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March 19

car

what brand car is in this vid http://www.youtube.com/watch?v=4vS4U1xXQwQ — Preceding unsigned comment added by Wdk789 (talk • contribs) 02:00, 19 March 2011 (UTC)

This is a video clip running for 3 minutes and 10 seconds. It shows a very un-funny prank in numerous fast-food driveways. The car is entirely irrelevant to the prank. You can't see enough of the car to determine its brand. I suggest no-one even bothers to download the video or watch it. Life is short enough as it is without wasting a few minutes on boring stuff like this. Dolphin (t) 04:25, 19 March 2011 (UTC)

It is pretty funny. At points it sounds like this. Bus stop (talk) 01:54, 20 March 2011 (UTC)

lights

how do they change the head lights in this http://img.ibtimes.com/www/data/images/full/2011/03/17/75371-dd.jpg — Preceding unsigned comment added by Wdk789 (talk • contribs) 04:26, 19 March 2011 (UTC)

This is just a link to a photograph of spent fuel rods at the bottom of a pool of water in a nuclear reactor. There is no car, or any other vehicle, visible in the photograph so there are no head lights. Don't bother. Instead, spend the time checking out the contributions from Wdk789. Dolphin (t) 04:31, 19 March 2011 (UTC)

Perhaps he meant to ask how they change the lights in the radioactive areas of a nuclear plant, and mistakenly called them "headlights" ? StuRat (talk) 17:22, 19 March 2011 (UTC)

yes— Preceding unsigned comment added by Wdk789 (talk • contribs) 22:06, 19 March 2011

The glow on that reactor, though, is Cherenkov Radiation and a natural effect in the air above energetic particles flying about. Whatever additional lights are used are probably fluorescent tubes energized also by the reactions themselves, thus not needing to be changed. Of course, the nature of such a reactor design is such that it's actually safe to walk around it with an open top. SamuelRiv (talk) 05:34, 20 March 2011 (UTC)

Assuming those are ordinary electric lights, I would change them by lowering the level of the water (they keep the water level higher than necessary as a safety margin). Then I would suspend someone in harness from a crane or hoist in the ceiling and have them change the light. Ariel. (talk) 00:38, 21 March 2011 (UTC)

Liver question

What is difference between compensatory hyperplasia and regenration of liver? —Preceding unsigned comment added by 210.2.181.244 (talk) 07:47, 19 March 2011 (UTC)

Does bicarb remove the acidity of acetic acid (apple cider vinegar)?

Can I just confirm that adding any amount of bicarbonate of soda would lower the acidity affects of vinegar (acetic acid)? The fact that bicarb is an 'amphoteric' (react as an acid as well as a base) doesn't clarify whether it would make vinegar more effective or less? 220.244.35.181 (talk) 09:43, 19 March 2011 (UTC)

It reduces the acidity of acids, because it acts like a base when in contact with acids. Grandiose (me, talk, contribs) 10:40, 19 March 2011 (UTC)

Thanks! you know what's also interesting and confusing, is that there is a formula for getting rid of mould/mildew in showers - and it instructs that you mix white vinegar with bicarb: the vinegar is to kill the mildew and the bicarb is to eliminate the odour of the vinegar - but how would that work if the two cancel eachother out???

220.244.35.181 (talk) 10:49, 19 March 2011 (UTC)

It confuses me too, when the ingredients are mixed, they no longer act as two substances with distinct properties. The new substance produced, is a solution of sodium acetate with completely different properties. Plasmic Physics (talk) 11:15, 19 March 2011 (UTC)

that's simplistic. vinegar + bicarbonate forms a buffer solution at some fixed pH (so long as there is not an overwhelming amount of either the vinegar or the bicarbonate.). This pH is still acidic enough to kill unprotected mildew. The free acid CH3COOH is what is smelling like vinegar (vinegar is volatile and evaporates). That's because it's at a considerably low pH (vinegar has around a pH of ~2.4) so there's a lot of free acid. A buffer solution of sodium acetate and acetic acid I believe, has a pH of around 4.76. That's still acidic enough to hinder growth, but not that acidic. Also, the acetate ions help sequester the free acid RCOOH molecules from evaporating. 199.111.169.216 (talk) 16:34, 19 March 2011 (UTC)

Just remember that mixing the two gives you a nice release of CO2, making it ooze bubbly foamy stuff. Fun thing to show your kids. SamuelRiv (talk) 05:36, 20 March 2011 (UTC)

• OP here. Thanks for the help. Then it's confirmed, I won't be mixing any bicarb with the vinegar because we want a lower pH level. Thanks 220.244.35.181 (talk)

What does the atmospheric pressure of CO2 have to be for the dominant equilibrium to be: carbonic acid + acetate <------ -----> acetic acid + bicarbonate? 199.111.185.182 (talk) 16:40, 20 March 2011 (UTC)

Identifying an actual triquetral bone

Triquetral is marked "D"

On File:RightHumanAnteriorDistalRadiusUlnaCarpals.jpg and File:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg, which bone is the triquetral? I've left an image note on the anterior image for what I think is the triquetral, but I can't be sure, and I don't think it's visible in the posterior image. Nyttend (talk) 12:00, 19 March 2011 (UTC)

According to the article triquetral bone, it is the triangular bone marked C, not D. See the summary notes here.. Cuddlyable3 (talk) 13:50, 19 March 2011 (UTC)

According to Gray's Anatomy here the small bone marked 'D' is the pisiform and the other bone, 'C', is called the triangular or os triquetrum. Richard Avery (talk) 14:46, 19 March 2011 (UTC)

So I marked the bone labelled D? I know that it's C — my problem is that I can't easily figure out which bones in the diagram correspond to which bones in the photograph. If I marked the wrong one, would you please remove the note and place it on the correct bone? Nyttend (talk) 17:43, 19 March 2011 (UTC)

Oh, I just realised that I gave the wrong caption to the image here. Sorry — that was a typo, and I meant to say "C" on the caption. Nyttend (talk) 17:55, 19 March 2011 (UTC)

Which is this?

Video. Is this a MiG-23 or a MiG-27? 1:16 in the video or so is probably the best image. These are very similar aircraft, so maybe we can't tell. SDY (talk) 13:53, 19 March 2011 (UTC)

Libyan air force#Current air force equipment says "On 19 March 2011, the rebels shot down one of their captured MiG-23BN over Benghazi", but only sites as a reference that same video, which doesn't explicitly make that identification. -- Finlay McWalter ☻ Talk 14:00, 19 March 2011 (UTC)

Agenzia Giornalistica Italia identifies it as a MiG-23 (but doesn't specify which type) here, but the Sydney Morning Herald says it was later identified as a Mirage here. -- Finlay McWalter ☻ Talk 14:20, 19 March 2011 (UTC)

Sky News also claims it's a MiG-23 here. -- Finlay McWalter ☻ Talk 14:25, 19 March 2011 (UTC)

It can't be a Mirage, the planform is completely wrong. SDY (talk) 14:37, 19 March 2011 (UTC)

Matter to energy

If matter is converted to energy, and the matter happens to be in a gravitational field, then what happens to the matter's gravitational potential energy? —Preceding unsigned comment added by 86.183.1.249 (talk) 14:36, 19 March 2011 (UTC)

See gravitational redshift. Icek (talk) 15:29, 19 March 2011 (UTC)

Matter is NOT converted to energy. Matter IS a form of energy. When matter is converted to a different form of energy its potential energy remains there because the new form of energy still possesses a relativistic mass given by the famous formula E=mc² identical to the mass that the matter had before. Dauto (talk) 16:07, 19 March 2011 (UTC)

Is this connected to the fact that an object weighs more when it is heated? The gravitational potential of the heat energy is manifested as extra weight? 86.160.211.135 (talk) 18:47, 19 March 2011 (UTC)

Yes, that's it. Any form of energy has a mass given by E=mc². Dauto (talk) 19:29, 19 March 2011 (UTC)

Thanks for your help. 86.160.211.135 (talk) 20:05, 19 March 2011 (UTC)

Aquatic minibeasts

Okay, this is a long shot. What minibeasts might I have seen in a sunny ditch in Oxfordshire? The ditch was calm and a sort of temporary (but recurring) pond in the middle of a field. It still had alive-looking grass at the bottom. There were a few minibeasts that looked like pale mites or ticks, gliding through the water, but the ones I'm most interested in were there in large numbers, and looked like small ants although I didn't see legs. They were reddish-brown and moved constantly in a jerking motion: their movement was made up of lots of little straight-line pushes, a bit like Brownian motion but with acceleration that looked like little repeated pushing glides. Perhaps they move by releasing something suddenly behind them?

I'm aware this may not be possible without a picture, but I appreciate any information. 212.183.128.107 (talk) 15:03, 19 March 2011 (UTC)

I'm not sure about jet-type propulsion, but at that size class*, a high density critter in an ephemeral pool is likely an aquatic insect larva. See a visual overview of shapes here [1]. Did they look at all like mosquito larvae? Some sort of Dipteran larvae would be my guess with such limited info. *I assume 'small ant' size is ~1-2mm. SemanticMantis (talk) 16:50, 19 March 2011 (UTC)

Another guess which fits with "moved constantly in a jerking motion" is Daphnia which are very common even in quite small pools in the UK. Country folk call them "water fleas". Mosquito larvae tend to wriggle and it may be too early in the year for them. Another slightly smaller relative is the Cyclops. They both have a little pair of arms with which they do a sort of butterfly stroke - hence the jerking action. The best thing is to fish some out in a jam jar next time you're passing and have a look with an ordinary magnifying glass. This page is a simple key to pond invertibrates; click on the drawing for more details. This page is more comprehensive, but not so easy-peasy. Alansplodge (talk) 19:50, 19 March 2011 (UTC)

Me again. Looking at the naturegrid.org.uk page linked above, it says that "Daphnia contain haemoglobin - which is also found in human blood. This substance can hold and process a lot of oxygen. It turns red when it contains oxygen." That fits with the reddish-brown colour that you reported. Alansplodge (talk) 20:16, 19 March 2011 (UTC)

Thanks (I'm the OP), this is all really good. I agree that a jamjar and magnifying glass would make this a lot easier: I might be able to try that in a couple of days. I was pretty sure they weren't mosquito larvae, partly because it seems too early, but also because I first went to look closer because of the sparkles on the water: I wanted to see if it was air bubbles or little creatures like mosquito larvae. And these weren't doing the tube-to-the-surface thing that mosquito larvae do (unless they don't always do that: I shall look it up). I didn't think they were water flea or triops/cyclops shape, although maybe the angle they are in the water makes them look different. 86.164.66.59 (talk) 23:25, 19 March 2011 (UTC)

Daphnia are roughly disc-shaped, so viewed from above they would look different to the linked photos which all show the side view. However it may well be something else; I'm an amateur at pond-dipping. Good hunting! Alansplodge (talk) 01:51, 20 March 2011 (UTC)

Ocular dominance vs. amblyopia

If one cannot read (discern letters) with his left eye when the right eye is closed, is this an ocular dominance or rather amblyopia?--89.76.224.253 (talk) 16:01, 19 March 2011 (UTC)

It isn't either one of those things. Ocular dominance and amblyopia are both conditions in which one eye dominates the other when both are open -- neither says anything about what happens when one eye is closed. See ocular dominance and amblyopia for more information. Looie496 (talk) 18:20, 19 March 2011 (UTC)

Um, let me correct that. Amblyopia is a condition in which one of the two eyes sees poorly in an absolute sense -- but there are many conditions other than amblyopia that can cause one of the two eyes to see poorly. Looie496 (talk) 20:08, 19 March 2011 (UTC)

I recently spent some time reading about various eye conditions. Lazy eye seems to present in a way that it can be observed by other people (check google for images). Eye dominance is natural preference of one eye over another (muck like beeing right or left handed). What you describe might as well be something else (say, a refraction error in left eye) ~~Xil (talk) 10:07, 20 March 2011 (UTC)

Identifying the contents of a 55-gallon drum by the torn remnants of its MSDS

During a recent binge of idiocy my friend decided 55-gallon drums would make awesome trash bins. Except he didn't want to buy them new, so he dumpster-dived a few. The several we already have work fine (as their MSDSes were intact and didn't show anything freaky)... but one of them is kind of worrying. This particular black plastic 55-gallon drum was discarded by a now-defunct steel and wire processing company and most of the attached MSDS was destroyed by the elements. From what we can read though it's kind of awful, so I really want to know what's on the rest of the MSDS. I know there are different categories of danger based on the wording of the sentence (i.e. "may be harmful if ingested" and "harmful if ingested" and "toxic if ingested" and "poisonous if ingested" denote totally different levels of toxicity). So can anyone get an idea of what this crap is (or give me tips as to doing the same) based on this meager information? (Words that have worn off replaced with #)

On the barrel itself was a stamped sequence of numbers "USA/R-1608/RL/03/10".

SKIN CONTACT
Remove contaminated clothing. Wash affected #### with soap and water for at least 15 minutes #### medical attention of irritation persists.
EYE CONTACT
Remove contact lenses. Hold eyelids apart and flush with plenty of water for at least 15 minutes. Seek immediate medical attention if irritation persists.
INHALATION
Remove victim to fresh air. Restore breathing if necessary. Seek medical attention if irritation persists.
INGESTION
Seek prompt medical attention. Do NOT induce vomiting. Never give anything by mouth to an unconscious person.
########
########
## be harmful if swallowed. May cause mild to severe eye irritation upon prolonged, repeated exposures. Prolonged or repeated exposure may cause skin ### defatting and irritation ranging from mild to severe. May cause mild to severe respiratory irritation with repeated, prolonged exposures.
See MATERIAL SAFETY DATA SHEET for additional health-related information.
OTHER PRECAUTIONS
Use all personal protective equipment. Observe good personal hygiene practices, such as washing after handling and before eating, drinking and/or smoking.
KEEP OUT OF REACH OF CHILDREN
##################
##################
appl##############
enter s###########
has enter#########
exte##############
WASTE ############
Uncontaminated ###
tim### Recyclin###
disposal. Foll####
H#################
Keep from freezing. Store######
area away from all ignition s##
incompatibles. Keep containe###
MSDS Rev No. 01 MSDS Date: 03/12/10

I'm thinking of just googling the longest intact segments or running them through a MSDS search engine, but anything else that works better would be a hell of a great help. ZigSaw 20:41, 19 March 2011 (UTC)

One hopes R-1608 might be a product number (no guarantees). But isn't there a company name on the barrel (not the wire company that bought it, but the manufacturer)? Wnt (talk) 21:23, 19 March 2011 (UTC)

Let's just hope he doesn't find the number 311-555-8674 stenciled on it. ;) Wnt (talk) 21:26, 19 March 2011 (UTC)

You've forgotten to put the thing canvcelling the small type. 92.24.178.214 (talk) 23:23, 19 March 2011 (UTC)

R-1608 is one of the names for an herbicide more commonly known as EPTC or eptam. It appears to have toxicity data similar to that on the label. Looie496 (talk) 23:26, 19 March 2011 (UTC)

The points listed above are on just about every MSDS ever made. I would suggest looking for a different drum. Or at least rinse it out and line the drum with a couple garbage bags to keep a barrier between your nice new garbage and whatever was originally in it. 50.92.121.76 (talk) 22:39, 20 March 2011 (UTC)

Humans from Africa

When humans spread out from Africa, were there already some human-like creatures (such as Neandertals and others) in the land they expanded into? Thanks 92.24.178.214 (talk) 23:20, 19 March 2011 (UTC)

The answer is yes. Just be careful to define what you mean by human. Neanderthals may also be considered human depending on your definition. Dauto (talk) 23:39, 19 March 2011 (UTC)

The article Early human migrations will get you started on this question, and you may find further relevant details by following links from it. You will also find a useful table of the different known Human/Homo species in the Homo article, and further details towards the end of Timeline of human evolution.

Briefly, when the only (known) now-surviving human subspecies Homo sapiens sapiens first spread beyond Africa (though many stayed there), there were likely still some closely related sub-species in Africa such as Homo sapiens idaltu, perhaps also some of the last Homo antecessor and/or Homo heidelbergensis whose earlier emigrants to Europe had evolved into Neanderthals, and possibly some surviving Homo ergaster (aka "African erectus") from whom H sapiens had evolved (also via H antecessor and heidelbergensis), and Homo rhodesiensis.

(Remember, when one species evolves "from" another, it often does so in one particular locality because of special conditions there, leaving populations of the first species still continuing to live elsewhere, from whom further species may subsequently evolve - there is not necessarily a strict line of succession and immediate replacement.)

