Wikipedia:Reference desk/Archives/Science/2008 October 6

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October 6

Sleep Noises

As people fall asleep I've noticed (through my limited experience) they make some sighs/moans/grunts/little noises. Is there a cause, or reason for this?207.172.71.243 (talk) 00:14, 6 October 2008 (UTC)

According to our articles on sleep stages and myoclonus, these seem to result from normal involuntary muscle movements when entering the "N1" stage of sleep. Claiming my unsigned edit from 22:21 06Oct08. Franamax (talk) 01:49, 8 October 2008 (UTC)

See hypnagogia and hypnic jerk for related subjects, although I don't see anything specifically about making noises. --Anonymous, 22:24 UTC, October 6, 2008.

Volume of human voice

Is an increase in the volume of a human voice, be it shouting, talking louder, or full-on-screaming--mostly created through the larynx, or lungs?

I'm really just wondering about the ability for humans to raise and lower the volume of their voices, how is that controlled?207.172.71.243 (talk) 00:19, 6 October 2008 (UTC)

I do not know for sure, but I think it's controlled by the volume of air permitted to pass over the lungs... much in the same way that a whistle gets louder as you blow harder into it. ---J.S (T/C/WRE) 01:24, 6 October 2008 (UTC)

Today is a bad day for people NOT doing experiments here on the science desk! Put your hand just in front of your mouth...whisper something...did you feel any air flow? Probably not. Now yell as loud as you can...do you feel air flow now? I guess so...hence a greater volume of air is being moved when you shout. Now - how on earth could your larynx cause air to flow? Just feel what happens to your lungs when you shout - it's really obvious. The larynx controls the pitch (frequency) of the sound - not the volume. SteveBaker (talk) 13:26, 6 October 2008 (UTC)

Well, the larynx certainly enters into the picture. When you produce a soft sound at a given frequency, your vocal cords open and close at that frequency. When you shout at the same frequency, your vocal cords open and close at the very same frequency. When a greater volume of air passes, the vocal cords must open more widely, i.e. they vibrate with a greater amplitude. To achieve that requires that the laryngeal muscles be kept tighter. Amplitude corresponds to volume. The increased amplitude of the vocal cords is transmitted to the resonant cavities (chest, sinuses) resulting in the louder sound. By the way, to be precise, it isn't your lungs that cause the increased air flow, it's the diaphragm and chest muscles. --NorwegianBlue ^talk 19:05, 6 October 2008 (UTC)

That's right. Trained singers (and speakers) keep good control of their diaphragm so that they can control the amount of air (well, CO2 to be precise) they expel. That way they can sing a long phrase, in which the volume might vary from soft to loud and back again, without needing to take a breath and in the process interrupt the musical phrasing. If they try to do it by just allowing their lungs to deflate, they'll run out of breath too quickly. Far better to use a taut diaphragm to push the air out in a controlled way. -- JackofOz (talk) 23:33, 6 October 2008 (UTC)

Jack, not to be a stickler or anything, it's actually air (N, O2, CO2, etc) your exhaling... with co2 being only a minority part of it. ---J.S (T/C/WRE) 03:39, 7 October 2008 (UTC)

Thanks, J.S. I'll remember that. Also not to be a stickler, but let me repay the kindness by alerting you that it's "you're exhaling"  :) -- JackofOz (talk) 01:22, 8 October 2008 (UTC)

What Jack is referring to is commonly known as the rule, "Sing/Speak from your stomach, not your chest." Some people naturally use their diaphragm. Others use their chest. The voice produced usually sounds very different. -- kainaw™ 03:45, 7 October 2008 (UTC)

Hypnic jerk

Is there a way to decrease the strength and frequency of hypnic jerks? Plasticup ^T/C 02:22, 6 October 2008 (UTC)

Not medically speaking mind you but it seems to occur more when I'm sleep deprived so in my case I'd say to me-self "get more sleep"  ;) -hydnjo talk 03:09, 6 October 2008 (UTC)

Are they, neurologically speaking, similar to seizures? Have they ever been treated with anti-seizure medications? Plasticup ^T/C 03:37, 6 October 2008 (UTC)

Now that is seeking medical advice and therefor we'all must resist the temptation to further diagnose or offer treatment suggestions for the affliction of which you speak - seriously. -hydnjo talk 03:56, 6 October 2008 (UTC)

Oh darn, because I really was going to walk down to my local pharmacy and buy some anti-seizure meds. I just want to know where the science stands. Humor me, I promise I won't sue. Plasticup ^T/C 04:05, 6 October 2008 (UTC)

If you wanted to know where the science stands, you would search medical journals for "hypnic jerk" and "seizure". Instead, you are asking random strangers who likely have no medical experience of any kind. It shouldn't be too difficult to understand how stupid that appears. A proper question would something like, "Does anyone have any links to medical studies on hypnic jerk?" For, you see, this is a reference desk, not a "does anyone have any medical opinions based on years of watching the Simpsons and Family Guy that I can use to try and diagnose and treat an annoying problem that I think I might have" desk. -- kainaw™ 04:09, 6 October 2008 (UTC)

Don't be facetious. A link to a medical journal is exactly what I am looking for. If you cannot answer without referring to the Simpsons then don't answer. Leave it for someone else. Plasticup ^T/C 04:13, 6 October 2008 (UTC)

C'mon now Plas, no one is being a dick here, we're just trying to comply with the arduously arrived at guidelines with regard to the phrasing of your question. Of course a different phrasing would bring a different response. -hydnjo talk 04:26, 6 October 2008 (UTC)

That is more or less the definition of facetious. Why should the wording matter? If someone is aware of an article in a medical journal on this subject they will share it no matter how I word the question. Besides, where did I ask for advice? I have only asked for information. Plasticup ^T/C 04:39, 6 October 2008 (UTC)

Unfortunately, the result of being stepped upon by the "community" in these matters has left the desks with an uneasy feeling about all things that could be interpreted as "medical advice". I agree with you but past experiences have left us impotent. So, careful wording is more important than you could imagine but please try:

I'm seeking information beyond what is cited in the Hypnic jerk article. Specifically, and in neurological terms is that jerk similar to a seizure and has it ever been treated with anti-seizure medications such as gabapentin or the like? Any links besides those available when I googled "hypnic jerk"would be appreciated. Thank you (wimp-ally ), (say), - hydnjo talk 05:18, 6 October 2008 (UTC)

Yes but it falls into personal experience which I don't want to publish here. If you wish I would be glad to share my experiences via email. (say), - hydnjo talk 05:41, 6 October 2008 (UTC)

I'm glad to see that nobody's succumbed to the temptation of calling you a "hydnjic jerk" just because they disagree with you, Hydnjo.  :) -- JackofOz (talk) 23:23, 6 October 2008 (UTC)

At the risk of stepping into the discussion, here is a reference that appears to be freely available in PubMed. It appears to be a general review about sleep disorders but has a small section on "Sleep Starts (Hypnic Jerks)". There seems to be a dearth of medical research into this subject, but according to this reference there are no known treatments. Perhaps someone interested in the subject could improve the Hypnic jerk article? —Preceding unsigned comment added by Medical geneticist (talk • contribs) 13:59, 6 October 2008 (UTC)

