Wikipedia:Reference desk/Archives/Science/2007 September 16

From Wikipedia, the free encyclopedia

Science desk
< September 15 << Aug | September | Oct >> September 17 >
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.


Contents

[edit] September 16

[edit] Carbon based fossil fuel

Is the supply of fossil fuels like crude oil, coal, etc, diminishing? If so, when will the supply run out? And why is combustion of carbon fuel still the most popular method to obtain energy? Are there many alternatives available? Thanks for answering. Oidia (talk) 02:31, 16 September 2007 (UTC)

Yes - see the lead section of Fossil fuel.
It's hard to tell, but some people suggest we're already on the downward slope - see Peak oil.
Because it's (currently) cheap, easy and plentiful enough that people haven't been too bothered to seriously look into alternatives until somewhat recently. See Energy economics.
Yes, but they are generally eiter expensive, inefficient, or in some cases still purely theoretical. See, for example Nuclear energy and Renewable energy. Confusing Manifestation 03:52, 16 September 2007 (UTC)
As fossil fuels become more scarce, their price will go up, and the more expensive of the alternative fuels will be more on par with the cost of fossil fuels. So I think eventually things will even out. --24.147.86.187 13:09, 16 September 2007 (UTC)
Note that peak oil is about the rate of production which is related to things like how much of the supply we have found and how much we have used. I think even most of the more extreme 'optimists' in the area agree that overally supply is diminishing. They just argue there is still so much out there we don't have to worry and/or we will always find a way whatever happens. The only way the overall supply could not be diminshing is if more was being produced then we are using which is supported by virtually no evidence Nil Einne 20:36, 19 September 2007 (UTC)
Fossil fuels are being used, so naturally the supply is diminishing (possibly, some is still being produced the way it used to be, but that will be negligible compared to the amount that is used). When the supplies 'run out' depends on how you define that. It will become ever more difficult (read: expensive) to extract the oil (or whatever). The low hanging fruit has already been picked. The murky oil fields in Canada that didn't receive any attention in the past because the oil was too hard to extract, are now receiving large investments because there is nothing else left. So oil won't 'run out' until we decide it's become too expensive - which is never, because our societies are so dependent on energy that we will pay any price. Unless alternatives become cheaper. But that requires investment in those, of which there hardly are any (in comparison). Fossil fuels are still popular because a lot of money has been invested in the knowledge and infrastructure (think of the many petrol stations, for example), so there is a huge (really, really huge) invested interest in maintaining the use of those. Even now, the amount of money invested in fossil fuels is more than ten times (for got the exact figures) larger than in other energy sources, and the biggest usurper of that remaining money is still nuclear energy. If, say, the development of solar cells had received the same level of investments as oil, then we probably would have stopped using fossil fuels years ago, when the low hanging fruit was all picked. DirkvdM 10:47, 16 September 2007 (UTC)
  • Is the supply of fossil fuels like crude oil, coal, etc, diminishing? Yes
  • If so, when will the supply run out? It will become more expensive to extract as its deposits are used up - eventually other fuels will be cheaper.
  • And why is combustion of carbon fuel still the most popular method to obtain energy? It's the least expensive, given the current industrial infrastructure.
  • Are there many alternatives available? Yes, see Ethanol fuel in Brazil, Nuclear power, Fusion power and Future energy development for examples. --Duk 14:55, 16 September 2007 (UTC)
Fossil fuels are still the most popular because, in their way, they're still the cheapest. They are, in effect, a conveniently-stored form of millions of years' worth of accumulated solar energy.
Suppose you inherit $1,000,000 from your rich uncle. You know that the money won't last forever, especially if you indulge in expensive pastimes. But on the other hand, it's fun to indulge in expensive pastimes, much more fun than, say, working for a living.
On any given day, you have a choice: (a) get a job, or (b) play some more (and spend down your inheritance some more). If you're like most people, you'll keep choosing (b) until it's almost too late, or maybe even actually too late. And the situation is (I believe) exactly the same, on a macro scale, with human society and our inheritance of fossil fuels. —Steve Summit (talk) 16:05, 16 September 2007 (UTC)
But there's not just the added cost of having to develop alternatives faster in the future if we don't start (seriously) investing in it already. There's also climate change, and the cost of that could dwarf all that. The problem is that large companies have too many invested interests in fossil fuels and small companies don't have the money to invest. So governments should step in, but the democratically elected ones won't do that because their electorate is brainwashed with the help of the big money from the big companies (funding 'scientists' who spread all sorts of doubt about climate change). As usual, a disaster has to happen before anything is done about it. Such as the North Sea flood of 1953 that led to the Delta Works in the Netherlands. Except that it's worldwide now. DirkvdM 08:19, 17 September 2007 (UTC)