Beyond Africa there were already: the species/subspecies Homo neanderthalensis/Homo sapiens neanderthalensis in the Levant and Europe (with whom H sapiens sapiens then interbred); Homo denisovan (or H sapiens denisovan?) in parts of Eurasia, (with whom some H sapiens sapiens also interbred); Homo erectus (divided into several localised sub-species) throughout Eurasia, Indonesia and possibly parts of Australasia (with whom H s s probably did not interbreed - though see Homo erectus soloensis - and whom we replaced), and Homo floresiensis (perhaps a descendant from erectus, perhaps from an Australopithecus species, perhaps something else - the jury is still out) in Flores and perhaps elsewhere.

There may well have been other localised Homo species and subspecies that we have not yet discovered. Several of the above-mentioned varieties of humans are known only from very few fossils, so future finds may well extend their currently confirmed time spans nearer to the present day. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 01:24, 20 March 2011 (UTC)

March 20

What would it take to invent a vacuum-operated toilet?

If we don't have enough time in the day to even answer the call of nature the normal way, could there be a vacuum toilet that sucks out all the bodily wastes so that we wouldn't have to spend as much effort pushing it out ourselves? How much faster could this process be if this was vacuum assisted? Would it do a better job than normal? Would it be able to suck out more waste than we can push out?

So how come there hasn't been a vacuum-operated toilet yet? --70.179.169.115 (talk) 02:33, 20 March 2011 (UTC)

Astronauts use something similar, but you don't want so much suction that it can do damage. A minimal vacuum, just to suck the stench out, might work. StuRat (talk) 02:40, 20 March 2011 (UTC)

Before anyone goes through the effort, can you show that it's even necessary? Who says that we don't have enough time in the day to go the normal way? Dismas|^(talk) 03:08, 20 March 2011 (UTC)

It wouldn't work as you expect. To avoid disgusting mental images, think of this scenario: You have a plastic bag full of liquid. It has a narrow rubber hose so the liquid can drip out. To get it out, you squeeze the bag. That is how it should work. To make it faster, you suck the liquid out. The result is that the rubber hose collapses. Sucking harder makes the rubber hose squeeze tight. Nothing come out. The solution is to shove a stiff straw up the rubber hose to keep it from collapsing. Then, you have no problem sucking the liquid out (that's how those juice bags that kids drink work - they use a hard straw, not a flimsy little tube). So, your vacuum would actual keep you from evacuating your bladder or bowels instead of making it faster. The solution would be a stiff tube shoved in one hole or the other before attaching the vacuum - which will likely take longer than just going to the bathroom. So, what do people do? That's why they make magazine racks for bathrooms. Some people have televisions in their bathroom. Whatever you need to do, find something that allows you to sit for a while. -- kainaw™ 04:16, 20 March 2011 (UTC)

Well then Kainaw, I guess I'll have to resort to a liquid-based "straw" called the Washlet. I wonder if that's what they have in the space stations. --70.179.169.115 (talk) 08:09, 20 March 2011 (UTC)

Read Packing for Mars by Mary Roach; she discusses this stuff in enjoyable detail. --jpgordon^{::==( o )} 04:56, 20 March 2011 (UTC)

Death of Abigail Taylor tells me that no one should ever attempt sucking his or her butt. If the issue is that you just don`t want to go to bathroom, you might try catheter (not sure if it would work for moving bowels though) ~~Xil (talk) 10:48, 20 March 2011 (UTC)

If you are concerned about the time and effort involved in voiding waste, those are both related to diet, notably dietary fiber intake. SemanticMantis (talk) 14:22, 20 March 2011 (UTC)

I agree, if you have this problem, then its a sign that you should be eating more vegetables fruit and wholemeal grains. 92.15.21.23 (talk) 23:08, 20 March 2011 (UTC)

I think they already exist, front side anyway. Fighter pilots like these http://www.bbc.co.uk/news/uk-12798613 have white tubes as part of their jumpsuit. On an eight-hour trip they are going to need one. Perhaps they are required to have an enema before leaving too. 92.28.241.202 (talk) 15:52, 20 March 2011 (UTC)

But note that any vacuum used in such suits is low, only sufficient to remove the waste once voided, not to actually pull it out of the body. StuRat (talk) 19:23, 20 March 2011 (UTC)

Likewise for the ones astronauts use. The vacuums in "space toilets" just replace gravity, they don't replace the body's own forces. --Tango (talk) 21:35, 20 March 2011 (UTC)

How do Tomahawk missiles get to the target without getting shot down?

The Tomahawk cruse missile was used in several recent conflicts against countries with late Soviet air defense systems. They apparently reached their targets without interference, even before radar, antiaircraft defense, and fighter jets were incapacitated. The Tomahawk is a jet powered drone rather than a ballistic missile or rocket. The WW2 V1 flying bomb flew along at 400 mph, and WW propeller fighters could sometimes shoot them down, even with the primitive radar of the time. The Tomahawk only flies at 550 mph, comparable to a commercial airliner, and a fraction of the speed of even the old Mig and Mirage fighters operated by such countries as Iraq and Libya. Flying at low level to avoid radar was a common practice even in WW2, and did not really protect bombers from detection and damage. The ability to fly at 100 feet through canyons or whatever would not help while they are still out over the Mediterranean, where fighters might be deployed as a defense. Do second rate air defenses like Libya rely on ground based radar, and have nothing comparable to Awacs to "look down" and detect the Tomahawk in tome to fire a ground to air or air to air missile at one? Do the best Libyan fighter planes have "look down, shoot down" systems? Would a first rate world power be able to detect and shoot down Tomahawk quality missiles? This report from the Gulf War claims that only 60% of the Tomahawks actually hit their targets. Were some of the "misses" actually shootdowns? Edison (talk) 03:12, 20 March 2011 (UTC)

They are sometimes shot down. This PBS page says that as many as 6 were shot down in the Gulf War (out of 297 fired). It also lists counts for many other reasons they didn't reach the target. The point of the Tomahawk is that it is cheap and dependable (and what they blow up costs a lot more than a few Tomahawk missiles). -- kainaw™ 04:10, 20 March 2011 (UTC)

Cheap and dependable? The things cost $569,000 each in 1999 dollars,[2] which for a single-use weapon makes "cheap" a stretch. And according to the source cited by Edison, more than 40% of the time Tomahawks don't hit their intended target (often blowing up innocent civilians instead), which makes "dependable" a stretch. Red Act (talk) 09:39, 20 March 2011 (UTC)

Cheap depends on context. If the alternative is even a 1% chance that your billion dollar bomber is shot down, then a cruise missile would look cheap. Dragons flight (talk) 11:12, 20 March 2011 (UTC)

Is that really how much one of those missiles cost? I would have guessed a much higher price in the range of several million dollars. I think that's a relatively cheap price tag. Dauto (talk) 14:21, 20 March 2011 (UTC)

I think you've identified some of the deficiencies in third rate militaries. Another big one is the lack of communication between systems. You need the radar systems (ground, sea, air, and satellite), to all be hooked to each other, so they can identify a "bogey", track it, and fire a missile at it when it comes into range. Even if you have all the components, if they aren't connected properly, it's just about useless. StuRat (talk) 08:37, 20 March 2011 (UTC)

News media sometimes give the impression that when a destroyer or sub fires one of these things at a country, the target is doomed, but I still haven't seen arguments as to whether a country such as India, Pakistan, or the UK or US, for that matter could spot and intercept one or more fired, say from a submarine a hundred km offshore. If they are following a canyon or flying between hill, a few might be expected to hit those geographic features or even powerlines, and skimming treetops and wavetops was certainly a WW2 tactic. Radar at 30,000 feet looking down should spot it better than ground based radar, and jet fighters for the past several decades have flown much faster than these devices. If everything works right, the GPS should let the launching country put 1000 pounds of high explosive close enough to a target to blow it up, at about a million dollars per explosion, but I wonder if it has a positional uncertainty in tens or hundreds of meters, making it less effective against hardened targets than laser guided bombs, which (at least in selected footage from the attacks on Iraq) could be flown right in a window. They tend to use about 5 Tomahawks per target. Edison (talk) 20:13, 20 March 2011 (UTC)

Then there's the additional problem that the Israelis had when using the US-built Patriot missile, during the Gulf War, to shoot down Iraqi SCUDs. The SCUDs were inaccurate, and carried minimal warheads, meaning they weren't likely to create much damage when they hit. Shooting them down meant that both the remnants of the SCUD and the Patriot would then fall, frequently in a populated region, causing as much damage as the intact SCUD would have. StuRat (talk) 20:50, 20 March 2011 (UTC)

There is a significant difference in the consequences of shooting down a low flying cruise missile and that of shooting down a ballistic missile during its terminal phase. -- 119.31.121.89 (talk) 23:02, 20 March 2011 (UTC)

A reasonable proportion of them are shot down, equally a proportion of them crash or miss. There are percentages out there for the various elements of that but you can track them down yourself. The real success figures are classified.

The targeting process accounts for the likelihood of losing weapons and enough are launched to assure a sufficiently high number reach the target to deliver an effect.

ALR (talk) 10:43, 21 March 2011 (UTC)

Knowing where the enemy radar and missile sites are and their performance parameters allows a route to be planned that avoids as many of these defences as possible. Flying very low and using terrain masking also helps. A Tomahawk flying at or below 100 feet and 500+ mph will only be in the line of sight of someone on the ground for a matter of seconds - rendering manual weapons such as MANPADS or anti-aircraft guns fairly ineffective. Roger (talk) 14:42, 21 March 2011 (UTC)

A country which expected an attack, like Libya, could be expected to deploy fighters at high altitude near the coast, or AWACS equivalent if they had such. Libya has Mig 21, Mig 23, and Mirage F1 fighters with service ceilings above 60,000 ft and speeds over Mach 2.1, compared to the Tomahawk's 550 mph (mach 0.7) speed. Did those or other Libyan aircraft have the ability to see and intercept Tomahawks better than the "man on the ground" defense discussed above? What defense would, say, India, Pakistan, the UK, the US, China, or Russia use against cruise missile attack, that was not available to Iraq? Would world powers rely on satellites to see and track cruise missiles? Edison (talk) 20:29, 22 March 2011 (UTC)

See Look-down/shoot-down - it describes the ability some modern combat aircraft have to firstly detect a low flying target and distinguish it from "ground clutter" and secondly the ability to effectively engage such a target. Roger (talk) 20:51, 22 March 2011 (UTC)

Not a conspiracy theory question but a true scientific question

Was reading about the conspiracy theories floating around about the Earthquake and Tsunami in Japan. This is not a political or a conspiracy theory question, neither is it in any way intended to insult the suffering people now. I would like to know, is it possible( does technology exist) to artificially create earthquakes at an intended site and plan a tsunami? Whats the science behind this, how does this work?--Fragrantforever 05:13, 20 March 2011 (UTC) — Preceding unsigned comment added by Fragrantforever (talk • contribs)

No, it is not possible for mankind to create earthquakes or tsunamis. The technology does not exist. The technology does exist to pinpoint the epicentre of any earthquake, and it is now known that earthquakes occur many kilometres below the Earth's surface. This is a depth at which mankind has never had any influence. Also, the energy involved in an earthquake is truly immense. It makes manmade sources of energy look miniscule.

Psychology is the science of behavior. This science does exist. It is known that when people are deeply distressed they display a range of emotions (anger etc) not normally seen in people who are free from distress. Some of these emotions are demonstrably irrational, and can be of extreme intensity. One of the characteristics of anger is the ability to display antipathy towards another person, or other people. When people are angry they often display a readiness to accept suggestions and rumors about how another person has, or other people have, deliberately brought about the event that caused the deep distress in the first place. For example, during a war people have displayed a naive readiness to accept suggestions and rumors that the enemy is extremely bad and wants to cause extreme suffering and hardship. After the war, these suggestions and rumors have usually been found to have no foundation. Similarly, in the aftermath of an accident the victims often display a naive readiness to target a person or group of people, and to believe that the accident was either deliberate or solely due to the criminal negligence of this person or group of people.

With this in mind, it is to be expected in the aftermath of the truly tragic earthquake, tsunami and nuclear radiation problems in Japan that conspiracy theories will quickly take root and circulate rapidly. Some of the victims of these tragedies will derive a little comfort from focussing on the idea that their tribulations were actually designed and caused by one or more very bad people. A conspiracy theory that the earthquake and tsunami were deliberately caused by human action is entirely consistent with some elements of our understanding of human psychology. Dolphin (t) 05:38, 20 March 2011 (UTC)

It appears to be possible to induce very small earthquakes at a site by using injection wellbores to inject fluids. It can be a problem in oil and gas field development amongst other things. That's about it. Getting a fault to move by several metres over hundreds of kilometres of its length is a bit out of our league although I suppose it's theoretically possible in the same sense that dropping a copy of Yilmaz's Seismic Data Processing book out of a window in the middle of a city could, in prinicpal at least, make all of the buildings fall down if you were really very exceptionally unlucky... Sean.hoyland - talk 06:38, 20 March 2011 (UTC)

An explosion can cause seismic wave and water waves, which probably is the reasoning behind conspiracy theories. Not sure, though, if explosion can mimic devastation of earthquake and tsunami ~~Xil (talk) 10:59, 20 March 2011 (UTC)

The closest we can get to an artificial earthquake is to detonate a nuclear bomb underground, even this is of many orders of magnitude weaker than the earthquake that did happen in Japan. Besides, it's not something you can prepare and execute without drawing a lot of attention.

Some kind of "Tesla-earthquake-machine" present in some cheap science fiction or video games is completely absurd. The Earth is not of uniform density to allow waves to resonate enough, and even if such thing would be possible, it's utter nonsense to be the cause of the current events: such a thing would need a lot of resources, a lot of scientists working on it, which needs a huge infrastructure, a lot of people who support this infrastructure, then the whole international scientific community, all current ad future university professors and students who would find out what caused it, and soon we get to a point where millions of people would need to be involved in such a conspiracy all over the world, from every country. For such a conspiracy to remain a secret is completely implausible, even if the technology required for it would be possible, which I highly doubt. The problem with most conspiracy theorists is, that if what they believe has a 0.001% chance of being true, they regard it as proof of it being true.

Another "possibility" would be to deliberately not stop the reactor in time, but as in the above discussion, it would need millions upon millions of people from all over the world to be involved, so it's stupid to even consider it as a possibility.

Conspiracies can and do happen in the world, but they are mostly in the range of "bribe a politician to buy a property cheaper", or "manipulate the media to get a slightly better image of your company or ideology", or "steal some money by misusing legislative loopholes". To invent some completely new technology, or manipulate the currently existing highest technology, and hope no one will find out, is complete nonsense. --87.169.11.121 (talk) 15:51, 20 March 2011 (UTC)

A great deal of effort has been made to distinguish between earthquakes and underground explosions as part of monitoring the Test Ban Treaty using seismometers. Basically the computed focal mechanism shows whether the event involved movement on fault plane (producing the classic 'beachball plot') or was the result of an explosion (or in some cases an implosion such as in the collapse of old mine workings) where the plot is uniformly compressional (or tensional in the other case). Mikenorton (talk) 18:12, 20 March 2011 (UTC)

One of the top results of a Google search claims that the nuclear accident was much bigger than we believe it to be, and happened before the earthquake, killing many thousands, and irradiating even more. The whole tsunami was than artificially created as a cover-up, just to wash away the bodies, and to add to the realism, some agents were later planted as "survivors" to be rescued. The proof: so few bodies have been found, because the water washed away most of them.