Hypnic jerks are at one end of a spectrum leading up to periodic limb movement disorder (nocturnal myoclonus). Hypnic jerks are usually regarded as a trivial normal phenomenon. If your patient's hypnic jerks are so disruptive that he/she is considering taking medication, it is more likely to represent periodic limb movement disorder. I recommend referral to a sleep specialist (in the UK a subspecialty among pulmonologists) for a sleep study. Treatment options for PLMD are the dopamine agonists ropinirole and pramipexole. Axl ¤ [Talk] 19:23, 6 October 2008 (UTC)

multinucleate cells

What's the difference between a syncytium and a coenocyte? --Anakata (talk) 03:03, 6 October 2008 (UTC)

The articles say a syncytium is "cell-like" (but, presumably, not a cell) with multiple nucleii, while a coenocyte is a "cell" with multiple nucleii. And that's as far as I can go. ៛ Bielle (talk) 04:46, 6 October 2008 (UTC)

Maroon Clowns

Transferred from Miscellaneous desk Gwinva (talk)

Can a Gold-stripe maroon clown fish and a normal Maroon clown mate together?--Pufferfish4 (talk) 20:19, 5 October 2008 (UTC)

I couldn't find anything, but I bet the folks at http://www.fishforums.net/ would be able to help you. Alternatively, you could ask some of the contributors at Wikipedia:WikiProject Fishes. If they don't know the answer offhand I bet they would know where to look. Plasticup ^T/C 03:52, 6 October 2008 (UTC)

Languages in dreams

Has anyone ever researched languages in dreams? I was speaking with a couple of friends (both Greek Cypriots who are fluent in English), both of whom said that they dream both in English and in Greek. Any idea if such is common? I looked at dream, and I couldn't find anything even about speaking in dreams in general, let alone the language in which the speech is conducted. Nyttend (talk) 04:49, 6 October 2008 (UTC)

Well, speaking for myself, I certainly dream both in English and Finnish, absolutely. I think someone brought this up here before, but I can't seem to find that discussion now. -- Captain Disdain (talk) 07:30, 6 October 2008 (UTC)

In contrast, I'm fluent in Hindi, English and Bengali but have never had a dream in any language apart from hindi, which is my native language.Leif edling (talk) 11:37, 6 October 2008 (UTC)

I don't remember my dreams but in waking life I don't think in language much anyway except when thinking about communicating with other people. It's more about connections and movement and probabilities - gut feel but structured if you like. Dmcq (talk) 12:17, 6 October 2008 (UTC)

I used to dream in broken Spanish. It was horribly frustrating, because my limited language skills would impede the progress of my dream. Apparently this book discusses a "pidgin Malayalam used by Todas in trance states", but I couldn't find the passage. Plasticup ^T/C 15:57, 6 October 2008 (UTC)

I've always thought that the assumption that most people experience the world in generally the same way was a particularly limiting facet of contemporary psychology. How most people see the world is often confused with how everyone sees the world. --Shaggorama (talk) 05:58, 7 October 2008 (UTC)

For info, I dreamed in French for about two years and after a gap began to dream in French again until I tracked it down to an early life event. After that English only (so far). Julia Rossi (talk) 07:14, 11 October 2008 (UTC)

marine engineering

ship is using heavy oil during sailing in sea.But in port it is using diesel oil why —Preceding unsigned comment added by Rajulramachandran (talk • contribs) 07:35, 6 October 2008 (UTC)

I presume that the heavy oil is used for running the main engines - but in port they only need smaller diesel generators to produce electricity. But that's just speculation. SteveBaker (talk) 11:33, 6 October 2008 (UTC)

Ships at sea use bunker oil, pretty much the worst and dirtiest petroleum-based product there is. The lower parts of an oil refinery fractionator produce a very low quality type of oil, and in particular, the wash zone just above the inlet feed is used to remove heavy metals from the stream. This is the most worthless of crap in the petroleum (NB asphalt is even worse, but it goes out the bottom and gets put on roads, also vast effort is expended on getting anything good out by means of the vacuum fractionator). All the junk that can still flow gets sold somewhere, and that somewhere is ships at sea, where no-one can hear you scream. No right thinking harbourmaster would allow such junk to be burnt anywhere near people - so ships switch over to half-decent fuel when they come into port. Out on the ocean, they use the really cheap and nasty stuff. Franamax (talk) 22:02, 6 October 2008 (UTC)

SOUND

WILL SOUND PASS THROUG SOLIDS —Preceding unsigned comment added by 59.93.6.27 (talk) 11:49, 6 October 2008 (UTC)

Yes, see the article named sound. It normally goes very well through solids and liquids as well as the air, the only problem it has is going between different mediums - that's why soundproofing is made of mixtures of odd shaped materials and air. Dmcq (talk) 12:22, 6 October 2008 (UTC)

This being the science desk - I recommend an experiment (actually, a "thought experiment" should do here). Sit inside a car on busy road - shut all the doors and windows and turn the engine and radio off. Can you hear the other cars on the road? Yes? Then sound passed through the solid surface of the car. Sound is just a vibration. The air vibrates - your ears pick up that vibration. In the case of our experiment, vibrations in the air outside of the window caused the glass to vibrate. On the inside of the car, the vibration of the glass started the air inside the car vibrating - and that's what you could hear. If you gently touch the glass with your fingertip as a big truck goes by - you can feel the glass vibrating. SteveBaker (talk) 13:19, 6 October 2008 (UTC)

I think that is wrong. it could it ber comming from throught the air conditioning pipe from outside and not throught the solids? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:27, 6 October 2008 (UTC)

Have you ever heard a sound? If so, it's because it went right through your solid eardrum. --Sean 14:41, 6 October 2008 (UTC)

Even those not blessed with the faculty of sound can feel low tones resonating in their chest cavity. Plasticup ^T/C 15:50, 6 October 2008 (UTC)

Sound actually travels *faster* through most (all?) solid objects than air. In steel, sound travels at 5,100 m·s^-1, about 15 times faster than in air. If you yell at your friend underwater, it will get to them about 4 times faster than having a conversation above ground. -- MacAddct1984 ^{(talk • contribs)} 18:57, 6 October 2008 (UTC)

It should be possible to demonstrate this if you have access to a straight metal bar at least 100 feet (30 meters) long and preferably somewhat more (an abandoned railway track would be ideal, but please don't try it on a working railway, where you might get run over by a train!). Perhaps you can find a long, continuous metal railing somewhere in a public park or plaza. Okay, now you need a friend to assist you, or maybe you can trick an enemy into doing it, if you don't have any friends. :-)

Have your assistant bang on the bar every few seconds with something hard like a rock or a small hammer (if the bar has a decorative finish, it would be safer to stand a flat piece of metal on top of it and bang on that, to avoid damage). If you stand far enough away along the bar, you will hear the sound lagging behind the your assistant's motions. 100 feet will give a lag of about 1/10 second; at 200 feet the lag is 1/5 second and will be more obvious. Now put one ear against the bar and you should hear the tapping in that ear ahead of the other ear. That proves that the sound is traveling through the solid bar faster than the air, and therefore that the sound is traveling through the solid. --Anonymous, 22:39 UTC, October 6, 2008.

the question is backwards. the fact is, sound doesn't pass through a solid, the solid carries the sound. if there's nothing to carry the sound, well in space nobody can hear you scream. Gzuckier (talk) 06:13, 11 October 2008 (UTC)

Light from the remote visible in the video image?

when i has my video camera and my tv remote i can sees the light from the remote in the video camera but not irl, so what is the thing thats happerning here? why is this? —Preceding unsigned comment added by 194.80.240.66 (talk) 12:19, 6 October 2008 (UTC)

I moved the question from the Miscellaneous dek, as this is really a Science question. (Also retitled it.)

