Wikipedia:Reference desk/Science

May 10

Constellations of stars

where to look for it : the Big Dipper, the Little Dipper, the Orion and the Andromeda? —The preceding unsigned comment was added by 72.187.17.165 (talk) 00:08, 10 May 2007 (UTC).

I'm not sure what it is that you're looking for: we have articles on the Big Dipper, the Little Dipper, Orion, and Andromeda. We also have an article on star chart that will link you to a useful star map. Let us know if you were looking for something else. - Nunh-huh 00:19, 10 May 2007 (UTC)

Stellarium is my favourite way to locate things in the sky. It's the easiest star software for beginners because it very closely mimics what you actually see with your eyes. Vespine 00:21, 10 May 2007 (UTC)

Where to look for these in the sky depends totally on where you are on earth, and the time of year. Orion, in particular, is not visible all year from most places, though it is unmistakable. Get yourself a cheap pocket planisphere from anywhere that sells telescopes.--Shantavira 08:50, 10 May 2007 (UTC)

Measuring Potential Difference

[[Image:NonFreeImageRemoved.svg -->|thumb|When in doubt, use electrochemistry!]] Hello. If electrons are not flowing into the circuit, is it possible to measure the potential difference across the terminals of the dry cell? Thanks. --Mayfare 00:31, 10 May 2007 (UTC)

In theory: no. In practice: no. Please see voltmeter. To measure a voltage, one needs a current. With an exceptionally good insturment, the current can be exceptionally small, but some electrons must flow. -Arch dude 01:41, 10 May 2007 (UTC)

An electrostatic voltmeter draws no current (not even a little bit). Also see potentiometer for measuring voltage: no current is drawn at balance. —The preceding unsigned comment was added by 88.110.183.42 (talk) 02:03, 10 May 2007 (UTC).

Well, no continuous current. There's still a transient, and probably a very small leakage current. -- mattb 05:20, 10 May 2007 (UTC)

The link is at electrometer. And in principle, a virating-reed electrometer could draw no current, not even a charging current (if the vibrating reed were placed near but not in contact with the already-charged object). Electrons would flow on the charged object but none would "leave".

Atlant 12:30, 10 May 2007 (UTC)

So many electrical engineers and so few chemists! You could calculate the electric potential based on the concentrations of the chemical in the battery. See dry cell for the OP's question, and electrochemical cell for a brief discussion of how to do this. Nimur 08:19, 10 May 2007 (UTC)

There are quantitative details at Standard electrode potential, with examples, and this [[:Image:NonFreeImageRemoved.svg -->|handy chart]]. Nimur 08:21, 10 May 2007 (UTC)

A potentiometer in the older sense was a bridge device with a standard cell, a slidewire and a galvanometer. The standard cell furnisshed a relativly constant voltage with a correction for temperature. Certainly tiny currents flowed from the standard cell and the external source of EMF to be measured as the slidewire was adjusted to null the current, but it was likely microamperes or less. At the instant when the voltage was said to be "measured," i.e. determined, no measurable current would be flowing, as shown by the non-deflection of the galvanometer. A modern digital voltmeter such as the Fluke 87V has a 10 megohm input impedance, so is if is measuring say a 1.5 volt emf, it would draw 0.15 microamperes. If it were measuring the max allowable voltage of 1000 volts, it would draw 100 microamperes. In a potentiometer bridge circuit, this could be reduced to a fraction of a microampere.Vacuum tube voltmeters from the 1940's on had this high or higher input impedances. Edison 16:05, 10 May 2007 (UTC)

Shouldn't it be 'yes', it is possible to measure the potential difference, but it will be 0 :] HS7 17:54, 10 May 2007 (UTC)

HS7: No, it is not zero. The potential difference is unquestionably there when there is no current flowing; the question was whether it can be measured without drawing current. --169.230.94.28 00:58, 11 May 2007 (UTC)

Principle,law,hypothesis,theory.theorm

What is the difference between principle, theory, theorm, law and hypothesis? —The preceding unsigned comment was added by Invisiblebug590 (talk • contribs) 08:04, 10 May 2007 (UTC).

Principle, theory, theorem, physical law, and hypothesis? Laws of science seems to be a good introduction as well. Nimur 08:25, 10 May 2007 (UTC)

Embalming and eyes question?

This is a bit morbid but I just want to know whether the eyeballs are removed for embalming and are the eyelids sewn or closed shut in some way like the mouth? I remember hearing somewhere that the eyelids are sewn shut to stop them 'popping' open during the viewing and that many years ago a penny would be placed on each eyelid for this reason. I don't know whether this was ever really done or whether it was instead a cultural/tradition thing but have always wondered about it and thought more about it recently when thinking about organ donation and the eyes were on the list. I'd appreciate any relevant answers or info, particularly from morticians/embalmers. Jocee 13:18, 10 May 2007 (UTC)

There are two methods that are widely used for keeping the eyes shut. The most common is the "eye cap", which is a bit like a contact lens with "grippers". It's placed under the eyelids, over the eyeballs, and keeps the lids in position. Another less-used technique is to glue the lids together. Eyeballs are not removed. Even if the corneas have been donated, it's just the corneas that are removed, not the entire eyeball. Coins on the eyes is a very old tradition, but usually explained religiously (e.g. payment for Charon's ferry) rather than practically. - Nunh-huh 13:36, 10 May 2007 (UTC)

I always assumed that the coins were placed on the eyes to assure that as rigor mortis set in, the eyelids were closed; if they were open at that time, it'd be impossible to fix until after the rigor had passed. ("He's not dead, he's just starin' at Wikipedia! Honest -- hold a mirror to his mouth!")

Atlant 16:34, 10 May 2007 (UTC)

The timing of rigor mortis makes it unlikely that this would be the reason unless the coins are placed there as soon as death occurs and would only be useful if the body is being displayed fairly shortly thereafter. Many people forget that rigor mortis is only a transient state. DMacks 16:54, 10 May 2007 (UTC)

According to our article, you've got 3-4 hours to get the coins on, else Aunt Bertha will be staring at you for the next 36 hours. And lots of people don't die by surprise, so application time often wasn't a factor.

Atlant 22:25, 10 May 2007 (UTC)

Freezing Points

Hello, My question is: What is the freezing point of a 25mM sodium bicarbonate solution? —The preceding unsigned comment was added by 208.38.54.242 (talk) 15:28, 10 May 2007 (UTC).

See our article about freezing point depression to learn how to calculate this. DMacks 16:15, 10 May 2007 (UTC)

Why elliptical orbits?

This is not an assignment, it is simply a discussion. My teacher suggested that I post it here. We were wondering why planets travel in an elliptical orbit? Why not just a circle? What is the other focal point? We haven't found it anywhere, but we're looking. Thanks for any insight you can give us! Someone999456 17:43, 10 May 2007 (UTC)

Hmm, tough one. I can't answer your question outright, but I suggest you take a look at Kepler's laws of planetary motion Aiyda 18:26, 10 May 2007 (UTC)

Our orbit article says that there is "nothing present at the other focus." --LarryMac | Talk 18:27, 10 May 2007 (UTC)

Orbits can be perfectly (or very nearly) circular, but it takes some very precise starting conditions - given the immense number of "non-circular" orbits compared with the (technically one) truly circular orbit, its no surprise that most orbits seen are elliptical, as a matter of probability. As for what is present at the other focus of the ellipse - as far as I'm aware, this has no real physical meaning, and is just an artifact of the mathematical description - someone please, correct me if I'm wrong. Of course you could say it's the point at which the orbit would be unchanged if the orbitted body was moved to it... Icthyos 18:30, 10 May 2007 (UTC)

The fish's last sentence is wrong because the speeds would be wrong. —Tamfang 02:00, 11 May 2007 (UTC)

(eC) Kepler's laws of planetary motion are just applications of the usual laws of nature involving moving objects (force, inertia, gravity, etc). In addition to that Kepler page, see also Orbit equation and Orbital mechanics for various levels of related mathematical and physics discussions. The simple answer for "why not a circle" is because as the Earth (for example) swings past the Sun (for example), it's moving too fast for gravity to slow it down and pull it back around in a circle (note that there are cases of circular orbits, but they are relatively rare; you can think of a circle as just a special case of an ellipse, one where the two focci are at the same point). There's nothing really "at" the other focal point per se. DMacks 18:31, 10 May 2007 (UTC)

A circle is a type of ellipse (where the minor axis equals the major axis and the two focus points coincide). Consider what would happen if all orbits started as circular. After that, any impact or gravitational tug from nearby planets or objects would perturb it into a non-circular elliptical orbit. StuRat 20:25, 10 May 2007 (UTC)

Another way to look at it is that an ellipse forms a perfectly stable orbit - with all of the forces on the planet in perfect balance the whole way around. There is simply no left-over force to pull the orbit into a circle...so from an energy perspective - it makes no difference whether your orbit is elliptical or perfectly circular. SteveBaker 21:06, 10 May 2007 (UTC)

This question seems somewhat similar to the oft-asked question "Why do the vast majority of planets spin on an axis?". There's absolutely no reason for them to not spin, or orbit elliptically, considering the effectively random conditions that they formed under. Circular orbits and no rotation are such incredibly precise conditions for a planet to have that it's almost impossible. 213.48.15.234 09:00, 11 May 2007 (UTC)

SteveBaker's suggestion that the forces are balanced in an elliptical orbit cannot be true - negating perturbations from other planets, there is only one force acting on the planet - from the Sun. It's all basically down to how much angular momentum the planet has. Angular momentum is constant throughout time for a planet - neglecting perturbations from other objects.

In an ellipse, near to perihelion, the planet has more angular momentum than a planet orbiting in a circle at that distance (so will begin to draw away from the sun). Near to aphelion, the planet has less angular momentum than a planet orbiting in a circle at that distance (so will begin to fall inwards towards the sun). Angular momentum increases with distance from the sun for planets in a circular orbit, i.e. Earth has much more angular momentum than Venus, despite similar mass and Venus travelling faster.

So it will not orbit in a perfect circle, unless it had the required angular momentum to match that for a circular orbit at that distance from the sun. As angular momentum for a circular orbit rises as distance from the Sun increases, an object which is getting further from the Sun soon falls behind on the required angular momentum (because its individual angular momentum is constant through time), so it falls back inwards into the solar system, where it suddenly gets ahead of its angular momentum requirement, so it rises back outwards from the Sun. It might have enough speed in the first place to escape completely, but that is another question.Richard B 13:49, 11 May 2007 (UTC)

I thought the other focus of the planets' orbits was the center of mass of the solar system? --froth^t 18:49, 15 May 2007 (UTC)

Since the orbits have different eccentricities, and their long axes point in all different directions, they can hardly have a common second focus. —Tamfang 23:12, 15 May 2007 (UTC)

life question

If the sun were to switch off instead of exploding and destroying the earth, would the bacteria that live in volcanoes and use sulpur as a source of energy, or the creatures that eat them, ever evolved into an inteligent, human-like specis? And would they be able to live outside of the volcanoes, somehow extracting sulphur from rocks? Apart from these, are there any other possible sources of energy that living organisms can use if there wasn't a star nearby? HS7 17:50, 10 May 2007 (UTC).

First of all, assuming that the outward pressure supplied by the sun's nuclear fusion is replaced in equal quantity (ie preventing the sun from collapsing on itself), then on a simplistic level, we wouldn't actually notice any difference - since the mean free path of the photon within the sun is so small (typically a few mm according to [[Sun#Core|the article]) the photons' "travel time" between being produced and reaching Earth is around a million years or so, though the lower limit given in the article is 17,000 years - we certainly wouldn't notice a lack of sunlight without our generation - Just an aside.

As for life continuing on without the light of the sun - I'm skeptical. Perhaps some xenobiologists could help out? Icthyos 18:25, 10 May 2007 (UTC)

I see no reason why life in, say, deep oceans wouldn't continue to exist for quite some time, as the sun has little to no energy input in those systems. Ecosystems surrounding black smokers would be one such example. However, evolving from that state to one of human-level intelligence is quite a stretch. — Lomn 20:03, 10 May 2007 (UTC)

Yeah - it's not that life up here on the surface is somehow preventing those creatures from evolving - it's that in their ecological niche - they are better off being how they are right now. Whilst there is energy to be had in those weird setups - it's pretty pathetic compared to sunlight - my guess is that they are using all the energy they can get just to be what they are now. It's a commonly held myth that all creatures evolve towards the pinnacle of intelligence and everything is moving steadily "up the evolutionary ladder". Evolution doesn't work that way - it works to provide the best match between the creature and it's environment. That can also mean evolving to be less sophisticated - smaller, weaker, slower or more stupid. When ordinary land creatures get stuck in a deep dark cave (where their eyes are useless) - they gradually evolve so as not to have eyes anymore. Whilst that seems like a setback for them - it's quite the opposite. By not spending the energy required to make and maintain eyes - and all of the brain to make use of them - the creature has more energy left over for reproduction - and that's all evolution "cares about". SteveBaker 21:03, 10 May 2007 (UTC)

Steve, are you sure that life up here couldn't, at least in principle, be impeding the evolution of those creatures? Sidestepping the practical question of survival of life without sunlight... if most life on earth were magically destroyed, wouldn't we expect to see adaptive radiation among the survivors? --Allen 03:12, 11 May 2007 (UTC)

I don't see how - they use completely different resources to creatures at the top of the water column and on land - it's hard to imagine what we could be doing to prevent them from evolving - they are trapped by their very weird life-styles. But you are certainly correct in saying that if we all magically disappeared one day, they would evolve to fill our niche - but that wasn't the question. The questioner specifies that all of the resources in the 'upper world' have vanished due to the abrupt loss of sunlight - so there is no resource for these creatures to evolve to take advantage of. Heat from the earth's core is the only remaining source of energy for them to extract. SteveBaker 03:30, 11 May 2007 (UTC)

You're right; I think I misunderstood the emphasis of what you had said. --Allen 03:49, 11 May 2007 (UTC)

There is evidence that there are no organisms or groups of organisms living on earth which are independent of the sun's energy for life, including the above-mentioned deep-sea vent communities. This was discussed (though consensus was not reached) on this reference desk in an article entitled "when the sun goes red giant" which was at least partially edited on September 27, 2006, I don't know how to link this conversation personally, but perhaps someone else could help me out. ^tucker/_rekcut 22:40, 10 May 2007 (UTC)

[I provided your link.] --Tardis 23:09, 10 May 2007 (UTC)

Shouldn't all life on the top of the planet cease to exist in such a contest? Wouldn't it be just a giant ice cube? Bastard Soap 13:26, 11 May 2007 (UTC)

the earth did become a giant ice cube (well actually a ball but...) a while ago and a lot of life survived. But they did still have sunlight getting through the transparent ice to the water at the bottom of the oceans. So nothing could live just on the heat from the earth? How does the sun affect the sulphur creatures?

old books

can anyone reccomend any places (in england) where I can find old books. I am looking for both books that were written a few decades ago and aren't available in bookshops any more, and for books written a few centuries ago. In particular I am interested in classical greek and roman books (translated into english).HS7 18:02, 10 May 2007 (UTC)

Try Book collecting. Some folks on the Talk page there may have an interest in the subject and can speak more for where to look for these things. You're probably going to be looking at eBay or finding small book collecting shops to do this. -- Kesh 18:44, 10 May 2007 (UTC)

As places, Hay-on-Wye or the Charing Cross Road in London are certainly the ones to go for. Johnbod 20:00, 10 May 2007 (UTC)

I suppose we need to know your location a bit more precisely if we are to recommend particular brick and mortar stores. For online bookstores, I believe Amazon.com also sells used, recent books. StuRat 20:06, 10 May 2007 (UTC)

I found Totnes almost as interesting as Hay-on-Wye. —Tamfang 01:58, 11 May 2007 (UTC)

Pollination

What types of bees did most of the pollinating in the Western Hemisphere before the importation of the European honeybee? Corvus cornix 18:06, 10 May 2007 (UTC)

In my little garden I see lots of different insects visiting the flowers. If you look close, there are manny different types of flies among them. 84.160.220.235 19:37, 10 May 2007 (UTC)

That's right, it's not just bees that pollinate flowers, and not just insects, either. Hummingbirds do their share, as well. StuRat 19:58, 10 May 2007 (UTC)

paper cut

After getting a papercut, how long should I expect it to take before I can't see it any more. I've had a cut on my finger for hours and there is still a faint orange line. And is paper cut one word or two? HS7 18:06, 10 May 2007 (UTC)

You shouldn't be worried!! If all there is after a couple of hours is a faint orange line, there is no problem what so ever. I would expect it to take 1-4 days to heal, but other factors can affect it. Someone999456 21:47, 10 May 2007 (UTC)

There are many factors in healing, including your age, the location and severity of the cut, whether it gets infected, whether it's wet or dry (cuts kept moist heal much faster), and so on. I once was reading in bed and when I turned the page, got a nasty paper cut on my eyeball. I thought I'd be suffering for a while, but by the next day it had totally healed, probably due to being kept moist. You may have noticed that small injuries in your mouth heal very quickly, too. Paper cuts on fingers usually take me 2-4 days to repair. Wound healing might have more information for you. --TotoBaggins 19:01, 10 May 2007 (UTC)

Seriously, on your eyeball? Ouch! Aiyda 19:43, 10 May 2007 (UTC)

One of my friends, the same thing happened to him, but he said not to worry about it because the eye is the fastest healing of all body tissues. Is that right? [Mac Δαvιs] ❖ 01:04, 11 May 2007 (UTC)

I once cut my finger about 3mm deep with a simple sheet of paper. It took weeks to heal. I suppose, with enough bad luck, a paper can cut all the flesh right to the bone. 84.160.220.235 19:05, 10 May 2007 (UTC)

One important factor is that the two sides of the cut should be held together. Normally this isn't an issue, but if the cut is on your hands and you are using them, the cut can be stretched apart from time to time, slowing the healing process. A bandage can help with this, but also can keep oxygen out, and oxygen promotes wound healing. StuRat 19:45, 10 May 2007 (UTC)

The cut I had was clean and smooth and nearly painless. A surgeon would have been proud of it. 84.160.220.235 20:53, 10 May 2007 (UTC)

Wound glue can be helpful with these "surgical-grade" paper cuts. ;-)

Atlant 12:17, 11 May 2007 (UTC)

I once cut my foot open on the disc draw of my DVD player. It hurt like all hell and was quite deep and long. Moral of the story? Don't operate your DVD player with your toes... Nebuchandezzar 08:10, 11 May 2007 (UTC)

Doesn't a scab forming on cuts stop them separating :? I asked this question becuase I am used to my cuts dissappearing in a few hours or sometimes a day :) Is it possible to get 'out of practice' at something like that :( And I still don't know if it is one word or two :( HS7 20:01, 13 May 2007 (UTC)

Yes, but that takes some time, especially if the wound isn't held together while the scab forms. I have seen them start at the edges of a wound and then bring the two sides together, though, much like sutures. I bet this would look cool on time lapse photography, like zipping the wound closed from both ends. If the sides are two far apart, however, you end up with a scar. StuRat 22:03, 13 May 2007 (UTC)

What's the difference between a pathogen and an antigen?

