Wikipedia:Reference desk/Archives/Science/2007 June 1

From Wikipedia, the free encyclopedia

< Wikipedia:Reference desk | Archives | Science

Science desk
< May 31	<< May \| June \| Jul >>	June 2 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

1 June 1

[edit] June 1

[edit] Why do we need a continuous supply of air?

This is probably a stupid question because the answer is probably "it just is that way", but still. According to cellular respiration (of which I admittedly understand little, not being a student of biology), the reason that cells die when deprived of oxygen is because waste products build up through processes that would normally produce energy.

Aerobic organism mentions that there are facultative aerobes, which do not require oxygen because they have alternate methods of generating energy, while obligate aerobes cannot live without oxygen. Why do obligate aerobes exist at all? That is, why do obligate aerobes use such an "always on" model that fatally breaks down if no oxygen is present? Why can't cells simply "shut down gracefully" and become inert in such a way that they can continue their work when the oxygen supply is restored? On a macroscopic scale, this would of course become complicated because the organism as a whole has to shut down gracefully, but you get my drift. Not needing air continuously seems to be a significant advantage, so I'm guessing there are deep-seated design issues for obligate aerobes that prevent this from being possible -- but which?

Also, if facultative aerobes can forego on oxygen because they have alternative means for generating energy, does this mean they have essentially the same problem with regards to those methods? That is, do all living things require a constant supply of energy to continue existing or is some life suspendable? 82.95.254.249 00:01, 1 June 2007 (UTC)

This is a timely question! In just the last several weeks, there was an article in one of the journals (New Scientist, maybe?) that was suggesting we could go a long time without oxygen if only we could be re-introduced to respiration without causing massive cell apoptosis. The suggestion was that cells don't need a continuous source of oxygen and could exist for a long time in a stable, non-respiring state, but that rapidly reintroducing them to oxygen causes them all to get confused and deliberately trigger cell death.

Atlant 00:06, 1 June 2007 (UTC)

I read aobut something like this in PopSci. And yep, they were experimenting with something like chilling the body to extremely low tempretures to slowly reintroduce oxygen or something like that. -- Phoeba Wright^OBJECTION! 00:15, 1 June 2007 (UTC)

Very good question, actually. Obligate anaerobes exist simply because they lost the ability over the course of evolution to operate without oxygen. Cellular respiration, as opposed to anoxic fermentation, is far more efficient a method of producing energy than anaerobic methods. As to why they lost the ability to operate without oxygen, assume for a moment there is a species that can do both. Let's also assume there is another such species, or one that is completely anaerobic. If either of these others can outcompete the first facultative species for resources, but only in anaerobic environments, there is no reason for the first species to retain the ability to use anaerobic respiration. Now, evolution doesn't always get rid of things that aren't useful anymore, just look at vestigial organs. However, as an example of how it might happen, say that some of the members of this species get hit by genetic mutations that stop the anaerobic processes from occuring at all. It won't affect their survival, as none of them can outcompete the other anaerobic species anyway, but a nice population bottleneck might seperate the ones that are still facultative from those that aren't (pure speculation on my part, I don't know if this ever actually happened). Now, as far as "turning off" for a while, some bacteria do do this, although I don't know of any doing this from lack of oxygen. Look at endospores for more. Someguy1221 00:17, 1 June 2007 (UTC)

[edit] How to muffle the sound of dripping water

Hey Wikipedia! I have water dripping just outside a window (from an air conditioning unit a few floors up) making constant noise with water drops hitting the ground (soil about 50% covered with low vegetation). Before taking on the source of the water, are there any simple ideas for reducing the noise when the water drop lands? Peter Grey 00:14, 1 June 2007 (UTC)

Towel? -- Phoeba Wright^OBJECTION! 00:16, 1 June 2007 (UTC)

Instead of letting it hit a horizontal surface, let it hit a nearly vertical surface.

I think it makes noise when it falls on a leaf. May be you can clear a patch of vegetation around where the drop falls and put sand ? -- WikiCheng | Talk 05:22, 1 June 2007 (UTC)

If you have access to the air conditioner, tie a long string to the source of the drip, and let the water run down the string. Maybe tie down the lower end to keep it from blowing around. Bunthorne 05:23, 1 June 2007 (UTC)

Place a piece of open-cell plastic foam (for example, air filter foam) at the landing site. Other similar materials may help: perhaps a pot full of sand? The key thing is to distribute each droplet's kinetic energy without producing a single distinct acoustic wave from the impact of the droplet.

