Wikipedia:Reference desk/Archives/Science/2007 April 3

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April 3[edit]


In electronics&communications what this word IFF stands for?please give me a brief idea about this..regards ambuj

IFF gives a few possibilities. JackofOz 06:15, 3 April 2007 (UTC)
Identification Friend or Foe - It's usually a technology to help fighter pilots and anti-aircraft batteries know who to shoot. Midway down this page is a news article with photographs. Nimur 06:48, 3 April 2007 (UTC)
Aside from the aforementioned Identification Friend or Foe (which seems unlikely since it's an entirely military radar term) - I don't know of a meaning for IFF that seems relevent. Are you sure it's 'IFF' and not just 'IF'? IF stands for Intermediate frequency - which is an important concept in communications technology. SteveBaker
Context would be helpful... -- mattb @ 2007-04-03T13:08Z
It might mean "if and only if". That's probably the most likely explanation within the electrical engineering and computer science fields, anyway. --Elkman (Elkspeak) 23:17, 3 April 2007 (UTC)

Tree stumps in dams[edit]

I suppose the answer to this depends on the type of tree concerned. When artificial lakes/weirs are created, the existing trees are usually killed and reduced to a stump sticking out of the water. I know of tree stumps that have been sitting surrounded by water for over 40 years, with no apparent signs of decay. How long would it take for a tree stump sitting in water to rot, disintegrate and fall apart? JackofOz 06:21, 3 April 2007 (UTC)

Sometimes bog-water can have a preserving effect on organic material (I recall something about dissolved tannins from oak-trees "mummifying" animals and human remains in England. "Under certain conditions, the acidity of the water, the cold temperature and the lack of oxygen combine to tan the body's skin" - I don't know if a similar effect can preserve wood, but it may contribute. Nimur 06:59, 3 April 2007 (UTC)

There is definitely a preservative effect under certain conditions. Check out the scant underwater logging; it's a fascinating topic. --TotoBaggins 12:12, 3 April 2007 (UTC)

Ta muchly. JackofOz 04:45, 4 April 2007 (UTC)

quantum physics[edit]

hi guys, is there anything new in QM? any new insights? interpretations? findings? what's the consensus?

Yes? No? There are many ways answer this, because quantum mechanics has evolved so much since its inception. There is definitely more theoretical work being done; new particle accelerators are built, new simulations are run. The applications of QM penetrate farther into the peripheral sciences than ever before; electronics and materials science often use QM techniques, and even molecular biologists find the rules of quantum physics relevant. As far as "the consensus": in summary, quantum mechanics has been experimentally verified many times, and as technology progresses, the implications of quantum mechanics are more relevant than ever before. Nimur 06:56, 3 April 2007 (UTC)
Yes and no.[1]
Atlant 13:57, 3 April 2007 (UTC)
Im more concerned about the talking poof. Capuchin 14:52, 3 April 2007 (UTC)

treating mental health disorders[edit]

what are the reasonble methods of treating a mental disorder IE paranoid schizophrenia I have heard of some practioners advocating not using medication and working with clients to recognise their voices and somehow manage them - a client I work with is completely unmotivated to regain his social life and he blames his 'dulling medication 'however there is a high risk he may have to be re admitted if any changes to his medication occur any theories case studeies or links are greatly appreciated

Mental health treatment practices vary not only from country to country, but within regions and even jurisdictions. It is probably not very fruitful for you to investigate treatments that may not be available to your client in her/his area. Go to the blue pages of your phone book and look for the number for local mental health boards or an advocacy groups, or if you want to let us know where you are in the world we can do a little work to find an agency that has both the information and the mandate to guide you. Anchoress 08:09, 3 April 2007 (UTC)
For advice on "methods of treating a mental disorder" you should ask someone with years of training, experience, and the responsibility that comes with licensure, not a bunch of high school students, layabouts, and barflies like us. Of course there are people willing to try "talking therapy" in preference to drugs. Who wouldn't favor that (except insurance companies, pharmaceutical companies, and doctors who can't get paid to spend more than a few minutes with people many of us would pay to avoid)? The question is not whether "some practitioners" try it, but whether (1) it works as well as drugs for your client and (2) is available to your client. I offer two additional observatons for no extra charge. If you are a professional responsible to your client, your value to him/her is likely to be in your ability to see things differently (like excuses for not taking medicine) while being sympathetic. Second, you have to be supportive of the treatment or you have to have a constructive alternative or you are doing him a disservice, since he can find a guy on the next barstool with whom to play "aint it awful" while avoiding changing anything. Paranoid schizophrenia is indeed an awful disease. alteripse 11:02, 3 April 2007 (UTC)