It's pretty simple: your eyes can only see light within a certain visual spectrum. The infrared light your remote emits is outside that spectrum, and thus it isn't visible to the naked eye. The video camera, however, detects it. (Not all cameras do this; it's a question of filtering the light properly, and cheaper or older models in particular don't necessarily do it very well.) Therefore, when you look at the video image, it looks as if there's a light shining from the remote. (And there is, you just don't normally see it.) -- Captain Disdain (talk) 13:24, 6 October 2008 (UTC)

Ah, thank you. Also i has another question = with thr remote when i use it near an readio on fm or longwave i head a buzzing noise from the radio. but only when the remote was in useing. again, how would light be affecting my radio? —Preceding unsigned comment added by 194.80.240.66 (talk) 14:25, 6 October 2008 (UTC)

While I'm not sure of exactly what frequencies would be responsible, it's worth remembering that light and radio waves are both forms of electromagnetic radiation -- they're just at different frequencies. Infrared and radio are far enough off, though, that I don't think this is necessarily what's responsible. If you use the remote next to the radio, you get interference, right? But I bet if you back 10 feet away and just point the remote at the radio (and then press buttons), nothing happens. That would suggest that it's not the IR light but rather the circuitry internal to the remote that's responsible. Circuits tend to leak EM radiation as well, and remotes aren't likely to be shielded to prevent interference at close range. Electronic circuits are also more likely to operate at frequencies near common radio bands. — Lomn 14:43, 6 October 2008 (UTC)

(ec) That's nothing to do with the IR light - it's because the remote contains a small computer. Computers do their calculations at rates that vary a lot from machine to machine. Your PC probably has a processor that runs between 1GHz and 3GHz - but the small computer inside the remote has to operate for long periods on one tiny battery and it doesn't have much work to do to figure out what IR light pulses to send when you push a particular button - so it's pretty slow...perhaps below 1MHz. At those sorts of frequency, the speed that the computer works at is close to the frequencies that your radio is designed to pick out of the air and amplify. The radio has to be sensitive enough to pick up very faint radio signals from a transmitter 20 miles away - so if the computer circuitry in your remote is leaking even a tiny amount of radio waves and you hold it close enough to the radio - then the radio will pick up the signal and you'll hear it. Back in the early days of home computers, I had a TRS-80 computer - which didn't have a sound chip inside. Some enterprising programmers figured out how to make the computer play music by running certain program sequences that could be picked up by holding a radio close to the computer chip! SteveBaker (talk) 14:46, 6 October 2008 (UTC)

certain brands of cameras can turn into effective IR cameras by removing an internal IR filter, and thus became notorious a few years ago for taking pictures of people through their clothes. still available if you lurk around the unsavory parts of the internet. Gzuckier (talk) 06:16, 11 October 2008 (UTC)

Biology word

I'm having trouble recalling a word that began with the letter "A", having something to do with organs becoming unimportant / unused over time, like the appendix, or tonsils. —Preceding unsigned comment added by 69.16.88.147 (talk) 15:18, 6 October 2008 (UTC)

It doesn't begin with "A", but I have heard the term vestigial structure used to describe those phenomenon. Plasticup ^T/C 15:24, 6 October 2008 (UTC)

(edit conflict) Such organs are called vestigial. The only word beginning with 'A' that I can think of that could be relevant is atrophy, which could be used to describe an organ shrinking down to a small remnant of what it was when it was being used, however I don't think that would be a strictly correct use of the word. --Tango (talk) 15:25, 6 October 2008 (UTC)

Adventitious? "Developing in an unusual place or from an unusual source", though that may be even further afield. -- 128.104.112.147 (talk) 23:03, 6 October 2008 (UTC)

Atrophy? — DanielLC 23:42, 6 October 2008 (UTC)

Atrophy doesn't seem quite right - that suggests a single creature losing an organ during it's lifetime. Here we're presumably talking in an evolutionary sense - like creatures who spend their entire lives in caves gradually evolve into a form that has no eyes (see: troglobite). Adaptation would perhaps be an appropriate term - but it means a lot more than just losing organs. Regressive evolution is another term that you see a lot. SteveBaker (talk) 11:28, 7 October 2008 (UTC)

Atavism? -- Ferkelparade π 15:33, 7 October 2008 (UTC)

Debunking Ghosts

They say that ghosts are not real and that most scientists say they truly don't exist and have proven so. Exactly what scientists are they referring to? I am looking to get specific branches of science that these scientists are from. --Anilmanohar (talk) 15:38, 6 October 2008 (UTC)

See Princeton Engineering Anomalies Research Lab and everyone who criticized their poorly designed experiments. That would be physicists, psychologists, chemists, economists, and statisticians. That lab, by the way, was eventually closed as an embarrassment to the good name of Princeton University. Plasticup ^T/C 15:46, 6 October 2008 (UTC)

It's not really possible to prove something like "ghosts don't exist", and no reputable scientist is likely to claim to have done so. What they can confidently say is more along the lines of "there is no evidence that ghosts exist", and then it's up to you to decide whether you believe in things for which there is no evidence. --Sean 15:58, 6 October 2008 (UTC)

I don't think anyone believes in things for which they think there's no evidence. Some people just think that there is evidence that ghosts exist, in the form of bright spots in photographs or mysteriously moving objects or what have you. So I think the operative question is, who scientifically investigates the evidence proffered by such people? I don't think the answer is CSICOP, in spite of its name. They have on occasion scientifically investigated a claim of the paranormal, but mostly they seem to report the claims and scoff at them without any substantial investigation. -- BenRG (talk) 17:02, 6 October 2008 (UTC)

It's notable that the claims of the existence of a hypothetical or doubtful entity cannot be refuted by experiments. There is only scope for affirming the existence of such entities (eg the case of the mountain gorilla). So long as there is no experiment affirming the existence of such entities (especially something as preposterous as ghosts) I think it would be safe to presume there aren't any. As far as branches of science go, parapsychology is a field of related research.Leif edling (talk) 16:56, 6 October 2008 (UTC)

In such cases where proving a negative is impossible, we have to fall back on a scientific principle called Occam's razor. This isn't a law of science - but it's a good principle to live by. It says that if all else is equal and there are multiple explanations for a phenomenon, you should pick the simplest - the one that requires least change to established science. In the case of ghosts - where there is absolutely zero solid evidence for them, we're left with two possibilities: (a) that there is an entire range of common, complex phenomena that science has somehow completely and utterly missed or (b) that some idiots are lying to us. Guess which we pick? SteveBaker (talk) 18:19, 6 October 2008 (UTC)

I choose (b), but how did the Bush administration creep into this discussion? (Hey, I gotta get my shots in while I still can.) If somebody from the Secret Service is reading this, I mean it figuratively. Clarityfiend (talk) 22:37, 6 October 2008 (UTC)