Atlant 12:40, 1 June 2007 (UTC)

Which is why I recommended a Towel -- Phoeba Wright^OBJECTION! 18:19, 1 June 2007 (UTC)

Yes, but a perpetually wet towel will degrade (e.g., mildew) pretty quickly.

Atlant 22:19, 1 June 2007 (UTC)

Combining three of the above ideas: place a towel on a nearly vertical surface with open-cell plastic foam under the towel. Velour will be better than terry cloth. Combining thee ideas in a different way: roll sand into a towel and tie it up with the string to make a weighted bludgeon. Use the bludgeon on the air conditioner or its owner. -Arch dude 21:35, 1 June 2007 (UTC)

I like the idea of the long string - the droplet will probably either soak into the string - and then eventually evaporate without ever making a sound - or it'll elongate as it dribbles down and the energy will be so diffused that it won't make much sound when it gradually arrives at the soil at the bottom. SteveBaker 22:48, 1 June 2007 (UTC)

A chain is also an old-fashioned standard solution. Let a chain with rather large links hang down from the place where the drops fall from. They will instead trickle along the link, making no noise. Simon A. 07:20, 2 June 2007 (UTC)

[edit] Please Help

in the reaction 2NO2 <--> N204

the forward reaction causes a lowering of color when the temperature is reduced.

My question is: Will the delta H (a triangle with a H) be positive or negative if the temperature is reduced?

[edit] Ignition Coil (Update)

I previously posted this question and received the following response:

[edit] Transistor breakage

I skimmed through the transistor article but could find no answer to my question. Suppose you have a typical NPN transitor. You have 15 MV running from the collector to the emmiter but zero volts from the base to the emmiter. The transitstor would be in cutoff mode but would there be an arc or would the transistor break due to the extreme voltage. Ozone 04:18, 22 May 2007 (UTC)

15 million volts? Most likely the transistor would have gone right past Zener breakdown (tunneling) and avalanche breakdown (impact ionization) and be well into toasty dielectric breakdown. 15 MV across a typical transistor implies absolutely huge electric fields which cannot be sustained by most (if any?) materials without breaking down, and the transistor would surely fry. I'm not sure what you mean by 'arc' since arcing is usually associated with dielectric breakdown in a gas. -- mattb 05:39, 22 May 2007 (UTC)

At 15 million volts, the transistor would not be the only thing breaking. This is well above the dielectric breakdown threshold of air (assuming a standard sized 3-pin transistor package); so unless the transistor is very unusual, this voltage will be wreaking havoc, arcing between pins, leads, circuit traces, and anything else. Nimur 05:58, 22 May 2007 (UTC)

Thank you, Mattb and Nimur. Mattb, I meant arc as in if the transistor didn't fry would there be a arc from the collector to emmiter leads. I'll take a screenshot of the circuit I'm thinking of and post it here soon. Ozone 06:25, 22 May 2007 (UTC)

Ahh, here it is, Circuit. Please ignore colors. My idea was to create a circuit which every few seconds arced (arc in the past tense I assume) between those two leads at the bottom. Would this lower the voltage strain on the transistor or would it be better If I use a relay instead? Or would the relay itself arc or break? Ozone 06:39, 22 May 2007 (UTC)

I have no idea what you're trying to do here, but there's not really an open circuit between the collector and emmitter, meaning there will still be current through it, albeit small. Although, with 15 megavolts, or 15 million volts, that current would still be huge and will easily fry any NPN transistor. Did you maybe mean millivolts? --Wirbelwindヴィルヴェルヴィント (talk) 07:42, 22 May 2007 (UTC)

Here's my idea, the current runs through the inductor for a couple of seconds then it forced to stop by a transistor, this fast change creates a huge emf, it either arcs between those two points or fries the inductor. I do mean MV, that particular number might just be BS from my simulator though.