The problem is, that there is no known technology to cause an earthquake this big, so the conspirators either managed to create, deploy and use it in a matter of hours, or they invested those horrible amounts of resources to build such an installation in the past, on the off chance that a nuclear meltdown might happen and than they could use that device to cover it up, while not using such groundbreaking new technology for anything else. --87.169.11.121 (talk) 18:54, 20 March 2011 (UTC)

That is an amazingly silly conspiracy theory. --Mr.98 (talk) 22:05, 20 March 2011 (UTC)

See: tautology. ;) --Tango (talk) 00:44, 21 March 2011 (UTC)

The energy of the recent earthquake in Japan was about 3x10²² joules. The largest nuclear bomb (and nuclear bombs are the closest we've ever got to making our own earthquakes) ever tested had an energy of about 2x10¹⁷ joules. That's more than 10,000 times smaller. There is no way we could create our own earthquake on that scale. I guess it might be possible to trigger an earthquake that would have happened sooner or later anyway. There have been proposals to try and do that before too much energy builds up so we can trigger a small, harmless earthquake instead of the very large earthquake we would get instead. However, no-one has come close to inventing a way to actually do that. --Tango (talk) 21:51, 20 March 2011 (UTC)

Thanks for all the answers. The article I was reading mentioned something about HAARP Project in Alaska being behind the quake and tsunami. When I read the wikipedia page on HAARP i ended up more confused. As a secondary question to my initial question - AGREED ALL THIS IS BASELESS ASSUMPTION AND CONSPIRACY- where does HAARP fit into this? And let me remind everyone I dont beleive in these theories I was asking these questions for better understanding of the scientific issues behind this. Even when I posed my initial question, there was not an iota of doubt in me about all this being baseless theories but the idea of this reference desk is to spread the correct and valuable info and I decided to ask this so the informed would answer the less informed. thanks again. — Preceding unsigned comment added by Fragrantforever (talk • contribs) 06:30, 21 March 2011 (UTC)

HAARP fits in because it's a common element of conspiracy theories. --Carnildo (talk) 01:46, 22 March 2011 (UTC)

global warming

one big argument for nuclear power is it is better than coal for greenhouse gasses that cause "global warming," but what about all the excess "heat" that nuclear power releases plus the warming of the cool liquid used to keep the core cool? Isn't that contributing to global warming by definition, or has that already been considered in the comparison?98.221.254.154 (talk) 05:27, 20 March 2011 (UTC)

Nuclear fission does produce heat, just as coal does, but the concern about global warming comes from the carbon dioxide produced, not the initial heat produced. Carbon dioxide keeps sunlight from escaping Earth's atmosphere, reflecting it back toward the Earth's surface. So when you release CO2 into the air, it contributes to global warming via sunlight for as long as it is there. Nuclear fission does not produce CO2, so it doesn't really contribute to global warming.Aaron (talk) 05:51, 20 March 2011 (UTC)

Aaron's last sentence makes more sense as Nuclear fission does not produce CO2, so it doesn't really contribute to the Greenhouse effect. Greenhouse effect is retardation of the escape of heat from the Earth. Nuclear fission produces heat so it contributes to warming, but it doesn't produce CO2 so it doesn't contribute to the greenhouse effect. Dolphin (t) 07:03, 20 March 2011 (UTC)

Is there some way to relate the global warming effects of greenhouse gas emission to that of heat production? That is, how many joules of heat would I have to add to the atmosphere to bring about an equivalent warming to that caused by the release of one ton of CO2? -- 119.31.126.66 (talk) 08:19, 20 March 2011 (UTC)

Total global energy consumption is about 15 terawatts. The man-made effect of accumulated greenhouse gases is about 820 terawatts. So the man-made greenhouse effect is about 50 times the direct heating effect. Also, because greenhouse gases accumulate and have a long residence time in the atmosphere, that ratio is likely to increase over time. Dragons flight (talk) 08:42, 20 March 2011 (UTC)

Also any direct heating increases the amount of infrared radiation emitted by the earth's surface which has a cooling effect which substantially cancels the direct heating. That's why any direct heating is essentially negligible. Dauto (talk) 14:07, 20 March 2011 (UTC)

(It should be noted, of course, that while the act of fission releases no greenhouse gases, the full fuel cycle is not carbon neutral. It's just tremendously better, per megawatt of energy produced, than fossil fuels. It produces about .5-4% the CO₂ emissions as coal.[3]) --Mr.98 (talk) 15:34, 20 March 2011 (UTC)

May I suggest that the IAEA is not a particularly non-partisan source, and that any paper that starts with "the Uranium Institute (UI) decided to examine these claims and to attempt to refute them in more detail" is dubious as a scientific source. --Stephan Schulz (talk) 15:52, 20 March 2011 (UTC)

IAEA is a global independent organisation that reports to the UN. It's as unbiased as it gets. --85.77.43.229 (talk) 16:20, 20 March 2011 (UTC)

The numbers they cite look fairly legit to me. If you have better numbers, have at it. The real bait and switch here is obviously comparing it to coal and coal only — it would be more useful to compare it to things other than the dirtiest form of energy production we have. However I find it completely plausible that nuclear does pretty good when stacked up against coal when measured in terms of CO₂ emissions — or practically anything else. Coal is bad news. --Mr.98 (talk) 17:25, 20 March 2011 (UTC)

I don't think anybody needs to actually read that paper to realize that nuclear power produces much less Co2 than coal. Dauto (talk) 18:03, 20 March 2011 (UTC)

But why is the average temperature of the atmosphere the gauge for this phenomenon, when you say it is about the CO2 level? why wouldn't a gauge be CO2 PPM, and call it global smogging? —Preceding unsigned comment added by 98.221.254.154 (talk) 03:24, 22 March 2011 (UTC)

Expression for Thrust and Power coefficients

Hey, can anyone tell me the expression for Thrust Coefficient and Power Coefficient for a propeller in terms of Re, Mach Number and J ? Yes Michael? •^Talk 10:45, 20 March 2011 (UTC)

$T=C_{T}\rho n^{2}d^{4}$

$P=C_{P}\rho n^{3}d^{5}$

The relationship between these two coefficients and advance ratio J is shown graphically. I am looking at Chapter XI of Theory of Flight by Richard von Mises (1959), Dover Publications. This is now a very old book and I'm sure this information is available in all modern books on practical aerodynamics. Dolphin (t) 11:03, 20 March 2011 (UTC)

In Aerodynamics by L.J. Clancy (1975), Pitman Publishing Ltd, Section 17.3, there is also a definition of the Torque Coefficient, C_Q:

$Q=C_{Q}\rho n^{2}d^{5}$

Dolphin (t) 11:14, 20 March 2011 (UTC)

Well, I was looking for an expression for $C_{T}andC_{P}$ itself. Also, if there is an expression for Thrust by Torque, can you let me know? Yes Michael? •^Talk 11:32, 20 March 2011 (UTC)

These three coefficients vary with advance ratio in a way that is unique for any given design of propeller. There is not a mathematical relationship between coefficient and advance ratio, and the relationships must be determined empirically (ie by experiment) in the same way that the lift coefficient of a particular airfoil section varies with angle of attack and must be determined empirically. Firstly, determine exactly which propeller you want to consider, then go looking for three diagrams which show the relationship between advance ratio and each of the three coefficients for this propeller. Such diagrams will be available for a range of advance ratios from zero up to some maximum value, just as the lift coefficient of an airfoil can be shown on a diagram for a range of angles of attack from zero (or even negative) up to the stalling angle and a bit beyond.

Propeller manufacturers are likely to be reluctant to supply this information about their products, but all advanced text books about propellers should contain this information for at least one design of propeller. Dolphin (t) 21:47, 20 March 2011 (UTC)

Have a look at Figure 2 in THIS web article. Dolphin (t) 03:43, 21 March 2011 (UTC)

Flat roof vs. sloped roof

Where is each of the options necessary? Can you have a flat roof in places where it snows?

Snow ifself is not an absolute showstopper. If only the snow melts in the summer, all you need to do is make the roof construction strong enough to carry the weight of one winter's worth of snowfall.

Liquid water is much more of a problem. Even slight deviations from perfect flatness will make rainwater (or meltwater) stand in shallow pools on the roof instead of running off, and it's hard to construct a roof surface that is watertight enough not to be damaged by this in the long run -- especially if temperatures reach freezing in the winter.

Anecdotally, flat roofs were popular in Denmark abound 1970, but most of them have since been overbuilt with peaked roofs due to recurring water damage. –Henning Makholm (talk) 15:06, 20 March 2011 (UTC)

OR: We have a flat roof in southern Ontario (Canada) where we get a lot of winter snow and a lot of days below freezing. Parts of the tar-and-gravel roof are 30 years old and parts only about 5 years old. We had one problem with a leak along one seam when storms came driving out of the east. It was repaired with an overlay of tar. Aside from that, we are warm and dry. The norm, however, is a pitched roof in such climates. Bielle (talk) 15:16, 20 March 2011 (UTC) P.S. Almost all commercial buildings of whatever floor area or height have flat roofs, and it is a rare one (though it does happen) that collapses under a snow load or leaks. Bielle (talk) 15:24, 20 March 2011 (UTC)

One factor seems to be the width of the building (by width I mean the direction in which the roof would have an elevation difference, if sloped, which is usually the narrowest dimesnion). The wider the roof, the higher it has to be, if sloped, so snow will tumble off. This means the material required varies roughly with the square (width×height) of the width. (It just varies linearly with the length, as expected.) So, if a building is 10x as wide, a sloped roof would take 100x as much material, cost 100x as much, etc. This quickly makes sloped roofs impractical for large buildings (an exception being perhaps the pyramids, where the roof and the building are one in the same ?). StuRat (talk) 19:16, 20 March 2011 (UTC)

As StuRat says, for a building of significant width, say more than 80 feet (24 m), one finds that the volume of structure for an appreciable slope becomes expensive. Multiple adjoining sloped roofs have issues with snow and water retention in the valleys that tend to discourage the use of that configuration. Simple sloped roofs are in general less vulnerable to leakage, since water doesn't linger. However, nobody nowadays designs a "flat" roof - there's always a modest slope to encourage drainage, although it may not be obvious on casual examination. Acroterion (talk) 22:09, 20 March 2011 (UTC)

In addition to the roof installation being more expensive, having a sloped roof on a large building would cost more to heat/insulate/etc. If you have a sloped roof, the heat is going to want to accumulate in the peak of the roof. That's not where the people are in a large building. And if you have a ceiling with attic, then you have to insulate the floor of the attic as well. Dismas|^(talk) 07:15, 21 March 2011 (UTC)

Flat roofs are not actually flat normally. It may only be a 1 in 200 slope or even less for a hard concrete roof where it isn't going to sag and form ponds but a slope is put in so any water runs off. Dmcq (talk) 16:24, 21 March 2011 (UTC)

One reason for at least a minimal slope is to avoid cumulative deflection under ponding, where water accumulates in an uneven section, the roof sags, more weight, more sagging, more water ... problem. Acroterion (talk) 21:03, 22 March 2011 (UTC)

Birdsong, UK

Yesterday in the suburbs and the countryside of south-eastern England I heard a lot of bird calls similar to this: Low-High-Low-High-Low-High-Low-High. Different birds sang between four and nine notes, all done quickly and without any pause in between the notes. The notes sounded more like something being plucked or twanged rather than whistled.

Is this sufficient to identify a particular species, or are there several species that sound similar? Is there anything like a Flora for birdsong? Thanks 92.28.241.202 (talk) 16:08, 20 March 2011 (UTC)

Basically this is the call of the Tit species. Great Tits sound like "teacher, teacher". The smaller tits call higher and quicker. --TammyMoet (talk) 16:57, 20 March 2011 (UTC)

Thanks, the song description matched. I did not realise there were so many of them. Perhaps they have been eating the bees. Does anyone know which are the commonest tit species in SE England? 92.28.241.202 (talk) 17:05, 20 March 2011 (UTC)

I suspect the blue tit is the commonest in SE England, but populations can fluctuate wildly from year to year. By the way, there are a number of websites where you can check out bird songs. This is one.--Shantavira|^{feed me} 18:01, 20 March 2011 (UTC)

From that wonderful link of Shantavira's, it must have been a great tit. 92.28.241.202 (talk) 19:35, 20 March 2011 (UTC)

Why do old AA batteries appear to sweat?

I've often found that old batteries in transistor radios etc are often covered in tiny drops of clear fluid, like sweat. The batteries that I've just looked at are metal-covered alkali batteries, so the "sweat" may be simply condensation. But very old zinc-carbon batteries often appear to have moisture underneath their plastic sleeve.

Why do batteries appear to sweat? Thanks 92.28.241.202 (talk) 16:57, 20 March 2011 (UTC)

Probably because they build up deposits of some sort of salt, which draws moisture out of the air, especially if you live in a very humid place such as Great Britain. Looie496 (talk) 17:42, 20 March 2011 (UTC)

Thanks, but GB is not a "very humid place" as our American chums seem to believe. Fogs are infrequent or rare. 92.28.241.202 (talk) 18:23, 20 March 2011 (UTC)

Oh please. I live in Britain, and it is indeed a damp, humid place most of the time. It has lower precipitation rates than many places in the USA, but it spreads them out over many days so we get days of mist, drizzle and, yes, fog. Fogs are not infrequent, especially in the cooler part of the year in the early morning and evening. We get river-mist here most mornings. How are our houses traditionally built? With sloping roofs that protrude past the walls, and with gutters when people can afford them. Because of all the rain. Recent improvements? Cavity walls anywhere even slightly exposed, because of all the rain and drizzle that gets driven against the walls by the wind. We have damp coursing as standard, and basements are rare. Mould and damp are common in certain parts of houses, because we live in a damp country. It is humid here most of the time: it is considered noteworthy when it is warm and dry, and people get over-excited.

This is why we were good at growing corn for the Romans. This is why we did so well at wool manufacture. This is probably why your batteries behave this way. Unless you live somewhere with a specially dry microclimate? 86.164.66.59 (talk) 19:42, 20 March 2011 (UTC)

Your experience is very different from mine - where are you? What you describe sounds like an extreme exaggeration. (I detect the Northern/Midlands mantra of "We're miserable, and it's all your (comfy southerners) fault!") You must be living in one the wettest parts of the country, somewhere like Manchester or the Lake District, or Scotland. In London its about 20 inches of precipitation a year. Its hardly a rain forest or the kind of place where they have monsoons - they are "very humid places", and has less rain that most parts of europe or the western side of the US. Corn needs a dry climate to ripen by the way - as far as I understand it will not grow in Scotland, hence the oats. Wool thread manufacture was purposedly done in a damp rainy part of the country. You forgot to mention the mushrooms growing out of the carpet, lol. 92.28.241.202 (talk) 20:05, 20 March 2011 (UTC)

This image of unclear provenance seems to support the claim that London is a humid place. It's true that London is not very foggy. According to Wikipedia, London fog was pea soup fog, which is actually smog, and disappeared with the end of the coal-burning era. -- BenRG (talk) 20:44, 20 March 2011 (UTC)

I agree that in mid-winter it may be more humid than it is in most parts of North America, the reason being because in England its above freezing most of the time, and so the water vapour in the air does not freeze into snow etc. 92.15.21.23 (talk) 22:20, 20 March 2011 (UTC)

That humidity scale is grossly exaggerated. Where I am now, the humidity is only 42%, which is fairly typical. Its 42% indoors: outdoors it would be less. "Mould and damp are common in certain parts of houses" says our friend above - rubbish! Only if you are living in a cave or a slum. According to that image, a "wet day" is a day with more than 0.1mm of precipitation - you would have great difficulty measuring a tenth of a millimetre. I think that image is a fraud, as it also says that the hottest temperature is only about 60 degrees farehnheit in the summer ...... hey, is this London, Canada? Very funny. 92.15.21.23 (talk) 21:49, 20 March 2011 (UTC)

Who in Britian can't afford gutters? They are just a few bits of plastic... --Tango (talk) 22:03, 20 March 2011 (UTC)

Britons are not pieces of plastic. Their Rain gutters are constructed from materials such as cast iron, lead, zinc, galvanised steel, painted steel, copper, painted aluminium, require an outflow channel leading away from the building at ground level, need leaves to be cleared in case of blockage, and occasionally need repair e.g. after loading by snow or leaves. None of this comes free. Cuddlyable3 (talk) 09:44, 21 March 2011 (UTC)

If we didnt have gutters we'd be living in a desert. And even primitive houses in deserts have rudimentary gutters. The picture linked to above was taken in Australia. 92.15.25.108 (talk) 11:27, 21 March 2011 (UTC)

The UK has a wide range of annual rainfall (from about 15 inches to more than 200 inches). In an area such as the one where I live, with up to 100 inches a year, it does tend to feel damp (with high humidity) for most of the year, and it is very difficult to keep damp out of houses, though mould growth tends to be quickly dealt with to avoid slum conditions. Yesterday was 100% humidity all day in the low cloud. Dbfirs 14:36, 21 March 2011 (UTC)

100 inches a year is very rare and is almost the worst rainfall you can find in Britain, and is nearly five times worse than what you get in London. I think there is somewhere on top of a hill in the Lake District that gets 150 or more inches a year, but apart from a farmhouse or two nobody lives there. 92.15.25.108 (talk) 16:56, 21 March 2011 (UTC)

Yes, it's not quite as wet where I live as it is in Seathwaite(Seathwaite, Allerdale), but 100 inches is not particularly rare in the valleys between the "fells" - and people do live there! I agree that 100 inches a year would be rare for densely populated areas in the UK. Dbfirs 08:05, 22 March 2011 (UTC)

As you know this is due to the prevailing south west wind in Britain sweeping in rain clouds from the Atlantic. They dump their rain over the high elevations mainly to the west, such as the Lake District and Wales, and the east is consequently comparatively dry and sunny. You are unlucky/lucky to live close to the Lake District. 92.15.6.157 (talk) 10:42, 22 March 2011 (UTC)

Most modern gutters in Britain are plastic. They aren't free, sure, but they aren't something only rich people have by any stretch of the imagination. Any modern house will be built with gutters. Almost all old houses have gutters too. If you don't have any gutters, rain just falls straight off the roof onto the ground, which isn't a good idea. The ground around your house would get very wet and so would you when you walked past. --Tango (talk) 19:51, 21 March 2011 (UTC)

See Alkaline battery#Leaks Potassium hydroxide electrolyte can leak out of old alkaline batteries. When it dries it can leave a white residue I would expect electrolyte leakage is the source of moisture on an old failed alkaline battery, rathre than condensation of atmospheric moisture, unless the battery was brought into a moist place from a cold place. Carbon zinc batteries were worse in this respect in terms of destroying an device when the batteries were left in it too long. Edison (talk) 20:00, 20 March 2011 (UTC)

"This is why we were good at growing corn for the Romans.": your assertion is ridiculous. The Roman didn't know corn until the XVI century, when there were not Romans anymore... 212.169.178.75 (talk) 22:55, 20 March 2011 (UTC)

"Corn" was (and still is) the generic term used in the Old World to cover all cereal crops, including wheat, barley, rye and others. When John Constable painted "The Cornfield" he wasn't looking at maize. (The term could also refer to non-food granular particles - "corned beef" is so called because it is preserved using salt in the form of coarse grains, or corns). As applied to New World maize, "corn" is a contraction of the original "Indian corn", i.e. a particular type of cereal. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:37, 21 March 2011 (UTC)

Please make at least a small attempt to stay on topic. "Corn" has nothing to do with alkaline batteries. Edison (talk) 02:04, 21 March 2011 (UTC)

However they were responding to an incorrect or confused assertion (which IMO shouldn't have gone unchallenged) by 212 (who were responding to a point by 86). Edit: Forgot to mention this but the big long discussion up there which has gotten longer since I first posted about whether or not the UK can be considered a 'wet' country (which considering 'wet' is subjective seems a bit pointless) is IMHO a bigger issue then the clarification that the Romans did grow corn. Nil Einne (talk) 08:53, 21 March 2011 (UTC)

About duck being a red meat...

