk) 22:45, 10 April 2009 (UTC)[reply]

We have an article Neutron bomb in popular culture, which has many verifiable facts, such as a given quote in Repo Man. You could rephrase from the survey-requiring "it is commonly believed ..." to the easily sourced "it is commonly depicted in popular culture ...". --Sean 22:37, 10 April 2009 (UTC)[reply]

AQFK, while you are at it, may I also humbly suggest that the points given in the article be presented in a structured way to avoid confusion? For example, one of the points says "Snapping or cracking one's knuckles does not cause arthritis.[59]". Now there will be a confusion for the reader whether the statement is a myth (i.e. snapping the knuckles does cause arthritis) or whether the statement is a myth buster (i.e. snapping the knuckles does not cause arthritis). May be we can add the word Myth, state the myth and then explain why it is a myth ? - WikiCheng | Talk 05:55, 11 April 2009 (UTC)[reply]

Rolling hemispheres and moments of inertia

Here's a question that appeared on the math reference desk and didn't receive any responses. I wanted to know the myself and thought it might have more luck here. --Bowlhover (talk) 20:43, 10 April 2009 (UTC)[reply]

Hi there - I'm working through a bit of mechanics revision and have been looking at some of my uni past exam papers from a good few years back when the syllabus was different, so I'm not familiar with a lot of the material covered - it's not strictly relevant to my current course but I've found myself stuck on this question about hemispheres and it's bugging me, relevant or not. Could someone please give me a little help with how to progress? Thanks a lot.

i) Use the parallel axis theorem to calculate the moment of inertia of a uniform hemisphere of mass 'M' and radius 'a' about an axis through its centre of mass and parallel to the base (the centre of mass is located at a distance of 3a/8 from the flat face of the hemisphere).

Well the moment of inertia of the hemisphere about the axis which would be through the centre of mass of a full sphere is ${\frac {2ma^{2}}{5}}$ , as it is for a sphere, so by the parallel axes theorem, $I_{c.o.m}+M({\frac {3a}{8}})^{2}={\frac {2Ma^{2}}{5}}$ so $I_{c.o.m}=Ma^{2}({\frac {2}{5}}-{\frac {9}{64}})={\frac {83}{320}}Ma^{2}$ . Now for a start, 83/320 seems like about the ugliest moment of inertia coefficient I've ever seen, so I'm pretty sure I've gone wrong somewhere here - but where?

ii) The hemisphere initially rests on a rough horizontal plane with its base vertical. It is then released from rest and rolls on the plane without slipping. Let $\theta$ be the angle that the base makes with the horizontal at time t - express the instantaneous speed of the centre of mass in terms of b and the rate of change of $\theta$ , where b is the instantaneous distance from the centre of mass to the point of contact with the plane. Hence write down expressions for the potential and kinetic energy of the hemisphere and deduce that $({\frac {d\theta }{dt}})^{2}={\frac {15gcos\theta }{(28-15cos\theta )a}}$ .

Now I really have no idea what on earth to do on this one, and I can see that part (i) is probably relevant but it's not rotating around the centre of mass ('C') so I can only assume they want us to calculate another moment of inertia which is just plain annoying. The picture I have has that the midpoint of the 'base edge' (where the centre of mass of a full sphere would be - call this point 'P', say) is always directly above the point of contact of the sphere and the surface - call this 'B' say - I'm pretty sure this is correct because at the very least it's true at the start and the end of the motion. In that case, by the cosine rule for the triangle CPB, the length of side CB squared is $b^{2}=a^{2}+{\frac {9a^{2}}{64}}-2(a)({\frac {3a}{8}})cos(\theta )=a^{2}({\frac {73-48cos\theta }{64}})$ which again seems wrong. Even if that is the correct expression for $b^{2}$ , I'm not sure how to express the speed of the centre of mass in terms of $b$ and ${\dot {\theta }}$ , and will the kinetic energy expression include an ${\frac {I{\dot {\theta }}^{2}}{2}}$ or an ${\frac {mv^{2}}{2}}$ or both? Apologies for my cluelessness, as I said this is a fair bit off the syllabus I'm meant to know! Thanks a lot,