For more on this approach see: "The pursuit of schizophrenia and bipolar disorder" in New Scientist 20 January 2007 Magazine issue 2587 Colinvincent 23:13, 6 April 2007 (UTC)

Nuclear Attack on polar regions[edit]

Hi, What would happen if someone were to launch a nuclear attack on one of the polar ice caps? Would it accelerate global warming? Would it raise the sea level? How big would it have to be to destroy the whole ice cap?

Just hypothetically speaking, of course, eh? Aaadddaaammm 09:54, 3 April 2007 (UTC)
It does sound suspiciously like the plot of an Austin Powers film, doesn't it? Spiral Wave 11:03, 3 April 2007 (UTC)

Probably something similar to when the USSR was doing atmospheric tests on their tundras: not much. --TotoBaggins 12:06, 3 April 2007 (UTC)

A recent question about how much water a large nuclear weapon could boil produced the answer "a cube roughly 400m on a side" - the amount it could melt would be about 7 times greater - so quite a bit less than a cube one kilometer on a side could be melted. In reality, some of the energy would be spent in melting ice and some in boiling water - and the precise mix of the two effects would be hard to guess. The result of this direct melting would not be all that great - comparable to a few extra large iceburgs breaking off and heading south to melt. Then we might consider the mechanical effect of breaking up the ice. At the North pole, the ice is quite thin (just a few feet in most places) - so the effect might be to spread out the sea ice over a larger area. At the south pole, the ice is a kilometer deep and resting on dry land - unless you hit the critical point on the edge of an ice shelf, I don't think this would matter much. The effect of boiling all of that water would be to put an immense white cloud up in to the high atmosphere. Water vapor reflects sunlight quite well - so the local increase in albedo might actually cool the polar regions quite a bit initially. However, water vapor is also a greenhouse gas - so it would help to trap heat eventually. Personally, I doubt that the effect would be very significant...but there are enough complicated things going on here to make it hard to form a simple answer. SteveBaker 12:47, 3 April 2007 (UTC)
I hadn't really thought of the albedo or mechanical effects. Here's the back-of-the-envelope reasoning I had for thinking not much would happen:
 # Annual average area of north pole ice, in square meters
 # From
 arctic_ice_pack_area =  10^13
 # Annual average insolation, in watts per square meter
 # From Image:Insolation.png
 insolation_at_north_pole = 120
 wattage_to_ice_pack = arctic_ice_pack_area * insolation_at_north_pole
 seconds_in_day = 24 * 60 * 60
 # A watt is a joule per second
 daily_joules_to_ice_pack = wattage_to_ice_pack * seconds_in_day


 # World megatonnage, at historical maximum (around 1969)
 # From
 world_warhead_yield = 25000

 # From Megaton
 joules_per_megaton = 4 * 10**15

 world_warhead_yield_in_joules = world_warhead_yield * joules_per_megaton

 days_of_sunlight_to_equal_world_arsenal_energy = world_warhead_yield_in_joules / daily_joules_to_ice_pack

So according to that calculation, the north pole absorbs the full energy of all nuclear weapons at their historical high point every day. That said, most things that can be put in a nutshell belong there, so maybe I'm way off base. :) --TotoBaggins 17:38, 3 April 2007 (UTC)

Also, keep in mind that melting floating sea ice has no effect on sea level (since a floating object displaces its weight in water, so when it melts, it becomes the same amount of water it displaced). Only melting ice caps on land can raise sea level. --Spoon! 20:52, 3 April 2007 (UTC)

This item disputes that common claim on the grounds that salt water is denser than fresh water. --TotoBaggins 22:52, 3 April 2007 (UTC)
Sea ice is frozen salt water. Pfly 07:08, 5 April 2007 (UTC)
Oh, OK, thanks. I see now that the paper I linked to is only talking about the effect of floating ice that originated on land. --TotoBaggins 01:48, 6 April 2007 (UTC)

Monitoring glycemia[edit]

Do the beta cells of the pancreas directly respond to changes in glycemia? Or are they alerted to abnormal glycemia by other cells? —LestatdeLioncourt 15:41, 3 April 2007 (UTC)