With all the current hoopla about the risks of red meat, I'm trying to determine if duck is counted as one for the purposes of said elevated health risks. The article about red meat is unclear here... Egg Centric 18:52, 20 March 2011 (UTC)

That's a good question, and I agree that the article may be contradictory. It says that red meat includes 'duck' but then goes on to talk about a bunch of health risks associated with 'red meat' when in fact the studies may or may not have included duck. What you'd have to do is go to the studies themselves. 220.244.35.181 (talk) 19:16, 20 March 2011 (UTC)

Red meat is a phrase that was invented and pushed by the beef industry to refer to "beef" whenever health risks of eating beef are discussed. Thus, when beef is bad for you, it is called "red meat", but when beef is good for you, it is called "beef". Sort of a form of reverse marketing, so in your mind, you don't associate beef with unhealthy qualities. Duck does not fit into the "Standard" American triumverate of meat protein (Beef, Pork, and Chicken), so I am not sure that most people would think of duck as being substantially different from Chicken, excepting that ALL duck is, culinarily and probably nutritionally, closer to "dark meat chicken" (i.e. lower quarters, thigh and leg), even duck breast is more like chicken legs than anything. Whiter meats (including chicken breast meat, turkey breast meat, and some parts of the pork, like the loin and the tenderloin) are lower in fat, so for people who care about fat intake, they advise people to stick to "whiter" meats. Also, with regard to duck being "red meat", it can be culinarily treated more like "beef" than "chicken", so for example, duck is still tasty when cooked to "medium rare", like beef is, but unlike chicken where "medium rare" chicken is disgusting. Nutritionally, however, I don't know that duck is distinctly more like beef or chicken. --Jayron32 22:35, 20 March 2011 (UTC)

I disagree with your contention about the origin of the term "red meat", Jayron, though I agree some anti-meat nutritionalists may use it in that way now. I can recall many references to "good red meat" or just "red meat" in an approving tone from writings going back many decades: the term simply distinguished redder mammalian meats from the whiter meat typically found in domesticated birds. Wild birds' meat tends to be darker than that of domesticated fowl, though not "red", because the wild birds exercise it more. Although some domesticated ducks are bred for meat, they are less distant from their wild forebears than domestic chickens, and of course wild ducks are also often killed for the table. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:49, 21 March 2011 (UTC)

Origins aside, many kiwis are probably familiar with the promotion of red meat (sometimes under that name) by Beef & Lamb NZ [4] some of which are available here [5] Nil Einne (talk) 08:30, 21 March 2011 (UTC)

@90.201/Jayron - I was under the same impression as Jayron regarding the origin of the term, but it occurs to me know that I have absolutely no reference to back that up. Do either of you have anything to offer in terms of support? I did some Googling, but didn't get anything much at all and our article doesn't really cover it. Matt Deres (talk) 01:40, 22 March 2011 (UTC)

The (1933) OED has two citations: the first, purely descriptive one is from M Donovan's Domestic Economy Vol II of 1837; the second is from P Manson's Tropical Diseases of 1898 and advises avoiding it (though presumably in a particular context). Beyond that I can only say that I (being in my 50s) have always been familiar with the term , and have only encountered suggestions that red meat might be unhealthy within, say, the last 15. Personally I take such claims with a large pinch of salt. (Only a metaphorical one, before we start down that road as well!) {The poster formerly known as 87.81.230.195}90.201.110.155 (talk) 18:32, 24 March 2011 (UTC)

Nutritionally, duck is definite more chicken than beef. The biggest problem with red meat is the mammalian hemoglobins--not the fats. Imagine Reason (talk) 11:21, 22 March 2011 (UTC)

What, exactly, is wrong about those mammalian hemoglobins? 93.132.164.231 (talk) 21:38, 22 March 2011 (UTC)

Potassium Iodide

Would it be bad to store potassium iodide in water? I diluted potassium iodide (SSKI) in water, would it make the shelf like any less or would it make it less effective if it was stores like this overtime? —Preceding unsigned comment added by 76.169.33.234 (talk) 20:54, 20 March 2011 (UTC)

Potassium iodide is fully soluble, highly stable, and not likely to be a food source for any microbes. In other words, I can't see anything happening to it whether it is in solution or solid form. In either solution or solid form, it should outlive all of us. --Jayron32 22:26, 20 March 2011 (UTC)

Sea kelp and iodine

If I have sea kelp that says it has 0.06% iodine, how much would I have to take for it to be equivalent to 100mg of iodine which is what I read is equivalent to the amount of iodine in a 130mg tablet of potassium iodine pill? Thanks —Preceding unsigned comment added by 76.169.33.234 (talk) 21:01, 20 March 2011 (UTC)

0.06% of what? Is it 0.06% of the total mass of the seakelp or 0.06% of the Recommended Daily Allowance of iodine for an adult human? If it is the former, you would need to eat 100mg/.0006 = 16,667 mg or 16.667 grams. If it is the latter, you would first need to know what the RDA for iodine was... --Jayron32 22:24, 20 March 2011 (UTC)

I think you slipped a decimal place somewhere, Jayron: I make it 166.67g both on my calculation and on your figures. Happy munching, OP! Incidently, this all assumes that the iodine in the kelp is as assimilable as that in the potassuim iodide in the tablet, which is unlikely. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:23, 21 March 2011 (UTC)

You shouldnt take any iodine, unless you are in Japan close to the reactors. See http://www.bbc.co.uk/news/health-12784774 92.15.21.23 (talk) 22:33, 20 March 2011 (UTC)

Or you have some medical condition for which your doctor has prescribed iodine supplements. (And, by the way, when we say "close to the reactors" we mean actually being one of the people working on fixing them. Even if you are just a few hundred metres away, you shouldn't need iodine supplements.) --Tango (talk) 00:40, 21 March 2011 (UTC)

Not to be pendandic, but this conversation should be about iodide, not iodine. If you are considering consuming them, mixing up the two could be dangerous. 71.185.49.174 (talk) 22:40, 20 March 2011 (UTC)

No, it couldn't. Iodide is just iodine with an extra electron. The best way to get extra iodine into your body is taking ionic compounds of iodine and something else, usually potassium, so it that context we say "iodide", but it's the same thing. --Tango (talk) 00:40, 21 March 2011 (UTC)

Um, excuse me, but chloride is just chlorine with an extra electron, and its effects on the body are quite different. That extra electron makes a big difference. Looie496 (talk) 01:14, 21 March 2011 (UTC)

I just went into this above, but since this is a more appropriate title I'll paste it here for the archive: "for edible seaweeds e.g. kelp: "12 different species of seaweeds were analyzed for iodine content, and found to range from 16 microg/g (+/-2) in nori (Porphyra tenera) to over 8165 +/- 373 microg/g in one sample of processed kelp granules (a salt substitute) made from Laminaria digitata.";^[6] "Edible seaweed contained I levels of between 4300 and 2,660,000 micrograms/kg";^[7] (summarizing these two) "the average iodine content of kelp of 1,500 to 2,500 μg/g".^[8] So we're looking at roughly 2 mg of iodine per gram of kelp (I assume these are all dry weight), if you happen to get an average sample, with a just ridiculous amount of variation. So eating 65 grams, a plausible dose, would be equivalent to the 130 mg tablet - though you might end up getting four times as much if you are unlucky. Or you might get less than a mg. Wnt (talk) 02:38, 18 March 2011 (UTC)"

In some sources I read while preparing that last, iodine and iodide were used almost interchangeably, in the sense that the weight of iodide is the same as the weight of iodine. (neglecting the minisule electron mass) Actually eating iodine in its elemental form (or as tincture of iodine) is inadvisable for a variety of reasons, the least of which being that whatever physically reacts with and stains your sorry gullet is not going to your thyroid. Wnt (talk) 02:21, 21 March 2011 (UTC)

A quick raid on NCBI suggests that kelp stores iodide as just plain iodide, noncovalently associated with other molecules.^[9] So its iodide should be interchangeable with that from KI, at least in theory. Wnt (talk) 02:34, 21 March 2011 (UTC)

I was asking about this product http://dealnay.com/1011927/natures-way-kelp-100-capsules.html I heard you can take it in the place of potassium iodide, I guess you can't... Thanks —Preceding unsigned comment added by 76.169.33.234 (talk) 02:59, 23 March 2011 (UTC)

Tidal energy from the Wash and the Severn

How many typical nuclear power stations would harnessing the tides of the Wash and Severn be equivalent to? 92.15.21.23 (talk) 22:01, 20 March 2011 (UTC)

It would depend on the placement of the barrages and also which types of nuclear power stations you wish to compare them to. For instance, the proposed Severn Barrage may generate from 0.75-15GW depending on which plan you read. The proposed Hinkley Point C nuclear power station could produce 1.6GW. Nanonic (talk) 22:21, 20 March 2011 (UTC)

The 15GW figure is peak power, which isn't terribly informative when you're costing it, compared with a source with a fairly steady rate. Unfortunately the article isn't very good at giving idea (beyond the rough "average" numbers below) as to how long a given barrier would spend delivering power at that level, at the average level, and at lower levels. -- Finlay McWalter ☻ Talk 22:31, 20 March 2011 (UTC)

There are many different proposals for designs for a Severn Barrage, with quite a range of costs, power levels, and impacts. Looking at that article, the 1987 proposal would generate 313 MW on average, the 1989 design 2,000 MW on average. If you compare that to Torness Nuclear Power Station, the most productive of the UK's Advanced gas-cooled reactors, which produces at 1250 MW over two reactors. the Severn Barrage article, using those 1989 figures, puts the yield at 3 reactors worth, and observes that the estimated cost is "about the same as six nuclear reactors, but different lifespan". If Torness serves its planned 35 years of service, you'd expect a Barrage of the 1989 design to pass nuclear at some age shy of 70 years. But that's a hopelessly simplistic calculation: on the nuclear side it doesn't count the comparative cost of operating and maintaining both plants, and the cost of the fuel cycle; on the tidal side it doesn't count the (presumably fairly low) running and maintenance cost, or the (difficult to put into numbers, but not trivial) cost of the environmental impact the barrier would bring. So, handwaving a bit, power yield of 1 1/2 nuclear stations, more expensive in the short term but cheaper in the long term. -- Finlay McWalter ☻ Talk 22:24, 20 March 2011 (UTC)

I hate this "environmental impact" twaddle - who cares about a few ducks. 92.15.21.23 (talk) 22:30, 20 March 2011 (UTC)

Nobody cares that you don't care about a few ducks. This is a reference desk. Personal opinions are off-topic. --Tango (talk) 23:09, 20 March 2011 (UTC)

The ducks probably care. Sean.hoyland - talk 04:00, 21 March 2011 (UTC)

Personal opinions from the OP about what the OP is or isn't interested in are perfectly on topic, and in fact define the topic. Turns out the scope of the question does not include impact on ducks. Now we know. 81.131.35.68 (talk) 06:08, 21 March 2011 (UTC)

Ducks and the pro-duck lobby are relevant because they can scupper plans to use tidal energy instead of building more nuclear reactors. However the plans to end repair of coastal defenses along the east coast may introduce more habitat for them, although the crowd-pleasing current government seems to be appearing to reverse that policy. If you've ever been to Hunstanton you can see how ugly the mud beaches are (Old Hunstanton on the corner of the coast is much nicer) so damming the Wash will be a big improvement for recreation. 92.15.25.108 (talk) 12:08, 21 March 2011 (UTC)

By "the pro-duck lobby" you may mean the Ramsar Convention, which is an international treaty designed to protect the fundamental ecological functions of wetlands. Both the Severn Estuary and the Wash are listed here as being of international environmental importance. Perceived "ugliness" has nothing to do with it. Ghmyrtle (talk) 12:21, 21 March 2011 (UTC)

See what I mean? 92.15.25.108 (talk) 13:47, 21 March 2011 (UTC)

Not really. Many people including some locals consider the protection of wetlands in Malaysia and Indonesia important. I don't believe ducks are even commonly present in these Nil Einne (talk) 16:06, 21 March 2011 (UTC)

The solution would be to find a poison to put in the water that is lethal to ducks but nothing else. 92.24.188.210 (talk) 20:42, 24 March 2011 (UTC)

Chernobyl vs Deepwater Horizon

In terms of environmental damage (both present and predicted by environmentalists), how does the Deepwater Horizon incident compare to Chernobyl? Thanks. 72.128.95.0 (talk) 23:06, 20 March 2011 (UTC)

They're not really comparable. --Tango (talk) 23:11, 20 March 2011 (UTC)

Deepwater did almost nothing - it requires intense study to find any negative effects at all. Chernobyl caused a 30km area to be uninhabitable for centuries. I should point out that the environmental damage from hydrocarbons comes in the burning, not the extraction, so comparing accidents is not very meaningful. Ariel. (talk) 00:01, 21 March 2011 (UTC)

I wouldn't say it did almost nothing, see Deepwater_Horizon_oil_spill#Consequences. --Jayron32 03:55, 21 March 2011 (UTC)

Yes, broadly Chernobyl was devastating and Deepwater comparatively marginal, after all oil is a biological product which degrades in a few years. However in one case there is a government wanting to deny it and move on, a lobby industry to try to downplay it and no one except people too poor to move to care. Interesting that a single NGO medical centre is still treating 200 new children a year for radiation sickness in 2011 [10] whereas based on reliable sources (cough) Wikipedia claims only 237 people have suffered from radiation sickness since 1986. In the case of Deepwater by contrast there is a well funded government and media desperately searching for "animal touch stories" to try to make cash from them. --BozMo talk 06:24, 21 March 2011 (UTC)

The charity says it's treating children for "cancer and other diseases related to radiation exposure"; this is not the same as radiation sickness. -- BenRG (talk) 10:31, 21 March 2011 (UTC)

As BenRG notes, there is a world of difference between radiation sickness and diseases (potentially) related to radiation exposure. As well, I do wonder – and this is not to in any way negate the value of the work they do – if there isn't a significant fundraising advantage that the charity enjoys from stating that they treat "cancer and other diseases related to radiation exposure" instead of just "childhood cancer". Belarus has a population of roughly ten million people; even in the absence of any unusual radiation exposure, a few hundred childhood cancers per year wouldn't be abnormally high. The number might be even less remarkable if we knew exactly what "other diseases" were included. (Some very quick searching seems to indicate that there was the expected increase in thyroid cancer due to radioiodine exposure, but that accounted for most of the increase in total cancer rates following Chernobyl. Cancer incidence in most categories appears to be comparable to that observed in the United States: [11]. No increase in childhood leukemia was observed: [12].)

Incidentally, BozMo, do you really think that there aren't lobby groups and governments who would benefit from denying and downplaying the effects of the Deepwater spill? (When I started to read your comment, I initially thought you were talking about Big Oil and its lobbyists.) For that matter, aren't there well-funded, multinational, media-savvy pressure groups who are very active in publicizing the disaster at Chernobyl? TenOfAllTrades(talk) 13:18, 21 March 2011 (UTC)

There is a valid criticism of my comparison above since our article just quotes radiation sickness in the immediate aftermath as 237, whereas the chronic stuff is further down the page. There is quite of lot of info on the types of illness in the medical centre but it all needs translating; it looks to me as though chronic radiation sickness is the main problem but I have sent off a few queries. On the fundraising and lobby groups as far as I know this is the only major NGO working in Belarus, and you do not get to be an orphan NGO working in Zimbabwe, Sudan, Israel, Gaza Strip, Somalia etc by saying things which governments don't like. As for "Big Oil" (I left working there 6 years ago) compared to the money vultures in the USA I regard the BP lobbying group as scoring about 0.1 on the Geoffrey Howe scale of savage dead sheep. --BozMo talk 13:42, 21 March 2011 (UTC)

BTW an excellent article on the effects of Deepwater and its complicated mix of science, politics, and the media, is this New Yorker piece from a few weeks ago (behind a pay-wall here, but worth tracking down). --Mr.98 (talk) 13:06, 22 March 2011 (UTC)

March 21

Why aren't Washlets common in the US yet?