What about the coelacanth? Scientists regarded it as having been extinct for millions of years, based on the fossil record and the utter absence of any evidence - known to them - that it had survived. Then they discovered it had indeed survived, and had been regularly if infrequently caught by islanders since time immemorial. It was certainly no stranger to the people of the Comoros. It all depends on who you talk to and where you look when you're gathering your evidence. Not having looked in all possible places does not equal "it does not exist". -- JackofOz (talk) 23:18, 6 October 2008 (UTC)

There are innumerably many things that exist that we haven't discovered. As much as it is, it doesn't compare to the number of things that don't exist that we haven't discovered. Nobody claims that everything that we don't have evidence for is false. Quite the contrary, any scientist will tell you that we have no evidence for almost everything that's true. We also have no evidence for almost everything that's false. Because the number of things that we have no evidence for that are false astronomically exceeds the number that are true, it is reasonable to suppose that a given thing that we have no evidence for is false. For example: it is generally believed that the number of living species exceeds the number we have discovered by several orders of magnitude. Despite this, if you just made up a species, you could safely say it doesn't exist. By the way, the coelacanth is a bad example, as we at least knew it existed at one time. Every time we discover a new species of fish, until that point we had no reason whatsoever to believe that it existed. — DanielLC 23:41, 6 October 2008 (UTC)

Oh, I don't know. I agree with your last point, but in relation to the coelacanth, scientists confidently claimed "it no longer exists", when that was not true. They didn't just say "we know of no evidence that it has survived". -- JackofOz (talk) 00:03, 7 October 2008 (UTC)

Actually, the coelacanth is always a bad example, because its an aquatic species, and there are such vast areas of the earth;s oceans that have gone unstudied. Were scientists mildly intrigued to find one alive? Certainly, but its not like finding an extinct land-based animal alive. If someone found a live T. Rex, for example, it would be far more shocking... --Jayron32.talk.contribs 03:27, 7 October 2008 (UTC)

Mildly intrigued? That would be rather an understatement. This gets back to Steve Baker's options (a) and (b) above. They chose option (b) with the coelacanth, as they do with ghosts and other claimed phenomena - but option (a) turned out to be the one they should have chosen. It wasn't as if the evidence wasn't there for those with eyes to see it, but they based all their findings of non-existence on published research papers etc, none of which had ever looked in the numerous places where the coelacanth is now known to have thrived for millions of years after it supposedly became extinct. -- JackofOz (talk) 06:03, 7 October 2008 (UTC)

Before the discovery of a modern coelecanth, we have these two competing hypotheses:

1. The coelecanth is extinct.
2. Nobody has happened to catch one recently (or nobody who had ever caught one has ever come forward to mention it).

Using Occam's razor to choose between these two options is dubious at best. Neither of them breaks any extant scientific laws or principles or requires any rewriting of the rest of science. The existance or non-existance of this fish doesn't really change much of what we know about the remainder of the universe. Perhaps our notion of cuttlefish population densities and breeding rates off the coast of one small stretch of South African coastline may need tweaking - but that's hardly a big deal! This is a case where archeologists and marine biologists simply made an overly hasty assessment due to an understandable lack of evidence - science is not infallible and we can easily be wrong about the small details. But for ghosts to exist, huge swaths of biology, physics and chemistry would need to be rewritten - things that we've carefully measured and graphed and calculated for two hundred years or more would have to be proven wrong. The chances of that being the case (versus "a few idiots are lying to us") is close to zero. Hence the use of Occam's razor in that case is entirely appropriate. SteveBaker (talk) 11:06, 7 October 2008 (UTC)

And back to the original question; the reason scientists don't reliably believe that ghosts exist is that all paranormal experimentation lacks the one property that all true scientific proof requires: repeatability. In every case, independent verification of the results fails; it always depends on the the individual performing the experiment. That is why there is no scientific proof of ghosts; and why it is assumed they don't exist; any "proof" of their existance falls apart under controlled conditions... --Jayron32.talk.contribs 03:30, 7 October 2008 (UTC)

It's useful to understand the argument from ignorance fallacy (aka: lack of proof is not proof of lack) in any discussion of paranormal proof like this. --Shaggorama (talk) 05:48, 7 October 2008 (UTC)

"Proof" is too strong a term here. Let me state this very clearly and carefully: We do not have proof that ghosts don't exist. But proof isn't everything. What we must have (for sanity's sake) is the general principle that we don't go around believing in things just because there is no proof to the contrary. I don't believe that the Invisible pink unicorn (mhhnbs) exists - but I don't have a shred of proof for that non-belief (although the otherwise inexplicable existance of pineapple and ham pizza could certainly use some in-depth research). So, yes, User:Shaggorama is right: Absence of evidence is certainly not evidence of absence (ie it is not proof that something doesn't exist). But it is quite solid grounds for the only-slightly-weaker statement that we do not believe in something. The absence of evidence for ghosts is more than enough reason to disbelieve in them. There are quite literally an infinite number of things that we cannot prove do not exist. Does that mean that we should go around with the default hypothesis that those things do exist? Certainly not! That way lies madness. If you have to believe in a literally infinite number of improbable things until you have solid proof that they do not exist then your life becomes quite impossible to live. You can't get up in the morning for fear that an previously undiscovered species of mothball-scented purple velociraptor has been nesting in back of your sock drawer for the last 100 million years and is about to pounce...you can't prove that it hasn't, and this certainly explains all of those odd socks! SteveBaker (talk) 11:06, 7 October 2008 (UTC)

Just to clarify, I wasn't trying to say I beleive in ghosts :) --Shaggorama (talk) 20:36, 7 October 2008 (UTC)

I'm going to start checking for those mothball-scented purple velociraptors though. That provides an ideal explanation for my unmatched socks. The evidence is compelling - the only question now is whether those sock-eaters evolved or were created by God on Oct. 23, 4004 BC. Thanks Steve, for clearing that up! Franamax (talk) 02:17, 8 October 2008 (UTC)

This is why Occam's Razor shouldn't be paraphrased to "The simplest solution is usually the best". Simplest is a super subjective term. A velociraptor that instinctively steals socks seems like a pretty 'simple' solution to me. Even if it does involve needlessly multiplying entities it's a lot simpler than figuring out where the socks really go. APL (talk) 01:51, 9 October 2008 (UTC)

LCD Spectral Lines

I was curious one day so i got a pocket spectroscope and looked at my LCD monitor with it. Curiously, very defined spectral lines appeared. I can't find anything on this and i want to know why this happens. Can someone help? PS I don't know how to take a picture of these lines, sorry guys :) 31306D696E6E69636B6D (talk) 16:26, 6 October 2008 (UTC)

I think the backlight is a kind of fluorescent lamp. These can have sharp lines, depending on the design. See the article for examples. -- Coneslayer (talk) 16:48, 6 October 2008 (UTC)

The backlight is designed to produce pure colors when filtered through the LCD panel - so ideally it needs one spectral line at the center of each of the red, green and blue filters - putting out frequencies between those three colors would produce a 'muddy' display with all sorts of nasty colors and no decent, solid black. I don't know how they get it that good - but evidently, they do. SteveBaker (talk) 18:22, 6 October 2008 (UTC)