Maybe both. The beta cells clearly respond directly to changes of blood glucose and we have a fairly detailed understanding of the mechanism, which involves glucose transport into beta cells, phosphorylation by glucokinase, and changes in the intracellular ATP:ADP ratio resulting in shifts of the transmembrane calcium levels and shifting of insulin-containing secretory granules to merge with the plasma membrane, releasing insulin into the blood (or reducing the amount of insulin into the blood). The degree of influence of other cells on this process is much less understood and may largely be secondary "fine tuning", but probably involves hormone signals from other cells to the beta cells, and neural signals from the brain via the autonomic innervation of the islets of Langerhans. alteripse 15:53, 3 April 2007 (UTC)

So, the beta cells cannot directly "measure" glycemia? They need other cells to transport glucose to them? I'm not very interested in what happens in the cell as a response to changing glycemia, but rather the way information regarding glycemia reaches the beta cells. "which involves glucose transport into beta cells" is a bit vague for me. Thanks for the detailed answer, though :) —LestatdeLioncourt 16:17, 3 April 2007 (UTC)

No, other cells do not transport glucose to the beta cells, nor do the beta cells have a little hand stuck out in the bloodstream counting the glucose molecules as they drift by. The glucose moves directly from the blood into the beta cells by the GLUT2 transporter, and intracellular glucose levels are directly proportional to the blood levels (the glycemia). Does that make sense? alteripse 16:40, 3 April 2007 (UTC)

Yes, thank you; that's what I wanted to know. —LestatdeLioncourt 18:22, 3 April 2007 (UTC)

Semiconductor Memory[edit]

I am currently researching for a Physics project on Semiconductor Memory. I am at a 6th form college so the standard of work has to be around A Level standard, well higher would be good as long as i understand it.

I have found that the main type of storage is done using a Floating Gate MOSFET. From having basic knowledge of any electrical engineering i decided to research from the ground upwards.

First off i found information about PN Junctions, from there i found information about different types of transistors. From there i've come across Bipolar Transistors and Field-Effect Transistors. I've assumed only the FETs are relavant in a MOSFET so i havent paid much attention to the Bipolar Transistors. When Searching for FET i came across JFET and MOSFET, i've only briefly looked into JFET. I have a fairly good understanding of how a MOSFET works, but i can't find much information on Floating Gate MOSFETs. What i have seen shows a normal MOSFET with a floating and control gate, however they dont describe how theyre used.

I have a few questions, any other help and advice would be good. Are Field-Effect Transistors just a special type of transistor, and what are the characteristics?

Do Biploar transistors or JFETs have much importance in a Floating Gate MOSFET?

How do Floating Gate MOSFETs work?

If there are any resources you think would help i would be very greatful if you could suggest them.