It's popular in Japan; what's wrong with it being sold in US stores? Why do we still have to deal with it the old way when a newer form of hygiene already exists? --70.179.169.115 (talk) 04:07, 21 March 2011 (UTC)

This was recently asked here: [13]. (Based on the similarity in the I/P address, it looks like it was asked by you.) StuRat (talk) 05:06, 21 March 2011 (UTC)

As soon as I read the article I said "I want one." Maybe you should try importing some and try to sell them. You would soon find either the answer to your question or you would make a profit.--Shantavira|^{feed me} 09:04, 21 March 2011 (UTC)

Shanta, you can get a varying range of cost of bidet-seats at http://www.BioBidet.com. —Preceding unsigned comment added by 70.179.169.115 (talk) 22:35, 21 March 2011 (UTC)

The cost of importing a washlet is high, reportedly $660 or so[14] bought online. It requires behind the toilet an electric outlet that is properly installed for use near water, with a ground fault interruptor. A Google search for "Washlet" finds many suppliers. Low enthusiasm for washlets in USA is comparable to the low acceptance of a similar bathroom accessory, the bidet. Cuddlyable3 (talk) 09:28, 21 March 2011 (UTC)

Are showers as common in Japan as in the U.S.? It is not unheard of for someone in the U.S. to duck into the shower after an especially... sticky... experience. Wnt (talk) 09:33, 21 March 2011 (UTC)

When someone was promoting bidets in Australia some years ago it was discovered that plumbing rules demanded an independent warm water supply because of the possibility of gravity allowing unwanted solids to enter the water supply. Cost then became a big issue. HiLo48 (talk) 11:12, 21 March 2011 (UTC)

Radiation dose inside a working nuclear reactor?

If you can get inside a working nuclear reactor without disrupting the reaction and stay there for a minute, what dose of radiation would you get? F (talk) 09:48, 21 March 2011 (UTC)

Based on this chart which breaks down lots of various radiation dosages, standing next to the Chernobyl reactor for one minute during the meltdown would give you about a 5 Sv dose. I'd say that's a good ballpark number for normally-operating reactors, too. That's on the very upper edge of "if you're lucky, you don't die straightaway of radiation poisoning." — Lomn 12:38, 21 March 2011 (UTC)

Even with the author's caveat, I'm not sure that xkcd cartoon is a "reliable source," let alone encyclopedic. Here's Radiation in Perspective from the Department of Energy's Radiation Protection Policy. Each reactor type is different; usually, if you were working with a reactor, you'd have to take a DOE or an OSHA training course. Radiation levels inside the reactor would probably be fatal, maybe or maybe not instantaneously; but if you were actually inside the reactor, you'd have other problems besides radiation to worry about! The temperature isn't comfortable for human life in there, either - and there's not much breathable air - in fact, the nuclear reactor core is not a suitable place for you to go inside, even for a minute. You might equally well ask about environmental safety hazards if you were inside the combustion chamber in an automobile's engine cylinder. Nimur (talk) 14:24, 21 March 2011 (UTC)

Indeed. The inside of a boiling water reactor such as those at Fukushima contains superheated water and steam at a temperature of about 285 °C and a pressure of about 75 atmospheres. It is basically a huge pressure cooker. Gandalf61 (talk) 14:39, 21 March 2011 (UTC)

Even inside a tiny research reactor, the radiation would be quickly toxic if you were inside the unshielded core while it was undergoing criticality. The amount of neutrons alone in an operating reactor, much less gammas and other nasty things, is just fantastic. That's the whole point of a reactor. --Mr.98 (talk) 16:23, 21 March 2011 (UTC)

The sievert article has some interesting equivalent dose values. Sean.hoyland - talk 17:19, 21 March 2011 (UTC)

An alternative interpretation of the question would be if you were inside the containment building of a reactor while it was operating. Early on in the Three Mile Island accident, a spokesman for Metropolitan Edison asserted that he could "walk around inside the containment building, right now, without harm from radiation," implying that the radiation level in the building (and outside the reactor) would not be impossibly high. (He was later shown to be quite wrong: he would have gotten a lethal dose in less than an hour). When a reactor is being refueled, humans work in the containment building and around the reactor, since the valves, switches and pipes do not fix themselves, and a reactor is a very high maintenance device, with constant testing repairs, replacements, and retrofits. While the reactor is operating, I doubt that it is considered safe to wander around in the containment building. Edison (talk) 18:35, 21 March 2011 (UTC)

Containment building says that you can be in the containment building while it is on full power, but implies you are getting a non-negligible amount of radiation (you can only stay in there a limited amount of time before getting your safe dose). That is about what I would guess. A reactor, even one on full power, is still relatively shielded by the water and the reactor vessel. --Mr.98 (talk) 00:26, 22 March 2011 (UTC)

Some people saw this short blue flash when something goes supercritical for example in the Cecil Kelley criticality accident or things while Tickling the dragon's tail. This is only a few microseconds and they die relative soon (days), so with a full blast nuclear reactor it should be over in seconds.--Stone (talk) 18:52, 21 March 2011 (UTC)

Buffalo

Is it true that Buffaloes do not have sweat glands ?  Jon Ascton  (talk)

Not quite. According to this report, "buffalo skin has one-sixth the density of sweat glands that cattle skin has, so buffaloes dissipate heat poorly by sweating." Ghmyrtle (talk) 14:16, 21 March 2011 (UTC)

Which of the various bovine species commonly called ""buffalo" are you referring to? Roger (talk) 14:23, 21 March 2011 (UTC)

The OP is from India so probably Water Buffalo or perhaps the Wild water buffalo Nil Einne (talk) 16:04, 21 March 2011 (UTC)

Neurons and memories

Are memories believed to be stored with the same set of neurons throughout the years? Is an individual neuron believed to be able to be a part of multiple completely different memories? 20.137.18.50 (talk) 13:10, 21 March 2011 (UTC)

I think the answers are both "no", but we await an expert to confirm and expand the answer. Meanwhile our article Neuroanatomy of memory might be of interest. Dbfirs 14:19, 21 March 2011 (UTC)

It's basically impossible for us to know the real answer right now, but some have hypothesized the existence of specific neurons that store a representation of a complex concept or object (presumably by linking up a whole network of neurons that "remember" different aspects of that concept or object). The classic example is the grandmother neuron which is hypothesized to fire whenever you think of your grandmother, or whenever a stimulus (such as a scent, or the memory of a particular location) evokes a memory of your grandmother. --- Medical geneticist (talk) 15:19, 21 March 2011 (UTC)

Most neuroscientists believe that memories are stored, not in neurons per se, but rather by altering the strength of the synapses that connect neurons to each other. An individual neuron in the cerebral cortex makes on the order of 10,000 synaptic connections to other neurons, so this gives quite a large potential storage capacity. With synaptic storage, each individual neuron can participate potentially in thousands of memories, or conceivably even millions. Whether a memory is stored in the same set of synapses across the years is a controversial issue -- some neuroscientists think that memories need to be "refreshed" periodically and that this may involve bringing new synapses into play. Our article on synaptic plasticity contains some relevant information, although most of it is pretty technical. Looie496 (talk) 17:50, 21 March 2011 (UTC)

Expiry date of bottled water

Looking at some bottled water today, I was surprised to notice an expiry date printed on the bottle. Does pure water become unfit for drinking after long periods, assuming the seal of the bottle is not broken? The label on the bottle read 'purified tap water'. 60.48.212.9 (talk) 17:34, 21 March 2011 (UTC)

Plastic bottles can contaminate the water over time via leaching (chemistry) of chemicals from the plastic. 82.43.90.38 (talk) 17:40, 21 March 2011 (UTC)

Good to know, thank you. 60.48.212.9 (talk) 17:51, 21 March 2011 (UTC)

Look up bisphenol A, endocrine disruptors, etc. Wnt (talk) 19:47, 22 March 2011 (UTC)

A follow-up question: what are those expiration dates based on? Do the manufacturers or maybe the professional organizations have studies that show the leaching rates or demonstrate safety after known periods? Are they just arbitrary? SDY (talk) 17:55, 21 March 2011 (UTC)

They may have reason to believe that it's of "Acceptable" quality up to that point, but don't study it much beyond that. Still, how long something lasts is so dependent on the conditions under which it is stored that a "look, smell, and taste" test is far better than a date stamped on the package. If your water bottle spent time on the dashboard of your car in the bright summer sun, then it would deteriorate far quicker than in a fridge, probably quicker than the date. There also could sometimes be a sleazy angle to them printing short expiration dates, if they want consumers to toss out their product, while it's still good, and buy more. StuRat (talk) 18:38, 21 March 2011 (UTC)

Here in the UK there is a difference between Use by dates and Best before. Here's some guidance from the FSA about the difference (http://www.eatwell.gov.uk/foodlabels/labellingterms/bestbefore/). In terms of 'leaching' from plastic you may be interested in EFSAs opinion on the safety (http://www.efsa.europa.eu/en/efsajournal/pub/428.htm), the concerns of leaching from plastics (from my limited understanding) are not particularly high. ny156uk (talk) 18:44, 21 March 2011 (UTC)

As far as I know, in some markets (*cough*EU*cough*) there is a requirement that all material for human consumption has an expiry date. And there also is a requirement that prescribes maximum and minimum expiry times, independent of the product (probably in a directive invented by a different, but similar committee). Put the two together, and... --Stephan Schulz (talk) 19:04, 21 March 2011 (UTC)

Do you have a citation for that? I ask because we don't have "expiry dates" in the EU, some products have "use by" dates and some have "best before" dates, as noted by Ny156uk above. DuncanHill (talk) 22:55, 21 March 2011 (UTC)

Here in the UK, I've never seen an "expiry date" on foodstuff, and, of course, fresh unpackaged food has neither a "best before" nor a "use by" date because its condition is usually fairly obvious. In some cases, the "use by" date on packaged goods is mainly for the convenience of the seller to ensure efficient stock rotation. Dbfirs 07:52, 22 March 2011 (UTC)

Annoying. Annoying. Annoying.

Most or all people eventually become annoyed by a sound or short phrase that is repeated ad nauseum. Can anyone point me to any studies or articles about this phenomenon? The closest thing I could find on Wikipedia that was at all related was our semantic satiation stubby article, which isn't really about the same thing. Comet Tuttle (talk) 18:30, 21 March 2011 (UTC)

"HeadOn. Apply directly to the forehead ..." hydnjo (talk) 22:39, 21 March 2011 (UTC)

There's the phonological loop, which is implicated in earworms. We have a dedicated bit of short-term memory for storing things we've heard recently, and if this were to be repeatedly filled with the same information ... well, I can't see the harm in that at all, actually. Not sure how to make this answer your question, but I feel it must be possible with effort and OR. 81.131.46.134 (talk) 01:59, 22 March 2011 (UTC)

Temple Grandin says in Animals in Translation (on 49-50) that intermittent noise triggers the "orienting response" in mammals. I'm not sure if that's the same thing you're talking about, but it's something. --Mr.98 (talk) 00:46, 23 March 2011 (UTC)

vacuum electricity

Nikola Tesla observed that electrons transmitted through a near perfect vacuum in his vacuum tubes appeared as corona several feet through the air surrounding the tube. If there is nothing in the tube between the electrode and the glass, then how do the electrons convey through the vacuum and into the surrounding air. could this be explained by http://en.wikipedia.org/wiki/Electric_current#Vacuum — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:12, 21 March 2011 (UTC)

I think that's somewhat of a red herring. The vacuum is an insulator unless electrons are moving through it, yes - but that doesn't answer the issue of why the electrons move through it.

In a vague sense, my impression is that the metal anode fills with extra electrons, typically positioned at the boundary of the conductor, which fill up the conduction band to a level high enough that they can escape it. Once free, the electrons will be pushed away from the electrode and can move in response to any small electric field in the area. But someone with a better understanding of articles like Electronic band structure, Nearly-free electron model, Empty Lattice Approximation, and so on needs to give a better answer. Wnt (talk) 20:59, 21 March 2011 (UTC)

Abnormal darkness

There are some sources claiming that there were relatively short periods of abnormally intense, unexplained darkness, sometimes even spread over the cities (specifically over Wimbledon, London on April 2, 1904 and over Louisville on March 7, 1911). Is there any explanation for that or it's indeed abnormal?--89.76.224.253 (talk) 21:46, 21 March 2011 (UTC)

(The book linked to by the querent is a compilation of The Book of the Damned, which is also available to read on Wikisource, along with other books by the same author.) Comet Tuttle (talk) 22:17, 21 March 2011 (UTC)

Big Bang echo

Just watching Dr Jim Al-Khalili's latest BBC programme, in which he explains about the microwave background radiation being the remnant of the Big Bang. I've known about this for some time, but the following question has just popped into my head. Is it possible to calculate at what point this radiation was in visible light, and what would the sky have looked like at that point? Or is it possible to say when the sound waves from the Big Bang would have stopped being audible to human ears? (OK I know humans weren't around then. Humour me, it's a thought experiment!) --TammyMoet (talk) 21:58, 21 March 2011 (UTC)

Sound waves only take on meaning in a medium, such as air. In the hard vacuum of space, there is no sound. --Jayron32 22:23, 21 March 2011 (UTC)

Yes, but right after the big bang the universe was much denser. This question is not completely meaningless. Dauto (talk) 01:09, 22 March 2011 (UTC)

The microwave background has a black body spectrum with a temperature of around 2.7 Kelvin. Blackbody radiation is visible to human beings at temperatures from 1000 K to 10000 K, more or less, with the colors shown here (although human beings couldn't exist at those temperatures, so this is all somewhat unrealistic). The ratio between the temperature now and the temperature at an earlier time is given by the redshift factor z. So the radiation would be visible for redshifts from z=1000/2.7 to z=10000/2.7, or z=400 to z=4000, more or less. Ned Wright's Cosmology Calculator will give you the age of the universe for any value of z (enter the value in the box labeled "z", then click "flat"). This gives an age range of 40,000 to 2,000,000 years after the big bang, more or less. But prior to 400,000 years after the big bang the universe was filled with an opaque plasma and there wasn't really a photon background, so it's probably better to say that the photon background was visible from its time of origin (400,000 years after the big bang) until 2,000,000 years after the big bang. It was initially yellow-orange (3000K) and then red (1000K) before fading into the infrared. As for what the sky would look like, take the present-day night sky, remove the stars (since there were no stars), and replace the uniform black with uniform yellow-orange or red. -- BenRG (talk) 02:20, 22 March 2011 (UTC)

Cool, thanks Ben! --TammyMoet (talk) 09:27, 22 March 2011 (UTC)

Are you sure there is an upper limit to visible temperatures? While the peak will be out of the visible spectrum, there will still be plenty of visible light emitted too. --Tango (talk) 19:39, 22 March 2011 (UTC)

Yes, you're right. Oops. (Although at some point it will be bright enough to instantly blind you, making it effectively invisible...) -- BenRG (talk) 08:00, 23 March 2011 (UTC)

Isn't space a gas?

I was going to smugly reply to the previous question (about the big bang) with "sound waves can't propagate through the vacuum of space, duh". Space isn't a perfect vacuum, though, and it contains a certain amount of hydrogen, so is space actually a very sparse gas, through which sound could travel? 213.122.13.4 (talk) 22:27, 21 March 2011 (UTC)

Lower density, implies higher isolation. Quest09 (talk) 22:55, 21 March 2011 (UTC)

Does that mean yes, sound could travel through space, extremely poorly? 213.122.13.4 (talk) 23:07, 21 March 2011 (UTC)

I don't see why not, though it would soon get lost amongst the random jostling between whatever atoms and compounds are out there. So, even if you scream really loudly, nobody is likely to be able to hear you. However, there's also this intriguing article (okay, a preview of an article). Clarityfiend (talk) 23:56, 21 March 2011 (UTC)

The interstellar medium does propagate pressure waves - in essence "sound" - provided the wavelength is large enough. The typical example is the pressure waves associated with the galactic spiral arms, which have a length scale measured in thousands of light years. Of course, this is a "sound" that is so low frequency that no organic ear could ever hear it. Typically to avoid dispersion, one wants the wavelength of the pressure wave to be much larger than the distance that individual particles will travel between collisions. In the interstellar medium, with about ~10 atom / cm^3, one would expect a wave to propagate successfully (rather than dissipate) if the wavelength is greater than ~20 AU. The intergalactic medium (with only 1 atom / m^3) would require the pressure front to be thousands of times larger than that, but it is possible if you had an astrophysical process capable of generating a large enough perturbation. Dragons flight (talk) 00:01, 22 March 2011 (UTC)

And right after the big bang the universe was much denser than today allowing for short waves to propagate. Dauto (talk) 01:13, 22 March 2011 (UTC)

Why is work - often - not enjoyable?