  • That's a great analogy. --Sean 14:02, 17 September 2007 (UTC)
We had this question (about oil specifically) the other day. At present rates of consumption, we expect to run out of oil in 500 years. Coal and natural gas would be available for much longer. Nuclear fuels would also eventually run out - but we don't know how large the reserves are - possibly tens of thousands of years. Fusion power (if we ever manage to get the technology right) will last until we've boiled the oceans dry - there is no practical way to run out. Solar, Wind, Tidal....same deal. However, it's a completely academic question. We now know that throwing carbon-dioxide (an inevitable by-product of burning oil, gas or coal) into the atmosphere is going to kill the planet LONG before we run out of oil (let alone gas and coal) - so we absolutely have to cut back on our consumption at least 4-fold, possibly 10-fold. This stretches our reserves out to a point where it no longer matters because improved technology will push down consumption faster than our supplies are shrinking. However, we DO have to cut back on our consumption somehow - and that's not easy. At this point, running out is NOT the issue. SteveBaker 15:02, 17 September 2007 (UTC)
It's nonsense to talk about 'when we will run out'. Using up all fossil fuels would be total madness, because at one point it would be so hard to retrieve that it would cost more energy than it would yield. The question is when it would run out economically, and that depends on how fast alternatives are developed (ie when do they become cheaper than oil). As for Uranium (and other fission fuels - not too many of those), some wild numbers are given for how long that would last (billions of years), but for that all Uranium would have to be used up and most of that is spread all over the Earth's crust, so we'd have to completely overturn the entire Earth's crust, down to 10 km or so. So same story there.
Btw, you're overstating the effect of climate change. It's probably going to be sheer misery for the next milennia at least if we don't act quickly and most life on Earth might disappear. But not all of it. Some life will survive, even if only bacteria. It'll be just another catastrophy hitting the planet, and life will overcome it. What matters more is that we will probably survive too, as a species - we're resilient enough. But it's likely to not be a lot of fun for the next few generations (or 10 or 100 (1000 anyone?)). DirkvdM 18:41, 17 September 2007 (UTC)
I don't think it will be miserable for everyone. Those living in Canada, Alaska, Russia, Finland, Norway, and Sweden will likely benefit in some ways (such as the Northwest Passage opening up in Canada). Also, Greenland and Antarctica may become habitable. However, those in equatorial climates or with major population centers on ocean coasts (and/or near sea level) will suffer, such as Bangladesh. The most important thing is that the climate change happens slowly enough for us to adjust. As for plants and animals, they will generally do better with a warmer climate, although there will be many exceptions (like polar bears). StuRat 03:52, 18 September 2007 (UTC)
The major problem with climate change lies not in the new climate but in the change. First of all, life in general and human infrastructure in particular are not adapted to the new climate, so most animals will die and humans have to rearrange their economies and infrastructure (to what extent is a great unknown). Shorelines will change and agriculture will have to look for new foodcrops. Humans will adapt, but those living during the adaption will not have it easy, to say the least. Nordic countries indeed have an advantage in that the most likely new climate will be better for humans in general (if it really will be warmer - mind the regional variations) and that most are among the top ten richest countries on Earth, which will make the transition a lot easier.
But a second factor is that we don't suddenly jump to a new climate. Only after the greenhouse gas concentrations have settled to a certain level (which will take a long time) will the climate(s) settle to a new equilibrium. In the meantime, the climate will go all over the place. Climate is consistency in weather patterns, so effectively there will be less climate, however odd that may sound. Farmers need to know what weather to expect when, so they will know what to do when (plough, plant, harvest, what have you). If they don't, crops will fail or not be optimal and there will be less food. So we're increasing our luxuries at the expense of our basic necessities, which is downright silly, if you think about it.
As to the speed of change - the Permian–Triassic extinction event killed some 90% of life on Earth but that took thousands of years (if not millions). It looks like we're recreating that, but in just a few hundred years. Note that I say this based on the theory that that event started with a temperature rise of 5 C, which led to the freeing of frozen methane (such as on ocean floors), which raised the temperature by another 5 C. And that initial rise of 5 C is not unlikely to happen even in the next century - just one century! And it is quite likely to happen in the next few centuries. It's actually the incredible speed at which this might happen that is so scary. Note that I say 'might'. We don't really know what we are doing, and that might just be the scariest part. We're doing this wild experiment, but we have only one test tube - and we live in it. Sorry about the shouting, but that has to do with the huge importance of this. DirkvdM 08:16, 18 September 2007 (UTC)