What's the difference between a pathogen and an antigen? Anchoress 19:01, 10 May 2007 (UTC)

A pathogen is a whole infecting organism alive that causes pathology and disease, whereas an antigen is merely a molecule that triggers an immune recognition and reaction. An antigen is never the whole infecting organism (virus or bacteria) but a molecule on the organism's surface that is recognised (a protein or glucoprotein). Hence one infecting bacteria may be recognised by several antigens on its surface, and a purified antigen may be given on its own as a non-infectious non-pathogenic vaccination to teach the immune system to recognise and deal with the real pathogen if ever encountered. David Ruben ^Talk 19:10, 10 May 2007 (UTC)

Cool, thank you very much for that answer. Anchoress 19:57, 10 May 2007 (UTC)

I wonder if a prion could be called both an antigen and a pathogen. --JWSchmidt 19:20, 10 May 2007 (UTC)

A protein based antigen is typically only a small piece of protein, and not the whole protein, so probably not. Someguy1221 21:53, 10 May 2007 (UTC)

Also, is there any evidence that prions provoke an immune response? Anchoress 15:00, 11 May 2007 (UTC)

According to Clearance and prevention of prion infection in cell culture by anti-PrP antibodies, antibodies to prion protein can be made by mice. see also. --JWSchmidt 19:54, 11 May 2007 (UTC)

Leaf (species) identification for Commons images

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I just uploaded two images to Commons, photos I took a while back at the Montreal Botanical Gardens. They're of some leaves of a particular plant which was either a small tree or a large bush. I'd like to name the species of the plant on the description page, but I have no idea what it is. If someone would identify it for me, I would be grateful, although this is low priority. Above are the two images in question (don't worry, they're GDFL/CC:SA-AT licensed). I would appreciate a reply through my user talk page if possible (use the t in my signature). Nihiltres^(t.c.s) 20:28, 10 May 2007 (UTC)

A Pawpaw trees perhaps? I would guess that it would be some member of the Annonaceae family. S.dedalus 01:29, 11 May 2007 (UTC)

Onion milk?

I just peeled away the first layer of two onions and both leaked some kind of white, watery liquid from the ends. Any idea what this might be? --84.137.28.204 20:43, 10 May 2007 (UTC)

The natural juices of the onion. Mmmm... Onion juice. Tasty! Dismas|^(talk) 20:47, 10 May 2007 (UTC)

Are you sure? I've never seen onions do this and I am kinda scared it might be poisonous. --84.137.28.204 20:53, 10 May 2007 (UTC)

Some varieties, or some ripenesses, do it; some don't. But yes, Dismas is right, it's perfectly normal, and not at all hazardous (other than to your eyes, of course! :-) ). --Steve Summit (talk) 21:11, 10 May 2007 (UTC)

Onions spoil fairly quickly, and when they do the liquid coming out is milky rather than clear. Granted, there may be onions for which the fluid is cloudier than others. Edison 23:53, 10 May 2007 (UTC)

I've cooked with such onions with no problem. Its actually rather common with the yellow onions I've bought, even the ones freshly bought from the store. I didn't even know that they were supposedly "spoiled". (Though I tend to cook them even if I see green stalks growing out.... if the bulb is brown though, it'd obviously be time to throw them out or maybe even replant.) Root⁴(one) 03:59, 11 May 2007 (UTC)

The liquid I've seen in the center of onions is clear. StuRat 03:36, 11 May 2007 (UTC)

Titration Question !

Is a titration in the lab a good way to determine the concentration of an acid or base? Thanks for any help! —The preceding unsigned comment was added by 76.188.176.32 (talk) 21:59, 10 May 2007 (UTC).

Yes. That one was easy :-) Someguy1221 22:00, 10 May 2007 (UTC)

Mhmm.. any reasons why???

Well, the point of an acid-bade titration is to determine what relative quantities of an acid and a base (one of known concentration, one of unknown concentration) achieve a certain pH (indicated by a change in color of the indicator chemical you're using, usually phenolphthalein). Practically, it's the easiest and most error free way to directly measure the concentration of an acid/base without using an actual pH meter (that I know of). Someguy1221 22:10, 10 May 2007 (UTC)

Technically, titration could even be seen as more accurate than using a pH/ion electrode since electrochemical measuring devices actually quantify the ionic activity—which can be affected by temperature, concentration, etc. -- MarcoTolo 23:17, 10 May 2007 (UTC)

The titration is an excellent way of determining the concentration of an acid or a base, however you do need to know a few things first! Whether you're dealing with a weak acid or base, as this will effectthe indicator that you need to use, as the end point will have a different pH. You also need to know wether the acid or base you are assaying is monobasic/acidic or mutibasic/acidic, as this will affect the stoichometry of the chemical equation, and therefore the amount of acid or base present. To work out the amount of acid or base present you need to know the chemical formula or the relative molecular mass of the acid/base. Using the formula Mass = Relative molecular mass/moles, and Moles = Volume x concentration (in moles/dm^3)/1000 you can work ou the number of moles of acid/base you used to titrate, and then adjust for the stoichometry, and you have the moles of base/acid used.

Climate /United States/lowest rainfall

What is the place and amount of the lowest average rainfall? —The preceding unsigned comment was added by 71.143.16.157 (talk) 23:02, 10 May 2007 (UTC).

The nation’s driest area is the Desert Southwest, specifically southwestern Arizona, southern Nevada and southeastern California. The average annual rainfall across most of the region is less than 5 inches per year. This area includes the driest large city in the USA – Yuma, Ariz., which receives just less than 3 inches annually. —Preceding unsigned comment added by 76.188.176.32 (talk • contribs) 23:31, 10 May 2007

And Death Valley gets less than 2 inches of rain per year. StuRat 03:34, 11 May 2007 (UTC)

Titration

This is a continuation of a previous asked question ..

Are there any limitations to the titration method? What are they? —The preceding unsigned comment was added by 76.188.176.32 (talk) 23:25, 10 May 2007 (UTC).

Yes. The titration method cannot readily be used to make a planet-eating robot, to name but one. Can you be a little more specific about what kinds of limitations you're looking for? Algebraist 11:17, 11 May 2007 (UTC)

Going back to my high school and college chem classes many years ago, an obvious limitation is that the user must make a subjective determination of whe he has dripped enough of a reagant into the solution to cause a color change, which has an inherent subjectivity. The process is repeated with the two sources and the amounts noted, to use statistical averaging to achieve a more precise number. Edison 13:18, 11 May 2007 (UTC)

The first thing I thought is that titrations are only good at quantifying concentrations of acid or base (not, for example, concentration of glucose or sodium chloride). This is because there are no good glucose-neutralizing additives, nor are there easy brightly-colored indicators. The premise of the titration is that adding Substance B will neutralize Substance A; this might be extended to some non-acid/base reactions, but it could never be generalized to quantify any type of solution concentration. Nimur 07:03, 12 May 2007 (UTC)

Historically, titrations didn't just involve acid-base reactions, but also other reactions such as redox and precipitations. There are methods in the literature for titrating both glucose and sodium chloride, not that they would be used nowadays. I think the main limitations of titration are accuracy and speed. Hexane2000 08:24, 12 May 2007 (UTC)

I'd be interested to see that literature! Nimur 07:48, 13 May 2007 (UTC)

May 11

Vascular bundles

I understood from the monocotyledon article that vascular bundles are randomly interspersed in monocotyledons and annularly arranged in dicotyledons, but how are they arranged in the stems of woody plants? Thanks, anon. —The preceding unsigned comment was added by 162.83.152.149 (talk) 01:38, 11 May 2007 (UTC).

Try vascular cambium and cork cambium as a starting point. David D. (Talk) 03:56, 11 May 2007 (UTC)

drug names

Where do drug names come from? One expects brand names to be arbitrary, but the generic names also seem to have very little in the way of etymology, as if the syllables were chosen like Bingo numbers. —Tamfang 02:04, 11 May 2007 (UTC)

See the International Nonproprietary Name page. DMacks 02:26, 11 May 2007 (UTC)

That article tells me only that an authority exists; nothing about its principles or its procedures. (Compare planetary nomenclature.) Is a name proposed by the developer, or does the developer ask the INN authority to pull some syllables out of a hat? Does the IUPAC name (which has less apparent freedom) come first, and if so does the INN tend to reflect it somehow? —Tamfang 04:46, 11 May 2007 (UTC)

It uses syllables from the "INN stems and modifiers from the WHO" document listed in the External links. That thing is almost 200 pages of fairly detailed and specific meanings for each syllable, not really amenable to a short list in the wiki article. DMacks 05:43, 11 May 2007 (UTC)

(glancing at the huge PDF) Wow, so there's more etymology than I thought. Thanks. —Tamfang 04:22, 12 May 2007 (UTC)

Bioethics and astrobiology

From what I understand, most people think it's perfectly ethical to use animals for academic purposes-- capture the animals, study their behaviour in a controlled environment, disect them, other expirements that may involved killing the animal, etc, so long as you don't cause unnecessary suffering or do really cruel things (definions of that vary greatly, but anyway). Ok what my question is, would it be the same for life on other planets? Obviously it would be okay for microbial life, and plant-like things if we find any. What about animals (or animal-like beings, aliens whatever)? On earth, we kinda think we're superior to animals, and human life much is more precious probably because of the enormous intelligence gap between us and the next most intelligent animals (apes, monkeys, dogs?). What about on other planets. Let's say we found a planet that resembles ours: millions of different species with one intelligent, dominant (perhaps civilized) one. Would we treat that one as an equall to us or just like any animal? Afterall, if aliens landed on earth and decided to study organisms, we would expect them to treat us different than the rest of the animals, right? (For example, we would be outraged if they rounded up a village of people and took them back home to study, but maybe not so much if they took a school of fish or something.) 209.53.181.150 03:17, 11 May 2007 (UTC)

I would think the same rules for deciding which animals get which protections would apply. It might be a bit more difficult to decide which alien animals are intelligent, though, if they are very different from us. For example, a creature which lives for a million years and has one thought a year might appear to us to be unintelligent. StuRat 03:31, 11 May 2007 (UTC)

"Perhaps, on alien worlds, we will be the ones bringing the anal probes." StuRat 03:31, 11 May 2007 (UTC)

Are you asking for an ethical principle or for a prediction of what's likely to happen? Either one is, I think, inappropriate here. —Tamfang 04:38, 11 May 2007 (UTC)

H Tristram Engelhardt has a book called "The Foundations of Bioethics" out there. He writes about creating a distinction between "person" and "human" for ethical purposes. He discusses criteria for persons, those who ethically cannot be experimented upon, and nonpersons, those that can. Check it out, I'll scan a few pages in for you or type in some quotes if you're interested. It's pretty heavy reading. [Mac Δαvιs] ❖ 07:19, 11 May 2007 (UTC)

Google Books has it here. --TotoBaggins 13:59, 11 May 2007 (UTC)

Nice find; I don't remember "Christian" being in it though. [Mac Δαvιs] ❖ 18:53, 11 May 2007 (UTC)

Dang, you're right, they're totally separate books. You can browse the, er, secular one here. --TotoBaggins 20:32, 11 May 2007 (UTC)

If aliens smarter than us by the same amount as we are smarter than chimps landed here and rounded us up by the village-load for dissection, our opinions on the topic would matter about as much as the opinions of the chimps matter when we do such things to them. --TotoBaggins 13:59, 11 May 2007 (UTC)

But chimps and other animals don't have opinions! That's the point, if they're not intelligents, they are not entitled to er "personness" or "personhood". 209.53.181.69 22:56, 11 May 2007 (UTC)

I think animals have opinions. For example, they tend to have opinions about which mates are, and are not, appropriate. StuRat 02:04, 12 May 2007 (UTC)

True in most cases, Stu. But bonobos couldn't give a damn. :) JackofOz 05:41, 13 May 2007 (UTC)

Even they must have some standards, if only that their mates must be warm and/or breathing. StuRat 21:58, 13 May 2007 (UTC)

That's my point. If we're as much dumber than the Martians as chimps are dumber than us, we're not going to qualify for Martianhood, which will probably mean they'll have no compunctions about doing things like this to us. --TotoBaggins 01:03, 12 May 2007 (UTC)

There is a spectrum of what is acceptable, varying with each type of creature, which is at least partly normalized by the perceived intelligence or proximity to human-ness. We have no problems destroying bacteria en-masse with bleach or penicillin as part of a routine experiment. Lab rats, which are often killed for science research, are often treated well (often subject to the institutional ethics review board). Dogs and chimps are rarely killed; and human experimental subjects are treated fairly well. Hopefully the hypothetical extra terrestrials would have a similar spectrum which does not involve sever mistreatment of humans. Nimur 07:09, 12 May 2007 (UTC)

Alzeimer's Disease

I read in an article that Insulin can spur Alzeimers Disease. What if the patient is a diabetic??? Would it effect them neurologicaly? Would it effect thier motor skills???

TamaraDissa 05:01, 11 May 2007 (UTC)

A quick google search seems to say that Alzheimer's disease causes a drop in insulin or something, I am not a medical practitioner. Splintercellguy 06:37, 11 May 2007 (UTC)

Alz has nothing to do with diabetes or pancreatic insulin. Certain brain cells apparently produce small amounts of insulin within the central nervous system and it may play a role in maintaining neurons. Alz was associated with lower CNS insulin levels in one study [1] but whether low CNS insulin levels cause Alz or are simply an effect or associated problem has not been determined. Peripheral circulating insulin levels do not seem to have much effect on the brain, and the CNS insulin does not have any known effect outside the brain. alteripse 13:47, 12 May 2007 (UTC)

EyeBrow Growth

Hypothetically speaking, If removed by using a blade, Will they grow back but to a slightly shorter length, slightly longer length, or no discernable difference in length? Its just i lost half an eyebrow in an accident and i really liked them incase you were wondering about such a bizzare question.

Thankyou. Weoyreb321 07:20, 11 May 2007 (UTC)

Assuming they were just cut, and there was no damage to the follicles, your eyebrows should grow back good as new same as before eventually. Just remember, not all follicles are growing at any given time, so it will be slightly thinner until all come back. Czmtzc 13:53, 11 May 2007 (UTC)

Note also that it's a myth that shaving causes hair to grow back coarser or thicker than it was previously. It can just seem like it since short hairs are stubby and stiff. --TotoBaggins 14:04, 11 May 2007 (UTC)

And after a while (when it returns to its normal equillibrium of hairs "wearing out" and falling out and growing back) it won't stay stubby like that. 209.53.181.69 22:59, 11 May 2007 (UTC)

Vaporisation of Sweat

I was asked an interesting question in a heating and cooling test, and I'd like to be able to either justify my answer or understand why it was wrong by the time I talk to my teacher next. If a person's body gains 300J of heat every second while running a marathon, how much sweat must be produced in order for the body to remain at a constant temperature, ignoring heat loss by means other than perspiration? The question also gives a value for the latent heat of vaporisation of sweat, although I forgot what it was. I assumed that the average body temperature is 310K (although it is probably closer to 309.6K) and that the specific heat capacity of sweat is very close to that of water. Given this, should my formula for the amount of sweat needed to absorb 300J of heat contain the energy required for the water to heat from 310K to 373K, or should it just contain the energy required to vaporise the unkown mass of sweat? Or is there something else I'm forgetting entirely? Any help in understanding this question would be appreciated :) Vvitor 08:22, 11 May 2007 (UTC)

You know how when you're running a marathon, you don't writhe in agony? That's because the sweat on your body does not get heated to 373K before it evaporates. I would guess you're expected to assume that sweat evaporates at body temperature (don't know how true this is, but it's probably pretty close). So you're presumably meant to only count the latent heat of evaporation of sweat, which is probably close to that of water, giving about 0.13g of sweat a second. However, none of this matters much, since the energy required to evaporate is so much greater than that required to heat (about 260J to heat 1g by 63K). Algebraist 11:11, 11 May 2007 (UTC)

Bah! I feel like such an idiot! That makes sense, many thanks. If you have the time, though, could you please tell me if the question was correct in listing the "specific heat of vaporisation of sweat" and if a similar formula to boiling (mass x latent heat) would be used? This concept of a latent heat of evaporation is new to me. Thanks again! Vvitor 11:37, 11 May 2007 (UTC)

According to Standard enthalpy change of vaporization (latent heat is out of fashion, it seems), the energy involved depends on temperature but the dependence is so small it's generally ignored. Thus using the standard value and the standard formula seems good enough. Algebraist 15:01, 11 May 2007 (UTC)

Well, there goes my two marks :P. Thank you once again! Vvitor 02:30, 12 May 2007 (UTC)

I would bet that ignoring other means of cooling is quite a big error. I am not sweating a lot when I sit here, but it's not like I stop eating unless I do sports. My guess is direct heat exchange from skin to air and breathing make up a good portion of the heat exchange. Yes, that wasn't the question. —The preceding unsigned comment was added by 84.187.19.133 (talk) 22:05, 12 May 2007 (UTC).