Thanks for any help 16:02, 3 April 2007 (UTC) Pete

Did you read Floating Gate Transistor? It has a link to a good article on HowStuffWorks. If you are already past what is in there, please ask for more information. --Kainaw (talk) 16:07, 3 April 2007 (UTC)
Wow, you have a lot of questions that I don't believe can be answered briefly. I can try to hit the high points, but I suggest you pick up an introductory book on semiconductor physics and devices. The texts by Neaman, Sze, and Pierret are all pretty good.
First off, there are several types of semiconductor memory and several ways to realize each one. Floating gate transistors are used in non-volatile memory like flash. Unfortunately that particular type of transistor isn't the simplest to understand since you need to know a bit about how field emission (quantum tunneling) and hot electron effects proceed.
I'm not sure what level of detail you're looking for here, there are literally volumes of books and papers on each of the topics you've mentioned. If you just want a very high-level overview, you should read the corresponding Wikipedia articles. DRAM and SRAM usually use MOSFETs (the former actually uses a capacitor for storage and a FET for control), flash memory and EEPROMs use some form of floating gate transistor, ZRAM (a new beast) uses the floating body effect associated with SOI (similar principle to the floating gate transistor, but very different structure), MRAM (also newish) stores bits in the magnetic domain orientation of a thin film ferromagnetic material.
In general bipolar transistors aren't used for semiconductor memory. It's possible, but it isn't an optimal solution for many reasons. JFETs aren't used in many places period as they have few advantages over other types of transistors. Field effect transistors all change the conductivity of a certain region of the device (the channel) by using an electric field to move charge carriers in and out of this region. There are many types of FETs and a lot of things to be said about the details of how they operate and are constructed (though again, I have no idea what level of detail you are looking for). MOSFET is actually a misnomer these days because in the strictest sense a metal (the "M" in "MOS") isn't being used for the gate in most semiconductor memory processes (though you're sort of arguing semantics).
You really should start reading articles on transistors and figure out exactly how deeply you want to get into this topic. -- mattb @ 2007-04-03T20:53Z
Thanks for your help, a lot of useful points. The books im sure would be very helpful, although i only need them for a short time so buying them is a bit of a waste and my local library has a pretty appalling range of non fiction books.
I think the main problem i have is i'm taking one example of memory and only focusing on that one when in reality there are many different types. As mentioned floating gate trasistors seem a little more difficult to understand. I've looked at DRAM and SRAM as you suggested, and they seem a little easier. From what i've read through, they only require normal MOSFET's rather than the complexity of Floating Gate MOSFETs. What other examples would you suggest i write about that are along the same lines?
Again thanks very much for your help. I've seen your member page and was wondering if you mind me putting you as a reference, i need a variety of different resources and so i can say talking direct is different from taking information of a webpage. Thanks again 13:23, 5 April 2007 (UTC)
DRAM and SRAM are probably good structures to concentrate on if you had to pick two. They are easily the most important types of solid state memory today. Both can be manufactured with a CMOS process (though in truth, DRAM has its own process optimization, though there are some folks working on processes that allow DRAM and VLSI logic to easily be integrated onto one die), so you really only need a cursory understanding of MOSFETs and capacitors to understand their principles of operation.
You should not cite me as a reference as I am by no means a recognized expert in this field. You should take the information I've given you, do additional research, and cite those as your sources. While I appreciate your wanting to give me credit for the leads, it's not necessary to explain where you found some general introductory information, just where you found facts and figures that you may use. -- mattb @ 2007-04-05T16:24Z

Black Holes[edit]

Black holes with a mass greater than the Planck mass would have a frequency greater than 1/Planck time (E = mc2 E = hf). Since time scales smaller than Planck time are not phisically meaningful, what would that do to black holes of this size? Thanks *Max* 16:52, 3 April 2007 (UTC)

Cause them to evaporate? (just a guess from an ignoramus!)
Every black hole currently in existence has a mass greater than that, so I'm not really sure what you're asking. I have a mass greater than that, and Planck times don't bother me. Is your question about primordial black holes? Ones that small would have evaporated long, long ago (if they could even form at all; there must be a lower practical limit of some sort). Spiral Wave 00:50, 5 April 2007 (UTC)
I am talking about large black holes, not primordial black holes. Other things have a mass greater than the Planck mass, but they are not single objects in the way that black holes are. *Max* 21:57, 5 April 2007 (UTC)

Asian people less resistent to alcohol?[edit]

Hi all. I've heard from my mother, who is a nurse, that Asians are "weaker" to alcohol than other people, since they lack a certain gene that reduces alcohol's effect, though I've had no luck finding more information about this on Wikipedia. I trust my mom and her colleagues, but I can't find the right page that explains this phenomenon. Does anyone know where on WP it is mentioned? (if it even is, though I trust it is) --MathiasRav 18:02, 3 April 2007 (UTC)

Asian people share a higher predisposition to a genetic trait to process alcohol poorly (though it's not, of course, a blanket statement for all Asian people). See [2], a reference from effects of alcohol on the body. — Lomn 18:15, 3 April 2007 (UTC)
See Alcohol flush reaction. -- 04:25, 4 April 2007 (UTC)
As linked about, only about half (if not less) the Asians. So saying Asians are "weaker" to alcohol is pretty inaccurate. I for one, don't fall in that half. --Wirbelwindヴィルヴェルヴィント (talk) 05:32, 4 April 2007 (UTC)

one theory is that as racial types evolved, asian/oriental types tended to drink teas, using boiling as the preferred method to purify drinking water. caucasian types tended to use alcohol to make water safe, and ale or watered wine was the usual beverage. so asian peoples were not exposed to as much alcohol and have not needed to develop overworked livers. but then the japanese did come up with saki! for primitive westerners the diet was poor and the alcohol provided much needed calories.Calorine 20:48, 4 April 2007 (UTC)

See Marginated Tortoise's talk page[edit]

Waiting for an anser for my Question in Marginated Tortoise's talk page. Hope this is an OK place for notices like this.