Otherlobby17 (talk) 01:18, 4 April 2009 (UTC)Otherlobby17[reply]

Despite the moments of self-doubt the calculations done so far are all correct. The calculation of the speed of the center of mass is actually quite simple. The semi-sphere is rolling without slipping, which means that the contact point is momentarily at rest and the center of mass is momentarily in a circular motion around that point.

v=b{\dot {\theta }}

. Now we apply energy conservation. The amount of potential energy being released is

\Delta V=Mghcos\theta \,

, where

h={\frac {3}{8}}a

is the distance between the center of mass and the flat surface. That energy released must be equal to the kinetic energy which is the sum of the rotational and translational kinetic energies

K={\frac {I{\dot {\theta }}^{2}}{2}}+{\frac {Mv^{2}}{2}}

. We have than

2Mghcos\theta =Mb^{2}{\dot {\theta }}^{2}+I_{cm}{\dot {\theta }}^{2}=Ma^{2}{\frac {73-48cos\theta }{64}}{\dot {\theta }}^{2}+{\frac {83}{320}}Ma^{2}{\dot {\theta }}^{2}=Ma^{2}{\dot {\theta }}^{2}{\frac {448-240cos\theta }{320}}=Ma^{2}{\dot {\theta }}^{2}{\frac {28-15cos\theta }{20}}

{\dot {\theta }}^{2}={\frac {40ghcos\theta }{a^{2}(28-15cos\theta )}}={\frac {40g({\frac {3}{8}}a)cos\theta }{a^{2}(28-15cos\theta )}}={\frac {15gcos\theta }{a(28-15cos\theta )}}

Dauto (talk) 04:27, 11 April 2009 (UTC)[reply]

April 11

Blowing out a candle

When you blow out a candle with your breath, what causes it to go out? Bubba73 (talk), 01:23, 11 April 2009 (UTC)[reply]

A flame is maintained by A) combustible material, B) sufficient oxygen, and C) sufficient temperature. For any flammable fuel, burning is an exothermic reaction; that is, it produces excess heat (that heat maintains the temperature necessary for more fuel to burn, continuing the process). When you blow on a candle, your breath is separating the heat of the flame from the combustible material. Without that heat the candle cannot continue to burn. The more heat that is generated by the fire, the harder it is to "blow out" (which is why you can't blow out a campfire, for instance). – 74 02:46, 11 April 2009 (UTC)[reply]

Thanks. Bubba73 (talk), 02:48, 11 April 2009 (UTC)[reply]

New born animals cute

Is there a reson why new some born animals are cute like puppys. Why are only some new born animals cute while some are not so cute such as birds. --Sivad4991 (talk) 01:24, 11 April 2009 (UTC)[reply]

Scientists have identified and researched a phenomenon known as "cute response" (see cuteness). Essentially, humans have an innate response to particular infant features: oversized head, large eyes, shorter limbs, rounder figure, less pronounced nose, etc.^[16] This response carries over to some other mammals (like puppies, kittens, and pandas) which share similar newborn traits^[17] (and some even theorize that common pets have evolved to retain infantile features in adulthood for maximum advantage from our cute response; see neoteny). – 74 02:28, 11 April 2009 (UTC)[reply]

It also conveniently explains why many larvae, lacking features that could be considered "juvenile" are always given such a hard time, whereas fish and crustacean larvae are considered by some as "cute", and their bodies reflect juvenile proportions. 124.154.253.25 (talk) 06:35, 11 April 2009 (UTC)[reply]

Are you talking about "the spectres or spirits of the dead", Lemurs or the larvae of animals (like tadpoles or caterpillars)? Nil Einne (talk) 12:30, 11 April 2009 (UTC)[reply]

Some new-born birds are cute (IMO) - some of the precocial ones, at least. On the other hand, the tiny, blind, bald youngsters remind me of premature foetuses. --Kurt Shaped Box (talk) 01:57, 12 April 2009 (UTC)[reply]

Physics of "Knowing"

I just caught the movie "Knowing" tonight and have two questions. First, what are the chances of a "super flare" (as described in the movie) being accurately predicted (or even occurring), and, second, if such a super flare were to occur, would it cause the kind of global annihilation as shown in the movie? —Preceding unsigned comment added by 216.154.22.157 (talk) 04:53, 11 April 2009 (UTC)[reply]