Intelligent Dinosaurs

Human beings have been around for thousands of years and we evolved to intelligent beings. Dinosaurs had been around for millions of years. Is it possible (or any evidence) that an intelligent race evolved from the dinosaurs? If so, do you think that they probably left the planet? --Juliet 13:01, 11 May 2007 (UTC)

Well, scorpions and dragonflies have been around for a longer time yet, and still they never built a decent spacecraft ;) . Seriously, being around for a longer time impoves neither intelligence nor dexterity of a species, generally speaking. As for having left the Earth - I wouldn't subscribe to that point of view, unless presented with a very, very compelling piece of evidence. Cheers, Dr_Dima.

If our current thinking is correct, it's likely that modern birds are evolved from dinosaurs. African Grey Parrots haven't left the planet yet, but once they acquire a complete, developed system of language from humans, I'd watch out...

Atlant 13:28, 11 May 2007 (UTC)

I read about intelligent dinos somewhere but I don't remember where. Does anyone have a link to it? --Juliet 13:28, 11 May 2007 (UTC)

I recall a series of science fiction books (sorry but I don't know titles or author) which imagined a world in which dinosaurs survived and developed intelligence and existed in competition with humans.

Bloodcancerguy 09:56, 14 May 2007 (UTC)

Evolution isn't teleological — it doesn't necessarily lead towards big brains at all, in fact most species do not require them and never even began to evolve them (think about how successful insects are even though they are pretty dumb). Dinosaurs evolved into thousands if not millions of species, all working within their evolutinary niches. They evolved flight, they evolved great size and small size, they evolved all manners of spikes and armor and the like. They, nor too many other species, evolved much intelligence. Most of them never bothered to evolve much of a forebrain, a necessary prerequisite. So there's no reason to think an intelligent race would have evolved from dinosaurs. Additionally any intelligent race with the abiilty for space travel would have left behind ample signs of this ability, if not in intelligently built structures, then likely in the record of their resource consumption (we'd find empty oil wells, evidence of ancient uranium mines, etc.). So no. --24.147.86.187 13:32, 11 May 2007 (UTC)

Evolution ... doesn't necessarily lead towards big brains at all. Indeed, our big brains will likely cause us to be selected against as a species. Does anyone really think humanity will fail to kill itself for as long as the scorpions and dragonflies have been around? So long as we don't do it by something like creating a laboratory black hole that doesn't immediately evaporate, I think big brains will just be an interesting evolutionary dead-end, not nearly as successful as a great set of wings or a really rad stinger. --TotoBaggins 14:17, 11 May 2007 (UTC)

I am sure we will not create a laboratory black hole, that's just something that gets in the press to try and make science more exciting. Also intelligence is selected against in terms of big brains taking lots of energy to run, but in certain circumstances can be worth the extra effort. However evolution is about filling niches, to go with the brains you'd also need the dexterity to use tools, the ability to make a range of sounds to form a complex language, all things probably necessary for intelligence to thrive. And why is space travel the definition of intelligence?Cyta 07:24, 14 May 2007 (UTC)

Even so, 24, wouldn't all of that evidence rotted or decayed away? Also, I thought that Velociraptors and other types of raptors were intelligent? Isn't possible that they could have evolved into something greater?

Sure, and maybe they still will, if the aforementioned grey parrots ever get their act together, but there is no evidence that dinosaurs lived in cities or had nuclear reactors or aircraft carriers or even manhole covers. All of these things would be preserved at least as well as simple bones. FWIW, here's a paleontologist's *very* speculative view of what an intelligent saurian might look like: Troodon#The "Dinosauroid" --TotoBaggins 14:31, 11 May 2007 (UTC)

I think you're right that the most intelligent dinosaurs were Deinonychus and its relatives (judging from brain and body masses).

An interesting thought experiment: What would a fossilized car look like? The steel would oxidize, but the glass would probably only lose its organic components (AFAIK car windows are made of layers of glass and some synthetic material between them). Would the platinum catalyst survive?

I think from an intelligent species with an industrial civilization one would expect to find at least some durable metal alloys.

A thought about intelligence: Intelligence is hard to define. If you come up with a rigorous definition of intelligence - or if you say that IQ tests measure intelligence - most people will probably disagree and say that your definition does not include all aspects of intelligence. So to a certain degree we don't even know what we are talking about. What would constitute a "superhuman" intelligence?

That Dinosauroid looks like an alien that everyone describes as one should look like. Perhaps all aliens that are visiting/probing humans are Dinosauroids! --Juliet 14:36, 11 May 2007 (UTC)

Even if the dinos had an incredibly advanced civilization, more advanced than our own, all evidence would have been wiped out millions of years ago when Xenu dropped H-bombs all over the earth. Don't you guys pay any attention to L. Ron Hubbard? Someguy1221 16:04, 11 May 2007 (UTC)

There's an interesting New Scientist article, Imagine Earth Without People, which discusses how long it would take for all traces of a post-industrial civilisation to disappear; there's some quite interesting prospects: core samples from the ocean would show layers of heavy metal pollution and higher-than-normal levels of long-lasting radioactive isotopes, there would large concentrations of glass and decaying organic matter concentrated around old landfills, and there most likely would be a strange order to the fossils, indicating organised burial. None of these have be identified so far in prehistoric animals (for example, dinosaur fossils appear to be completely random and no-one has ever found any signs of dinosaur-caused pollution, although there is that mysterious iridium layer...). I particularly like the idea of herds of feral poodles roaming the plains, but sadly this particular theory is debunked. Laïka 22:05, 11 May 2007 (UTC)

Proof: [2] Capuchin 22:41, 11 May 2007 (UTC)

The most intelligent dinosaurs were, probably, dromaeosaurids, Compsognathus, Coelophysis and other quick and small theropods with large brains and eyes. In any case, they lacked our extremely sophisticated hands, brain-to-size ratio and, obviously, it's so improbable it's impossible they developed any kind of technology. --Taraborn 12:08, 13 May 2007 (UTC)

But they didn't need to go into space, or build cities, they already had everything they wanted. (unsigned comment)

Had there been technological dinos, I would expect that we would find obvious evidence in the form of mine tailings, and likely also there would be very little coal or oil left in the present day. --BenBurch 20:25, 13 May 2007 (UTC)

Kidney donor?

Is it legal in Canada or other countries for a person to sell their kidney to somebody who needs it? Kidney_transplantation didn't have much.--Sonjaaa 13:39, 11 May 2007 (UTC)

In the UK the Human Tissue Act (and specifically this section) makes it an offence to "[offer] to supply any controlled material for reward", as this man just found out. — Matt Eason ^{(Talk • Contribs)} 14:31, 11 May 2007 (UTC)

It's not legal in the US either, although there are some doctors who want it to be in order to prevent a black market developing. You might find this article in the New York Times interesting. --TotoBaggins 14:33, 11 May 2007 (UTC)

In the US, selling of your (or anyone else's) organs is illegal, as TotoBaggins noted, per the Uniform Anatomical Gift Act. It does appear to be legal in Iran, according to the Transplant#Compensated_donation article (with sources, even). -- MarcoTolo 20:09, 11 May 2007 (UTC)

artificial symbiosis

how can we induce artificial symbiotic relationship between two microorganisms,knowing their genome.can you please tell me the actual sceintific process. —The preceding unsigned comment was added by 220.225.77.230 (talk) 14:39, 11 May 2007 (UTC).

I'm sorry, but what kind of symbiosis are you referring to? There are quite a few different ways for organisms to be in symbiosis. Have you looked at its article by chance? Someguy1221 15:59, 11 May 2007 (UTC)

Well, you could knock out the ability of one microorganism to make an amino acid, say Alanine. In another organism you knock out the ability to make a different amino acid say Lysine. Now neither of the organisms can survive independently with out a source of the protein that it is unable to synthesize itself, but together they could live symbiotically off of each other. --Czmtzc 19:45, 11 May 2007 (UTC)

I will give you a million dollars if you can get two bacterial colonies to sign a trade agreement ;-) Someguy1221 20:49, 11 May 2007 (UTC)

Body acts as a wireless radio antenna

I've got a little shower radio whose coated wire antenna snapped off a while ago. Now when I turn it on the output is mostly noise, but when I put my hand within about four inches of it the signal becomes crystal-clear - I don't even have to be touching the metal where the antenna snapped. Why? — Matt Eason ^{(Talk • Contribs)} 14:59, 11 May 2007 (UTC)

I guess (emphasis on "guess") that your hand and some conducting parts inside the radio form a capacitor which allows the high-frequency current to flow without you touching the radio. Then your body works as an antenna. Cheers, Dr_Dima.

Your body definitely interacts with and somewhat channels EM radiation. I don't know if there's a very simple mechanism for explaining what you observed, though. -- mattb 15:59, 11 May 2007 (UTC)

You're probably affecting the ground plane the antenna uses. Single wire antenna's (like car antenna's) use the earths or the hood as a ground plane. This essentially acts a mirror and for analysis purposes turns the antenna into a diploe. By putting your hand that close, you move the plane for the stub of antenna that was left when the wire broke off. This can affect gain and directionality of the antenna and improve ir diminish the reception depending on a number of factors that would probably be not worth modeling. Our article on this, Image antenna is somewhat lacking. --Tbeatty 03:45, 12 May 2007 (UTC)

Compact fluorescent lamps

According to compact fluorescent lamp, the length of their life is dependent upon, among other factors, "frequency of cycling on and off". I am trying to find out just how significant this is. I know it is significant in old style fluorescent tubes that use a starter. Does this mean I should leave, say, a CFL in a hallway on for most of the evening to maximize its life? Obviously I don't want to leave it on for too long, otherwise I don't save any energy.--Shantavira 15:23, 11 May 2007 (UTC)

No, you shouldn't leave it on. here is the best source I can find on this. --Allen 15:58, 11 May 2007 (UTC)

"...so if you turn your fluorescent lamp off and on more frequently than every 5 seconds, you will use more power than normal." Very interesting. A myth exploded. Thank you.--Shantavira 18:06, 11 May 2007 (UTC)

Gaslighting

What is the evolutionary purpose behind gaslighting? I just got gaslighted at work (very successfully, btw), and after reading the article, I recall several times I have gaslighted friends or have been the victum of gaslighting, in particuar I've always felt a *strong* compelling desire to gaslight people. Is there some reason we seek to test/improve our ablity to manipulate others, or is it perhaps a way of putting someone in a position of uncertanity? XM 15:42, 11 May 2007 (UTC)

I would differentiate between cases where the perpetrator admits to the deception ("I was just playing with you"), which seems to be a type of joke, versus cases where no admission ever comes, which seems to be more a type of abuse aimed at increasing the perps power relative to the victim, by making the victim unsure of himself/herself. StuRat 18:36, 11 May 2007 (UTC)

I'm not sure there is a "evolutionary purpose" to this sort of very high-level psychological behavior (that is, I doubt it is selected for or against with any specificity, and I'd be dubious that there is any genetic specificity for it). As for why people would want to do it, it is probably just the old, basic desire for power over others. We like to feel powerful, and quite often at the expense of others. --24.147.86.187 00:12, 12 May 2007 (UTC)

Eggplant IQ

I heard a rumor that the eggplant has an IQ of 3, and since I am a vegetarian that really freaks me out. What is the real IQ of an eggplant? —The preceding unsigned comment was added by 66.92.72.238 (talk) 18:22, 11 May 2007 (UTC).

Eggplants do not have IQs - as they would not be able to take an IQ test to obtain a score. --Ali 18:27, 11 May 2007 (UTC)

Yes, it is most likely just a rumor. Once I asked from a professor studying the human brain what the meaning of the IQ associated to plants, animals, computers is (as found on some nice graphics in some newspapers). He replied that it is all nonsense. The IQ is calculated specifically based on the average human intelligence, so not only is it impossible to calculate on, for example, animals; it gets very inaccurate in the case of outstandingly intelligent/unintelligent people. --V. Szabolcs 18:41, 11 May 2007 (UTC)

I suppose it means that plants are, actually alive and actually do have some small bit of intelligence. Vegetarians seem to treat them as almost, unalive. They seem to treat eating live plants as different from dead animals, yet eating animals is barbaric and plants is intelligent. [Mac Δαvιs] ❖ 18:51, 11 May 2007 (UTC)

You know you have to kill the animal, right? They don't come dead. --User:bmk

they do now, unless you are a farmer/butcher.

I take it that was sarcasm. Plants do some things, like repositioning themselves in the sunlight, that, in animals, is often accomplished by intelligence (a cat finding a sunny patch to warm up, fur example). However, in plants, this type of thing is accomplished by different mechanism. StuRat 19:57, 11 May 2007 (UTC)

Plant behaviour follows similar basic mechanisms to animals with respect to interacting with the environment, sense, signal, respond. These mechanisms do not require intelligence although intelligence might improve the response. David D. (Talk) 20:16, 11 May 2007 (UTC)

In any case, an eggplant is certainly less "intelligent" than a gnat, and I am sure few of us weep after swatting. At some point everyone has to draw the line between the animals they care about and the ones they don't. Vegetarians often set that bar a bit lower than others (saying that fish, cattle, pigs, and fowl count as "non-expendable" whereas omnivore humans generally think they are) but at some point there's a bar nonetheless. Lowering that bar to the level of plants would be somewhat insane, in my opinion. --24.147.86.187 00:16, 12 May 2007 (UTC)

See breatharianism for the limit. Rmhermen 02:53, 12 May 2007 (UTC)

You may find Plant perception (physiology) interesting. Personally, I think that just because we can't understand plants' equivalent of a CNS, doesn't mean that they don't have one. Aaadddaaammm 03:28, 13 May 2007 (UTC)

Yes, plants have positive IQ and therefore are intelligent. Rocks too, that's where the comparison between an idiot and a rock's intelligence comes from. So never eat plants nor rocks, because they have intelligence. My God. --Taraborn 19:41, 14 May 2007 (UTC)

Soap Bubbles

Can anybody tell me the effect of water temperature on soap bubble forming? As surface tension is a function of temperature and the higher the temperature the lower the surface tension. So, are the soap bubbles less stablized in hot water as the surface tension is lower? —The preceding unsigned comment was added by Lucia12321 (talk • contribs) 18:35, 11 May 2007 (UTC).

Another factor is that soap bubbles tend to evaporate and pop rapidly in dry air, and temperature affects humidity. I'm not sure what the net effect is, however. StuRat 18:40, 11 May 2007 (UTC)

Astronomy : Black dwarf stars

It seems from information already in Wikipedia that white dwarfs take an exceptionally long time to cool into hypothetical black dwarfs. They cool more slowly as time progresses, and the coolest known white dwarfs are about 3900 K. It also seems that not enough time has passed for any stars in the universe to have cooled enough to become black dwarfs. Therefore my question is: Exactly how many Gyr will it take for a white dwarf currently at 3900 K to reach thermal equilibrium with the space in which it sits (presumably single digits of K), and become a black dwarf? I know this can vary with the mass and elemental content, so if necessary just assume common values.

This is not homework, just personal curiosity. 70.171.11.122 21:32, 11 May 2007 (UTC)

According to NASA it takes tens to hundreds of billions of years. Someguy1221 21:40, 11 May 2007 (UTC)

I believe there was a mistaken assumption in your question, however, that temps must fall to below 10°K for it to stop emitting light. I believe dwarf stars will stop emitting significant amounts of light at much higher temps than that. StuRat 21:49, 11 May 2007 (UTC)

I would probably say a few hundred K, I mean, the stuff around you is only glowing significantly in the infra-red. You have to heat a metal bar significantly above room temperature for it to start emitting enough light for it to be visible. Stars will be similar. Richard B 23:04, 11 May 2007 (UTC)

I wonder if it might be different though for something a million times the density of water. Someguy1221 23:53, 11 May 2007 (UTC)

Not really; see blackbody radiation. When you're not talking about special things like synchrotron radiation or LED light, but just "glowing" from disorganized matter, you and a white dwarf and a charcoal briquette are about the same. Even black holes can be assigned a temperature, although that has not been experimentally verified. --Tardis 01:16, 12 May 2007 (UTC)

Oh, dear. our black dwarf article uses the term "significant radiation'.Significant is a qualitatitave term that is subject to arbitary interpretation. Pick a definition (in degrees K) for significant, and we can then calculate a time in the future at which the black dwarf will be indetectable. -Arch dude 01:53, 12 May 2007 (UTC)

Hi, I tried to be specific in my original question, but it seems that people are confused over when a star becomes a black dwarf. That's why I originally asked how long it will take for a cooling white dwarf to reach thermal equilibirum with the interstellar medium, which is very specific. It seems at this point nobody has an exact answer, the "tens to hundreds" of billions of years is what I found myself, I wanted something more specific than that. 128.227.68.119 13:04, 15 May 2007 (UTC)

Shouldn't it take infinite time to reach thermal equilibrium, being an asymptotic process and all? Especially since the background is a moving target, what with the continuing cosmological redshift of the photons in it... --Tardis 20:09, 15 May 2007 (UTC)

Homogeneous and Heterogeneous

I have 9 items that deals with which one is which is homogeneous or heterogeneous.