Fatigue relief

Is there any method whereby one may be relieved of fatigue and pain due to lactic acid deposition? Could ice packs be of any help?Leif edling (talk) 16:45, 6 October 2008 (UTC)

Rest would be best way to treat fatigue. If you want more of an answer than that, you'll need to ask a doctor, we can't medical advice here. (Ice could numb the area and reduce the pain, but then again it could give you frostbite or hypothermia or both, hence the need to ask someone more reliable than a random guy on the internet.) --Tango (talk) 17:00, 6 October 2008 (UTC)

Never place ice packs directly on the skin, no matter what you're trying to alleviate. Always put a towel or bandages between your skin and the ice. -- MacAddct1984 ^{(talk • contribs)} 18:44, 6 October 2008 (UTC)

We do have an article on Fatigue (medical), but it has no discussion on relief. --—— Gadget850 (Ed) ^talk - 18:54, 6 October 2008 (UTC)

Ice packs do help with pain caused by exercise, as do warm baths. Other than that, rest is your only other option without seeing a doctor. —Cyclonenim (talk · contribs · email) 23:02, 6 October 2008 (UTC)

Sounds like you're talking about post-exercise cramps. If so, check out Delayed onset muscle soreness. Being proactive with a warm-up, cool-down and stretching is believed to help alot. Also, cramping is usually the worst when beginning an exercise regimen: after a few weeks, your muscles become acclimated to the workout and your metabolism adjusts appropriately. --Shaggorama (talk) 05:42, 7 October 2008 (UTC)

Gauge>Alum foil?

The metallic scale GAUGE? 75.60.90.25 (talk) 16:58, 6 October 2008 (UTC)

The "gauge" of some aluminium foil is its thickness, is that what you wanted to know? According to Aluminium foil, it's usually between around 0.006mm and 0.2mm. --Tango (talk) 17:03, 6 October 2008 (UTC)

If you are wondering why metal thickness is measured in "gauge" units, this is a shorthand notation to make it easy for people in the metal industries to refer to their products. The development of the gauge system is rooted in the history of metalworking and lets everyone produce a series of standard products. For instance, 24-gauge mild steel is .024" thick and weighs 1 lb/sq.ft. Going by our Sheet metal gauge (redirected) article, aluminum foil thicknesses fall below the established "gauge" range - but the thickness is still referred to as the "gauge", even though it should be called "thickness". One reason might be that thicknesses are measured with a gauge instrument; another might be that the term "thickness" implies a definite number, whereas a metal "gauge" incorporates variations in thickness produced by the rolling mill, for instance 10-gauge mild steel has a "thickness" of .1345" but this can vary between .1285" and .1405".[1] Short answer: when we talk about metal thickness, we speak in terms of its "gauge". Don't know if that helps at all :) Franamax (talk) 21:45, 6 October 2008 (UTC)

finger print sensors

just like other sensors ,are there some finger print sensors that could be interfaced with some microcontrollers(like 8051).plz tell me the sources of information about it as well. 116.71.187.243 (talk) 19:25, 6 October 2008 (UTC)

Most seem to offer a Serial Peripheral Interface Bus interface, which can be spoken to as described here. Search for fingerprint sensor to see a bunch of them. --Sean 20:26, 6 October 2008 (UTC)

Zombie Newton is haunting me

I'm trying to understand how any why momentum, kinetic energy and mechanical work ... well, work in classical mechanics. I took a few courses of physics and mechanics years ago, but they all skirted the deep questions about exactly why they take the forms they do. Why should work be the dot product of displacement and force? Why is the first integral of mass relative to velicity momentum, and then why is the second integral kinetic energy? Is that something to do with the conservation of {energy, momentum, mass}, but why velocity?

I know these are rather open questions, but my curiosity keeps nagging away at me, and I don't seem to be able to find the answers without taking a physics degree myself. 79.72.138.94 (talk) 19:30, 6 October 2008 (UTC)

Also, I realise full well that the answer might be 'because it is, and that's just how it works', which would leave me feeling rather unfulfilled but sated. 79.72.138.94 (talk) 19:31, 6 October 2008 (UTC)

Actually, the answer is the exact opposite of what you expect. It is because that's the way we as people have organized our thinking. There's nothing fundemental about the concepts of "force" or "work" or "velocity". They are just convenient ways for us to organize our observations of motion. When we push something harder, it moves faster, so the concept of "force" was invented to explain this observation. When an effort is used to move something, that effort can no longer be used to move something else; thus the concept of energy is created. If you want to get beyond classical mechanics, physicists have been working on explaining it all, indeed a few different times but there are some fundemental flaws in all of these. Some show promise, others have run into dead ends. Maybe someone else wants to take a crack at this, but that's the best explanation I can come up with... --Jayron32.talk.contribs 19:41, 6 October 2008 (UTC)

Good point. I probably should have included that disclaimer as well, that it might just be an artifact of the analysis. I can accept the definition of force, velocity or acceleration as arbitrary artifacts, but energy and momentum seem to be more fundamental, because of the laws of conservation. Even if this is just the way they are organised, I still can't see the reaoning behind the patterns that form, so there is still something I'm missing. And GUTs and TOEs are altogether to visceral for me :) 79.72.138.94 (talk) 19:54, 6 October 2008 (UTC)

Noether's theorem (warning: article is extremely equation-heavy) basically boils down to "where you have symmetries, you have conserved quantities". As such, once you've defined positions, velocities and forces, under Newtonian mechanics you find that there are symmetries (e.g. time reversibility of a system) that are then associated with conserved quantities that happen to correspond to energy and momentum. Confusing Manifestation(Say hi!) 22:36, 6 October 2008 (UTC)

I have "answers" in some sense for you, as I've thought about these points myself.