During evolution, only humans who enjoyed working could have survived. So, shouldn't we have a "I love work" gen? Quest09 (talk) 22:52, 21 March 2011 (UTC)

Conserving as much energy as possible by doing as little work as needed to survive is beneficial in situations where food is in short supply 82.43.90.38 (talk) 22:58, 21 March 2011 (UTC)

Not all work is equal. Humans love certain types of tasks — and you'll find that the jobs people love the most are the ones that satisfy them. For example (per Temple Grandin), we are hard-wired (like most mammals) to love seeking things out. We love the search, love the hunt, love the pursuit, love the flirtation, love the chase. We love the act of finding things more than we like the things found. I think most of us have experienced this in one way or another. That's a definitely genetic predisposition (though not unique to humans at all, which makes sense), but whether we enjoy "working" generally probably is not one. We like certain types of jobs. --Mr.98 (talk) 00:22, 22 March 2011 (UTC)

I like that theory, but I dispute it. People enjoy creativity (I haven't checked, but I expect the article backs me up on that). Hunting for things is a creative act, provided it's challenging for the hunter. Being a litter-picker involves hunting for litter, but is not a creative act, since old cans and gum and so on don't make much effort to escape. Being a hunter of something which you have mastered the task of hunting for is probably dull. Being an artist is a creative and probably fun job, but only in the most tenuous sense involves searching for anything. 213.122.13.4 (talk) 01:07, 22 March 2011 (UTC)

Well, that's not what Grandin has found, with humans or with animals. Just saying. "Creativity" is not the kind of category she uses — it doesn't correspond with some sort of basic neural circuit, whereas "seeking" does. --Mr.98 (talk) 12:56, 22 March 2011 (UTC)

Being an artist is a creative and probably fun job. Being an artist is, for most professional artists, very stressful! Just saying. Pfly (talk) 18:22, 22 March 2011 (UTC)

If work were enjoyable, the industrial revolution wouldn't have happened. Count Iblis (talk) 00:58, 22 March 2011 (UTC)

For a lot of people, even the most enjoyable activity can be made unpleasant by rigid bureaucratic demands and crappy bosses HiLo48 (talk) 01:12, 22 March 2011 (UTC)

I think happiness is relative to one's acceptance of the situation, and is related to homeostasis - that is, unhappiness is caused by a notion of things being wrong, and is always in some sense a form of indignation and of aspiration. So people in modern times might be unhappy about work that ancient people would accept as normal, because these days we're dimly aware that there must be a better way. In addition to this, I see you make the assumption that a human unhappy with necessary hard work is a human who refuses to do the essential work, and starves: does that really follow? Evolution has no particular interest in our having a nice time, so long as we breed. 213.122.13.4 (talk) 01:13, 22 March 2011 (UTC)

There's also the factor of conflicting priorities. People have different ideas about how to do things and different things that make them happy. If you work for a person or a department or a company whose goals and priorities conflict with yours, there's a good chance you won't be very happy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:24, 22 March 2011 (UTC)

Evolution is very slow. We mainly enjoy hunting and gathering, and perhaps farming and herding, because that's what we did for most of human history. The industrial revolution and information economy haven't been around long, and few people have died because they disliked such work, so there is very little evolutionary pressure for us to grow to like it. StuRat (talk) 02:25, 22 March 2011 (UTC)

I would just add my 2 cents in that I think what most people do for a "job" is not actually what evolutionally would be called work. Sitting at an office at a computer, or fixing some one's plumbing are "detached" from an actual sense of survival. Sure the money you earn gives you those things, but you are earning MONEY not the things you need to survive. Just a personal anecdote which might help illustrate what I mean, whenever I do some gardening at home, admittedly it's not something I particularly "like" doing, I don't "look forward to it", but when I physically OWN and enjoy the efforts of my labour I feel a far greater sense of achievement and pleasure then if I did it for someone else to earn some money, even if I then could use that money to hire someone else to fix my garden. Vespine (talk) 02:48, 22 March 2011 (UTC)

Joy is not the only motivator. Hunger is a motivator to hunt or gather food. Being cold is a motivator to build a fire or make clothes. Affection for others is a motivator to care for them. Joy is a major motivator in reproduction but most people wouldn't call that work. Also, most humans above a certain age are relatively good at predicting what will serve them in the future, and plan and act accordingly. Human intelligence enables us to make such predictions and actions in situations our basic instincts don't cover. PrimeHunter (talk) 04:38, 22 March 2011 (UTC)

I think that there should be some adaptation to favor productive labor in general; the problem is that society's notion of labor isn't the same as that. It's not just that people enjoy hunting and fishing - they enjoy gardening, fixing the house, editing a Wikipedia article. What they don't enjoy is when they are coerced by a badly designed economic system to spend their time harming other people or doing something useless - such as telemarketing, for example, which is particularly famous for burning out its workers quickly. They don't enjoy being stood over and threatened. I think it's all too clear that modern American society offers a whole lot of "work" that society would be better off without, and that people are coerced into it solely to prove the dominance of certain high-caste individuals and groups over themselves and others. Spending one's days in abject subjection, strictly as a rite of worship toward the "rich" (i.e. those who claim to themselves control of the Earth's resources or of means of using them) - that is not something people have evolved to accept. In fact, they are adapted to challenge it by violence. Wnt (talk) 04:53, 22 March 2011 (UTC)

Various things give us some kind of biological high - certainly sex and eating. This is the way that evolution makes a thing enjoyable; it makes us get a buzz out of it. (Perhaps some activities also soothe us.) It can't cause us to enjoy an activity in an intellectual way, it can't make us express sophisticated approval of it. It also has to be an activity which is easily identified on a biological level - it can't take cognition to identify that the thing is happening, or else our genes (which don't describe our plastic brains) have no handle on it. (I mean "dynamically formed" and not "made of plastic".) So, taking weaving as an example:

• It would probably be inconvenient if we got high specifically off weaving, and wove things constantly.
• I doubt any mechanism could evolve to reliably detect whether we were weaving, anyway, since it's not an instinct.
• Detecting productive labour in general is the same problem, multiplied many times (because of all the kinds of work).

The choice of the right work for a human to do requires thought, which puts it beyond the reach of evolution. 213.122.63.19 (talk) 05:34, 22 March 2011 (UTC)

And it's rarely a simple matter. After a mature aged career change I am now a high school teacher in a government school. The job is incredibly rewarding, when one realises the advances students have made, often in a lot more ways than just knowing more of their subject matter. But there can also be massive frustrations in the job, in the form of under-resourced schools, incompetent administration, and bureaucratic demands. It's a shame that we can't seem to get one without the other. (And a quick qualifier - the incompetent administration comment is not referring to my current school ;-) ) HiLo48 (talk) 10:40, 22 March 2011 (UTC)

Not to worry, the incompetent administration probably doesn't know how to use the Internet and never even heard of Wikipedia. StuRat (talk) 14:09, 22 March 2011 (UTC)

A common complaint about work is that it 'stresses me out'. So a 'love to work' gene may be tantamount to a 'work myself to death gene'. Hardly favorable for genetic propagation. Vranak (talk) 17:06, 22 March 2011 (UTC)

But that just leads back to the original question (restated) of why we find work stressful. StuRat (talk) 17:16, 22 March 2011 (UTC)

Well, it's like driving a car. If you drive it wildly, lots of hard acceleration and braking and turning, running over potholes, it's gonna wear down and need a vacation (go to the shop). Same thing with working -- if you are a calm and rational and sensible human being you can accomplish your work without a great deal of stress, one would imagine. However, there are issues like indoor air pollution, so no matter how calm you are at the office, you may be inhaling vast quantities of pollution. See Sick Building Syndrome. Vranak (talk) 17:36, 22 March 2011 (UTC)

(ec) We have the page Workplace stress. Lots of info and ideas there. The Happiness page might play into the question too. Many people are unhappy, stressed, anxious, etc, whether or not they're at work. Happiness is something we still don't fully understand—at least how and why it happens, and how to stay happy. I'd even suggest most people spend most of their time trying to find happiness, and then trying to stay happy. Seems like almost no one succeeds; the struggle is usually lifelong, no? I've met a few very dedicated (very very dedicated) Buddhists who seem to have a near-constant state of happiness or joy, even when doing work they don't "enjoy". Their happiness seems different from my ordinary understanding of the word (one such "dedicated" and happy person that comes to mind is Bonnie Myotai Treace).

Temple Grandin was mentioned above. I found her book Animals in Translation an excellent description of basic emotions in people as well as animals, how and why they work the way they do, and why emotions can often feel unpleasant or stressful; and, sometimes, all-too-fleetingly, pleasant. An interesting bit I always recall is her notion that while people will generally choose "powerful fear" over "powerful pain", animals (at least "higher" animals like dogs, horses, cows, etc) tend to be more traumatized by powerful fear than powerful pain. Pfly (talk) 18:18, 22 March 2011 (UTC)

March 22

Earth's tilt and space radiaton.

Greetings!

I have a rather complicated question concerning the tilt of the Earth, the way the atmosphere protects us from radiation, and the effects—for a limited time—of exposure to said radiation.

Right now, our planet's orbit is tilted 23-1/2 degrees to the ecliptic. (This is why the Sun rises 23-1/2 degrees north and south of due east on the solstices.) In the (northern) summer solstice, the Earth approaches perihelion—the closest it will get to the Sun—and approaches aphelion—the farthest away it will get—at the (northern) winter solstice.

In spite of this, however, the southern hemisphere gets just as hot a summer (and just as cold a winter) as the northern hemisphere. This suggests to me that it is not distance per se, but a property of the atmosphere that gives us our tellurian seasons. I'm not an expert at all in the sciences, but I do know that the atmosphere absorbs virtually all Gamma Rays, X-Rays, Ultraviolet Rays, and most Infrared Waves from space. (Only Visible Light, Radio Waves, and some Infrared Waves make it all the way down to the surface). And I also know that around the polar regions, there are "holes"—for lack of a more proper term—where space radiation penetrates far more freely.

Now, suppose that the Earth were tilted on its axis as, or more severely than, Uranus. For simplicity's sake, let's say at an even 90 degrees to the ecliptic. (Also, for all intents and purposes, let's say that all other factors remained unchanged: orbital speed, distance from the Sun, etc.) How would that change the way that space radiation affects us?

Over the course of one Earth day (23 hours and 56 minutes) the Sun would pass through both poles on each of the solstices.

Here are my questions:

As the Sun's radiation penetrated to the surface of the Earth through the "ozone hole" and other "holes" that exist at high lattitudes, what would change about life on Earth?

—Would we see an abundance of natural disasters? (floods, volcanic erruptions, cyclones, earthquakes, etc.)

—Would anatomy and physiology of Earthly lifeforms change? (We know for a fact, the photosynthesis in plants depends on the Sun, and even we humans synthesize Vitamin D from it.)

—Would geology change in any way; to wit, would rocks become lighter or more porous, or some way different. Would the magnetic field change direction or become stronger (or less strong)?

—Would the seasons change in length or demeanor, since the atmosphere would factor differently?

And finally:

—Can such a state be replicated today, under laboratory conditions, in a small, self-contained experiment?

--Thank You! Pine (talk) 00:31, 22 March 2011 (UTC)

So, assuming that you mean the North Pole would point directly at the Sun during one season, and the South Pole would point directly at it in the opposite season, with things being about how they are now, when halfway between the seasons, here's what I would expect to be different:

1) Far more extreme changes between the seasons. During winter at each pole, temperatures would drop low enough for carbon dioxide to form dry ice, and possibly low enough to produce liquid nitrogen from the air. During summer at the poles, water might boil. This would cause massive storms and currents in the air and water in-between. I doubt if (multi-cellular) animals could survive the extremes at the poles. Bacteria and some other simple life forms might, though. Migrations would become far more extreme, with animals moving to the summer side continuously. Unlike now, this would likely need to include humans. Life might be far more concentrated around the equator than it is now.

2) As for radiation at the poles, yes, there would be more, but this would be a minor concern compared to the temperature extremes.

3) I don't see how this would affect geology or magnetic fields.

4) You would see far more extreme weather (cyclones, hurricanes, tornadoes, etc.), but not earthquakes or volcanoes, because they don't get their energy from the Sun.

As for creating a physical model, I can't see how you would replicate the oceans and atmosphere in such a model. Therefore, a computer model (using computational fluid dynamics) would be the way to go. StuRat (talk) 02:08, 22 March 2011 (UTC)

Just to note that you've got the perihelion/aphelion–solstice business backwards, Twinpinesmall. At the summer solstice, Earth is approaching its aphelion; and at the winter solstice, its perihelion. See Apsis#The perihelion and aphelion of the Earth. This shows that it's the planet's tilt, far more than its distance from the sun, that determines seasonal variations in temperature (I'm not sure what you mean by your reference to a "property of the atmosphere"). Deor (talk) 02:29, 22 March 2011 (UTC)

The statement that the northern and southern hemispheres get equally hot summers is false, I believe. Even if they received equal insolation it would be hard to make valid comparisons, though, because (1) a much higher fraction of the southern hemisphere is ocean, and (2) the southern polar region is an ice-covered continent whereas the northern polar region is ocean. The statement that if the tilt were 90 degress the sun would pass over both poles at the solstice is also false -- in fact each pole would experience permanent day for 6 months and permanent night for 6 months. Looie496 (talk) 02:41, 22 March 2011 (UTC)

tidal energy backup

Would a tidal energy turbine be a good backup energy supply for nuclear power plants? especially in Japan where the plants are mostly on the coasts and they have alot of earthquakes. —Preceding unsigned comment added by 98.221.254.154 (talk) 03:30, 22 March 2011 (UTC)

No:

1) Being on the coast, they probably would have also been destroyed by the quake and tsunami.

2) The wires used to deliver electricity from them would have also been destroyed.

3) A backup power supply should be something with very little cost when not in use. However, tidal generators are exposed to the sea and weather, and, as such, would require constant maintenance. This could only be justified if they were producing constant energy.

4) The cost of building a tidal energy turbine is quite high, again meaning it only makes sense if it can be run at capacity for many years to pay off the costs.

Now, if you used the turbine to produce energy along with the nuclear power plant, normally, then issues 3 and 4 would go away. Issue 2 could possibly be addressed by putting the wiring underground, although quakes could still be an issue. Issue 1 is the toughest to overcome. StuRat (talk) 04:11, 22 March 2011 (UTC)

I think this sounds like an excellent backup system. The next time a company wants to build a nuclear power plant, they should build the tidal power system first... then scrap the rest of the plan. Wnt (talk) 04:24, 22 March 2011 (UTC)

I like to hijack that question: why don't they use stirling engines for backup cooling? As long as there is a need for cooling there is also a heat source to drive the engines. 93.132.164.231 (talk) 19:12, 22 March 2011 (UTC)

Interesting idea. Is a stirling engine quake-proof and tsunami-proof ? I suspect not, as it sounds a lot like the nuclear reactor's own cooling system. StuRat (talk) 03:24, 23 March 2011 (UTC)

Given that an earthquake can have arbitrarily high strength, nothing can ever be really quake-proof. But unlike a diesel a stirling engine won't mind being under water for some time and could be built very, very robust. 95.112.197.146 (talk) 08:58, 23 March 2011 (UTC)

I'd argue that there is an upper limit to quakes that can be expected on Earth (say 10.0 on the Richter scale), and a lower limit than this for most locations. However, I'd even settle for a design which would survive the latest Japan quake/tsunami. Is there some reason why a sterling engine can be built more robustly than the nuclear plant's own cooling system/steam engine ? StuRat (talk) 15:13, 23 March 2011 (UTC)

Escape velocity - vector or scalar?