• a)freshed-squeezed orange juice
• b)white vinegar
• c)red wine
• d)an antique bronze dagger
• e)a stainless steel knife
• f)an old lead water pipe
• g)humid air
• h)a cloud
• i)a dirty puddle

By the way, it's not homework.

"Deals with" what? Your question is not entirely clear. However, our articles on Homogeneity and Heterogeneous may help. Rockpocket 23:53, 11 May 2007 (UTC)

"Homogeneous" is one of those words I love so much for its multitude of meanings... Even within single disciplines folks can't settle on just one meaning (like its multiple meanings just in the context of differential equations). Anyway, back to your question... You're going to have to define what you mean by homogeneity more explicitly for your question to be answerable, and if you do this you will have answered your own question. -- mattb 00:17, 12 May 2007 (UTC)

Don't forget Phase (matter). TenOfAllTrades(talk) 00:28, 12 May 2007 (UTC)

What fun. I can construct a total of 18 defensible arguments, one for each substance that it is homogeneous, and one for each substance that it is heterogeneous. in each case, it's a matter of scale. -Arch dude 01:38, 12 May 2007 (UTC)

This is one place to start learning: Mixture deals with the chemistry definition for homogeneity and heterogeneity. Nimur 19:29, 12 May 2007 (UTC)

I think Arch dude is correct; this will depend on how homogeneous you set your threshold at. The best formal definition that I can think is that you determine homogeneity for a particular property (such as density); then take several random samples of finite size; then measure the absolute variance of that quantitative measurement. If the mixture is homogeneous then the variance must be less than some pre-decided threshold. Nimur 19:45, 12 May 2007 (UTC)

solutions and not solutions

Hi there, I have 9 items that deals with which one is solutions and which are not solutions.

• a)milk
• b)apple juice
• c)the gas in a helium-filled balloon
• d)pop
• e)pure water
• f)smoked-filled air
• g)silt-filled water
• h)rainwater
• i)14K gold in jewellery

—The preceding unsigned comment was added by 76.64.137.23 (talk) 23:49, 11 May 2007 (UTC).

See solution and then determine which fits (i.e. it has to be one material with another fully dissolved in it). Rockpocket 23:53, 11 May 2007 (UTC)

It doesn't have to be dissolved in a liquid. It usually refers to something dissolved in liquid, but it truly anything dissolved in anything. Someguy1221 23:57, 11 May 2007 (UTC)

This one is a bit easier. Just find a formal definition of solution and guage each item against the definition. -Arch dude 01:43, 12 May 2007 (UTC)

remember there is also a difference between compounds and solutions.

May 12

extinction

extinction —The preceding unsigned comment was added by 70.51.217.228 (talk) 02:31, 12 May 2007 (UTC).

The likely fate of every species. Edison 03:09, 12 May 2007 (UTC)

Our own fate? A.Z. 04:50, 12 May 2007 (UTC)

Extinction (disambiguation) —The preceding unsigned comment was added by Nimur (talk • contribs) 06:29, 12 May 2007 (UTC).

sunlight

Does sunlight affect hair growth? 68.231.151.161 03:17, 12 May 2007 (UTC)

A 1991 article in the British Journal Of Dermatology studied "androgen-dependent" hair growth in bald men living in temperate climates. Androgen-dependent hair includes scalp hair and most body hair, but not eyelashes and eyebrows. The study suggested that androgen-dependent hair growth is faster during the spring and summer months and slower during the winter months in temperate regions. Although this study was conducted in men, the authours suggest the results may also apply to women, but not to children (who have an altered response to androgens). Rockpocket 06:34, 12 May 2007 (UTC)

Children do not have an "altered response". They simply have no androgens. As soon as they get androgens, they grow androgenic hair too, at any age. alteripse 13:37, 12 May 2007 (UTC)

What's the verb that means 'to move by peristalsis'?

Peristalse? Peristalsise? Peristalsisticate?

Thanks,

Adambrowne666 03:29, 12 May 2007 (UTC)

I've heard peristalse, but I believe it's a rare enough formulation as to not actually appear in dictionaries. - Nunh-huh 03:42, 12 May 2007 (UTC)

The OED lists the noun, adjective, and adverbial forms, but no verb of peristalsis. I suppose I should ask you to use peristalse in a sentence, but I'm a little afraid what such a beast would look like.... <grin>. -- MarcoTolo 04:25, 12 May 2007 (UTC)

I thought it was just peristalate. -sis is kind of a suffix you know. [Mac Δαvιs] ❖ 05:18, 12 May 2007 (UTC)

like osmosiate and mitosiate, both of which also don't seem to exist. But really it doesn't matter as it still means the same whatever you write, it just might be difficult to understand.

Thanks all - I'll allow your suggestions to peristalse through the ideational guts of my brain and inspect what comes out the other end... Adambrowne666 22:25, 13 May 2007 (UTC)

A doctor I work for refers to it when referencing flow- "It appears to peristalse."

Peristalsis refers to the rhythmic contractions whereby material is propelled through a tube, commonly where food is propelled through the GI tract. At least within the institutional in which I work, "peristalse" is the commonly used verb to refer to the GI tract functioning properly; "The colon appears to be peristalsing properly," or "We are administering Relistor to allow the gut to peristalse while we continue to control his post-operative pain with opioids." I don't know if it's correct, but it's in the lexicon of my attendings. Jeffhall318 (talk) 16:02, 24 March 2010 (UTC)

Hair

Can hair products such as mousse or hairspray cause baldness for men?

According to this site "hairspray, mousse or gel.. weaken the hair and dull its texture," but this site reports that "there is no hair care product that can cause direct hair loss". When asked what about hair colorings, hair spray or excessive washing leading to hair loss?, Marc Avram MD, a dermatologist replied

What you should be careful with -- you should be careful about using excessive chemicals, relaxants, hot combs. There are things that can burn the hair out and pull the hair out, but everyday shampooing, combing, blow-drying is not a problem. [3]

Rockpocket 06:49, 12 May 2007 (UTC)

Observing influences results?

Hello there,

I'm studying a BA in English and have an understanding of physics up to the level of your standard pop-science book such as A Brief History....

I remember reading somewhere that by observing a particle one must also influence the position of the particle. For example, to see something we must shine light on it, but the act of bombarding something with photons mens that by the time those photons return to us, the object has changed.

What is this theory called? Does this mean that one can never take a 'fair' result? 139.184.30.18 10:00, 12 May 2007 (UTC)

You're thinking of the Heisenberg Uncertainty Principle, though "measuring influences results" is not really what it says, that's merely a popular misinterpretation. A more accurate way to describe "measuring influences results" is as an observer effect. :) - Nunh-huh 10:05, 12 May 2007 (UTC)

Absolutely spot-on advice. Thanks so much! My essay is going to be so much fun 139.184.30.17 14:59, 13 May 2007 (UTC)

Body Electricity

i held the cable to to my cale box and my other hand touched the cable circuit where i plug the cable into and when i touched it it zapped me and i held my fing on it but the zap was not that strong of course but the tv turned on?why is that? also when i just held the metal part of the cable while it was in the box the cable blacked out? could it be possible that my body can generate electricity or hold electricity without me getting shocked to death?could it be possible that the reason why the tv turns on and how it blacks out is becuase of my sub consciousness? becuase i go into my subconsious sometimes and my body cant move but i can see everything and i breathe automaticly? do i have super powers? im only a 12 year old kid and i wonder how is this possible? when my dad did it the tv didnt turn on or anything, it didnt even zap him? after the zapping my finger, the one that got zapped it was red on the tip of my finger?why?if i hold a lightbuld and touch the outlit will it kill me or will the light bulb turn on? -StaticJosh posted on 5/10/07 —The preceding unsigned comment was added by StaticJosh (talk • contribs) 10:15, 12 May 2007 (UTC).

I don't have an answer to your question, but am going to advise you not to mess with electricity. There are a number of variables which could cause a current to either kill you, or pass through you unharmed, and in many cases it can just appear to be luck whether or not you are seriously injured, so please do not risk it. On the matter of the cable box/cable, I have done the same thing with an aerial cable and aerial input on a television, recieving a signal on the TV when connected up (however, I would not encourage anybody to do the same). Appartely, a current passed through me, from the cable to the input port, seemingly bypassing any organs which could be severly damaged if struck by such electricty (or, the current was very low). Martinp23 10:58, 12 May 2007 (UTC)

Your body can't generate electricity but it can hold a charge. This static electricity results from normal activities, like walking in your socks on carpet. You can't detect a small electrical charge but a large electrical charge will make your hair stand on end. When handling electrical circuitry a spark can sometimes affect the circuitry. In your case it sounds like the spark affected the part of the circuit which turns on the TV. Sparks can also damage sensitive circuitry, so there is even a procedure using a grounding wire connected to the hand recommended for people who work with computer hardware. StuRat 15:18, 12 May 2007 (UTC)

Actually I believe both the brain and the heart generate a tiny electrical charge. Anchoress 21:38, 12 May 2007 (UTC)

That's true, in fact all nerves do. However, this charge is fully contained, and not sufficient to cause a spark that could affect electronic equipment, in any case. StuRat 05:06, 13 May 2007 (UTC)

See Electrostatic discharge —The preceding unsigned comment was added by 88.110.7.232 (talk) 01:15, 13 May 2007 (UTC).

Lupins in New Zealand

What species of lupin are most commonly found on roadsides, dunes, etc. in New Zealand? --superioridad ^(discusión) 10:15, 12 May 2007 (UTC)

Russell lupin (Lupinus polyphyllus), according to [4] and [5] . Cheers, Dr_Dima.

Earth, Moon and Venus

The Moon occults the planets, like Venus, quite frequently. In case of such an event, and if we were observing Earth from Venus (obviously high above the clouds), I wonder what we would observe? A transit of the Moon? A very bright conjuction of the Earth and the Moon? Something else altogether? --(cubic[*]star(Talk(Email))) 10:20, 12 May 2007 (UTC)

Yes, assuming it was nighttime on your part of Venus, you would observe both. The Moon and the Earth would both be illuminated, and the disc of the Moon would pass in front of the Earth.--Shantavira 13:17, 12 May 2007 (UTC)

You would see nothing but sulfuric acid clouds, if you were on the surface on Venus. However, if you were above the clouds, you wouldn't see much different from the normal star-like appearance of the Earth from Venus, if using the naked eye. You would need a telescope to distinguish between the Earth and Moon. StuRat 15:10, 12 May 2007 (UTC)

Much the same way you need to do the same in reverse. :) Since Venus also has moons, and is similar in size to Earth, I think it'd be pretty damned identical. Obviously you wouldn't have just a black dot moving in front of a full-lit earth, but under certain (lighting) circumstances I imagine one should be able to tell through use of a very good telescope. —The preceding unsigned comment was added by 81.93.102.185 (talk) 16:52, 12 May 2007 (UTC).

Er, I'm pretty sure Venus has no moons... 68.231.151.161 17:34, 12 May 2007 (UTC)

Correct (Venus#Orbit and rotation) Tugbug 18:09, 12 May 2007 (UTC)

The earth is unusual amongst the planets - it's a relatively small planet - yet is has this gigantic moon - orbiting very close in. It would almost be correct to call the earth-moon system a "binary planet" (it's not because the center of rotation of the system lies beneath the surface of the earth...but it's close). Hence an observer above the clouds on Venus would see a much more dramatic occultation of the Earth by the Moon than is the case with the tiny fly-specks that orbit other planets. When there is a solar eclipse on Earth, the view from Venus ought to be pretty spectacular - especially if Venus were close-by at the time - because both the earth and the moon would be fully lit and the moon's shadow would be huge (by the standards of moon shadows on other planets). But as previously pointed out - viewing conditions from the surface of Venus are far from ideal. The view from Mars is going to be much worse because at closest approach, the earth and moon are presenting their dark sides to Mars - so not a whole lot to see there. SteveBaker 22:41, 13 May 2007 (UTC)

Coral reefs dissapeering from global warming

You guys are not doing homework for me-I need to know if there are any sites to retrieve information about coral reefs disapeering. I need specific data about how much coral is in the world and ocean temperatures over a number of years. This is not homework, I am doing a science project and need this data to do it. —The preceding unsigned comment was added by Kfswimmer17 (talk • contribs) 20:08, 12 May 2007 (UTC).

Coral bleaching might be a good starting point if you haven't looked at it already. --Allen 20:26, 12 May 2007 (UTC)

Lighning safety in houses

I have read at several websites that there is no danger from lightning strikes in a house. Why would a house (let's say a typical family home with brick walls and a slate roof) stop lightning bolts from entering it?

I think there's a reason people have been using lightning rods for the last 250 years or so. I'd like to see those websites. Someguy1221 21:33, 12 May 2007 (UTC)

Here's a website that says you can be struck inside a house, especially if you're too close to a conductor [6]. Speaking of which, I think I'd better shut off my computer and go inside now. --Allen 21:35, 12 May 2007 (UTC)

There's lots of documentation for people being hit by lightning through windows (open and closed), as well as over telephone lines. Anchoress 21:37, 12 May 2007 (UTC)

So here is one of those documents (actually not a website): http://www.lightningsafety.noaa.gov/resources/Ltg%20Safety-Facts.pdf

That's a pretty sketchy document; I'm surprised NOAA is hosting it. (It's hard to take something seriously when it's Written With Every Word Capitalized.) —Steve Summit (talk) 22:11, 12 May 2007 (UTC)

My physics teacher once said that you can't be affected by lightning when in a closed hollow object (and away from the sides). That is why it is also safe to be in a closed car or an aeroplane during a storm (although the aeroplane could be affected in other ways by the lightning!). Regarding your house, the lightning would most likely strike the lightning conductor and dissipate into the ground. Or if it's like my house, strike the telephone wires and blow my modem and computer :) Perhaps someone would care to enlighten us with a scientific explanation of the 'hollow' theory? PS after e.c./ Closed window, Anchoress, really? (shudder) Sandman30s 21:44, 12 May 2007 (UTC)

Your physics teacher was talking about a closed hollow metal object. See Faraday cage. —Steve Summit (talk) 21:58, 12 May 2007 (UTC)

My personal house has a reinforced concrete roof, so I would bet that is pretty safe as it is a conducting grid covering the whole place. I once personally witnessed a ceramic roof being literally blown to pices by a lighting. The house subsequently burned down to the ground. Since then I am a little afraid of lighting, so that is why I ask this question. By the way, nobody was harmed in that incident. So were they just lucky?

I'd say they were lucky, yes!

The point of the exercise is to be avoid being in or near the current path between cloud and ground, i.e. the path along which the lightning bolt travels.

If you're outside, and especially if you're standing on flat ground with nothing tall around you, it's all too easy to be on the path. So that's the last place you want to be.

If you're inside a Faraday cage, you're just about maximally safe.

The skin of a house is not (usually) made of continuous metal, so a house is not a perfect Faraday cage. However, the materials the house is made of are probably better conductors than air, so once lightning hits a house, it's likely to travel down through the walls, and not (say) jump back out of the ceiling, through the air above your head, and down through you.

If as it travels down through the walls of your house, the lightning finds any wires, it will of course preferentially travel through them. But small wires (especially telephone wires) can't carry the high currents of a lightning strike, so they're liable to catch fire or explode. Also you obviously wouldn't want to be touching an appliance which is connected to a wire that finds itself carrying a lightning strike. That's why you're advised to stay away from wires, telephones, and other appliances during a lightning storm.

If the lightning hits a tall and well-grounded metal object, such as a water tower or church steeple, everyone else is quite safe. If the lightning hits outdoor power lines, those will have lightning arresters which shunt the current to ground before it has a chance to travel along the wires and hurt anyone (or even damage very much equipment). (Long-distance transmission lines have ground wires strung above the current-carrying wires, for even more protection.) So if you're in a built-up area, I think you're probably quite safe. In a rural area subject to thunderstorms, or if you happen to be in the tallest building around, you'd probably want to think about installing your own lightning rods. See the lightning rod article for more information. —Steve Summit (talk) 22:32, 12 May 2007 (UTC)

I believe in the US all telephone lines are protected at the point of input. In Malaysia this is not the case and modems and sometimes whole computers are killed by lightning. I haven't heard of human casulties or even injuries but I would say it's not imposible given the frequency of modems being killed. I once had an aerial on a hill to try and get better reception. Bad idea as it was struck by lightning and took out an aircon starter (the wire was touching the aircon), a LD player, a TV and a VCR (all interconnected devices). Nil Einne 10:53, 13 May 2007 (UTC)

Isotopes: the commercial uses of deuterium

How can deuterium be used to power nuclear reactors?--Daniel J. Keller22:49, 12 May 2007 (UTC)Harleydankeller

Deuterium is used in fusion reactors as fuel. I have never heard of any possible use for deuterium in fission reactors. All currently existing nuclear power plants are fission reactors. —The preceding unsigned comment was added by 84.187.19.133 (talk) 23:01, 12 May 2007 (UTC).

Deuterium is used in nuclear fusion reactors. See Deuterium#Applications. Deuterium oxide is called heavy water, and is used in fission reactors, ie standard nuclear power plants. See Heavy water#Neutron moderator. --h2g2bob (talk) 00:20, 13 May 2007 (UTC)

See our CANDU reactor article for a fission reactor that uses heavy water.