1. Your question about work can be answered in two ways. You can identify force with the negative gradient of potential energy, which makes intuitive sense because we expect things on hills to be gravitationally accelerated down them and more quickly for steeper hills; then, using the chain rule, $dU=\sum _{i}dx_{i}{\frac {\partial U}{\partial x_{i}}}=d{\vec {x}}\cdot {\vec {\nabla }}U=-d{\vec {x}}\cdot {\vec {F}}$, and then (by conservation of energy) $U+E=C\Rightarrow dU+dE=0\Rightarrow dE=d{\vec {x}}\cdot {\vec {F}}$. (Note that nonconservative forces are a simplification of conservative ones; we need not treat them separately.) Alternatively, take the derivative of kinetic energy with respect to time: ${\frac {dE}{dt}}=m{\vec {v}}\cdot {\frac {d{\vec {v}}}{dt}}=m{\vec {a}}\cdot {\frac {d{\vec {x}}}{dt}}={\vec {F}}\cdot {\frac {d{\vec {x}}}{dt}}$ and $dE={\vec {F}}\cdot d{\vec {x}}$ immediately: in other words, when you apply a force in the opposite direction of displacement, you're slowing the object down, and when you apply it in the same direction, you're speeding it up, so the dot product is natural.
2. Momentum must be linear in velocity for the simple reason that otherwise small internal motions (like those due to heat) would affect the collective answer. But if heating (or cooling) an object reduces its momentum, what happens to a stationary object? Momentum must also be linear in mass so that inconsequential gossamer connections between objects sharing a velocity do not change their dynamics.
3. Energy's quadratic nature is the interesting part, and derives from the fact that it and momentum are conserved are a scalar and a vector respectively. Thus a change of frame of reference changes velocity but not energy (in Galilean relativity). (The reason for this is that any such changes must be linear functions of observer velocity, so that we can compose frame shifts without changing the answer. For changes in (measured) velocity, the identity function serves the purpose well, but the only isotropic scalar function is the zero function.) Now consider two observers who place a compressed (massless) spring between a pair of identical objects. Then one of the observers starts moving along the direction of the spring, and it fires. Choosing convenient numbers ($m=1,|v|=1$) and coordinates, the stationary observer records velocities of $({\vec {0}},{\vec {0}})$ and $(-{\hat {x}},{\hat {x}})$, for a total momentum before and after of $({\vec {0}},{\vec {0}})$ and a total energy before and after of $(0,2E(1))$. (I'm writing $E(v)$ for the "unknown" function that gives the energy per mass associated with speed v; we know it's linear in mass by the same argument as for momentum, and we know it's just speed because it has to be independent of direction.) The moving observer instead records $({\hat {x}},{\hat {x}})$ before and $({\vec {0}},2{\hat {x}})$ after, for a total momentum of $(2{\hat {x}},2{\hat {x}})$ before and after. This is good; our linear transform of velocity has preserved the conservation. But what of energy? In the moving frame, the construct already had $2E(1)$ kinetic energy, and the spring must still have added its own $2E(1)$; the one moving object must have kinetic energy $E(2)=2E(1)+2E(1)=4E(1)$; evidently it is quadratic. (The ½ is arbitrary; we could just as easily define ${\vec {F}}=-2{\vec {\nabla }}U$, for instance.)
4. Other arguments about energy include that it should be a smooth function of velocity (since observers with slightly different velocities should see much the same thing), and yet it must be a function only of speed. This rules out $E({\vec {v}})\propto |{\vec {v}}|$, because the magnitude of a vector is only continuous and not smooth at 0. (Consider the plot of $f(x,y)={\sqrt {x^{2}+y^{2}}}$; it's a cone and is sharp at the origin.) $E({\vec {v}})\propto v^{2}$ is the obvious choice. Finally, consider throwing an object into a potential energy barrier (like gravity): if the force is uniform, the object will slow down uniformly. Then throw it twice as fast: it takes it twice as long to stop, and was making twice as much progress per time all the while, so it made it four times as far into the barrier. The force being uniform means that, were we to push the object in rather than throwing it, we would certainly expect the effort involved to be linear in the distance, so kinetic energy is again quadratic in speed since it only took twice as much speed to effect four times as much progress.

There's a certain mathematical circularity that's inevitable here, and even appeals to intuition are subject to the objection that they are merely descriptions of our intuition's basis in physics rather than explanations of physics based in intuition. But I find it helpful to understand better the connection between the mathematics and my intuition even if neither has any external justification. Hope this helps. --Tardis (talk) 17:34, 7 October 2008 (UTC)

False or true?

The keratitis that can occur in a contact lens wearer caused by Pseudomonas aeruginosa is an ocular emergency, as if left untreated it could destroy an eye within 24 hours(four tildes). —Preceding unsigned comment added by 79.97.241.246 (talk) 20:03, 6 October 2008 (UTC)

We're not allowed to give medical advice here. The article on keratitis says that it can scar the eye and permanently damage vision. (Or worse : "loss of the eye"! ) If this question is more than hypothetical I strongly recommend that you get to a doctor or E.R. right away. Don't trust your eyesight to strangers on the internet. APL (talk) 20:13, 6 October 2008 (UTC)

I can't tell you how disturbed I am when a single question falls foul of both "we can't give medical advice" and "we won't do your homework for you". --Sean 20:30, 6 October 2008 (UTC)

At least we didn't have to explain how to sue the contact lens manufacturer! SteveBaker (talk) 22:39, 6 October 2008 (UTC)

Just using the information you gave in your question, "is an ocular emergency as if left untreated it could destroy an eye within 24 hours". If that's true, you're damn right it's an emergency. —Cyclonenim (talk · contribs · email) 23:07, 6 October 2008 (UTC)

We have an article on keratitis, which mentions "pseudomonas aeruginosa", "contact lens" and "loss of the eye". It also says that "[o]ne should consult a qualified Ophthalmologist or Optometrist for treatment of an eye condition". Take from that what you will. Plasticup ^T/C 02:04, 7 October 2008 (UTC)

BTW, your supposed to type out four tildes like this ~~~~ not type out the words four tildes. The tilde key would usyally be besides the 1 key on your keyboard. You probably have to hold down shift to get the tilde Nil Einne (talk) 15:34, 7 October 2008 (UTC)

Ha, I'm tempted to create a sockpuppet named User:Four Tildes! (But I won't.) —Tamfang (talk) 15:38, 8 October 2008 (UTC)

Thank you 79.97 for taking trouble to read the intro box at top of page even if it might be clearer in reverse viz "four tildes (~~~~)". ;) Julia Rossi (talk) 07:33, 11 October 2008 (UTC)

Electricity and magnetism

Is it possible to relate the positive and negative charges of protons and electrons and such to the north and south poles of a magnet? For example, does the north pole of a magnet act in a way that implies that it is positively (or possibly negatively) charged? Or are the similarities between electricity and magnetism, such as like repels like and opposites attract, explained in fundamentally different ways? Thank you. 86.74.122.84 (talk) 21:47, 6 October 2008 (UTC)

Magnetism is caused by a changing electric field, such as a moving charge. As such, two particles of opposite charge moving in the same direction will have opposite magnetic fields, so in that sense there is some similarity between north and south poles and positive and negative charges, but it's a little more complicated than that. Confusing Manifestation(Say hi!) 22:30, 6 October 2008 (UTC)

Umm, magnetism is an inherent property of matter, a changing electric field is not required. Variations in the electric field can induce a magnetic field perpendicular to the direction of charge motion, but you don't need current to have a magnet. Or at least, the electric field doesn't have to be changing. See magnetism. Franamax (talk) 00:40, 7 October 2008 (UTC)

Indeed, nuclei of atoms (which are for all intents and purposes "motionless") can display magnetic properties. Generally, the nucleons (protons and/or neutrons) will "match" magnetic poles so as to cancel out, but in nuclei with odd numbers of them (such as C-13) there is a net magnetic moment. Nuclear magnetic resonance and Magnetic resonance imaging use this property of the atomic nuclei. --Jayron32.talk.contribs 03:13, 7 October 2008 (UTC)

You may be interested in the "Gilbert Model" of magnetic behavior; just remember that it's not really physically accurate. --Tardis (talk) 15:43, 7 October 2008 (UTC)

The answer is that north and south "charges" behave like electric charges of ±i. Neither one is closer than the other to positive or negative charge. If you define F = E + iB, then Maxwell's equations

$\nabla \cdot E=\rho$

$\nabla \cdot B=0$

$\nabla \times E=-{\frac {\partial B}{\partial t}}$

$\nabla \times B={\frac {\partial E}{\partial t}}+J$

can be written

$\nabla \cdot F=\rho$

$\nabla \times F=i\left({\frac {\partial F}{\partial t}}+J\right)$

and in that form you can introduce magnetic charges by simply making ρ and J complex instead of real. You could also treat magnetic charge as real and electric charge as imaginary, or each as a mixture of the two (provided they're at right angles to each other). There's nothing special about the electric "direction" in the plane of possible charges except that, for unknown reasons, all known particles have purely electric charge. -- BenRG (talk) 10:00, 12 October 2008 (UTC)

Is THIS version understandable?