I think it should be, but probably isn't, so someone may complain soon

Allow me to complain :D. It is more appropriate to post that question here, as this is a place to have general questions answered. The article talk pages are for discussion about improving the article, not general discussion of the topic. If I were you, I'd copy that question from that talk page to here.
Personally I do not know the answer to your question, I would think that a light-colored exterior would not prevent heat radiation rather it would prevent absorption. Of course the answers you get here may help in improving the article in which case that discussion should be on the articles talk page. phew that was alot more than i intended to type. :P -- Diletante 20:20, 3 April 2007 (UTC)
See emissivity. Dark objects (in whatever frequency range you're talking about) absorb and emit more efficiently. --Tardis 21:26, 3 April 2007 (UTC)

What's the point of finding non-intelligent life?[edit]

There seems to be little purpose outside of satisfying idle curiosity. Let us say we should find a few bacteria on some planet or moon in this solar system. So what? It's quite obviously never going to evolve much beyond that, given it is still alive, and they will probably have very few applications, if any, certainly not as many as Earth bacteria, which have had millions of years worth of evolution on a fertile and habitable planet.

So, my question is, why does anyone care about finding a bacterium or even water on Mars? Shouldn't we be more concerned about finding extraterrestrial intelligence, despite its currently low probability? 18:34, 3 April 2007 (UTC)