Atlant 01:12, 13 May 2007 (UTC)

The key point here is heavy water is not used as a 'fuel' source (i.e. to power the reactor) but is used as the moderator... Nil Einne 10:56, 13 May 2007 (UTC)

Deuterium is used in chemical analysis, particularly in Nuclear Magnetic Resonance spectroscopy. As the technique uses a magnet to alter the spins of hydrogen causing them to "flip" from one direction to the other. This generates a signal that can be interpreted. Deuterated solvents are needed, as they don't give a signal under a magnet, as it is a paired proton, allowing only the signal from the sample to be detected.

snowpack

How much snowpack has reduced in the past year and the current year? Coffsneeze 23:20, 12 May 2007 (UTC)

Where ? StuRat 04:59, 13 May 2007 (UTC)

Mother's Day questions

1. Why do hen lay unfertilized eggs?
2. Does a wild bird lay unfertilized eggs from time to time?
3. Can we artificially fertilize a freshly laid egg?
4. Can we artificially fertilize a refrigerated egg?
5. Isn't it stupid for a chicken to lay an unfertilized egg if they are in the wild? I know today's chicken are selected by human but did their ancestors lay unfertilized eggs?

I think hens are strange mothers -- Toytoy 23:34, 12 May 2007 (UTC)

1) Because the rooster has been lax in his duties. :-) Actually, I'm assuming you mean "why lay an egg if no fertilization has occurred" ? I'm not sure, but human menstruation is similar (purging some material which would have been used to grow a baby, had fertilization occurred).

2) I imagine so, if the male bird is AWOL.

3) No, I believe it's too late.

4) No, I believe it's too late.

5) It does seem inefficient, yes. I don't quite understand it myself.

StuRat 04:55, 13 May 2007 (UTC)

Note that chickens has been domesticated for many thousands of years. A "wild" chicken is perhaps more properly called a "feral" chicken. Could they survive without humans or apart from human created environments? I'm not sure. They have certainly evolved (via selective breeding or otherwise) to be what we humans want them to be. It should be no surprise they act in rather unnatural ways. 07:31, 13 May 2007 (UTC)

To answer question 5. No, I don't think it's stupid to lay unfertilized eggs. Think of it this way. If you have a clutch of 5 eggs, 2 of which are unfertilized. Then you'd have a 40% percent chance that a predator would take an unfertilized egg from the the clutch. This assumes of course that the predator takes one egg and not more. So maybe in a sense the unfertilized egg can be a decoy for the fertilized ones. This of course is just the babbeling of someone who has very little knowledge of chickens. But it does strnagely make sense to my laymans ears. PvT 12:06, 13 May 2007 (UTC)

In this case, you may lay 5 fertilized eggs as well. Sperms are cheap, aren't they? They also could lay decoy eggs without much nutrients or simplay eggs filled with bird droppings. -- Toytoy 14:33, 13 May 2007 (UTC)

As a lover of chickens with a hungover sense of rhetoric;

a. a domesticated chicken has been bred to produce masses of eggs - hundreds a year - regardless of fertilisation; in the wild birds usually produce eggs only 'on demand'. how long it took to breed them to the way they are now i am unsure of, i lost my chicken book a while ago.

b. a modern-day chicken is no toy poodle. two of mine escaped one night and the following morning a huge pile of feathers was sighted in the meadow: classic fox leftovers. naturally my parents and i assumed the poor buggers were both dead.

two weeks later one of them turns up, all casual, and helps herself to the feed as if nothing had happened. she'd been living in the woods for all that time, presumably finding safety from foxes and badgers using her limited flight, and a natural scavenger instinct to feed herself. we called her 'hero chicken' from then on.

incidentally (which is a poor way to start a punchline i know) the next week she was mauled by a customer's dog. what this story tells us about the domestication of animals i am unsure. as i said, hungover. thanks lovely people.

So even if you are chicken, you can still run wild and outfox your enemies, but you'll end up dogged by trouble in the end ? StuRat 21:54, 13 May 2007 (UTC)

I have seen a very few domesticated hens (probably Plymouth Rock) who could fly like a bird over any fence and to the top of the tallest tree. Edison 23:15, 13 May 2007 (UTC)

LIke a bird? No foolin? —Tamfang 23:27, 15 May 2007 (UTC)

Cats

Our article on felines states there's 41 species. Do you know where I can find a comprehensive list including both common names, and more importantly, scientific names of all 41 species? Surprisingly, neither a quick Google or Wikipedia search turns up anything useful. 209.53.180.107 23:59, 12 May 2007 (UTC)

Um, in the article you link to it lists 41 species with both common and scientific names. Here. --TotoBaggins 00:58, 13 May 2007 (UTC)

Dogs

Our article on canines says the domestic dog is either classified as a seperate species C. familiaris or a subspecies of Gray Wolf, C. lupus familiaris. Why does our Dog article list it as a subspecies of wolf? Is that the more widely accepted view? Can domestic dogs successfully interbreed with gray wolves? 209.53.180.107 23:59, 12 May 2007 (UTC)

I remember reading somewhere that all wolves and domestic dogs belong to one species: Canis lupus, with the possible exception of red wolves, which are hyprids of wolves and coyotes (or decendants of those hybrids). Which raises yet another curiosity to me, why the heck are wolves and coyotes different species if they interbreed.  Adam2288  T  C  00:11, 13 May 2007 (UTC)

Good question, Adam; see Species problem. --Allen 02:58, 13 May 2007 (UTC)

Oh, and domestic dogs can successfully interbreed with grey wolves (assuming there is no physical problem for that particular breed of dog). So the man at the rare-breeds centre told me anyway. I seem to remember them being in vogue as expensive pets not so long ago. More dangerous than dogs or wolves, if I recall, since they didn't fear people. Skittle 21:09, 13 May 2007 (UTC)

May 13

Lightning in the snow

Can lightning happen when it is snowing or only during rainstorms? —The preceding unsigned comment was added by M.A.D.M.D. (talk • contribs) 00:13, 13 May 2007 (UTC).

See thundersnow. --Tardis 00:28, 13 May 2007 (UTC)

Yes, but it's not common; link. --TotoBaggins 00:49, 13 May 2007 (UTC)

Here in Toronto I would guess that we typically get about 10 storms a year with significant lightning, mainly in the summer. Lightning in a snowstorm is something I see maybe once every 5 years. --Anonymous, May 13, 2007, 06:09 (UTC).

In several decades I have seen only one spectacular lightning/thunderstorm. Edison 23:09, 13 May 2007 (UTC)

CD-1 Mouse

I have been reading this study about emu oil, wherein emu oil is applied to "CD-1" mice. What makes these mice CD-1? Are there other classifications or grades of lab-mice (CD-2?) or other lab-test animals? Nimur 01:04, 13 May 2007 (UTC)

CD-1 is the designation given to a specific mouse strain. Check here for more info... — Scientizzle 01:09, 13 May 2007 (UTC)

Interesting. I would guess that comparative studies should stick to the same breed/strain for quantitative result comparison? What other scientific implications do these different breeds have? Nimur 01:24, 13 May 2007 (UTC)

See our articles on BALB/c and C57BL/6 for examples. However, Michael Festing's Inbred Strains of Mice is the definitive source, there is a online version here - just select your strain of interest and find out their characteristic of interest. Rockpocket 01:50, 13 May 2007 (UTC)

Limbs falling asleep

What's the term for a limb "falling asleep" when you sleep on it/lean on it/etc.? Basically where the limb goes numb. My leg fell asleep today and to my surprise, I didn't get the tingling sort of "pins and needles" feeling after I moved it. The feeling in my leg simply came back. So I thought that I could maybe find out why it didn't have the tingling feeling that sleeping limbs normally have after they "wake up" but I can't seem to get Google to give me the right page to read. Dismas|^(talk) 01:52, 13 May 2007 (UTC)

Thanks to this thread from back in February, we have learned that two relevant terms are paresthesia and obdormition. (Thanks, Lph!) —Steve Summit (talk) 02:04, 13 May 2007 (UTC)

Thanks, at least now I know what they're called but I still don't know why I didn't get paresthesia after my obdormition... Dismas|^(talk) 03:42, 13 May 2007 (UTC)

passive solar to generate electricity

I had a thought about a system to generate electricity, and would appreciate any comments or criticism. It is designed for a building, and consists of two fairly large transparent plastic cases, connected to each other with two pipes. One case (the hot case) hangs on the south side of the building (or somewhere else exposed to sun, the roof, etc), and the other (the cold case) hangs on the north side or behind a shaded wall, etc. The cold case is higher than the hot case. One insulated pipe travels from the top of the hot case, across the building to the top of the cold case. Another pipe travels from the base of the cold case to the side of the hot case. Perhaps the hot case will also have a reflective material on the base to assist. The whole system is sealed and contains air. So, as the sun hits the hot case, the air will be heated and rise towards the cold case, thus forcing air from the cold case to travel through the other pipe to equalise the pressure. My first question, will this happen? Or will relatively hotter and cooler air molecules simply pass by each other through the same pipe? As you can imagine, my vision is that air will constantly flow in one direction around the device. Because this air will definately not generate enough breeze in the pipe to run a wind turbine, I envisioned a valve which is placed in the pipe somewhere. The pressure builds up, then pops up the valve to allow air through. It drops back down and the cycle continues. This regular jerking motion can be used to spin a turbine (which sits outside the pipe) and generate power. As far as I can tell, the system will be fairly cheap. Can anyone point out any obvious flaws or drawbacks to this system? Will the energy generated be too small so as to not be worth the trouble? Drathr 02:50, 13 May 2007 (UTC)

So basically it's two large radiators which uses convection currents to generate electricity? I would suggest you not to use air as it is fairly inefficient in heat transfer, doesn't absorb all of the sunlight and has a low density. Something like water in a special solar collector would be much more appropriate. A similar system already exists which uses huge reflectors to reflect the sunlight into a a point which boils water and extracts energy from its steam, which is roughly the same as your concept, using water. --antilived^{T | C | G} 03:14, 13 May 2007 (UTC)

Agreed, use water instead. Perhaps add some dye to make it absorb more sunlight. Also use one-way valves to ensure that all flow occurs in the proper direction. StuRat 04:47, 13 May 2007 (UTC)

Thanks for the input. One-way valves would solve one issue. Although air is less efficient for heat convection, I was thinking of ways to construct an extremely low-cost and light system, that would generate a small amount of power on a local scale, not for generating large amounts of electricity. Use of water would make it much heavier (although I have no idea of what case size would be suitable) and also, my impression is that water flowing through a heavy one-way valve would simply keep the valve open constantly, and flow slowly through, while air would build up pressure, then simply rush through at once, allowing the valve to drop back down. Given that the pipe will not contain a turbine to capture energy from the moving gas or liquid, I think this violent motion is necessary to generate electricity. Can anyone tell me if this is correct or if I am missing something?Drathr 05:36, 13 May 2007 (UTC)

Another advantage of water is that it is readily available and inexpensive, so the tanks can be filled with a hose once installed. Why not use a turbine inside the pipes, BTW ? A continuous process is typically more efficient than an intermittent process, so it would be best if the valves stay open when the device is in use. Also, you might consider locating the cooling tank inside the house, so as to heat the house. And, if you really want a very low power output, why not just use solar cells ? The lack of moving parts makes them more reliable (although they do need to be cleaned from time to time). StuRat 05:59, 13 May 2007 (UTC)

The reason I didn't consider placing a turbine inside the pipe, is that I would like the system to be both extremely cheap and fairly easy to assemble from kit form. So I see the pipes as regular 5 cm diameter pipes. I think if a turbine were used inside the pipe, the volume would have to be quite substantial and the water flow quite fast for anything meaningful to be gained in the way of electricity generation. But this would probably make the system too heavy and complicated to fit its original purpose. So although the intermittent action would be less efficient than a continuously rotating turbine, I think it is necessary here to be suitable. I haven't established what the kinetic intermittent energy would be transferred to yet. Also, I intend this to be used in very hot and sunny areas. I understand that solar panelling and battery storage is a fairly easy and reliable method of electricity generation on a house, but I'm trying to theorise whether some system could be set up to generate some energy for a much much cheaper price, like well under a thousand dollars. Drathr 09:28, 13 May 2007 (UTC)

Battery storage is anything but fairly easy. They will cost a lot more than your generation system. But otherwise I think a better approach would be something like a small scale Solar updraft tower (black tarp on some conical support with a turbine on top?). This would solve all the issue of the one-way valves and would only require one large structure instead of two. Although neither are very efficient compared to other things like photovoltatic cells and I doubt it can even supply 1W for a tent sized structure. --antilived^{T | C | G} 10:17, 13 May 2007 (UTC)

I agree. Any mechanical system is likely to cost more per watt than solar cells, not less, and be less reliable. The one advantage of such a system (using water) is that it has the potential to convert a higher percentage of sunlight into usable energy than a solar cell. However, if it costs 10 times as much and produces twice as much energy, that's still less economically efficient. The air filled version would probably produce even less usable energy than solar cells, yet still cost more. StuRat 14:11, 13 May 2007 (UTC)

I am assuming that ease of assembly/repair and durability are also factors - I doubt that energy recovery from a one-way valve can be made mechanically simpler than a pinwheel type turbine. You might see some savings in the charging hardware by trading continuous (during daylight) input at variable power for known impulse power at intermittent intervals, but intuition says no. A [solar chimney] looks feasible and quite simple for remote but sunny areas. You might also want to consider that pretty much any implementation will be more efficient as a single large installation (say, at a village center) than trying to make individual houses self-contained. Eldereft 14:06, 14 May 2007 (UTC)

Fuel Cell

Any idea if we could run a fuel cell in reverse, then would it convert water and CO2 back to fuel??~~ —The preceding unsigned comment was added by 59.92.244.211 (talk) 05:14, 13 May 2007 (UTC).

Not exactly. Fuel cells use hydrogen and oxygen to create energy by combining them to form water. In reverse, water would be split (using energy) to create hydrogen and oxygen. --M1ss1ontomars2k4 ^{(T | C | @)} 05:21, 13 May 2007 (UTC)

i.e. Electrolysis of water -- Consumed Crustacean (talk) 07:37, 13 May 2007 (UTC)

Fuel cells don't produce CO₂ so maybe the question may be "can you run an internal combustion engine backwards?". I don't know the answer, but I would guess that with enough energy/pressure you could... Aaadddaaammm 09:47, 13 May 2007 (UTC)

At one point, you run into the Second law of thermodynamics. Titoxd^{(?!? - cool stuff)} 19:19, 13 May 2007 (UTC)

Fuel cells that run on H2 dont produce CO2, others well do so. The advantage of a fuell cell is that it's effectiveness is not limited by the effectiveness of a carnot process, not that they are more "clean" than a combustation engine. Cells that run on H2 are cleaner only when you put aside the process of the making of H2, which requires energy, from dirty traditional sources. 84.160.200.176 19:24, 13 May 2007 (UTC)

Or from less dirty sources, such as geothermal, nuclear, etc. Power plants are often far higher in efficiency than ICEs as well, even taking into account power loss during transmission. -- Consumed Crustacean (talk) 21:55, 13 May 2007 (UTC)

Water plus electrical energy produses hydrogen and oxygen. In principle, the addition of carbon dioxide and energy should be able to produce hydrocarbons, i.e. fuel. Edison 23:08, 13 May 2007 (UTC)

Respiration and photosynthesis are opposite reactions of I suppose 'natural fuel cells'. Respiration produces carbon dioxide, water and energy from oxygen and sugar, photosynthesis does the opposite, i.e. requires the input of energy from sunlight. Reversing a reaction that produces energy will require energy input, but is probably possible under the right conditions. Cyta 07:37, 14 May 2007 (UTC)

I'm kinda doubtful that you could just run a fuel cell in reverse - but there are certainly other chemical pathways that would allow you to make fuel from the byproducts of a fuel cell. But obviously the energy that would require would be more than the fuel cell generated in the first place (possibly MUCH more!) - so there isn't much in the way of a practical application for this. SteveBaker 01:18, 15 May 2007 (UTC)

Why don't corn cobs burn ?