Still confusing, but a lot better IMRHO.

Sail Car Preliminary Description Our sail car is a trapezoid with two parallel sides, front and back. One side, the back, is longer than the other (hence a trapezoid), requiring two straws linked together (for the purposes of this description, they will be referred to as one straw). Two hypotenuses lie on the side of the trapezoid. They extend from the back to the front, where they bend and then meet to form the front side. They bend out on the back, creating two extensions outside of the trapezoid. These extensions are two straws deep with the back side straw in the rear and the hypotenuse straws immediately in front. On these extensions are two wheels. They are supported by two pins on each side of each wheel. On the front, there are two wheels as well. They lie near the bends of the front side.

At the midpoint of the back side, two straws extend diagonally frontwards towards the bends of the hypotenuse straws to give the frame extra support. Roughly halfway between the hypotenuse straws and the midpoint of the back side are two straws extending vertically upwards. Between the two straws is a sail. The sails is pinned to the straws for support. The sail is bent inwards and is thus also supported by a crossbeam at the top.

--hello, i'm a member | talk to me! 23:38, 6 October 2008 (UTC)

Member, a simple diagram would really help you out in this. Maybe the better strategy would be (assuming you want to create a new article) for you to start a page in your own user-space, let's say by clicking here: User:Member/Sailcar. You could put some external references in there for us to click on, so we could better understand what you are describing. You (or us others) could then have a shot at creating graphics to better describe your concept. Franamax (talk) 00:29, 7 October 2008 (UTC)

And as you can maybe see from Edison's comments below, put your text into the wiki-space and we will all slice-and-dice it into an encyclopedia article. The safest place is your own user-space per the redlink I gave above. Give us a link to an image or site that describes your concept, we can work with you to make it all work. Honest! Franamax (talk) 01:38, 7 October 2008 (UTC)

I will count the title as a sentence. In sentence 3, why not call the rear "straw" the rear axle? Your use of "hypotenuse" in the paragraph is inconsistent with Trapezoid and with Hypotenuse. Call them the "nonparallel sides of the trapezoid." In sentence 5 you refer to the "front" where the straws bend, and to a different "front side" which is formed by the meeting of the side straws. Eliminate the ambiguity. Sentence 6: Replace "They" with a more explicit description of the members you refer to. How about eliminating pronouns in such a terse yet confusing description? No idea what sentence 6 refers to. Sentence 7 is obscure and confusing. Sentence 8:Which extensions? Sentence 9: What does "They" refer to? Sentence 11: What is the "back line?" The "rear straw," which should probably be called the "rear axle?" Sentence 14 and 15: No idea of the shape or orientation of the sail. Edison (talk) 01:21, 7 October 2008 (UTC)

A diagram - or a photo - is needed here. There are some things that just don't work when put into words. It's possible we could come up with some better words - but because the words you have aren't working, we need the diagram/photo in order to understand what we're writing about! SteveBaker (talk) 10:16, 7 October 2008 (UTC)

I'm still stuck right at the start. A trapezoid is a 2D shape. Is your car a trapezoid cut out of cardboard and held vertical? Or is it a 3D solid shape, like a prism of a trapezoid? You need to make that clear before you start talking of front and back. Itsmejudith (talk) 11:07, 7 October 2008 (UTC)

There are lots of patented mechanical devices far more complex than this thing which have clear and unambiguous descriptions in the patent specifications. Instead of "two straws which will be called one straw" call it a freakin' "rear axle," for instance. From the description, it could be a structure made only of straws, or it could have a trapezoidal planar body made of some unspecified substance. It does not say what the vertical straws are attached to. Edison (talk) 18:18, 7 October 2008 (UTC)

Here is a (eui) sketch of what I see this thing as. Heaviest lines are the wheels, lightest are the pins, in the middle are the stiffeners and sail assembly. All are in the same plane except the cirlces and curved line representing the vertical sail. Franamax (talk) 02:44, 8 October 2008 (UTC)

And here is the elevation view. The U-shaped sail-straw is pinned through the two stiffener straws near the midpoint of the vehicle. Franamax (talk) 02:57, 8 October 2008 (UTC)

Momentum and photons

Gah such a simple question I've forgotten the answer to. How the hell do photons have momentum when they have no mass? Is it due to rest mass? Cheers! —Cyclonenim (talk · contribs · email) 23:05, 6 October 2008 (UTC)

They have no rest mass, but due to E=mc² they have mass which gives them momentum (m=E/c² so p=mv=E/c - there is a lot of hand waving required for that derivation, but it gets the right answer!). --Tango (talk) 23:15, 6 October 2008 (UTC)

Likewise, Electrons are dimensionless (they have no volume), yet they have a "spin". Try to figure that out using classical mechanics... --Jayron32.talk.contribs 03:07, 7 October 2008 (UTC)

How do you know that an electron has no volume? Ohanian (talk) 06:22, 7 October 2008 (UTC)

See Electron#Fundamental properties. Axl ¤ [Talk] 08:29, 7 October 2008 (UTC)

...which is not very helpful, because it says "for convenience, <the electron> is usually defined or assumed to be a point charge with no spatial extent; a point particle", and a point particle is "an idealized object". We know that the "point particle" model cannot be the whole story, because then the electron would be a singularity. In quantum field theory fundamental "particles" like the electron are not really particles at all - they are excitations of a quantum field, and they don't have a volume because the "volume" concept just doesn't apply to such things - any more than the colour red or the number seven has a volume. Fundamental particles might have some multi-dimensional equivalent of "spatial extent" in string theory, but I am not sure whether that could be made to correspond in any reasonable way to our macroscopic concept of "volume". So in simple terms, we might say that we don't think that an electron has a property that we could interpret as a volume - which is not the same as saying it has zero volume. Gandalf61 (talk) 09:30, 7 October 2008 (UTC)

Gandalf, your response is one interpretation. Axl ¤ [Talk] 10:31, 7 October 2008 (UTC)

If I understood (and/or remember) my Feynman, he described the paradox of infinite charge given zero volume for the electron vs. the impossibility of making accurate calculations without assuming zero volume. As I recall, he advised the whole matter was best swept under the desk. Franamax (talk) 03:06, 8 October 2008 (UTC)

It would be worse than that - being of zero volume but having a non-zero mass - the electron would exert enough gravity to form a micro-black hole with it's very own teeny-tiny event horizon. SteveBaker (talk) 02:28, 9 October 2008 (UTC)

They just do. We cannot demand that the universe conforms to our everyday notions, which require an object to have a non-zero rest mass in order to have momentum. Note also that photons are never at rest in any inertial frame.Martin Hogbin (talk) 09:44, 8 October 2008 (UTC)

Even if an electron does have volume, it doesn't have any component parts (i.e. it's not made of two smaller "half-electrons" or something), which still means that it's counterintuitive for one to have angular momentum; since _normally_ we think of angular momentum as being from the movement of something's component parts relative to one another. --Random832 (contribs) 13:44, 10 October 2008 (UTC)