No BS, that transistor would be toast. It sounds like you need an Autotransformer to step up the voltage, just like Electronic Ignition systems do. In fact, you could use a surplus Ignition coil to experiment with before you try to wind that 7 henry monster. (_Donovan|Geocachernemesis|^Interact) 09:51, 22 May 2007 (UTC)

Power electronics devices such as thyristors can switch several thousand volts. Ratings such as 150kvDC are obtained by stacking the devices. See [1] for a description of some uses. A history of the devices is given at [2]. See also Power electronics. There is a free online course in the topic at [3]. Edison 17:32, 22 May 2007 (UTC)

Judging by the users name, he is probably trying to make an ozone generator. Heres how I would go about it; get hold of a car ignition coil, drive the low voltage winding with the transistor (make sure to use protection diode connected to +12v). Then attach your spark gap across the secondary. Be careful, you could get about 30kV at the output!

This link [4] looks like the circuit you need.

Thank you all. I was not looking to make ozone although that is a surprising coincidence. I'll try to do it with the ignition coil. Ozone 03:16, 23 May 2007 (UTC)

I did make the ignition coil circuit, you were all very helpful to me. Now I need more help: The sparks can only cross 5 mm though, are there any ideas to make that longer. BTW, I'm using the following circuit [5] with two 9Vs in series for the EMF, .1uF capacitor and 10K resistor, I only have access to one ignition coil: the Blaster 2. Ozone 01:10, 1 June 2007 (UTC)

To get a higher voltage on the output you either need to increase the current in the coil - by driving it with a higher voltage, or you need to interupt the current faster. Increasing the interrupt speed is difficult, but you could try some different switches that move the wipers faster, perhaps those that will not arc. There will be a limit where the ignition coil will arc internally or between the terminal and the case, and too much current may melt the winding in the coil too. A 5mm spark should be enough to detroy most transistors though. GB 06:54, 1 June 2007 (UTC)

Thank you GB, I think my family would dub it a waste to wire 8 9Vs in series, I could try 4 though. On the circuit it says you should use a capacitor to protect the switch, I am using a .1uF capacitor. I heard that was limiting the spark length. Could I decrease this without arcing the switch? What about the ohmage on that resistor, if I increased it would I get a longer arc? Ozone 19:03, 1 June 2007 (UTC)

[edit] dB

How can exposure to extreme level of noise kill someone?

DEpends on what you define as noise. Noise by itself isn't very "powerful", even very loud noise is barely perceived except by the delicate membranes in your ears, which will be destroyed long before you die from the noise. However, even a bomb blast can be defined as a noise since it is a series of pressure waves in air which can obviously be lethal. Straight dope seems to have a more detailed answer. Vespine 03:57, 1 June 2007 (UTC)

Also, see Resonance for a discussion on how sympathetic vibration can potentially lead to structural failure. For example, the Tacoma Narrows Bridge was destroyed due to a property of resonance. - CHAIRBOY (☎) 14:37, 1 June 2007 (UTC)

The shaking around of organs and their connections is pretty tough on the body. Rips and tears would occur in some places, enough to kill somebody. [Mac Δαvιs] ❖ 02:32, 2 June 2007 (UTC)

[edit] The first chemical equation

According to the article Jean Beguin, this is the first chemical equation:

How does it translate into a modern equation? I think the names translate as follows:

Jean Beguin's name	modern formula
Mercure	Hg
Regule	?
Antimoine	Sb
hydrochloric acid	HCl
Soufre	S

But that doesn't add up to an equation. Moreover, "Esprit vitriolic" sounds rather like H₂SO₄. — Sebastian 05:18, 1 June 2007 (UTC)

Regulé is an alloy of tin or lead with antimony (known in English as Babbitt metal). Oddly though, it wasn't discovered until the 19th Century. Hydrochloric acid would more likely be known as "Espirit salé". A possible reaction, assuming that they mean sulphuric acid rather than HCl, might be:

PbSb + S + Hg + H₂SO₄ → Sb + 2SO₂ + H₂ + PbHg

The sublimé bit refers to alchemical sublimation, allowing a chemical to boil out of solution, only to reform on the rim of the flask. It doesn't seem like the most plausible route (the hydrogen would probably want to become water rather than stay elemental), but perhaps someone else could help. Laïka 08:11, 1 June 2007 (UTC)

Vitriol is a modern (if not a scientific) name for sulfuric acid. I believe it is a common name used by jewelers and goldsmiths (i.e. non-chemists who often work with such chemicals). Nimur 12:22, 1 June 2007 (UTC)