Most other plant materials are flammable, so why aren't corn cobs, even when dried ? StuRat 06:32, 13 May 2007 (UTC)

If they don't burn, what do they do? Now I can't wait till fall to do some experimenting... Dismas|^(talk) 07:45, 13 May 2007 (UTC)

Well, sure they burn. In fact they make fine charcoal for use in stoves. I recall, but cannot cite, that they were used by many farmers in the era of steam tractors to stretch their coal supply. --BenBurch 19:43, 13 May 2007 (UTC)

They seem to be left, intact, in the ashes after a nice fire. Do you need to soak them in gasoline and burn them in pure oxygen ? StuRat 21:47, 13 May 2007 (UTC)

Make sure they are totally dry! --BenBurch 22:00, 13 May 2007 (UTC)

When Sweet corn is roasted (roastneers), the high moisture content of the cob preserves it somewhat from burning. The rule (only partly in humor) for cooking sweet corn is ideally to have a pan of water boiling, go to the field and pick the corn at the peak of sweetness, and run as fast as you can to the house. If you trip and fall, abandon the sweet corn and go get another batch. The point is that the sweetness and moisture content both decrease after picking. It can be judged in the supermarket by peeling back the shucks and observing whether the kernals are dimpled. If they are, it is too far postmature. It will be older than ideal , but still delicious. Field corn [7] is dried to a low moisture content of 15% to 30% so that the cobs which are left after shelling burn very nicely in cob stoves, which are similar to wood-burning stoves. Stoves of a different design have also been built to burn the shelled field corn itself. The cobs were also used (painfully in my judgement) as a toilet-paper substitute in outhouses. Edison 23:06, 13 May 2007 (UTC)

ring species

Mention above of species problem reminded me of this. There are multiple known species chains, sets of species or subspecies spread out over a long distance such that each can interbreed with its neighbors in the chain but the ends of the chain are clearly distinct. When the ends of the chain overlap in territory, as in the case of a genus of Arctic birds whose name escapes me, it's called a species ring. My question: are there any cases where the ring is truly continuous, where there are no "end" species that can interbreed in only one direction? (Presumably this would be the result of a climate change, or similar event, that made the core of the ancestor's range inhospitable but left it happy in the periphery.) When I've raised this question before elsewhere, I got only blank looks; perhaps I did not make clear the distinction between physical separation and breeding separation. —Tamfang 09:38, 13 May 2007 (UTC)

So you have initially an essentially homogeneous species with a wide range, then drop out the middle? If members tend to breed with geographic neighbors (as opposed to maintaining a central breeding ground, like seals) such that it would take many generations for an advantageous gene to be passed around the ring, I see no reason why the various regions would not begin to speciate. I seem to recall that there are precious few examples of [ring species] of any kind - those gulls, some California salamanders, and the [greenish warbler] runs the gamut of our article and what I recall from last time I looked into the issue. While not an evolutionary biologist, I suspect that the situation would be unstable - even without further habitat-altering events, sexual selection can drive speciation. Eldereft 14:43, 14 May 2007 (UTC)

LUNAR ECLIPSE

WHY LUNAR ECLIPSE IS VISIBLE ON ALL THE PLACES ON THE NIGHT SIDE OF THE EARTH ? —The preceding unsigned comment was added by 202.164.134.90 (talk) 12:01, 13 May 2007 (UTC).

Because the shadow that the Earth casts is much bigger than the moon, no light from the sun falls on the moon. Thus there's nothing to see, from anywhere on Earth. Contrast with a solar eclipse, where only a small shadow is cast, so only parts of the Earth can see it. Rawling4851 12:10, 13 May 2007 (UTC)

Because you can see the Moon from everywhere on Earth which is facing in that direction. During a lunar eclipse, the Sun must be on the opposite side of the Earth to cast the Earth's shadow on the Moon, making it night on that side of the Earth facing the Moon. The Moon is then only dimly lit from light reflected from the Earth and stars. StuRat 14:00, 13 May 2007 (UTC)

For this question, the important difference between a solar eclipse and a lunar eclipse is the effect of parallax. In a lunar eclipse you are seeing the shadow of the earth on the surface of the moon, both in the same plane, and so its appearance doesn't depend greatly on where you are looking from. In a solar eclipse, you are seeing the moon against the background of a much more distant sun, so its appearance changes according to your viewpoint.--Prophys 02:46, 14 May 2007 (UTC)

Do we have any pics of an eclipse as seen from space ?

I didn't find any when I searched, which seems odd. I would have expected many pics of the Earth with the Moon's shadow on it. StuRat 04:43, 14 May 2007 (UTC)

What you want is a picture of a solar eclipse as seen from space. Here's a good one.--Prophys 05:38, 14 May 2007 (UTC)

Thanks. Is it my imagination or is the Moon's shadow a pentagon in that pic ? StuRat 07:06, 14 May 2007 (UTC)

Definitely not just your imagination but I'm struggling to explain it. I'm a bit into astronomy and I've seen a lot of pictures, I'd be inclined to say this is more likely an artefact of the equipment used and conditions wile the picture was taken, rather then some astronomical phenomenon. Sort of like the famous face on mars, we are so hardwired to recognise patterns I think we're just seeing something that isn't really there. What could possibly make a round shadow into a pentagon? I believe the storms on Saturn taking uncannily geometric shapes, but a shadow travelling through space? Generally the only thing which creates geometric shapes with light in pictures is lenses. Vespine 23:47, 14 May 2007 (UTC)

Weird - I did some image processing on this photo and the shadow is definitely hexagonal - it's not an optical illusion - it's really there. It's not a regular hexagon though - the segment on the right side is much shorter than on the left - which is the opposite of what you'd expect due to perspective. I agree that lens effects are generally the cause of hexagonal artifacts (these are 'lens flares') - but I've never seen a dark lens flare. I guess it must be something to do with refraction through the atmosphere. After all, the atmosphere has a different refractive index than vacuum - and it's curved slightly due to curvature of the earth. I suppose it's possible that we're seeing some bizarre lensing effect of the atmosphere. Very interesting! SteveBaker 02:52, 15 May 2007 (UTC)

The ground's color is not even, and therefore the iso-whatsits of the shadow superimposed on that ground are not perfect circles. What's to be surprised of? —Tamfang 05:31, 15 May 2007 (UTC)

Yes, the shadow is falling on an uneven cloud layer, rather than a flat surface. Also the cloud densities vary, so their albedo varies from point to point. You are seeing the effects of patchiness in the cloud distribution. Notice that even where there is no shadow, there is still considerable variation in reflected light intensity between thick cloud, thin cloud and no cloud. The penumbra portion of the shadow is likewise affected. Remember that the shadow, even if it fell on a flat, uniform surface, does not have sharp edges, but grades steadily from none to full shadow at the centre (for a total eclipse). The shadow is falling on a sort of hexagonal-shaped irregularity in the clouds. --Prophys 11:13, 16 May 2007 (UTC)

Then I suppose the new question is: "Why is there a hexagonal-shaped irregularity in the clouds ?". StuRat 23:46, 16 May 2007 (UTC)

Because a hexagonal-flavored irregularity would be just silly. (Now, does someone want to tell me the difference between hexagonal-shaped and just plain hexagonal?) —Tamfang 22:06, 17 May 2007 (UTC)

Falling

I am not sure if I have the physics of this right or not, so I'd like someone to give me a hand here. I was told that the acceleration of a falling body is approx. 5m per second per second, and that there is a maximum speed at which a body which has no specific shape-related drag (i.e. not a feather or piece of paper) can fall. I was also told that that maximum speed was 35m/s. By my calculations, this would mean that a person falling from a height would stop accelerating after just over 2 seconds of falling and would remain falling at the same speed until hitting the floor.

Does this mean that a person will have the same injuries, ceteris paribus, if, a) they fell out of a three-storey window; b) they fell out of a 30-storey window; c) they fell from a plane at 33,000 ft? Manga 12:35, 13 May 2007 (UTC)

You have the concepts mostly correct, but your numbers are not too accurate. Standard gravitational acceleration is 9.8m/s² (not 5); every object (even feathers) has a terminal velocity determined by its aerodynamic properties, the local atmosphere, and its weight (so filling a hollow sphere changes its terminal velocity). There is no single maximum speed; the article gives humans an average of 54m/s, or 89m/s if you're trying. Also, your math doesn't seem to work out; it takes the obvious 7 seconds for an acceleration of 5m/s² to reach 35m/s.

Finally, a falling body doesn't accelerate uniformly up to its terminal velocity and then "stick" there suddenly; instead it gradually accelerates less as it approaches that velocity and, in theory, never actually reaches it. In reality, for long falls (like from the stratosphere), the air pressure is increasing relatively rapidly as the object falls, so the terminal velocity is reduced. This means that at some point a short distance into the fall, the object will actually be falling faster than its terminal velocity (because that velocity dropped) and will spend the rest of its fall decelerating to keep "up" with the air drag. Does that make anything clearer? --Tardis 13:09, 13 May 2007 (UTC)

Yes, it does, thanks. Manga 13:25, 13 May 2007 (UTC)

Also, in addition to shape factors, terminal velocity is also very much influenced by the density of the falling object. Thus, a bowling ball will fall faster than a soccer ball of the same diameter. StuRat 13:56, 13 May 2007 (UTC)

How much would it help to deploy an umbrella (34 inches)? How about a 60 inch beach umbrella? An 11 foot patio umbrella? Edison 22:51, 13 May 2007 (UTC)

They wouldn't work as a proper parachute, and could only hold up a small weight before the forces on the umbrella would break it. However, if it held together, an umbrella would slow the fall of a small object, say a baseball, considerably. StuRat 03:03, 14 May 2007 (UTC)

Rather than an umbrella, you might want to deploy a Drogue 'chute.

Atlant

Yep - you've got to ask yourself how your umberella would stand up to a 100mph wind - 'cos that's what it's gonna be doing if you open it to slow the fall of something like a human being. SteveBaker 21:09, 14 May 2007 (UTC)

Princess Peach did it. - 2-16 12:18, 16 May 2007 (UTC)

No, she used a parasol. 213.48.15.234 14:04, 16 May 2007 (UTC)

Motion through Spacetime (Special relativity)

I understand that all motion is relative, and that there is no absolute motion or rest, but if I am at complete rest relative to the universe, I have motion through time, but no motion through space.

As I move I convert some of that motion through time into motion through space. If I were to convert all that motion through time into motion through space, I would be travelling at the speed of light and time would effectively stop for me (again, I understand that at the speed of light, my inertial mass would be infinite and thus require an infinite force, making travelling at the speed of light impossible).

But say I was to accelerate further, impossible - I know. I would be travelling faster than light, and as the sum of my motion through space and my motion through time is equal to the speed of light, wouldn't travelling faster than light mean that my motion through time is negative, effectively reversing the flow of time? And wouldn't this be a direct violation of the second law of thermodynamics which states that time can only flow in one direction and that entropy increases over time?

Also, what does this mean for the electrons which travel faster than light in water in the Cherenkov effect.

Ignore the last bit, the speed of light in water is of course 0.75c, which particles can easily be accelerated to.

Aiyda 13:06, 13 May 2007 (UTC)

You've almost answered your own question there - you can't accelerate beyond the speed of light, so therefore you can't travel through time in the negative direction, and so you won't break the second law! →Ollie (talk • contribs) 13:22, 13 May 2007 (UTC)

I know that the question which I asked is purely hypothetical, as nothing can travel faster than light, but I am asking if it could, would the second law be broken by a reversal of time. Aiyda 13:26, 13 May 2007 (UTC)

[edit conflict] As far as "relative to the universe", you'll need to define this; the universe hath not a single reference frame. It's really only proper to say that if you observe an object as not moving, its motion is entirely timelike, and to restate the rest of your question in such terms. As far as "infinite force", it's more direct to simply state that a massful object travelling at c has infinite energy (kinetic energy, if you like); how would it acquire that much?

You are correct that the Lorentz factor stops being a positive number at superluminal velocity: in particular, it becomes negative-imaginary. Given a pair of objects moving at relative speed greater than c (which is itself understood to be impossible), we can always find a third object, moving at less than c with respect to one of the objects, which observes it as progessing forward in time and the other as moving backwards (arriving before it departs). Moreover, it is thought that there may exist tachyons which have the properties you describe; however, while in general FTL travel can create 2^nd-law violations, causality loops and a variety of other science-fiction-y complications, the tachyon article says that the special kinematics of tachyons actually make them much less disruptive.

[answering the last bit anyway] Finally, the Cherenkov effect is fortunately not this complicated; in special relativity it is always the true (vacuum) speed of light c that matters, not whatever effective speed it has in some local medium. Such electrons are certainly relativistic, but they are not in danger of youthening; their weird radiative output can be described in a largely classical manner. Does that help? --Tardis 13:27, 13 May 2007 (UTC)

Thanks, although I don't understand everything (currently in year 10 studying physics), I think I get the general drift. thanks for the help Aiyda 13:41, 13 May 2007 (UTC)

This is so widely misunderstood. What special relativity predicts is that an object going faster than light in one frame of reference will go backwards in time in some other frame of reference (moving quickly, but slower than light, with respect to the first one). So (assuming that your FLT drive works in every frame of reference) you could arrange to get back to an earlier time at a "fixed location" (such as Earth) in a two-step process, going faster than light in Earth's frame on the way out, then faster than light in a different frame on the way back. It doesn't predict that going faster than light in Earth's frame means you'll go backwards in time in Earth's frame, and it doesn't predict that you'll get younger on the way. --Trovatore 19:22, 13 May 2007 (UTC)

This question is horribly flawed - to the extent that it can't be answered:

but if I am at complete rest relative to the universe

There is no such thing as 'at rest relative to the universe' - it's a totally meaningless concept. Bits of the universe are moving every which way - there is no 'special' motion that you can count as 'at rest'.

As I move I convert some of that motion through time into motion through space.

That's just nonsense. There is no "conversion" between time and space - that's just meaningless. Time and distance are dilated because of speed - there isn't some kind of exchange between time and distance when you are moving. Meaningless concepts can't generate meaningful answers - so we can't answer that.

I would be travelling at the speed of light and time would effectively stop for me

No - when you are moving close to the speed of light (relative to some other object) - everything seems perfectly normal to you inside your spaceship. Time for you passes normally - it's whatever you are moving fast relative to that seems (to you) to have time dilation.

But say I was to accelerate further, impossible - I know.

It is impossible - but it's not impossible because somehow you can't manage to find enough energy to do it due to mass dilation effects. No, it's impossible because the consequences are impossible. The Lorentz transform is the mathematical description of how time/length/mass are distorted by relative motion. The math is '1/sqrt(1-v²/c²)'. When v (your velocity) is greater than c (the speed of light), v²/c² becomes greater than 1 - which means that (1-v²/c²) is a negative number. But now you have to take the square root of that number...which you can't do and remain within the bounds of 'normal' arithmetic. If you try to take the square root of -1 on your calculator it will produce an error. Mathematicians find it convenient to do math with the square roots of negative numbers - but the way they do that is to use "complex numbers" - which can't describe real world things like length, mass or time. So if you fly faster than light then all of your distances lengths and times are complex numbers. Complex numbers cannot ever happen through calculations of physical quantities because they are purely a mathematical abstraction - but at greater than 'c', they don't cancel out. So asking about what would happen if you flew faster than light is just not a question you can expect an answer to - there is no physical interpretation of a complex number. Time doesn't run backwards because that would require a negative result from the Lorentz transform - and you don't get a negative answer - you get a complex result.

Even moving at the speed of light is a problem - in that case v equals c - so sqrt(1-v²/c²) comes out to exactly zero - but Lorentz requires one divided by that...and once again, math falls apart when you divide one by zero. 1/0 is not infinity - it's undefined. Your calculator gives you an error again. So the math falls apart just before before you get faster than light.

Flying faster than light to cause time travel is pure science fiction - there is no math to support that. There are other ways to imagine that time travel could be possible - but superliminal travel ain't it. The premise behind the question is wrong - and the only valid answer is "You just can't do that" - speculation about what would happen if you did depends on a physical interpretation of complex numbers - which can't exist.

SteveBaker 04:26, 14 May 2007 (UTC)

Steve, I think your analysis relies a bit too heavily on extrapolations of known physics into unknown regimes. It doesn't make sense to say "of course there is no known mechanism to travel faster than light, but if there were such a mechanism, then observers using it would see their clocks move by an imaginary amount". Since we don't have any proposed mechanism, we can't say what observers using it would experience.

On the other hand, we can give some reliable predictions about what observers remaining behind would observe. If the spaceship is moving faster than light in one frame, then there's another frame, moving (slower than light) with respect to the first frame, in which the spaceship would be seen to arrive at an earlier date than it had left. This prediction is completely independent of the unknown mechanism, provided only that the mere fact of the ship's voyage does not affect the measurements of the observers remaining behind. --Trovatore 05:25, 14 May 2007 (UTC)

No - that's my entire point. You fail to notice the key point of special relativity - which is the symmetry between the observer and the observed. If we don't know what the universe would look like in the frame of reference of a spaceship travelling faster than light - then someone here on earth (which would also be travelling faster than light relative to the spacecraft) would have the exact same problems. The result isn't negative time effects - it's complex-number time effects - and that just can't be. The only chance one would have for something 'interesting' to happen would be if the theories of relativity were wrong. There is no evidence for that - so again, you can't speculate as to what the answer might be. SteveBaker 11:28, 14 May 2007 (UTC)

Steve, here what you're doing is conflating the physics that we know from observation, with Einstein's ideology. The physics is well established. The ideology, on the other hand, could easily be wrong.

To go faster than light, we'd obviously have to do something not provided for by known physics. That doesn't mean that known physics keels over and dies, just that it wouldn't apply to our posited spaceship. It would still apply, presumably, to the rest of the universe that's not under the influence of our funky FTL-enabling field or magic spell or whatever.

And that's my point: Provided only that the FTL-enabling effect, whatever it is, is local, then special relativity does in fact make the predictions I described. In a certain frame of reference you do predict the spaceship arriving before it leaves. You never have to take the square root of a negative number, because this second frame of reference is moving sub-light with respect to your original one. This is an easy calculation; I can give details if you want to see them. --Trovatore 18:14, 14 May 2007 (UTC)

I'm gonna have to call you on that one - I think it's B.S. SteveBaker 01:12, 15 May 2007 (UTC)

OK, let's take a simple case. Let's take two frames of reference, which we'll call unprimed and primed, and we'll ignore the y and z coordinates and focus on x and t (or in the primed reference frame, $x'$ and $t'$ respectively). For simplicity we'll use units in which the speed of light equals 1. The "primed" observer is moving at a speed of 0.8 in the positive x direction, as measured by the unprimed observer.

Now consider two event points A and B. The coordinates of A are

x_A=t_A=$x'_{A}$=$t'_{A}$=0.

The unprimed coordinates of B are

x_B=10

t_B=1

That is, B is the event point one year later than A, as measured in the unprimed frame (not the ship frame!), but ten light-years in the positive x direction (still as measured by the unprimed observer).