Mars and Jupiter and Saturn's moon over sun's RGiant Stage

If Mars still exist, does anybody know what Mars surface will be like over sun's R Giant? Will it be yellow-orange molten lava like Earth was 4.6 billion years ago? What about Europa-Jupiter's moon. Europa's tan-gray ice will melt into water, then what will ahppen next. Will it scorch like Mercury. Titan's orange smog might bluen out. By 6 to 7 years from now, it is learnt Titan is the only place going to habitat for life. I wonder what will happen to Uranus' moon when sun enters a R Giant.--SCFReeways 23:44, 6 October 2008 (UTC)

• Will somebody be able to answer it?--SCFReeways 01:04, 7 October 2008 (UTC)

• Come on, do anybody know this?--SCFReeways 01:43, 7 October 2008 (UTC)

Have some patience, we don't know this off the top of our heads. Plasticup ^T/C 02:07, 7 October 2008 (UTC)

And we live in a variety of time zones... (yawwn) --140.247.11.55 (talk) 02:29, 7 October 2008 (UTC)

And it says at the top of this page that we may need as much as four days to fully develop an answer. Anything that might be needed in less than four days is probably homework - which we don't do. The sun isn't going to do this for another 7 billion years - so this is hardly a time-critical answer. SteveBaker (talk) 09:58, 7 October 2008 (UTC)

It's tough to be patient though.--SCFReeways 02:48, 7 October 2008 (UTC)

The primary difficulty in answering your question is your poor grammar. Your first question appears to be "Does anybody know what will happen to Mars when the Sun turns into a red giant? It is not known. Mars may become superheated. It may escape the Sun since it will enlarge its orbit. So, no, nobody knows. Your next "questions" have leading assumptions that do not appear to be based on popular scientific evidence. Why do you assume Europa's surface will melt? Why do you believe that Titan will be the only habitat for life in 6 or 7 years? Uranus is very far from the Sun, why do you assume it will be heavily affected? Is this all based on an assumption that, as a red giant, the Sun will suddenly start producing so much heat that it burns up the Solar System? You must take into account how little heat reaches the outer planets right now and that they will move further from the sun when it loses mass. -- kainaw™ 03:34, 7 October 2008 (UTC)

They will move further out. Alot of sources said Titan might be habitatable at this time. I wonder about Uranus moon. Whole solar ssytem will heat up at this time. Mercury and possibly Venus and Earth will be engulf and destroy, then Mars will be the only inenr planets left. About Europa, after ice melt, even escaption Europa can be a little too hot. Uranus moon could get beenfit from sun's heating too.--SCFReeways 03:52, 7 October 2008 (UTC)

What about this?--SCFReeways 04:35, 7 October 2008 (UTC)

My understanding is that Titan may heat up to habitable temperature but it will lose its atmosphere so won't be habitable. The reason it can maintain such a dense atmosphere with its low mass is because it is very cold (cold gasses don't move around as much so are less likely to randomly achieve escape velocity). Once it warms up, the atmosphere will leak away into space pretty quickly. (That's just the theory I've heard, there are so many variables we can't pin down that it's difficult to say for sure.) --Tango (talk) 14:39, 7 October 2008 (UTC)

When you say "6 to 7 years" do you mean "6 to 7 billion years"? Plasticup ^T/C 15:19, 7 October 2008 (UTC)

I would guess so. It's still wrong, though, since by then the Sun will have gone past being a red giant and will be a white dwarf giving off very little heat. The red giant phase only lasts for a few million years, if that. --Tango (talk) 16:09, 7 October 2008 (UTC)

• This site said the tan-gray ice on Europa might melt into water, and possibly be warm enough.--SCFReeways 22:08, 7 October 2008 (UTC)

• THis site shows in 7 billion years, Europa's thick ice can melt into globe of liquid ocean, but artist say it's sky will still be black in 6 to 7 Gyrs when sun turns into giant star.--SCFReeways 22:15, 7 October 2008 (UTC)

  I question the reliability of those sites. For a start, it's 5 billion years, not 7. Secondly, Europa doesn't have the atmospheric pressure required for an ocean - the water would just boil away. --Tango (talk) 23:44, 7 October 2008 (UTC)

• you menat the ice will just boil away right? One source said only surface temperatu will be habitable. In about 1 to 2 billion year-time Mars can get bluer, possibly as the planet warm up the greenhouse effect will start to incrase, but after few billion year later, Mars could just black out right airless.--SCFReeways 00:17, 8 October 2008 (UTC)

  I'm afraid I don't understand. Mars is essentially airless now (from the point of view of liquids boiling and habitability) and I don't think it will get more air as it warms up. Likely less, in fact, since warm air escapes into space faster. --Tango (talk) 00:23, 8 October 2008 (UTC)

Mars has no magnetic field to speak of, so holding in an atmosphere is very difficult. Gasses need to increase in the atmosphere faster than they are lost into space. There is a theory that if it warms up enough a magnetic field will build up. Of course, this is all just theory. Give me any theory and it is trivial to find someone who disagrees. -- kainaw™ 00:22, 8 October 2008 (UTC)

I theorise that when I hold a pen about a metre off the ground away from any other objects and let go, it will fall. --Tango (talk) 00:25, 8 October 2008 (UTC)

I theorise that someone will come along and explain the difference between a validation experiment and a theory :) -- kainaw™ 00:27, 8 October 2008 (UTC)

It was a very restricted theory, but a theory nonetheless (ok, perhaps it was a law and I should have added some explanation to make it a theory). --Tango (talk) 14:16, 8 October 2008 (UTC)

This said Mars was once a blue planet, it just got too cold. In fact right now Mars is very cold. in about 1 to 2 Gyrs Mars might attain to the Earth surface temp today.--SCFReeways 00:39, 8 October 2008 (UTC)

At this time, Earth may be a greenhouse planet like Venus today.--SCFReeways 00:40, 8 October 2008 (UTC)

I think you are missing the point. It might turn blue again. It might not. It might get destroyed by a Vogon fleet to make way for an interstellar bypass. Whatever answer you want to get, there's a reference for it. That is why I stated that it is all theories. It is even possible that the sun may not turn into a red giant (though unlikely). -- kainaw™ 00:46, 8 October 2008 (UTC)

While it will probably heat up again that doesn't mean it will become Earth-like. It's already lost its atmosphere and warming up isn't going to bring it back. Without an atmosphere (and a significant one, not the few wisps of CO2 Mars has) you can't have liquids on the surface. Mars lost its atmosphere over millions, possibly billions of years due to its low mass and lack of an magnetic field (which allows solar wind to erode the atmosphere). --Tango (talk) 14:16, 8 October 2008 (UTC)

• Tango, let me backtrack a little bit. Europa is now white and smooth, and it's surface is like a crack eggshell. The problem with Europa is the planet is too small for an atmosphere, the sky is obviously black. I wonder if Europa ever had an atmospher later. Tango is right without an atmosphere we can't have a liquid atmosphere on the planet. So you menat when Europa heats up, it will just become a desert like Moon? Titan is known for it's orange-yellow color and it's sky is light orange. Titan's atmosph is 1.5 times thicker than Earth's. Tango, what you mean by when sun heats up it will drain it's atmosph?--SCFReeways 22:45, 8 October 2008 (UTC)