I haven't seen the movie, but big flares have caused some havoc on Earth. See, e.g. Solar storm of 1859. But no annihilation... yet! --98.217.14.211 (talk) 11:00, 11 April 2009 (UTC)[reply]

Bad movie alert! Imagine Reason (talk) 11:57, 11 April 2009 (UTC)[reply]

Thanks. Let me re-phrase my query: How probable is it that there could be a solar flare of such magnitude that the Earth as we know it would cease to exist? —Preceding unsigned comment added by 216.154.19.87 (talk) 17:13, 11 April 2009 (UTC)[reply]

Are you referring to the biosphere or the planet itself? If you mean the planet, IIRC, it's believed that the Earth will survive the sun becoming a red giant, so I'd say about zero. — DanielLC 18:01, 11 April 2009 (UTC)[reply]

The Earth is actually expected to plunge into the Sun, as depicted by computer models showing orbital fluctuations. However, the Earth is expected to become too hot for life in only about 500 million years. As for solar flares, a particularly massive one could leave the power grid damamged and 150 million North Americans in the dark. They're nowhere near large enough to destroy the Earth, but leaks have been found in the magnetic field that protects us from these flares, so this could be a problem. The Sun does periodicly undergo severe solar flares and Coronal mass ejections, and this sunspot cycle usually repeats every 11 years, with the next peak in activity arriving about 2012. The last solar maximum was pretty intense as well: 2001 saw a flare that ranked X22 on an intensity scale between 1 and 20 (this was even bigger than the flare that caused the 1859 "Carrington" event, but fortunately it wasn't pointed at Earth), 2003 saw a series of strong flares and CME's never before seen (one of them hit Comet NEAT as it approached the sun), and 2005 saw a flare that produced aurorae as far south as Florida. It's therefore possible to predict the approximate timing of flare activity (although 2006 - 2009 saw an unusual period of solar quiet), but your prediction may be off on the order of years. ~A H 1^(TCU) 18:26, 11 April 2009 (UTC)[reply]

I'd never heard that 500 million years number before. It would be sad to think that life is 88% finished. --Sean 01:00, 12 April 2009 (UTC)[reply]

rutherford model

Rutherford sent alpha and beta particles to a sheet and gold and most of the particles passed the sheet, how can we prove that most of the volume of an atom is empty? There may be a large distance between atoms and alpha particles are passing through them. How we can prove that these particles are passing through atom itself? Besides why we do not imagine that electrons are making nucleolus and protons are turning around them? —Preceding unsigned comment added by Logicman112 (talk • contribs) 11:25, 11 April 2009 (UTC)[reply]

I'm not sure I fully understand your question, but may I recommend that you read Geiger-Marsden experiment. —Cyclonenim | Chat 11:37, 11 April 2009 (UTC)[reply]

The Geiger–Marsden experiment involved alpha particles, not beta particles. Although Rutherford did not know about protons and neutrons in 1909, he did know a lot about the properties of the alpha particles used in the experiment - he knew their charge, their mass and their velocity. He understood that they were basically doubly ionised helium atoms He²⁺. It was not surprising that most of the alpha particles passed through the gold foil with little or no deflection - the plum pudding model of atomic structure predicted this. The surprise was that a small proportion of alpha particles were deflected through angles of 90 degrees or more, with no collision debris appearing on the far side of the gold foil. To explain this, Rutherford proposed the Rutherford model of atomic structure in which all of the positive charge and most of the mass of an atom is concentrated in a small region, which we now call the nucleus. Our article on Rutherford scattering shows how the size of the nucleus can be estimated. A nucleus that consisted only of electrons would have been too light to deflect the alpha particles. Gandalf61 (talk) 12:41, 11 April 2009 (UTC)[reply]

Prilosec as diet drug?