What are the primed coordinates of B? Just plug it into the Lorentz transform:

$x'_{B}={\dfrac {x_{B}-vt_{B}}{\sqrt {1-v^{2}}}}={\dfrac {10-0.8}{0.6}}=15.33$

$t'_{B}={\dfrac {-vx_{B}+t_{B}}{\sqrt {1-v^{2}}}}={\dfrac {-8+1}{0.6}}=-11.67$

So from the point of view of the unprimed observer, the ship leaves event point A and travels for one year at ten times the speed of light, and arrives at point B, one year later but ten light years away. From the primed observer's point of view, the ship arrives eleven years and eight months before it left.

Note that there is as yet no causal paradox -- there is no forward-facing timelike path from B back to A, so you can't get a causal loop in this one step. But you can get one if the primed observer at point B, on the arrival of the ship, works the same trick and sends a ship back the other direction at ten times the speed of light in the primed frame. This last point assumes that the mechanism works in any reference frame; that point can't be fully justified, since we have no idea what the mechanism might be. --Trovatore 04:08, 15 May 2007 (UTC)

That's bogus! To see why - understand that the 'unprimed observer' has nothing whatever to do with what happens - nothing the magical spacecraft or the primed observer does or sees depends on him. Let's just delete him from the discussion. That shouldn't change what the primed observer sees - because if it does then there are an infinite number of possible observers in an infinite number of frames of reference we could have chosen as 'unprimed' and you'd get different answers for what 'primed' sees depending on which one you choose. Poor old 'primed' can't possibly experience different things depending on where some 'unprimed' physicist doing the math happens to be watching him from! So given that the correctness of the answer cannot possibly depend on the existance of this extra person - we can ignore him. This simplifies things considerably. So now you have your 'primed' observer who might as well believe himself to be stationary - watching a craft shoot off at v=(10c-0.8c) and lo and behold you are back taking the square root of a negative number - as you should be.

If you still think you're right, either explain it to me again without any reference to the irrelevent unprimed observer or explain it again with a 'double-primed' observer who is moving at some other speed relative to primed - remembering that you MUST get the same answer from the point of view of 'primed' or you have an impossible situation that's just as bad as sqrt(-1). SteveBaker 19:46, 15 May 2007 (UTC)

The unprimed observer is not irrelevant -- he's the one from whose point of view the ship is moving faster than light, but forward in time. From the primed observer's perspective it's moving faster than light (by the way, you're using the wrong formula for addition of velocity) but backwards in time. The point of view of someone on the ship is unknown and irrelevant; all we're interested in is reconciling the accounts of the two "normal space" observers.

So it's just as I said -- if from one observer's perspective (unprimed) something is moving faster than light, then from some other perspective (primed, moving sublight with respect to unprimed), that thing is moving backwards in time. That's what I was trying to get across from the beginning. --Trovatore 19:54, 15 May 2007 (UTC)

Infinity and Speed of Light (Theoretical question)

Einstein said that when a body accelerates to the speed of light (theoretically), the body becomes infinitely small. Does it follow, then, if a body is absolutely motionless (i.e. there is nothing around to compare its acceleration with) it becomes infinitely big? Manga 13:20, 13 May 2007 (UTC)

I think it's impossible for any body to be absolutely motionless. It can be relatively (*no pun intended*) motionless, but not absolutely. Therefore, your question is without basis. -- JackofOz 13:24, 13 May 2007 (UTC)

Actually it's possible for a body to be completely motionless in the frame the measurement is made, i.e. motionless relative to the observer. In fact any body can deduce that it itself is completely motionless and everything else is moving. So observations on yourself are in effect observations of motionlessness. This is called the rest frame, as the body seems at rest. You are right, Jack, in the sense that another observer wouldn't necessarily see that body as motionless, but the question makes as much sense as asking what happens at the speed of light, you simply need to specify a frame to measure in. But yeah the correct answer is the Lorentz Factor mentioned below. Maybe see also length contraction and time dilation. Cyta 07:46, 14 May 2007 (UTC)

Doesn't the mass of an object increase while it is moving, as mass is a form of energy and energy a form of mass, as per Special relativity. Aiyda 13:30, 13 May 2007 (UTC)

The OP means absolutely as in "exactly", not as in "without need for a comparator". But no; see Lorentz factor, which controls such effects. It tends to positive infinity at $v=c$, but at $v=0$ it simply gives 1, which means "normal": nothing special happens for "complete" stopping. (So your rolling stops do not have a safety justification!) Moreover, at all small speeds, the limit of the special-relativistic equations is normal Newtonian mechanics, so everything is smooth and well-behaved.

As far as mass increase, this is largely a question of semantics; see relativistic mass. --Tardis 13:34, 13 May 2007 (UTC)

It is not a question of semantics. In relativity there is no physical difference in its descriptions and reality. It makes no difference whether or not the acceleration is due to movement or a fictitious gravitational field. The effects are the same, the reality is thus the same. --24.147.86.187 17:56, 13 May 2007 (UTC)

USA on Fire

I see on TV News that several US states, such as Florida, have fires all over the place. Fires in western states, that take a long time to get put out, have been part of our news for years. Are there credible theories to explain this phenomena of apparently serious fires in many different states of the USA?

Off the top of my head, the possibilities include:

• Forestry practices
• Wetlands removed for development
• Funding cuts for first responders
• Natural weather cycles ... this is not a new phenomena, we just have not witnessed it recently
• Global warming
• This is nothing new, except what the news media chooses to focus on.

User:AlMac|^(talk) 15:40, 13 May 2007 (UTC)

Large wildfires in Florida are also not uncommon. I don't think there are any odd or unusual causes to blame, with the possible exception of the theory that rigid suppression of small wildfires helps set the stage for eventual really big ones. — Lomn 17:39, 13 May 2007 (UTC)

some areas of forest need to be revitalised by fires, so stopping them can badly affect the area.

Just as there are areas which regularly flood (flood plains), there are also areas that regularly burn. This hasn't changed, the difference is that many people now live in those areas, making such fires newsworthy. StuRat 20:16, 13 May 2007 (UTC)

I call it 'summer'. Nothing new or different. The western areas are very large and seemingly close fires to previous years are not. Just random collection. You only have to look at how pine trees fireproof their seeds to see how natural it is. --Tbeatty 04:30, 14 May 2007 (UTC)

It's not some new thing, it perfectly falls into statistical probability and there isn't anything to blame. Sometimes people have a hard time getting past the fact that sometimes there isn't anybody to blame. [Mac Δαvιs] ❖ 07:03, 14 May 2007 (UTC)

Are there any actual data for the acreage burned, number of fires, or property losses/deaths this year compared to previous years, to allow viewing of any trends? The discussion sounds like a lot of hand waving in absence of data so far. The amount and prominence of news coverage can make the ordinary seem extraordinary (and contrariwise). [8] says that this year US wildfires have burned 3 million acres, which is three times the average for this time of year, and that since 1970, the number of wildfire worldwide has "soared." [9] says that 2006 set new US records for number of fires and acres burned, 125% above the ten year average. [10] gives acres burned 1960-2006. [11] has the forecast fire danger as of today. Edison 22:06, 14 May 2007 (UTC)

If you want to learn all about the history of fire, both controlled and wild, in the United States, try the book Fire in America: A Cultural History of Wildland and Rural Fire by Stephen J. Pyne. It is very thorough (although only up to the 1980s or so). Long story short, there are several distinct fire regime regions in the US, some with more frequent (and usually less intense) fires, some with less frequent (usually more intense) fires. The late 1800s and early 1900s saw some of the largest and most intense wildfires in the US. Curiously, during the same period the Forest Service and national forests came into existence.

The page List of forest fires has info on a few of the larger, more famous fires. The Peshtigo Fire of 1871 is particularly amazing to read about. Pfly 02:22, 15 May 2007 (UTC)

Scree plot

Holy cow, no article on scree plot en that with 89000+ hits in google: [12]. I wish I knew what is was/is. Then I could write about it. VanBurenen 18:21, 13 May 2007 (UTC)

Maybe it should redirect to principle component analysis, since it appears to be a graphical representation of this technique. I have never heard of it. Nimur 18:25, 13 May 2007 (UTC)

Newts: friend or foe?

I found a newt in my garden, under a piece of wood, together with some slugs. (With no lake or pond around anywhere.) What do they feed on? Do they eat my seeds like the slugs do? 84.160.200.176 19:27, 13 May 2007 (UTC)

My response has been moved here, where people still appreciate a joke: [13]. StuRat 17:50, 14 May 2007 (UTC)

It had 4 legs and didn't talk about politics. But, who knows if the slugs weren't camuflaged bodygards? Perhaps by suggesting it might by a terrorist I could get some intelligence agency to find out what it feeds on? Salmonella sure gives a link to biological warfare. 84.160.200.176 20:31, 13 May 2007 (UTC)

I believe they are carnivores, eating slugs, worms, and insects. I suppose you might prefer if the earthworms were left alone, to help aerate the soil, but it sounds like they do more help than harm to me. Also, the coolness factor would make me happy to have one in my garden. StuRat 21:38, 13 May 2007 (UTC)

Just to expand on the coolness factor:

"Newts have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and upper and lower jaws"

Nice. Vranak

The enemy of my enemy is my friend --- as long as he's small and not numerous enough to gang up against me. I hope it's carnivorious, but I don't know. The soil is heavy and aeration is mostly done by ants, I rearly see earthworms, even by rain or when digging. 84.160.200.176 22:08, 13 May 2007 (UTC)

Thermal expansion

Is there any material which undergoes significant thermal expansion in a relatively small range of temperatures (say, between freezing and body temp)? Preferably, this should be at roughly temp, rather than close to absolute zero or 1000s of degrees C. Laïka 19:46, 13 May 2007 (UTC)

Well, the easy answer is that when any element or substance reaches its boiling point, it undergoes rapid expansion, and that's over a very small temperature change. As to your conditions, I don't have a flat out answer for you, but this article might help: List of elements by boiling point. Anchoress 21:51, 13 May 2007 (UTC)

I don't know what the original question was at, but, if you want a robust and energetically effective shutter for your window, you'll need something that's not as sensitive to pressure as a boiling point. (after edit conflict) 84.160.200.176 22:33, 13 May 2007 (UTC)

Water! When it freezes it expands significantly over a very small range of temperature. --BenBurch 22:18, 13 May 2007 (UTC)

I assumed they meant something that expands as it heats up, not when it cools down, due to a phase change. I could be wrong, though. StuRat 23:05, 13 May 2007 (UTC)

Water is the ONLY thing we know of that expands like that when it freezes, and it is a larger density change over a small range than thermal expansion would ever supply. --BenBurch

Actually, that's a myth. There are some compounds of Tin that behave similarly. SteveBaker 03:47, 14 May 2007 (UTC)

As does Bismuth. Laïka 07:21, 14 May 2007 (UTC)

Our coefficient of thermal expansion article has a list of the thermal expansion coefficients of various substances at 20^oC. Mercury heads the list, with a linear thermal expansion coefficient of 60 x 10^-6/K - hence its use in mercury thermometers. If you want a common material that is solid at room temperatures, lead is high on the list, with a linear thermal expansion coefficient of 29 x 10^-6/K. Gandalf61 10:09, 14 May 2007 (UTC)

Certain waxes have useful expansion properties; see our wax motor and thermostat articles.

Atlant 12:12, 14 May 2007 (UTC)

Taco manufactures "zone valves" for hot-water heating systems. Instead of a motor the valve is activated by heating a solid metal cylinder, causing the cylinder to expand with great force the push on the valve head. The valve operates slowly, taking perhaps thiorty seconds to open or close, the total amount of movement is less than 1/4" (6mm). The metal looks like brass of some kind. -Arch dude 22:07, 14 May 2007 (UTC)

Oh yeah, I knew there was a third article: Zone valve. Thanks for reminding me!

Atlant 00:24, 15 May 2007 (UTC)

Coyote behavior dangerous?

Last night, out walking with my 70 lb dog at about 2 am, we were paced (about a half block back) by a coyote, for about two blocks. When a car and a cyclist crossed its path at the same time, it skedaddled. Now coyotes are very common in Vancouver, and I've never been concerned about their proximity (even when I've seen two together), partly because they are so timid and partly because of my dog. But with it behind us and my dog oblivious (and me in bare legs, a miniskirt and flip flops), I was a bit nervous.

What would make a coyote behave like that? Was I right to be worried? What should I do if it happens again? Anchoress 22:27, 13 May 2007 (UTC)

It obviously just wanted to see you in the miniskirt. —Preceding unsigned comment added by 68.117.135.99 (talk • contribs)

They claim that coyotes do not attack humans. I might surmise that they never leave anyone around to complain. They certainly carry off and devour cats, rabbits, and small dogs. A 70 pound dog should not constitute coyote food. Nor should an Anchoress. Perhaps the wiley coyote was only waiting for the delivery of his rocket powered Acme roller skates, the better to overtake you. Edison 22:43, 13 May 2007 (UTC)

Tee hee. Wyle E. Coyote is my favourite. I think if I were the road runner, I'd let the coyote catch me. Anchoress 23:59, 13 May 2007 (UTC)

"Allow me to present myself (*hands over business card*), I'm Wyle E. Coyote, Super Genius. There's absolutely no point in your attempting to escape, as you simple won't have a chance against my towering intellect. So, why don't you just avoid all the unpleasantness by surrendering right now ?"..."Me-meep (*roadrunner sticks out tongue and runs away*)."StuRat 02:35, 14 May 2007 (UTC)

I live in Texas - we have both roadrunners and coyotes - and I am pretty sure that coyotes can catch roadrunners - because I've seen one of my dogs catch one by sheer speed. However, the coyotes are obviously more cunning about it because I've seen no sign of rocket packs, volcano pills or any crates labelled "ACME" in my back yard. As for coyotes and dogs...any carnivore has to weigh up the risks and rewards of an attack. A coyote would be taking a significant risk of injury taking on a healthy medium sized dog - and even a small dog or a cat might be more than it would want to take on. The risky times must be when they are hungry, desperate or defending their young. SteveBaker 01:07, 15 May 2007 (UTC)

Of course, to know that neither you nor your dog are "food", they need to check you out first, which might be why they were following you. Once they figured that your dog was too large, they likely would have moved on. Another possibility is that they saw your dog as a rival for their territory, and were looking to pick a fight, but weren't going to so long as you were around. To be safe, however, instead of letting them stalk you from behind, I'd suggest you turn around and look at them, so they know they've been spotted. And, wearing that miniskirt, you might just find a wolf on your trail some day. :-) StuRat 22:53, 13 May 2007 (UTC)

That's my take on it too, but I'd rather be sure. Probably the coyote has gotten accustomed to eating what people throw away, and was hoping I'd discard something, but I don't know... maybe it had rabies? Anchoress 23:59, 13 May 2007 (UTC)

It doesn't sound anything like rabies, to me. Affected animals throw caution to the wind, but your coyote sounded as cautious as ever. StuRat 02:29, 14 May 2007 (UTC)

"In California there has only been one documented human death attributed a coyote attack." --JWSchmidt 23:37, 13 May 2007 (UTC)

Yeah, that's also in the coyote article, which also says that attacks on humans aren't unknown. But I was hoping for something to contextualise the info there. Thanks for the link. Anchoress 23:59, 13 May 2007 (UTC)

Wolves don't normally attack humans either, except if they are injured or crazed by hunger, which is commonly caused by injury. Are coyotes common in Vancouver proper? As in the habituated bits? I think you should call someone anyway to make sure, like the animal protection department or whatever you have there. Maybe you and your 70lbs dog are safe but what if that cyclist was a child and the coyote is hungry? Though at least this page seems to suggest rabies is not likely. Either way your local animal handlers will be much more likely to tell you if what you saw was abnormal or reason for concern. Vespine 00:34, 14 May 2007 (UTC)

Thanks for the info; I was thinking of calling it in, but I'm not sure where to. Yes, coyotes are extremely common in Vancouver; I've heard up to 1000 just in the City, thousands in the Lower Mainland. I see them all the time in my (very urban, just outside downtown) neighbourhood, but only at night. Aah well, I guess I'll give the City a call on Monday; they should be able to tell me where to report it. Anchoress 00:44, 14 May 2007 (UTC)

BCSPCA Might not be the right people but i bet they'll know who is. I always thought the moose/coyote thing in Canada was a bit like people saying kangaroos hop around the main streets in Sydney;), guess not.Vespine 02:00, 14 May 2007 (UTC)

Yeah, but if you want to see moose and grizzly bears in the same driveway, you have to go to Alaska. Anchoress 02:11, 14 May 2007 (UTC)

They'd better just hope to the bear doesn't decide to go fishing for salmon in their bathtub next. StuRat 02:54, 14 May 2007 (UTC)

It's possible that it was part of a group, looking to get the dog to chase it so that they could harass and exhaust it so that they could kill it. I recall when I worked on a golf course in Edmonton, hearing coyotes howling at each other for a while before hearing dogs barking and then an aweful noise before silence. Creepy stuff, and enough to keep your dog on a leash when walking through parks.

Thanks to all who answered. I was enlightened and entertained, such a rare occurrence. —The preceding unsigned comment was added by Anchoress (talk • contribs) 18:25, 16 May 2007 (UTC).

May 14

When is it first clear that a child is left or right-handed?