This hardly fits my definition of a chemical equation, and I doubt it was the first. In fact the use of modern English suggests that the image itself is a copyvio. I shall wait for other opinions before cleaning the article up. Physchim62 (talk) 13:43, 1 June 2007 (UTC)

If it is a copy-vio, it would be ridiculously easy to make a suitable replacement. Nimur 17:56, 2 June 2007 (UTC)

[edit] Twin "Paradox"

The article states: "It should be stressed that neither Einstein nor Langevin considered these deeply counter-intuitive results to be literally paradoxical. A paradox in logical and scientific usage refers to results which are inherently contradictory, that is, logically impossible, and both men argued that the time differential illustrated by the story of the twins was an entirely natural and explainable phenomenon."

So if Einstein and Landevin didn't consider this to be paradoxical, how did it get the name 'twin paradox'? Did they call it this, or did somebody else make up the name later? 68.231.151.161 05:31, 1 June 2007 (UTC)

Because the article is wrong on terminology. In the exact sciences, we distinguish a contradiction (a theory contradicts itself or another established theory, fact or empirical result) and a paradox (there seems to be a contradiction which, however, can be resolved by careful thinking about it, usually resulting in deeper insight into the theory). These two terms get confused annoyingly often. Simon A. 06:41, 1 June 2007 (UTC)

So you are saying that we should replace "paradox" in the article with "contradiction" each time it talks about this? — Sebastian 15:18, 1 June 2007 (UTC)

No - the Twins 'thing' is a paradox because because it only seems like a contradiction - we can resolve it (quite easily as it happens) - so there is no actual contradiction. The word 'paradox' is correctly used in this case. SteveBaker 22:45, 1 June 2007 (UTC)

In Quine's terms, the twin paradox is a veridical paradox, i.e. a highly counterintuitive result which is in fact true. Algebraist 08:42, 1 June 2007 (UTC)

[edit] oxygen outcome from pongamia plants

How much oxygen does each Pongamia pinnata plant would be able to genetare in units of tons and inturn what would be the output from one lakh of plants?Hemalatha prakash 07:52, 1 June 2007 (UTC)Hemalatha

OK - so to start pulling this question apart so we can answer it! A lakh is 10⁵ - so we're talking about 100,000 of these Indian Beech trees. I suppose we'd have to approach this by figuring out the dry mass of the tree - and assuming that most of that is cellulose. Then knowing how much oxygen is liberated as each cellulose molecule is formed (from water and CO₂) - that would give us some idea. Of course this is a deciduous tree - and a lot will depend on what's done with the fallen leaves. When they decay, they'll consume oxygen. The short answer is that I have no idea! SteveBaker 22:36, 1 June 2007 (UTC)

[edit] Global warming

Any idea if we can make some sort of a solar powered machine that can filter out CO2 and sequester it?How about a carbon nano-tube sort of reflective ribbon?~~

like these?

Yes - exactly. Those machines are cheap, plentiful, already known not to cause environmental damage and they even self-reproduce.

But aside from those, the whole concept of 'sequestering' CO₂ is kinda shakey. Pretty much all of the proposed methods have severe problems of one kind or another. See Carbon dioxide sink and Carbon capture and storage and CO2 sequestration - although my opinion is that all three articles are rather more optimistic than is reasonable. SteveBaker 11:14, 1 June 2007 (UTC)

Hmmm this is off-topic but if the carbon capture and storage thing is actually used, why not use some of the carbon dioxide to improve crop harvest? Bottle it and give it to farmers and release it in the greenhouses or something. --antilived^{T | C | G} 12:55, 1 June 2007 (UTC)

Oddly enough, we have cheaply available machines for that too! SteveBaker 22:06, 1 June 2007 (UTC)

[edit] Airplane safety.

If aircraft fuel is an fire hazard during a crash,Any idea why not fuel one wing with a type of oxidizer and the other with propellant,so that they combust only in the engine and not separately outside?59.92.246.109

First, it's only rockets that carry oxidizer. Airplane engines use the air as an oxidizer to burn the fuel. (Rocket fuel would burn with air as oxidizer as well; rockets carry an oxidizer because they have to operate where there is no air, or to achieve more intense burning than would happen using air.) If a plane crashes and a fuel tank is ruptured, the fuel will mix with the surrounding air; there is no avoiding it. And that means it had an oxidizer available to it: the air. --Anonymous, June 1, 2007, 09:34 (UTC).