Physicists have obviously been confused all these years. Escape velocity, contrary to what the name might suggest, is not velocity at all, but simply speed, and should be renamed as soon as possible. Well, at least, so a number of contributors (?) to the article would have readers believe. I'm amazed that this article could be allowed to spread these weird notions - WP obviously and desperately needs review panels to vet some of the rubbish perpetrated in its name. Androstachys (talk) 05:14, 22 March 2011 (UTC)

Escape velocity is infact a vector quantity, as it is relative to the centre of gravity. Plasmic Physics (talk) 05:49, 22 March 2011 (UTC)

If a craft travels at an accute angle relative to the tangent of centre of gravity, and its speed is slightly over the escape speed, then it can not escape the gravitational well. However, if the same craft travels radially from the centre of gravity, and at escape speed, then it will escape. Thus, a esccape velocity is a correct term that specifies the direction of the speed. Plasmic Physics (talk) 05:59, 22 March 2011 (UTC

(edit conflict) No, escape velocity is a scalar. It must be measured in the center of mass reference frame, but that alone does not make it a vector, as it has no direction. If the speed of the object exceeds the escape velocity at its location, then it will escape regardless of its direction of travel (provided it doesn't hit anything along the way). Similarly, exceeding the escape velocity implies an orbital eccentricity > 1, and a hyperbolic trajectory. Incidentally, the escape velocity article also stated plainly that it is a scalar before Androstachys started edit warring over it. Dragons flight (talk) 06:58, 22 March 2011 (UTC)

My edit warring your mumpsimus... Androstachys (talk) 07:30, 22 March 2011 (UTC)

Escape velocity is a scalar. It is the solution to ½v² = Φ, where Φ is the gravitational potential (relative to infinity). Since the velocity only shows up as v² (that is, v·v), the solution is directionless. Plasmic Physics is incorrect (as is the original poster). -- BenRG (talk) 06:47, 22 March 2011 (UTC)

Perhaps someone should tell NASA that the angle of launch of space probes is not important!! Androstachys (talk) 07:03, 22 March 2011 (UTC)

NASA launches have to fly through an atmosphere that adds drag and is best avoided. The definition of escape velocity assumes there is no drag or other additional forces. Dragons flight (talk) 07:57, 22 March 2011 (UTC)

Not to mention that NASA launches are rocket-powered, so escape velocity, with or without accounting for drag, is hardly relevant. The rockets leave the launch pad at a lot less than 11 km/s (which is the escape velocity at Earth's surface). It is relevant for probes like Pioneer after the rocket propulsion and gravitational slingshotting is over with. -- BenRG (talk) 08:21, 22 March 2011 (UTC)

Correct - the term for this particular type of continuously-powered flight is "gravity burn", indicating that the rocket expends some work against the gravity well that does not contribute to the kinetic energy required to reach escape velocity. One objective of a rocket engineer is often to minimize the amount of "wasted" energy that does not convert to kinetic energy of the rocket payload. On the other hand, if the objective is a lander rocket (such as the Apollo Lunar Module descent stage), the rocket engineer must optimize to minimize kinetic energy of the descent - that is, to land with a low impact-velocity and avoid "crashing." In that case, the spacecraft approaches the target gravity well, gains potential energy from gravity; and the rocket motor must supply enough energy to overcome the kinetic energy gained from losing the "escape velocity", plus additional energy to be "wasted" in gravity burn to control the descent speed through the entire time-integral of the trajectory. Nimur (talk) 16:39, 22 March 2011 (UTC)

You could fly parallel to the earth's surface at 11 km h^-1, and you wouldn't escape the gravity well. Plasmic Physics (talk) 09:56, 22 March 2011 (UTC)

Well, assuming you meant 11 km s^-1 not 11 km h^-1, then it all depends what you mean by "fly parallel to the earth's surface". If you took away the atmosphere, removed any inconvenient mountains, stopped the Earth from rotating and launched a projectile in a horizontal direction at 11.2 km s^-1 then yes, it would escape the Earth's gravity well. However, if you apply continuous thrust to keep its flight path parallel to the Earth's surface (i.e. to keep its height constant) then it is in a powered orbit, and the fact that its speed is equal to escape velocity is irrelevant because it is not on a ballistic trajectory. Gandalf61 (talk) 10:08, 22 March 2011 (UTC)

Yes you would (I assume you mean s not h). Low earth orbit is about 9 km/s, any faster and you will orbit higher (slowing down in the process). At 11 km/s you won't slow down enough to stay in orbit. Ariel. (talk) 10:18, 22 March 2011 (UTC)

As it said in the article's intro: Escape velocity is the minimum initial velocity imparted to an object that will enable it to escape a gravitational field without any further boosting. This is a vector as the imparted velocity is directly away from the body's centre of gravity or normal to its surface. Any other angle of launch at the same speed will not escape the gravity well. Anyone here done even a basic course in physics? Androstachys (talk) 11:03, 22 March 2011 (UTC)

Not so. If an angle of 90 works, and 180 works (the two extremes), then obviously anything in between will work too. The only think left is down toward the ground, but that works too (ignoring crashing into the ground, which has nothing to do with the mathematics of escape velocity). Stop thinking of the earth as a giant sphere, and instead think of it as a tiny dot. No matter which initial direction you go, at some point you will be heading away from the dot. Also, I think you are expecting escape velocity to mean the object is no longer under the influence of the mass - i.e. it will travel in a straight line. That's not necessarily the case, the object might travel in an infinite spiral around the mass, and still have escaped from it because the spiral will never bring it back to the mass - it will circle around it, at greater and greater distance, but forever making circles. Ariel. (talk) 11:09, 22 March 2011 (UTC)

Minor correction - a ballistic trajectory has to be part of a conic section, so this rules out a spiral path. A ballistic escape trajectory is either a parabola if speed = escape velocity, or a hyperbola if speed > escape velocity. "Straight up" can be regarded as a degenerate parabola or hyperbola that happens to go through the centre of the Earth. Gandalf61 (talk) 11:32, 22 March 2011 (UTC)

Reply to Androstachys - I am sure that everyone who has replied to you has done at least a basic course in physics, and I expect some have much higher qualifications. I have an A-level in physics and a degree in mathematics. It is you who are clearly out of step on this one. When you are in a hole, it is best to stop digging. Gandalf61 (talk) 11:43, 22 March 2011 (UTC)

"If you took away the atmosphere, removed any inconvenient mountains, stopped the Earth from rotating and launched a projectile in a horizontal direction at 11.2 km s-1 then yes, it would escape the Earth's gravity well." Well, no. Discounting gravitational effects from the Sun and the planets, it would go into a highly eccentric elliptical orbit around Earth. I would suggest you ask for your money back from whichever institute doled out the A-level in physics. Androstachys (talk) 13:07, 22 March 2011 (UTC)

Androstachys, you are incorrect and Gandalf is correct. If an A-level wasn't good enough for you, than may be my PhD in Physics will impress you more. A ballistic trajectory at a speed higher than the scape velocity will lead to a hyperbolic trajectory and object will scape if a collision can be avoided. No highly eccentric elliptical orbit will come out of it. So, indeed, Scape velocity is a scalar despite its name. Dauto (talk) 15:26, 22 March 2011 (UTC)

Please read Gandalf's statement properly: "If you took away the atmosphere, removed any inconvenient mountains, stopped the Earth from rotating and launched a projectile in a horizontal direction at 11.2 km s-1 then yes, it would escape the Earth's gravity well." Now read your own:"A ballistic trajectory at a speed higher than the scape velocity will lead to a hyperbolic trajectory". Small wonder the article is in such a mess. Androstachys (talk) 06:55, 23 March 2011 (UTC)

Androstachys - it would be fascinating to hear you explain just what exactly you think is inconsistent between my responses and Dauto's. I am saying that a projectile launched horizontally at a speed equal to escape velocity follows a parabolic trajectory; Dauto is saying that a projectile launched at a speed greater than escape velocity follows a hyperbolic trajectory. Both of these are escape trajectories. Gandalf61 (talk) 11:05, 23 March 2011 (UTC)

Indeed. Androstachys - stop digging and see if you can follow the demonstration from first principles given below. Gandalf61 (talk) 15:30, 22 March 2011 (UTC)

Everyone seems to be ignoring the effective potential well introduced by conservation of angular momentum. This is deeper the more angular momentum you have, and so your necessary escape speed will increase at greater angles from the radial. —Preceding unsigned comment added by 92.20.215.104 (talk) 12:04, 22 March 2011 (UTC)

No. A different angular momentum just means a different angle with respect to the radius vector at a given distance. Escape velocity is independent of the direction in Newtonian physics. In General Relativity, it isn't, but the deviations from Newtonian physics are tiny when speaking about planets. In the case of a non-rotating black hole however, even light won't escape if the direction of motion is tangential and the distance from the center (or more correctly: the radial Schwarzschild coordinate) is less than or equal to 3/2 times the Schwarzschild radius. Icek (talk) 12:19, 22 March 2011 (UTC)

Okay, gloves off, let's do this from first principles. From conservation of energy we know that the speed s and radial distance r for an object in a ballistic trajectory must satisfy

$s^{2}-{\frac {2GM}{r}}={\text{constant}}=E$

and from conservation of angular momentum we know that

$r^{2}{\dot {\theta }}={\text{constant}}=h$

Suppose that at some point in its trajectory, when r = r₀, the object's speed is greater than or equal to the escape velocity i.e.

$s\geq v_{e}={\sqrt {\frac {2GM}{r_{0}}}}$

then we know that

$E\geq 0$

The speed of the object is given by

$s={\sqrt {{\dot {r}}^{2}+r^{2}{\dot {\theta }}^{2}}}$

so if ${\dot {r}}=0$ we have

$s=r{\dot {\theta }}={\frac {h}{r}}$

$\Rightarrow {\frac {h^{2}}{r^{2}}}=s^{2}={\frac {2GM}{r}}+E$

$\Rightarrow Er^{2}+2GMr-h^{2}=0$

If E = 0 there is only one value of r that satisfies this quadratic equation, and if E > 0, there are two roots, but only one of them is positive, and we know r must be positive. So if E ≥ 0 there is only one value of r for which ${\dot {r}}=0$ i.e. distance from Earth is a maximum or a minimum. We know the object is not in a circular orbit - it is travelling too fast for that - and it cannot be in an elliptical orbit either, because then there would be two values of r for which ${\dot {r}}=0$ (at apogee and perigee). Therefore it is on an escape trajectory. QED. Gandalf61 (talk) 15:30, 22 March 2011 (UTC)

Another way to see this is to look at the orbit equation.

$r={{h^{2}} \over {\mu }}{{1} \over {1+e\cos \theta }}$

Where r is the distance from the center of mass, μ is the standard gravitational parameter, h is the specific relative angular momentum, $\theta \,$ is the direction to the orbiting body (true anomaly), and e is the eccentricity.

Note that the eccentricity is a constant such that

$e={\sqrt {1+{\frac {2\epsilon h^{2}}{\mu ^{2}}}}}$

Where $\epsilon$ is the specific orbital energy.

Since $\epsilon \geq 0$ if and only if $v\geq v_{escape}$, this implies $e\geq 1$ whenever $v\geq v_{escape}$.

If $e\geq 1$, then there exists $\theta$ such that $1+e\cos \theta =0$, which from the orbit equation implies that r goes to infinity. The angular momentum affects the eccentricity, and thus the direction of travel at infinity, but as long as $\epsilon \geq 0$ there is no value of the angular momentum (expressed in h) such that the eccentricity could be less than 1. Dragons flight (talk) 20:43, 22 March 2011 (UTC)

Refering to my earlier statement, I was of the impression that a vector description was not limited to linear paths, but also curved paths as in some matrices. Plasmic Physics (talk) 08:12, 23 March 2011 (UTC)

I understand the reasoning behind linear vectors, I was simply going by the definition of a vector. Plasmic Physics (talk) 08:15, 23 March 2011 (UTC)

I think the problem here is that the question itself assumes the speed-is-scalar-velocity-is-vector shibboleth drilled in in high-school physics classes. In high school, one of the hard questions to answer is "how can the thing be accelerating when it never speeds up?" and for this purpose it is very convenient to have two different words and insist on the distinction.

I don't think physicists, though, really pay much attention to it. It's pretty much always obvious whether you are referring to the velocity vector or to its magnitude, and so you don't need to disambiguate in the choice of the word. So we have escape velocity, phase velocity, the velocity of light, all used quite blandly and with no sense that anything is wrong. And why should it be? Velocity is just the Latinate word for "speed"; velox simply means "fast", not "fast in a particular direction". I suspect that using the Latinate word for the vector quantity and the Anglo-Saxon one for the scalar was a quite arbitrary choice at some point, made just for convenience. If it's not convenient for us, there's no reason to follow it. --Trovatore (talk) 08:56, 23 March 2011 (UTC)

That sounds like a solution to me - leave the article as it is. Plasmic Physics (talk) 09:19, 23 March 2011 (UTC)

What is the most efficient wind turbine design, in terms of dollars-per-watt?

Or hopefully, watts-per-dollar?

I'm sure the 3-bladed design that we're all familiar with is getting a little old; we already have eggbeater wind turbines and other designs. Now of all the available designs, which would be the most efficient? (Please provide stats and links to more info about that design of turbine.)

And if it is, why isn't it as popular yet? --70.179.169.115 (talk) 07:49, 22 March 2011 (UTC)

Does Wind turbine design help? The section on blade count concludes that 3 blades is best (more doesn't help much, is heavier, and has vibration issues). Ariel. (talk) 08:17, 22 March 2011 (UTC)

"Watts-per-dollar" alone doesn't define the ideal design:

1) Since construction cost is a major factor, this makes "watts-per-dollar" better, the longer it stays in operation. Maintenance cost also figures in.

2) Whether you have high or low wind speeds, and constant versus intermittent winds, would also effect the ideal design.

3) Some consideration also needs to be made for how the electricity is used. If it can be sold to a utility company at a constant rate versus being used immediately at a home, for example, which leaves open the possibility of "wasting" electricity which can't be used. In the second case, you'd want a design that produces a lower, constant rate of electricity over one that varies dramatically. StuRat (talk) 14:03, 22 March 2011 (UTC)

Reading through Wikipedia articles, I found that the "eggbeater" design was patented in 1931 but the three-blade commercial design only came about in 1957. You might also find Unconventional wind turbines interesting. 75.41.110.200 (talk) 15:05, 22 March 2011 (UTC)

1. What are some tougher game shows for Watson to tackle? 2. ...

1. What are some tougher game shows for Watson to tackle, and how will they be tougher for the A.I.?

2. What would it take to build an android named "Watson Jr." that'll have enough computing power crammed in its body to actually go to Kindergarten with warm-blooded classmates, get its height readjusted by its scientists every time it advances a grade, pass a high school with high honors, and enroll in a college?

Since a decade and a half is too long for IBM to conduct that experiment, how about one grade level every 2 weeks? What could enable a "Watson Jr." android to become feasible this way? --70.179.169.115 (talk) 07:55, 22 March 2011 (UTC)

1: Game shows are specifically designed not to be hard - they want the viewers at home to play along. 2: No one knows. Every prediction of the amount of computing necessary has come and gone, so no one will make predictions anymore. Besides the hardware (which everyone assumes will eventually arrive) there is also the software, and no one has a clue about how to do that part. I think most people assume the software will not be written, but rather the machine will learn or evolve on it's own, but both of those require a fitness function, and we don't have that either. Ariel. (talk) 08:12, 22 March 2011 (UTC)

Watson is a first step toward human A.I. the way climbing a tree is a first step toward reaching the moon (standard analogy). We just don't have the faintest idea how to do human A.I., and Watson doesn't help. IBM doesn't do A.I., anyway; it creates enterprise data management solutions for big corporations with deep pockets. That's what Watson is meant to advertise.

There's a lot of variety in game shows. "Who Wants to be a Millionaire?" would probably be much easier than "Jeopardy" since it's multiple choice. "Wheel of Fortune" is basically mindless and a computer could probably beat any human player, especially if you let it calculate the precise amount of torque to apply to the wheel. "The Newlywed Game" and "Survivor" are too human-centric to be playable. "The Price is Right" might be an interesting target for future research. -- BenRG (talk) 08:53, 22 March 2011 (UTC)

The Price is Right would be simple for Watson. The data for average prices could easily be loaded into Watson and then it's just a matter of probabilities for most of the games. I wouldn't be surprised if Watson hit every price within ~1%. Dismas|^(talk) 09:16, 22 March 2011 (UTC)

Actually, Price would be an interesting challenge for Watson, for a couple of reasons.

1. Even if accurate to 1%, guessing high (even by a dollar) knocks you out of contention -- so Watson would have to lowball the price. This is algorithmically easy, but it's not something you find in Jeopardy (in case we're talking "Watson-as-is" vs "Watson-with-minor-changes").
2. Unless Watson is the last player in the round, it would be easy for the human contestants to use the "Watson +$1" strategy. Watson's only actual defense against this would be to guess the price exactly, but that conflicts with problem #1.