I was wondering when it was first obvious that a child is left or righthanded. The article on right-handed has nothing on it. Capitalistroadster 02:46, 14 May 2007 (UTC)

I don't know, but the results of this google search might be helpful: first age handedness children. Anchoress 02:50, 14 May 2007 (UTC)

When they've been writing or painting for a few months it's obvious. Before that - it's really hard to tell. SteveBaker 03:46, 14 May 2007 (UTC)

My son could throw a ball at approx 10 months old. Surely you can tell then? Sandman30s 09:49, 14 May 2007 (UTC)

My son was using both hands equally for almost all activities - until he started drawing and painting - for which he used only his right hand. If you put a crayon into his left hand, he'd pass it over to his right and then starts doodling. I don't think a ball toss is sufficiently strongly associated with laterality to show a preference at early age. But hey - we're all individuals and handedness isn't a 'pure' left/right thing. There are degrees of the strength of preference - so it's possible you could tell earlier. SteveBaker 11:32, 14 May 2007 (UTC)

Even at that age I am fairly sure he used to pass the ball over to his right hand if it was in his left. Certainly, at age 12 months he was running, picking the ball up with eaither hand, and throwing with his right. Also kicking with his right foot. Being right-handed myself, I find it very unnatural to attempt a throw with my left. I think he would have found the same even at that age. Also early activities such as building blocks or opening a container etc. - way before drawing or painting. Sandman30s 12:19, 14 May 2007 (UTC)

The child would probably experience the preference well before the parents were aware of it. The question is when is it first clear, presumably meaning "clear to the parents". One of my sons is left-handed. We first noticed it when he was around 12-15 months. My mother was quite worried that he was not quite normal, as he was the first person from either side of the family in at least 2 generations who showed a preference for the left. I had to reassure her that it's quite ok to be left-handed, and had to resist her attempts to make my wife and me make him use his right hand over his left. JackofOz 12:43, 14 May 2007 (UTC)

insect identification

I found these guys on my windowsill today: [14] [15] [16] [17]. Does anyone know what they are? Jay Gatsby^(talk) 02:47, 14 May 2007 (UTC)

Unfortunately, all 4 pics appear to be out of focus. StuRat 02:58, 14 May 2007 (UTC)

It's the best I could do with my camera right now (the insects are really small). Care to take any guesses? Jay Gatsby^(talk) 03:01, 14 May 2007 (UTC)

I think they may be termites. What do you guys think? Jay Gatsby^(talk) 03:08, 14 May 2007 (UTC)

That's what they look like. Assuming I wasn't wearing my glasses at the time that is. If they are on your sill, you should call an extermination expert forthwith. --BenBurch 03:11, 14 May 2007 (UTC)

Thanks for your opinion. I think I can get better pictures tomorrow afternoon when there is more sun. To be continued! Jay Gatsby^(talk) 03:21, 14 May 2007 (UTC)

I don't think you need more Sun, I'd guess you need to hold the camera farther away or adjust it for a closer focus. StuRat 04:24, 14 May 2007 (UTC)

If you look at this image, there's really not much room for doubt (your guys look like the workers, not the toothy soldiers). I'd call a bug man. --TotoBaggins 03:51, 14 May 2007 (UTC)

You need to see if your camera has a 'Macro' setting - that's what's needed to take photos with the lens closer than maybe a foot or so to the subject. Most halfway decent camera have a macro option. SteveBaker 11:34, 14 May 2007 (UTC)

Sigma Replication

What is Sigma Replication? —The preceding unsigned comment was added by 59.93.16.61 (talk) 04:51, 14 May 2007 (UTC).

I don't know, but a google search with "sigma replication" has a few likely looking sites. The first hit's abstract ([18]) suggests it is a "mode of bacteriophage lambda DNA replication during its lytic development in Escherichia coli cells". The introduction of that paper would be likely to have a more precise description. Aaadddaaammm 08:09, 14 May 2007 (UTC)

Were you unable to access the article? Quoting from the article:

"rolling-circle (σ) replication occurs late after infection to produce long concatemers that serve as substrates for packaging of λ DNA into phage proheads. The mechanism regulating the switch from θ to σ replication remains unknown."

Someguy1221 09:15, 14 May 2007 (UTC)

Speeding up the aging process in paper

Does anyone know how aged parchment and paper can be reproduced chemically. I make reproduction lithographs as a hobby and would love to be able to print them on subtly toned paper. I know all the coffee and tea techniques but unsurprisingly they all stink of um, coffee and tea! I thought that I heard of a technique using alum that changes the cellulose in some way? Any information would be greatly appreciated even if it is completely unverified.

Thanks - Kirk UK —The preceding unsigned comment was added by 82.153.110.133 (talk) 07:19, 14 May 2007 (UTC).

High doses of UV light and acidic humid environment? --antilived^{T | C | G} 07:42, 14 May 2007 (UTC)

It depends on whether you want to replicate the phenomenon or the appearance. You can buy "old-style" paper or parchment at an art-supply store. Nimur 13:32, 14 May 2007 (UTC)

I would think they would normally just use yellow dye, since most people want it to look old, but don't actually want it to be as fragile as such an old document would really be. StuRat 14:33, 14 May 2007 (UTC)

Atlantis

What is your opinion on the existence of Atlantis? Do you think a super continent existed in which Atlantis resided? Do you think that the Altantians had a hand in the Eqyptian Dynasty? --Juliet 13:53, 14 May 2007 (UTC)

Since this question calls for opinion, I've answered here: [19]. StuRat 14:27, 14 May 2007 (UTC)

No, Atlantis could not have had it's own continent or supercontinent. If it existed around the time that is normally said it had existed. That's not an opinion. [Mac Δαvιs] ❖ 19:05, 14 May 2007 (UTC)

Glass

Hi my chemistry teacher has given me this question "Why is glass described as a supercooled giant covalent liquid?" and I can not find any explanations or information on Google, can anyone help me out?

The glass (windoe glass) is a silicate of potassium and sodium. If it cools down and findes its way to the termodynamical best point it would form crystalls. But molten and cooled to room temperature (supercooled) the crystalisation is not possible any more. Liquide is false, because the viscosity of glas is really high, even in centuries the glass windows do not get thicker at the bottem (even if many people tell this story). So its more a soopercooled amorphous solid.--Stone 14:12, 14 May 2007 (UTC)

Read the Pitch drop experiment for insight to a similar material! Nimur 15:07, 14 May 2007 (UTC)

To augment Stone's answer, you may be interested in reading our article on glass as a liquid. — Lomn 18:12, 14 May 2007 (UTC)

Apparent Mass vs. Invariant Mass

I have been reading several Wikipedia pages involving the effects of relativity. Now, I have read that as your velocity increases, your mass increases. After some more reading, I found that this was misleading; the object's mass stays the same from it's viewpoint, but it's mass as viewed by other observers (called relativistic mass) increases. But, we know for a fact that the number of atoms inside that speeding object has not increased.

My question: how do both reference frames (the speeding object and the observer at rest viewing that object) observe/interpret this increase in apparent mass? And what are the consequences for this increase in apparent mass?

Thanks in advance. =) —The preceding unsigned comment was added by 129.115.251.49 (talk) 16:57, 14 May 2007 (UTC).

A primary consequence of the relativistic mass is the change in inertia, apparent to outside reference frames. As you know from Newtonian mechanics, F=dp/dt, that is, the force applied to an object is proportional to the time derivative of momentum, However, here momentum is not merely mass times velocity, but is magnified by gamma (1/(1+(v/c)^2)^.5) (I need to figure out the math functions on here). And so a very strong force applied to an object that is passing you at relativistic speeds will appear to deflect its trajectory much less than you would expect using Newtonian mechanics. The observer on the fast moving object sees its trajectory altered by the normal classical calculations, but his reference frame is experiencing time at a much slower rate. For this reason, the observations don't conflict, you see the trajectory altered very slightly, and he sees the same alteration at such an accelerated rate that it appears normal (classical). I hope that made sense. Someguy1221 17:40, 14 May 2007 (UTC)

If I'm reading this right, I think you're confusion comes from assuming something along the lines of mass just meaning how many atoms are inside something. Sorry if I'm reading this wrong. Atoms have mass, and different atoms have different masses. The masses that we use for atoms, in everyday physics and chemistry, are their masses when they are stationary relative to us. When an object's velocity increases relative to us, its mass also increases relative to us. This means the atoms gain mass, not that there are extra atoms. Skittle 18:03, 14 May 2007 (UTC)

Yes, I was aware that the number of atoms remains the same but the mass per atom increases; I guess what I'm asking is that, if the observer views that the moving object has gained mass, wouldn't the observer also see that that object now exerts more gravity on the matter around it? But, on the other hand, from the point of view of the moving object, how would you explain the increased in gravitational effects you experience as your velocity increases, despite the fact that your mass has not increased from your point of view?

Sorry if I'm bad at phrasing questions...but I appreciate the responses so far! =) N3rday 18:37, 14 May 2007 (UTC)

Consider testing the gravity of a moving point particle by placing a (vanishingly small) test mass adjacent to its line of travel, so close that the gravitational force is non-negligible only for the moment of closest approach. We can then, accounting for how slowly the attracting mass was moving (thus how long the "moment" was), derive its inertia by noting the velocity of the test mass after the encounter. The same attractor at different speeds will give different resulting velocities, but an observer on the attractor will claim that the velocities are all the same and we are merely measuring them with varyingly slow clocks! Dealing with kinematics in special relativity is always difficult because the very definitions of such basic quantities as velocity contain variables (that is, time and length) that depend on who measures them. I believe this improves somewhat on Someguy1221's discussion of the non-gravitational case: it's not that anyone's observations of some objective reality are accelerated but rather that there is no objective reality and anyone's observations can be explained by someone else as resulting from "measurement errors".

Also, note that, say, a magically-powerful rocket has less inertia at 0.9c than it did at rest, because it has left so much fuel behind. So to really see this effect you'd have to constantly supply new mass to the rocket, at which point it's not so mysterious that the resulting mass-energy (in either form) has more inertia. Does that help? --Tardis 20:30, 14 May 2007 (UTC)

Orchids

I bought two orchids two years ago and they had beautiful flowers on them. Eventually the flowers fell off but never came back. The plant is still alive but how do I make them flower again? --Juliet 18:17, 14 May 2007 (UTC)

That seems to be a very common experience with orchids. Unfortunately, there is no real easy answer. There are an incredible variety of orchids, and they each may need different conditions in which to reliably bloom. From my own experience, I recommend these things, which have worked fairly well for me:

-Water consistently, never letting them dry out

-Experiment with different lighting conditions - keep them in one place for a month or two to see if anything happens before trying another spot

-Use fertilizer that is specific for orchids, often called simply "orchid food"

-Transplant to a larger container if the roots seem crowded and/or tangled

Even when you put the orchid in its ideal conditions, it may take months for it to start to bloom. It will slowly grow a new stalk for the flowers. But once it gets blooms, they generally last a long time. With orchids, patience is key. Hope this helps, at least a little. --Ed (Edgar181) 18:48, 14 May 2007 (UTC)

A google search for "making orchids flower" found some causes listed here including: Not enough light, poor soil, not enough temperature fluctuation, poor water. See the referenced site for more details. The one thing not mentioned above is the need for about 7 - 10 degrees F ( 4-6 celsius) change in temperature between night and day.Good Luck! --Czmtzc 18:50, 14 May 2007 (UTC)

Juliet, could you please say what kind of orchid are you asking about? I'm afraid there's too little information in your question as it is. Some orchids need winter rest, some don't. Some orchids need bright light to flower, some don't. Some are more tolerant to "bad" water than the others. Some are more sensitive to air quality (humidity, stove gas, air motion) than others. Each orchid has its preferred temperature range. So, could you please specify what kind of orchid is it? Cheers, Dr_Dima.

The Celestine Prophesy

The Celestine Prophesy

Is the idea of Synchronicity and the Insights described in the novel The Celestine Prophesy can happen or is there just way too much anger, hate, fear in the world for this to happen? --Juliet 19:45, 14 May 2007 (UTC)

The idea of synchronicity is that an apparent "coincidence" has some deeper meaning, and is not just a coincidence. These occurrences would take place regardless of there being anger, hate, and fear. The insights of The Celestine Prophecy, however, will almost certainly never occur, because it is spiritualistic mumbo jumbo. − Twas Now ( talk • contribs • e-mail ) 21:05, 14 May 2007 (UTC)

Sleeping Face-up

Why do I find it hard to sleep facing up (also known as supine position)?

The only conscious idea I can come up with is that I feel vulnerable.

Maybe fearing someone will hit me in the face, neck, organs/stomach, and genitals?

Is there another, deeper reason why it may be hard for me?

And how common is it that people find it uncomfortable to sleep in the position? PitchBlack 20:28, 14 May 2007 (UTC)

There can be lots of reasons. It could be tied to you being born at a time when parents were recommended to lie their babies on their fronts to sleep, since that was thought to reduce the risk of cot death. Since this was later found to increase the risk, the advice was reversed, however I know many people in that age group who prefer to sleep in a more 'face-down'y kind of way, while people I know who were laid on their backs as babies tend to prefer sleeping in a more 'face-up'y sort of way. But this is OR :-) On top of this, curling up is a protective position, so if it is sleeping straight, compared to sleeping curled up, that you find hard, vulnerability could be a factor. Skittle 21:10, 14 May 2007 (UTC)

Do you have allergies? Sleeping on one's back can be very uncomfortable during allergy season because of post-nasal drip. Sorry to be gross. --Trovatore 21:25, 14 May 2007 (UTC)

Your weight and the way it's distributed in your body, the type of mattress and pillow, and whether you have trouble with your back, neck, stomach, etc., can all influence which sleeping positions are comfortable. Also if the room is not completely dark, you may want to sleep facing away from the light source. It is possible that there are medical or psychological issues, which would be beyond the scope of the reference desk. --Anonymous, May 14, 2007, 21:30 (UTC).

I've never been comfortable sleeping on my back (or front). (Is this OR? :-) ) I always curl up, on one side or the other. This is an area where different people are just different, I think. Unless you don't have any positions that are comfortable, I wouldn't worry about it a bit. —Steve Summit (talk) 23:34, 14 May 2007 (UTC)

Obstructive Sleep apnea can be more of a problem for people susceptible to it when they sleep on their backs. Edison 22:04, 14 May 2007 (UTC)

Another factor affecting direction faced while sleeping (for me at least) is that I find breathing much easier when facing the room and the window than with my mouth facing the nearby walls. I have trouble sleeping straight, since most beds are slightly shorter than I am. But that's enough OR. Algebraist 00:11, 15 May 2007 (UTC)

Extreme p[H]s

Hi everyone - I was reading the superacid and superbase articles earlier in the week, which got me thinking: what is the highest pH measured thus far (and the lowest)? I appreciate that a lot of superacids may not be able to be accurately measured on the pH scale, so a rough approximation would do :) Thanks, Martinp23 21:38, 14 May 2007 (UTC)

Negative pH exists, see also this faq. this article tells us that magic acid has a pH of –25 (now added to superacid article). DMacks 22:59, 14 May 2007 (UTC)

Need help with definition: Atherosclerosis or arteriosclerosis?

Arteriosclerosis redirects to Atherosclerosis, but the article says that atherosclerosis is a specialised form of arteriosclerosis.

I'm trying to write a 'for dummies' definition of arteriosclerosis, but the article isn't helping. It keeps jumping back and forth between artho and arterio, and my head's starting to spin. Help please? Is arterio the main disease? Are they really that different? Anchoress 22:45, 14 May 2007 (UTC)

They are generally used essentially as synonyms, though there is a subtle shade of difference. Arteriosclerosis emphasises the hardening and thickening of the arterial walls, with accompanying loss of elasticity; atherosclerosis emphasizes the atheromatous (fatty) deposits that (usually) accompany the disease. - Nunh-huh 23:26, 14 May 2007 (UTC)

Drugs that affect long-term memories

Hi my name is John and I have a hard time to answer one of the question of my homework.

- A drug can prevent long term storage of memories is ?

First of all I thaught about the kind drug like GHB or Rohypnol but I think that's more like a type of drug. Can somenone could help me out please ??

J.

Surely the textbook for your class contains the answer? --TotoBaggins 23:49, 14 May 2007 (UTC)

Hmmm. I would have thought that there's one extremely well-known drug whose ability to interfere with memory is notorious... --Robert Merkel 23:51, 14 May 2007 (UTC)

Me too, but I can't remember it since I started taking the Ambien. But more seriously, I'm not certain this is the answer, as it's most noted for short-term memory loss. - Nunh-huh 23:59, 14 May 2007 (UTC)

John, it's hard to say without knowing what you have been studying, because there are so many possible answers to the fill-in question. There are many drugs which interfere with memory formation, but it sounds like the question is asking for one which specifically interferes with short-term to long-term memory transfer (the "consolidation" phase of long-term memory formation), rather than by interfering with attention, or short-term memory formation, or memory retrieval. The benzodiazapines are one type of drug which does this, but there are others as well, so it's hard to say (unless you've just finished a chapter on benzodiazapines.....) - Nunh-huh 23:59, 14 May 2007 (UTC)

May 15

Can anyone identify this bird?

File:Dead hummingbird.jpg

Other than the obvious (a dead one), what kind of hummingbird is this?

I took this picture of a dead hummingbird today. I know it's pretty low quality; but the number of hummingbird species that don't have images on Commons is staggering and I thought if anyone could identify it maybe it'd be useful someplace. So, does anyone know what kind of hummingbird this is? The picture was taken on the street in downtown Indianapolis. The bird is under a Honey locust tree. The nearest flowers are some Pansys in a pot on the corner. ~ ONUnicorn^{(Talk|Contribs)}problem solving 00:39, 15 May 2007 (UTC)