Any mechanism of containing energy is always "dangerous" - because that energy can be released accidentally. Even if you removed chemical fuel entirely and powered the airplane with 100% wind-up springs (quite an engineering task!), you would still run the risk that the springs might pop out of place and poke someone in the eye. The danger comes from storing energy, not the form it is stored in. Chemical fuels are probably among the safer ways to store energy. Nimur 12:27, 1 June 2007 (UTC)

Of course, there was that famous test-crash where they added flame-retardant to the fuel. See at right how well that worked. :) --TotoBaggins 14:19, 1 June 2007 (UTC)

In their defense, that crash didn't go as planned. >:/ 81.93.102.185 11:22, 2 June 2007 (UTC)

Probably for the best. Nothing worst than false confidence in a new technology, and nothing more misleading like the notion of a predictable accident. --24.147.86.187 12:27, 3 June 2007 (UTC)

Air contains oxygen which is an oxidizer, so your propellant is going to be in contact with one wether you like it or not. Philc 15:22, 3 June 2007 (UTC)

[edit] Breathable liquid

I remember seeing on the BBC that a scientist says we drown not because of liquid in our lungs, but because of the % of dissolved oxygen is less.So he puts a mouse in this liquid(presumably per-floro-oxy-chloride, guess)and it breathes and survives.Any idea whether such a liquid exists or it was just a gimmick??~~

It's real. See liquid breathing. --Anonymous, June 1, 2007, 09:36 (UTC).

The movie The Abyss pretty accurately portrays this as well. "[typing]Knew this was one way ticket, but you know I had to come." - CHAIRBOY (☎)

[edit] Torsion and Twisting

What is the difference between torsion and twisting?

Seven letters? Seriously, as stated in your question, there's not much difference except that "torsion" sounds a lot more technical. Would you like to add more context to your question?

Atlant 12:46, 1 June 2007 (UTC)

Torsion is normally defined as "the act of twisting". In mechanics and mathematics, the definition is very precise. So, as Atlant says, it is mainly a difference between a common word "twisting" and a technical word "torsion". --Kainaw ^(talk) 15:36, 1 June 2007 (UTC)

[edit] Spider identification

Last night I seen a spider in my room (which is in Scotland) and am having trouble identifying it! It is about 2cm long in total, it is brown all over, with no obvious patterning on its abdomen. Not significantly hairy either. Christopher

We'd really need a photograph of it at least. There are a lot of spiders that fit your descritpion. Bendž|Ť 17:08, 1 June 2007 (UTC)

[edit] This never got answered in computing, is it more appropriate here?

I have recently purchased an LG shine and when sending a text message i use the predictive text function. Today I added the word "yot" to my dictionary and now whenever i try to type "you" it automatically comes up as "yot" which has become an annoyance!! I tried adding "you" but as it was there and "yot" wasnt when i added it, "yot" still comes up first! Christopher

It isn't that nobody wants to answer your question. It is just a technical issue about a software product that most people do not have. So, you need to ask the LG shine people about it. --Kainaw ^(talk) 15:59, 1 June 2007 (UTC)

Perhaps you could remove the word from your dictionary? --TotoBaggins 19:54, 1 June 2007 (UTC)

Most phones work out what words you use most frequently and bring those up first - try typing "you you you you you you" in, and see if that works. Laïka 20:00, 1 June 2007 (UTC)

If you can't selectively remove the word from your dictionary, you may be able to reset all the phone settings which may reset the phone's dictionary. However this will mean you would lose all settings and obviously all words it's learnt that are useful. Also you would want to make sure you have a backup of all your messages and the like since it may or may not kill these as well. Alternatively, just try what Smurray suggests, this will usually work Nil Einne 14:41, 2 June 2007 (UTC)

[edit] unCircumcision

I was cirumcized can I get a transplant to be uncircumcized? —Preceding unsigned comment added by 71.185.140.166 (talk • contribs)

It isn't a transplant. It is just plastic surgery. They cut the skin around the shaft, stretch it, and reattach it in a stretched position so that much of it covers the head of the penis. It is not an uncommon surgery, but it isn't one most people discuss. --Kainaw ^(talk) 16:39, 1 June 2007 (UTC)

see Foreskin_restoration -- Diletante 16:57, 1 June 2007 (UTC)

[edit] The Dust Bowl, man made?