How effective would proton pump inhibitors be as a diet drug? I'm asking purely out of curiosity as I would rather gain than lose weight at this point. Imagine Reason (talk) 11:59, 11 April 2009 (UTC)[reply]

Legality of encryption

Our article Steganography states: "and may in themselves be incriminating in countries where encryption is illegal". However, I've been unable to find the legal status of encryption worldwide. In which countries is it illegal? --Taraborn (talk) 12:29, 11 April 2009 (UTC)[reply]

basically legal where there is free speech (seriously). no source sorry 79.122.103.33 (talk) 16:38, 11 April 2009 (UTC)[reply]

Too hungover to masturbate

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

TenOfAllTrades(talk) 14:34, 11 April 2009 (UTC)[reply]

The talk page discussion about whether this medical advice is here: Wikipedia_talk:Reference_desk#question_removed_as_medical_advice_request_.28hungover.29. StuRat (talk) 15:21, 11 April 2009 (UTC)[reply]

Identiy this water beetle

I saw this large water beetle in a pool beneath a waterfall at Chapada Diamantina in Bahia, Brazil on Christmas day, 2007. I've been very curious about what this critter could be for some time, but have just been sitting on this picture for over a year. Recently I read an article that mentioned Belostomatidae, and the possibility that I may have narrowly escaped an excruciating flesh-dissolving bug-bite has renewed my curiosity in this image. You can see a few more here. --Shaggorama (talk) 14:41, 11 April 2009 (UTC)[reply]

It certainly looks like a giant water bug, its similar in shape to some of the water scorpions but lacks the tube at the back. Mikenorton (talk) 15:13, 11 April 2009 (UTC)[reply]

Global warming, axial shift, sea level rise, seismic activity, and solar eclipses

Hi. First of all, the melting of ice sheets such as the West Antarctic and Greenland Ice Sheets are predicted to have an effect on the Earth's poles, moving them perhaps 500 metres every-which-way. This is also expected to have an effect on surface gravity in some regions, as well as the amount of light reflected from Earth, which could perhaps minutely affect the Moon's orbit on a negligible scale. Now, could all this conspire to ever-so-slightly drift the paths of future predicted total solar eclipses? For example, London, England, doesn't seem to have any predicted totality from total solar eclipses between now and 3000 CE, but this could be very different should eclipse paths shift (or if sea level rise floods the area, driving the city inland, if it remains intact).

Also, why is it that climate change experts always seem to refute any possible connection between global warming and seismic activity, past, present, or future (this isn't really an argument, just a basic question)? There are already sources linking increased seismic activity to global warming. I don't mean an increase in the observed number of global earthquakes or earthquake damage, which would probably be caused by better observational equipment, a higher population in earthquake-prone zones, or recent large disasters such as the 2004 Indian Ocean tsunami. What I mean is a regional increase in seismic activity over the span of several years. For example, a NASA press release about 5 years ago reported an increase in the the earthquakes around the Alaskan mountains, attributed to the melting of glaciers and permafrost, un-depressing the land (while subsiding it) over mountains near a seismic boundary. Here are some more examples of evidence and scenarios related to seismic activity (this isn't nessecarily from reliable sources, and some of it may involve speculation):