Well, it certainly would be interesting to see what differences there are in life that evolved somewhere else and life that evolved here on Earth. Perhaps, the extraterrestrial life doesn't use the same amino acids we do. Otherwise, if there are great similarities, it might help us find out where life on Earth came from.Coolotter88 18:42, 3 April 2007 (UTC)
One thing that springs to mind is new medicine, new technology, and so on. Nature is very good at mastering certain procesess, and understanding those processes in the natural world can have some very tangible benefits. Vranak
It also could present possible answers to some questions about the origin and nature of life both here on Earth and elsewhere. It also could provide information on the durability of life in harsh environments, or even eventually give insight into the actual artificial creation of new life. Dugwiki 19:00, 3 April 2007 (UTC)
I would point out that artificially creating new life doesn't have much of a point in and of itself, unless inflating the creator's ego counts. Vranak
Theoretically the ability to create new microbial life can lead to the ability to create life forms dedicated to specific tasks. In fact, we're already able to genetically modify life forms for certain specific purposes, and the creation of actual new life would be a logical extension. Dugwiki 20:26, 3 April 2007 (UTC)
I'll rephrase: creating new life doesn't neccessarily have any point. It's more a case of 'gee, look what I can do! Aren't I the greatest? Give me more money.' Vranak
Again, it's not just "aren't I cool". The ability to create new life can act as the corner stone for a number of important practical applications centering around the creation of new life intended to perform specific tasks. It could be an organic counterpart to robotics, for example, whereby artificial life is manufactured to perform a variety of functions (just as robots and computers and genetically engineered life are currently engineered for similar reasons). Dugwiki 22:17, 3 April 2007 (UTC)
As a specific (well, less generic) example, note that several types of yeast and particularly bacteria are used in biotechnology, waste disposal, chemical engineering etc.; but we're limited to what we can naturally find or otherwise create through recombinant DNA techniques. If we could one day create primitive life forms from scratch, such that they actually did what they were supposed to, the possibilities for their application would be vast. And that's aside from what you might learn about how cells work from having a simpler and purposely-designed cellular structure to experiment with. Spiral Wave 23:47, 3 April 2007 (UTC)
"satisfying idle curiosity." is what science does. When Newton described how gravity works we didn't have spacecraft. But now an understanding of those laws are what we use to send spacecraft into orbit. We will never know what's out there until we look! Ironically I would say that a marker of intelligence is attempting to understand the un-intelligent (natural) world around us. -- Diletante 19:46, 3 April 2007 (UTC)
It should be noted that Newton didn't do science to satisfy his idle curiosity, he did it to better understand and to glorify the God he believed ran everything. -- 00:27, 4 April 2007 (UTC)
One man's god is another's idle. I promised myself I'd never make a pun joke on the ref desk, oh welll ;D-- Diletante 01:25, 4 April 2007 (UTC)
I really must MontyPythonFootLeftSmall.jpg put my foot down on all these puns, but first let me say that "Idle hands are the devil's playground". StuRat 04:42, 4 April 2007 (UTC)
Finding extraterrestrial life (non-intelligent) would tell us an immense amount. Firstly, it would give us greater confidence in that the value to put on that term in the Drake equation - which would get us closer to a solid estimate of the number of intelligent civilisations in the galaxy. Secondly, if we found striking similarities beween (say) life on Mars and life here on Earth then the panspermia hypothesis starts to look good. If it's basic biochemistry is kinda sorta similar then that says something about the likelyhood that abiogenesis is truly the random event we think it is - and that the probability of it happening at least once per planet is pretty high. If the alien life is utterly bizarre - then we can learn a lot that we don't already know about biochemistry in molecules that are not commonly found in earthly life. Certainly there is an immense amount that would be learned from finding just the lowliest bacterium on another planet or moon. SteveBaker 20:21, 3 April 2007 (UTC)
Wouldn't any form of life on another planet/in space be a start? At least this would show us that the vast space beyond our planet does have places where live is still living. It may even serve as being as simple as inspiring the public to back further exploration and further delving into the great unknown. Even the most simple organisms will help the collective intelligence of our race to increase to a whole new level. ny156uk 20:38, 3 April 2007 (UTC)
  • If alien life exists on a particular planetoid it could give us clues about how we might go about terraforming that planetoid to ultimately sustain human life. Johntex\talk 20:52, 3 April 2007 (UTC)
Heh, I don't know about collective intelligence, but it would certainly further human knowledge. However, the scientific reasons put forth so far are very nice, but I'd suggest there's also a much simpler reason which people the world over would be able to grasp: we are not alone. Once is a fluke; twice is a coincidence, and coincidences that large don't exist. At some level this is related to the Drake equation, yes, but the philosophical aspects would be staggering. Just being able to look up and know we weren't the only ones here, rather than suspect or wish it (or otherwise)....
Of course, there'll be panspermia arguments, if it's found on Mars, and then the question will shift to whether or not it evolved independently; and if not, whether or not the Martians are actually Terrestrial; or we are actually Martians. But at the simplest level, we'll know that it's not just us. Lots of people might not care, but I promise you that lots more will think it absolutely wonderful. Spiral Wave 21:02, 3 April 2007 (UTC)
Many things scientists were historically interested were thought to have no practical applications in their day, but after a key discovery was made the practical applications came rolling in. Taking too utilitarian a view of the role of science ends up with a killing-the-goose-that-lays-the-golden-egg approach that sunk many fields of science in the USSR, for example, where theoretical science or impractical science was persecuted as "bourgeoise science" for many years. -- 00:27, 4 April 2007 (UTC)
Johntex, are you suggesting, if we found a planet with life on it, that we should just kick them off and claim it for ourselves? Think outside the box 17:03, 4 April 2007 (UTC)
I didn't read this whole post, so sorry if I'm repeating someone. If we found a living alien organism, it could be a completely revolutionary thing for biology, technology, etc. It kind of depends on the organism. Terrestrial bacteria are unbelievably complicated little machnies - anyone who has taken intro biology in college should appreciate that to some degree. Now, consider all the amazing advances that were made possible by emulating, harnessing, and studying bacteria!! If we found an entirely distinct, functional biochemistry, it would be a staggering discovery, and (again, depending on the biochemistry) it could spawn a totally new branch of biological science and techonology. --bmk
Reply to Think outside the box - you could say that, yes. If we found life on another planet, it might give us clues as to how we could survive on that planet. This could potentially include making modifications to that planet in order to suit ourselves. Those changes may be detrimental to the original life there.
I'm not saying we should or should not do this. You may think it would not be right to kick out that original life form, but imagine this example: There ise evidence that we are causing a dramatic warming to our own planet. This endangers many, many species of plants and animals, such as polar bears. If we could move part of our population off the planet, we could lessen our impact here. Some bacteria on Mars might be killled, but we might save the polar bears and the Monarch butterfly. Is that a good trade?
Of course, this assumes an advanced technology we don't have, so it is just hypothetical. Johntex\talk 17:45, 4 April 2007 (UTC)

Turning Earth Into A Gas Cloud[edit]