That said, assuming Watson got into the final round, it would hold a major advantage with problem #2 removed. — Lomn 13:37, 22 March 2011 (UTC)

Watson is a specialist machine. It is not a generalist. It could probably be tweaked to do similar trivia shows. But it's not like Watson, as is currently programmed, would be able to play Wheel of Fortune. The inputs and outputs would just not make any sense to its program. --Mr.98 (talk) 12:54, 22 March 2011 (UTC)

Off-topic slightly, I'll bet a piece of software to play Wheel of Fotune would be a lot simpler than Watson. APL (talk) 15:54, 22 March 2011 (UTC)

Indeed, and not off topic at all! The point is that Watson is a specialist. Even very easy computational tasks are probably well beyond the specific algorithm that plays Jeopardy. It is like the classic (perhaps true? I don't know) anecdote about frogs that only know how to eat flies when they are flying or moving around, and will starve if put into a basin of freshly-killed flies. --Mr.98 (talk) 16:26, 22 March 2011 (UTC)

2) Attending each grade for only 2 weeks wouldn't work. Watson learns by trial-and-error, like humans. As such, it would need the same number of trials and errors that children need (or perhaps slightly fewer, since it has perfect memory). Therefore, the only way to get it to learn quicker would be to provide input quicker. Since a regular school can't run at hyper-speeds, this accelerated input would need to be provided in another manner. StuRat (talk) 13:52, 22 March 2011 (UTC)

If you allow it to keep its current database, Watson could probably pass most highschool and college standardized tests now. If you skip the essay questions, anyway.

Erasing its brain and Learning purely from class would be problematic. For us that kind of classroom instruction depends on a huge amount of knowledge we just pick up from observing the world around us. Without background general knowledge even the simplest textbooks would be incomprehensible.

Imagine if you read in a text book "All animals with four legs are quadrupeds.", and then on an exam you were asked "Is a cat a quadruped?" you'd have no problem. You learned this in the book! But you didn't. You only learned part of it from the book. You had outside knowledge that cats have four legs.

IBM gave that kind of general knowledge to Watson by having it read and remember millions of pages of written material. (It wouldn't surprise me if Watson has Wikipedia in his brain somewhere.) Of course, no human could learn that way.

Even solving issues like speech recognition in the classroom, I don't think that Watson is compatible with human methods of learning. It was designed to use massive data-dumps in text format. (Even if the exam had a photograph of a cat it wouldn't help Watson.) APL (talk) 15:54, 22 March 2011 (UTC)

I always wonder why thinking like a human is still the gold standard for AI. (I know it was for Alan Turing, but a) he was thinking speculatively and b) it was a long time ago. I don't expect a car to get around as well as I do; I expect it to get around much more quickly. I don't expect my computer to sort a file of a million records in the way I would; I expect it to sort the file in minutes. From what's said above, it sounds like Watson solves problems in a very different way from a human. It should be quite good at Countdown, both the anagram games and the arithmetic. Itsmejudith (talk) 16:17, 22 March 2011 (UTC)

Even your filing algorithm is "like a human," it's just faster (and probably better optimized than most humans, but humans manually could do a insertion sort, too, if they thought to do it). Speed is not the interesting issue; even the most primitive computers and calculators can beat humans at speed. The reason humans are the gold standard is because as far as we can tell, the algorithms are well beyond what we can approximate with machines, even with all of their speed. --Mr.98 (talk) 16:29, 22 March 2011 (UTC)

Both ways of "thinking" have their uses. One use for a computer that "thinks like humans" is in search engines. The current methods often give results that any human can tell don't match the (intent behind the) search criteria. StuRat (talk) 16:30, 22 March 2011 (UTC)

But it's not even a way of "thinking". One can marvel at the speed in which computers do things, but their ability to do anything complex is very limited. They usually do just very simple things very fast. I don't consider that "thinking" in any meaningful sense. Just because a computer chip can shuffle cards faster than I can doesn't mean that shuffling cards is a form of "thinking". --Mr.98 (talk) 21:31, 22 March 2011 (UTC)

That's why I put "thinking" in quotation marks. Would you prefer "processing", to collectively refer to human thinking and machine calculations ? StuRat (talk) 03:20, 23 March 2011 (UTC)

First question of 1): University Challenge. Probably the toughest tv quiz in the world. 92.15.23.133 (talk) 17:58, 22 March 2011 (UTC)

By the way, when I said the Watson could "probably" pass an exam now, I mean its underlying technology. Some custom software would be needed to create an interface between the Watson engine and the test. (Like whatever software they wrote to handle the "game" aspects of Jeopardy!) APL (talk) 18:46, 22 March 2011 (UTC)

University Challenge is an interesting suggestion - of course Watson could know all the others, but the buzzer element is very interesting. If I said "Lima is" you could probably shout out "Peru" and be right, or something like but harder in UC. I'm not sure an AI would be able to play the probabilities like that. Grandiose (me, talk, contribs) 19:09, 22 March 2011 (UTC)

High altitude effects indoors

I was recently watching a basketball game on television, broadcast from Denver, Colorado. The announcers made reference to how the play of the game would be affected by the high altitude of the area. Because the game was being played indoors, would the effect be significantly less than if it were to be played outdoors? Kansan (talk) 13:27, 22 March 2011 (UTC)

The game being indoors vs outdoors won't change the altitude effects, assuming the basketball arena is unpressurized (I don't know of any that are). Naturally, playing indoors vs outdoors would affect many aspects of basketball, but those effects wouldn't be related to altitude. — Lomn 13:32, 22 March 2011 (UTC)

So all other things being equal, the air inside a building would have the same air pressure of the surrounding area, right? Kansan (talk) 13:34, 22 March 2011 (UTC)

Yes. There are stadiums with soft covers that are partially supported by increasing the air pressure inside, but I believe that pressure difference is tiny compared with that due to the elevation difference. StuRat (talk) 13:42, 22 March 2011 (UTC)

Certainly within the tolerance of "has a measurable effect on athletic performance". Any building is going to have slight positive or negative pressure relative to its environment, but that's orders of magnitude smaller than the overall change in air pressure from sea level to Denver. Sea level to Denver is a difference of about 17 kPa, which is also about a 17% change. We note that the differential of a positive pressure enclosure is only about 0.05 kPa, a change of 0.06%. — Lomn 13:47, 22 March 2011 (UTC)

Thanks for the help. Kansan (talk) 14:19, 22 March 2011 (UTC)

What is the maximum recommended amount of salt in water for dairy cattle?

What is the maximum recommended amount of salt in water for dairy cattle?

Back ground if your interested: My firm recently drilled a water well for a gentleman who in setting up a rather small dairy farm. The water contains 1520 ppm of sodium, ideally of course there would be none. We are trying to seal the lower parts of the well with a concrete mix, but the question remains. What is the maximum recommended amount of salt in drinking water for dairy cattle? Any help would be greatly appreciated. JohnQposter (talk) 14:00, 22 March 2011 (UTC)

This site says less than 3000 ppm of "total dissolved solids", which includes sodium, is "Usually satisfactory for most livestock". This site says (specifically about salinity) < 1000 is good, and for 1000-3000 ppm, "Generally no problems; possible temporary diarrhea to animals not accustomed to this water". --Sean 15:00, 22 March 2011 (UTC)

Time dilation

I remember reading some time ago an explanation of time dilation in special relativity based on transfer of information and the constancy of the speed of light. So if A is stationery and B travels some distance away they will observe each other's clock to tick slower than their own.

The explanation involved A (using his own clock) sending B one signal each second but due to c being constant for all observers, B receives the signals at more than one second apart (based on B's clock). Does anyone know of this explanation? Thanks. Zain Ebrahim (talk) 15:48, 22 March 2011 (UTC)

That sounds like the Doppler shift (which exists even in Newtonian physics). At relative rest, signals sent at a constant rate are received at the same rate, but with recessional motion, the received rate is slower:

         A/ / B         A/ / / B
         A / /B         A / / /B
         A/ / B         A/ / /B
         A / /B         A / / B
         A/ / B         A/ / B
         A / /B         A / /B

You can derive all of special relativity from the rule that the ratio of the sent and received rates depends only on the relative speed. Time dilation is not especially easy to derive, though, because it requires synchronized clocks. The twin paradox is easier. -- BenRG (talk) 18:53, 22 March 2011 (UTC)

Another question about neurons

How do axons and dendrites meet up? What is their physical method of motility? Layman's terms would be appreciated, even if simplification makes the answer less than perfect. 20.137.18.50 (talk) 19:16, 22 March 2011 (UTC)

They meet at specialized junctions called synapses. Dendrites don't extend very far from the cell body, and they grow in intricate tree-like patterns whose rules are not all that well understood. Axons, in contrast, can extend for enormous distances. The tip of a growing axon is a structure called a growth cone, which extends numerous tiny fingers of protoplasm called filopodia, which interact chemically with things that they touch, sticking to some and being repelled by others. These attraction-repulsion processes cause the growth cone to travel through the brain or body, sometimes by very complex routes, extending the axon behind it as it goes. Here is a link to a youtube video that explains the process and shows it in action. Looie496 (talk) 19:51, 22 March 2011 (UTC)

Real-time glacier data

Hi. Is there any reliable source on the Internet where I can select any monitored glacier from a worldwide database and get real-time or recent data on parameters such as flow rate, temperatures, height changes, precipitation, status of retreat or advance, density, any moulins or glacial lakes and dams, calving events, etc? Thanks. ~AH1^(TCU) 20:27, 22 March 2011 (UTC)

What questions are you trying to answer? Most glacier monitoring looks at things like mass balance (e.g. thickness) and edge location, which are variables that change slowly and hence can be recorded infrequently. The number of intensively monitored glaciers is probably very low. Dragons flight (talk) 00:13, 23 March 2011 (UTC)

Agreed. There's no need for real-time data on things which only change at a glacial pace. StuRat (talk) 03:16, 23 March 2011 (UTC)

Wikipedia has a stub article about the World Glacier Monitoring Service that collects standardised observations on changes in mass, volume, area and length of glaciers with time. Here are real-time data from the Hubbard Glacier (Alaska)] and the Tweedsmuir Glacier (Canada). You may also find glacier webcams. Cuddlyable3 (talk) 10:30, 23 March 2011 (UTC)

Poppy seeds

Could I grow poppies from the seeds on poppy seed bagels? --70.244.234.128 (talk) 23:14, 22 March 2011 (UTC)

Maybe if you bought some seeds directly, but the seeds on a bagel are baked, and thus dead. If you buy a bottle of seeds make sure they are not toasted. Ariel. (talk) 23:22, 22 March 2011 (UTC)

Or Irradiated. It wouldn't surprise me to find that poppy seeds are routinely irradiated (it's not uncommon for spices), which would kill parasites, but also the seed. Ariel. (talk) 05:24, 23 March 2011 (UTC)

You can grow the seeds from many other fresh fruit and vegetables. Experiment and see. Searching for growing pips (no ""s) on Google gives a lot of results. 92.15.14.45 (talk) 12:13, 23 March 2011 (UTC)

March 23

Why isn't irradiation used on sushi and sashimi?

Thanks. Imagine Reason (talk) 00:54, 23 March 2011 (UTC)

Irradiation has to take place in a specialized irradiating facility. Sushi and sashimi is prepared using extremely fresh fish. I think it would make it rather prohibitive, unless you're imagining that every Japanese restaurant would have a gamma irradiator or a radiation source on premises. The cost would be huge. --Mr.98 (talk) 01:08, 23 March 2011 (UTC)

I think that food irradiation equipment is dangerous in untrained hands, they contain Cobalt-60, which is not something you'd want your waiter fiddling with. APL (talk) 01:32, 23 March 2011 (UTC)

Why would you want to irradiate sushi and sashimi anyway? F (talk) 01:20, 23 March 2011 (UTC)

Presumably to kill off the parasites that are famously a danger of improperly prepared sashimi. APL (talk) 01:32, 23 March 2011 (UTC)

See Anisakis, Clonorchis, Echinostoma, Diphyllobothrium latum, and others... -- Scray (talk) 01:54, 23 March 2011 (UTC)

Irradiation could kill the microbes in raw fish, but it wouldn't do anything to stop a variety of chemical reactions that would rapidly reduce it to slime. Any sort of raw meat is full of enzymes that will rapidly break it down if they aren't either denatured by cooking or suppressed by refrigeratiion. Looie496 (talk) 02:56, 23 March 2011 (UTC)

I was just expanding on the "parasites" statement. That said, while irradiation "wouldn't do anything to stop" spoilage, I also don't know that it would necessarily cause spoilage. Couldn't one irradiate while refrigerating? I agree with APL's comment about cost as the most obvious problem. -- Scray (talk) 03:41, 23 March 2011 (UTC)

Radiation can change the taste, particularly if the food contains fat, eg fish, so it is reserved for things like herbs with strong flavour and low fat. Graeme Bartlett (talk) 09:29, 23 March 2011 (UTC)

The purpose of irradiation is to extend the shelf life of foodstuffs. Sashimi is not suposed to have a significant shelf life. Simply chilling the fish works well - don't fix what ain't broke. Roger (talk) 12:41, 23 March 2011 (UTC)

Why do you believe that they are not irradiating sushi? Since a couple of weeks, indeed, they are using irradiation on sushi, sashimi and many other foodstuff. 212.169.184.141 (talk) 12:58, 23 March 2011 (UTC)

In case it's not perfectly clear, 212.169.184.141 is making a joke about the accident at the Fukushima power station. APL (talk) 14:01, 23 March 2011 (UTC)

Although it's a pretty bleak joke, and, factually, not totally correct, as far as I know. Quest09 (talk) 15:07, 23 March 2011 (UTC)

Environmental Improvement Equipment

Hello

I am writing this question in reference to President Obamas Tax Proposal on enviormental improvment projects that gives the American Peaple a Tax break when purchasing an recycling item? Please send me any in formation regaurding this issue? I am also in the means of working in a working on a enviormental project of a large scale which objectives is to confine or section off unwanted flying debris.I aim on marketing my product and can use any information that will help the future coustomer. Thank you God Bless Joseph I.Montoya Alavedga (talk) 01:00, 23 March 2011 (UTC) Jim

I searched, but I can find no information about such a program or a proposal to make such a program. Can you give more information about it? Where did you hear about it? When? Is it a proposal, or an actual program? Ariel. (talk) 02:06, 23 March 2011 (UTC)

Edit: Is it one of these? Ariel. (talk) 02:09, 23 March 2011 (UTC)

Inflation, Big Bang terminology

From what I understand it, inflationary cosmology posits a rapidly-expanding primordial false vacuum which at a certain point is punctuated by the formation and growth of low-potential true vacuum bubble universes, of which our universe is one such bubble. In this view, which genesis corresponds to what people refer to when they refer to "the big bang"-- the original initial-state of the false vacuum multiverse, or the initial formation of each bubble universe? Cevlakohn (talk) 05:40, 23 March 2011 (UTC)

What you're describing sounds like "old inflation", which is dead as a theory as far as I know, having been replaced by slow-roll inflation—see Inflation (cosmology)#Early inflationary models and the following section. That doesn't really affect your question, though. The answer is that the "big bang" happens at the end of inflation. Technically, though, it refers to a time just before the end of inflation, when there would have been a singularity if the post-inflationary model were correct back to the beginning of time, which it isn't since the inflationary model takes over at some point. So the "big bang" that subsequent times are measured from never actually happened. (See Age of the universe#Explanation.) -- BenRG (talk) 07:56, 23 March 2011 (UTC)

Thyroxine and circadian rhythm

Is thyroxine released according to the body's circadian rhythm, or is it released continuously over the 24-hour period? I've looked at the article but it doesn't contain this information. --TammyMoet (talk) 09:52, 23 March 2011 (UTC)

Probably teaching you to suck eggs, but you might find further information and useful links from the Physiology section of the Thyroid article and from the Thyrotropin-releasing hormone article. At first glance it looks as if the primary known modifier is temperature, but I suppose that in turn may be affected by circadian rhythms. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 11:33, 23 March 2011 (UTC)

Just curious, why would he wan't to learn how to suck an egg? Plasmic Physics (talk) 11:41, 23 March 2011 (UTC)

Teaching grandmother to suck eggs 129.234.53.49 (talk) 14:09, 23 March 2011 (UTC)

You won't get the 'yolk' if you don't suck eggs Richard Avery (talk) 14:59, 23 March 2011 (UTC)

manmade earthquake

I was reading the previous posts about this and none address the possibility of setting off a bomb a a point in the fault that has been identified as having the most potential energy built up (where the most tension exists) to trigger a natural earthquake that might not have happened for another couple of years. Could this be plausible?165.212.189.187 (talk) 14:44, 23 March 2011 (UTC)

We've discussed this very topic before. Basically:

1) The force required would exceed that of even the most powerful nuclear bombs, unless the fault was ready to go anyway, in which case it would go soon on it's own.

2) The location is typically so far down that it would be difficult or impossible to dig down that far. StuRat (talk) 15:06, 23 March 2011 (UTC)

Null 4 vectors

Taking into account large scale effects (such as non-negligible evolution of the scale factor a(t)) is it right to say that the events which make up my light cone (i.e. those that I can see at a given point in spacetime) are all the points displaced by null 4-vectors (those for which the spacetime interval is zero).

Sorry, I don't know if I am being foolish, but I am having trouble taking into account the evolution of a(t) over the photons time of flight.