Volcanic flank collapses in the past, such as those at Mauna Kea in Hawaii, which triggered megatsunamis, have been linked to periods of warmer climate, higher rainfall (thus more erosion), and higher sea level.
The melting of methane clathrate deposits in the past have triggered subsea landslides, notably the Storegga slip, which caused tsunamis on the British Isles and Norway. If these landslides occur near a seismic boundary, it may be enough to trigger seismic activity.
Following the 2008 Sichuan earthquake, some people speculated that the Three Gorges Dam, which sits near an active seismic fault, may have been responsible for the quake. However, since this was largely a hypothesis made by anti-government sources, it is more of a conspiracy theory than anything. However, the point is that the melting of glaciers and sea level rise could create plenty of situations like this, where large amounts of water suddenly sit on a seismic fault, because ice jams and rock ahead of rapidly filling glacial lakes could allow them to form in mountainous areas, often where seismic faults lie.
West Antarctica has many active volanoes, particularly the one near the Pine Island Glacier, responsible for the largest eruption in Antarctica in the past 10,000 years. This is the area where scientists proposed could allow a destabilization of the West Antarctic Ice Sheet, which is largely anchored below sea level, if water encroaches into the region. Considering the seismically-stressing forces that would come with such a destabillization, which could happen in the span of only decades or centuries, sudden isostatic rebound would occur caused by a sudden lifting of pressure, many trillions of tons of seawater would flood these volcanicly-active basins within years, and cold water could contact sources of magma (this is what triggered the sonic boom and ensuing tsunami at Krakatoa). Since these forces are enough to shift the pole by a few hundred metres, it should be enough to trigger some level of seismic activity.
A sea level rise of about 25 metres could flood the Caspian Depression, which would increase the volume of the Caspian Sea by about 40% in about one year (by the way, is there an adequate formula for calculating how quickly water fills a depression?). Since this is a large area, and there are many neighbouring plate boundaries and mountainous regions, this could potentially trigger new seismic activity as well.
The Ethiopian volcano Erta Ale sits in a depression, surrounded completely by a basin below sea level. Seeing that sea water could quickly flow into this basin accompanying a sea level rise of about 15 metres, this might stress the active volcano, which sits on the active African Rift Valley.
Sudden pressure changes accompanying severe storms, such as the typhoon that struck the area during the 1923 Great Kanto earthquake, are hypothesised to stress seismic faults, due to the severe storm surge (a sudden increase in pressure) and low air pressure (a sudden decrease in pressure). Melting of glaciers near seismic areas, sea level rise in certain regions, severe rapid isostatic rebound, surface gravity fluctuations, and severe storms influenced by climatic change may be capable of this as well.
New York City is believed to be at risk from a magnitude 7 earthquake. Sea level rise could widen river and sea channels in the area, in fact a few metres could flood past Albany. This increases the risk of large storm surges, which again, may be capable of triggering an earthquake.

Now, after those exhausting scenarios, here's a related question. If the West Antarctic Ice sheet were lifted from the ground, also meaning if it melted but not considering the sea level rise associated, about how much sea level "drop" would occur worldwide as a result of this, when water floods into areas that are below sea level, notwithstanding the effects of isostatic rebound that are likely soon to follow? What about for the Caspian Depression, if the sea level rise required brings the area under water at that level, thus exacting a drop in global sea level, which would probably mean that, notwithstanding the effects of erosion, the sea levels could probably drop far enough that it would require more sea level rise to continue to flood the area? Also, when sea level rise turns coastal underground aquifers saline and this water encroaches inland, could this flood an inland low-lying depression from water seeping underneath, or does this depend heavily on the pourousness and permeability of the rock, and the extent of the bedrock? Thanks. ~A H 1^(TCU) 18:08, 11 April 2009 (UTC)[reply]

Probably too many "what if's" for a meaningful answer? (I note that our articles don't seem to agree with your description of Krakatoa (Plinian eruption). Rmhermen (talk) 18:31, 11 April 2009 (UTC)[reply]

April 12

Moment of Inertia of a Traingle

Hi. So I'm having a little trouble trying to find the formula of the moment of inertia of a triangle. I have the base width of the triangle (4.6 meters), the height (8.6 meters), the area (19.78 m^2) and the surface density (.101 kg/m^m). Now I know the moment of inertia = $I=\int r^{2}\,dm\,\!$ but I'm not exactly sure where to plug in what i have into that. My guess is something like $I=.101\int (r-x)^{2}\,dr\,\!$ but I'm not exactly sure. Anyone's help to point me in the right direction would be appreciated.

--RedStateV (talk) 03:36, 12 April 2009 (UTC)[reply]

@@ Line 457: / Line 457: @@
 = April 12 =
+== Moment of Inertia of a Traingle ==
+Hi. So I'm having a little trouble trying to find the formula of the moment of inertia of a triangle. I have the base width of the triangle (4.6 meters), the height (8.6 meters), the area (19.78 m^2) and the surface density (.101 kg/m^m). Now I know the moment of inertia = <math>I = \int r^2 \,dm\,\!</math> but I'm not exactly sure where to plug in what i have into that. My guess is something like <math>I = .101 \int (r-x)^2 \,dr\,\!</math> but I'm not exactly sure. Anyone's help to point me in the right direction would be appreciated.
+--[[User:RedStateV|RedStateV]] ([[User talk:RedStateV|talk]]) 03:36, 12 April 2009 (UTC)