Could one keep scaling up a themonuclear weapon or nuclear fission weapon to any amount of megatonnage or is there a limit? Could one even scale it up to the point of creating enough energy to turn all of Earth into a cloud of gas? 23:07, 3 April 2007 (UTC)

Generally speaking, fusion weapons can be scaled to any size you wish while fission weapons can't be.
Atlant 23:48, 3 April 2007 (UTC)
It would take something on the scale of a nova to vaporize the Earth. If some time in the distant future, one could be manufactured, you could consider it a fusion weapon - a very big fusion weapon. Clarityfiend 23:52, 3 April 2007 (UTC)
There is no upper limit to a staged thermonuclear weapon from a theoretical point of view, but it rapidly becomes impractical, even for science fiction designs. At some point you'll just end up having most of the energy radiating upwards, and if large enough a blast, you'll probably blow a hole in the atmosphere and most of the energy will just head out that way, I believe. -- 00:21, 4 April 2007 (UTC)
You could drill a deep shaft, put your mega fusion bomb at the bottom, and infill. Then the surrounding rocks might help contain the fusing fireball for a few milliseconds longer for a higher yield. But you'd need to be way, way down for a blast of the size required to do more than just pop off a few hundred square miles of crust. Then you have the engineering problems of drilling down hundreds of miles through molten rock at magma temperature and pressure... Greg Bear's SF novel The Forge of God has an interesting description of how to destroy planets. Malcolm Farmer 09:50, 4 April 2007 (UTC)
As does David Brin's novel Earth.
Atlant 15:48, 4 April 2007 (UTC)

The practical limit would be the ability to find enough radioactive fuel for the bomb. StuRat 04:28, 4 April 2007 (UTC)

A limit for fission bombs would be preventing them from detonating prematurely. If you have a large ball of plutonium, the fission reaction will run away and produce enough energy to destroy the bomb, but not enough energy to create a sizeable explosion. A larger ball of plutonium will also have a small surface-area-to-volume ratio, therefore requiring more powerful explosives to compress.
As for how much energy it takes to vaporize the Earth, consider how the moon was formed. The planet that hit Earth had more than 10 trillion gigatons of kinetic energy, yet nothing much was vaporized. --Bowlhover 05:10, 4 April 2007 (UTC)
I would recommend this site:[3], with a lot of information about the energy needed to destroy the Earth. And a more theoretical analysis can be found here: [4] -- 06:23, 4 April 2007 (UTC) had a wonderful article on how to destroy earth. It isn't easy. DDB 11:55, 4 April 2007 (UTC)

The problem with making really large bombs (fission or fusion) is that you need to set off all of the material at once or else the early stages of the explosion tear the bomb apart before the remainder of the reaction can complete. Whilst this might prevent you from making one really big bomb, it can't prevent you from setting off a very large number of smaller bombs instead - providing you have nice precise timers. However, the amount of energy required is well beyond what we could even theoretically produce. Even if we build a hydrogen bomb using all of the hydrogen on earth - it wouldn't make a big enough bang to break apart the planet's core. SteveBaker 15:59, 5 April 2007 (UTC)
I'm having trouble accepting the claim that there isn't enough hydrogen; are you considering all that seawater? (Admittedly, it's ordinary hydrogen and not deuterium or tritium, but if we get that fusion reaction going hot enough, even ordinary hydrogen will participate.)
Atlant 17:22, 5 April 2007 (UTC)
I just did a back-of-the-envelope calculation based on 1.4e21 kg water in the ocean == 4.3e17 kg heavy water == 8.8e16 kg deuterium == 2.5e42 D atoms, which you can fuse in the D+D reaction to get 12.5 MeV per pair, yielding 2.6e24 joules, which is rather less than the 2.2e32 J that this page says is needed to destroy the Earth. But they're talking about total annihilation, not just breaking up the core, so it might be worth a shot. --TotoBaggins 12:18, 6 April 2007 (UTC)

Nice this is all really intresting, thank you all.

On page 402 of the excellent Dark Sun, Richard Rhodes quotes Edward Teller as below. --TotoBaggins 02:03, 6 April 2007 (UTC)

Teller eventually realized that there is a limit to the destructiveness of even thermonuclear weapons. At somewhere around a hundred megatons, he estimates, "it would simply lift a chunk of the atmosphere ... into space. Then you make it a thousand times bigger still. ... You lift the same chunk into space with thirty times the velocity."