Isn't it a bit far fetched to suggest that a natural climate condition could have been affected so quickly by human actions? A few farmers not plowing their land well enough isn't exactly going to affect a thousand year old cycle of climate change in the midwest, I mean it used to an inland sea, and now it's dry and arid, obviously there haven't been human beings living there the whole time doing it, so why attribute it to human actions? It seems like this was more of an excuse for FDR to get the federal government involved in the personal affairs of farmers, then a serious study. So the question, in light of current science, does FDR's theory of 'Over farming' still hold water?--BowlerDust 18:19, 1 June 2007 (UTC)

As the article says, the dust comes from erosion, which is caused by plowing. What's unclear about that? — Sebastian 19:02, 1 June 2007 (UTC)

It was from the removal of grass. Even in normal conditions (not a drought) soil is eroded many times faster without vegetation (10 times faster if I remember right). When coupled with a drought, this spelled disaster. Global climatic conditions caused the drought. Lack of surface vegetation caused the dust bowl. --h2g2bob (talk) 09:52, 2 June 2007 (UTC)

[edit] Mailing address of Professor Richard Dawkins

How do you do.

Does anyone know the Oxford mailing address of Professor Richard Dawkins? I would like to address certain questions on his meme theory in person, as opposed to being continually dissatisfied with my science teachers' 'oh I don't know about that's. Assuming, of course, that he takes me seriously at all.

Also, what is the correct way to address him? I assume professor should be OK, but I know that he has a doctorate and may well prefer that title.

With all due respect,

Luthinya 19:44, 1 June 2007 (UTC)

His web page lists some contact information, and an encouragement to read his [ http://www.simonyi.ox.ac.uk/dawkins/FAQs.shtml FAQ] first. --TotoBaggins 19:47, 1 June 2007 (UTC)

Thank you very much, but it is not exactly a quick question I will be asking; rather, in order to make my inquiry clear, it would be necessary to present a logical argument demonstrative of my views, which cannot be fully accomodated in the email format. This is why I would prefer to contact him in writing, and thus ask for a specific mailing address. It would also be nice to circumvent that personal assistant of his...but I recognise that this is probably impossible.

Nonetheless, thank you for your help, and please send in more information if you can.

Luthinya 20:22, 1 June 2007 (UTC)

Well, he's not on the contact list for staff at the university. JoshHolloway 21:15, 1 June 2007 (UTC)

Well, presumably a letter to Richard Dawkins in care of his department at Oxford will make its way to him. People in the public eye, and particularly outspoken people with controversial views such as his, have a right to use caution and discretion in managing their correspondence, so I don't think your ideas will get a favorable hearing if you deliberately circumvent whatever he has in place. --TotoBaggins 21:19, 1 June 2007 (UTC)

And as is almost always the case with published authors, sending a letter to him care of his publisher will get to him too. I have actually corresponded with him on two separate occasions (both many years ago) with a question about his 'BioMorphs' and a comment about the possibility of true evolution happening in a system as brutally simple as Conway's "The Game of Life" - and I got long, detailed and thoughtful answers on both occasions - although on the second occasions many months went by between writing and getting a reply. So I think that if you have something interesting and relevent to say - you'll get a reply - but he's a busy guy so don't expect anything prompt! SteveBaker 22:00, 1 June 2007 (UTC)

You could also try leaving him a message at User_talk:RichardDawkins! No promise that he'll be back to read it, though... --mglg_(talk) 22:24, 1 June 2007 (UTC)

If you have no luck with Dawkins (though I too have had enlightening correspondence with him in the past) you could try other influential memeticists such as Susan Blackmore or Daniel Dennett, see here. Rockpocket 09:03, 2 June 2007 (UTC)

I took a look at User_talk:RichardDawkins and I don't think he uses it much - under 'user contributions' there is one minor edit to the article about him and one small post to his talk page - both about a year ago. I doubt you'd get a great response from a post to his Talk: page. SteveBaker 15:36, 2 June 2007 (UTC)