[edit] Delicious but dangerous

What foods are the most dangerous to eat? Not as in "highest probability of harm", but as in "most serious worst-case scenario". I'm especially looking for foods that are deadly if prepared incorrectly, like fugu and false morel. —Keenan Pepper 04:42, 16 September 2007 (UTC)

Raw manioc is bad for you. A.Z. 05:43, 16 September 2007 (UTC)
I think the most serious worst-case scenario is probably beef infected with mad cow. Frankg 07:32, 16 September 2007 (UTC)
Rotten meat > food poisoning. DirkvdM 10:50, 16 September 2007 (UTC)
Not what I'm looking for, because you can just get fresh meat instead. I'm looking for foods that are intrinsically dangerous. Many foods become dangerous when spoiled, but they also become less palatable. —Keenan Pepper 17:35, 16 September 2007 (UTC)
Well, Death Cap is poisonous, it even came out in Eragon. Just out of curiosity, is it just a regular question or are these stuff meant to be put in someone's meal? --Zacharycrimsonwolf 14:09, 16 September 2007 (UTC)
Um, I don't think you understood the question. You can't eat death caps at all, if you want to live. On the other hand, fugu is served to people every day, and they are perfectly safe unless the fugu is incorrectly prepared. That's the kind of thing I'm looking for. —Keenan Pepper 17:35, 16 September 2007 (UTC)
Probably not that much help, but I do remember reading a long time ago about a type of mushroom that was perfectly edible and pleasant, unless consumed with alcohol - at which point it becomes deadly poisonous... --Kurt Shaped Box 17:43, 16 September 2007 (UTC)
That sounds like Coprinopsis atramentaria, though that one does not appear to be actually deadly. Unpleasant, however ... --Pekaje 12:25, 17 September 2007 (UTC)
Interesting - thanks. It's always good to fill the gaps in the pieces of knowledge I attained as an 8 year old... :) --Kurt Shaped Box 14:38, 17 September 2007 (UTC)
Anything from a dented tin can. TenOfAllTrades(talk) 14:14, 16 September 2007 (UTC)
Again, that's not an intrinsically dangerous food, just spoilage. —Keenan Pepper 17:35, 16 September 2007 (UTC)
Hmmm. Steak tartare? Probably not deadly but I know that you *can* get sick off it... --Kurt Shaped Box 17:38, 16 September 2007 (UTC)
Good, that's much closer to what I'm looking for. I had never heard of a dish containing raw beef before. —Keenan Pepper 17:55, 16 September 2007 (UTC)
I had some once (without knowing exactly what it was). It was actually quite nice. As I understand it, it's pretty safe it it's prepared with carefully-selected, properly-stored-and-handled muscle meat. --Kurt Shaped Box 18:02, 16 September 2007 (UTC)
Eating the liver of a polar bear will actually cause you to OD on Vitamin A, although polar bear livers are large enough that they can be easily removed without leaving too many traces (unlike the poisonous parts of fugu). Potatoes are also poisonous if you forget to cook them (they contain glycoalkaloids, especially if you eat wild or over-ripe ones). Laïka 19:33, 16 September 2007 (UTC)
Oh yes, and bitter almonds contain hydrogen cyanide, which must be thoroughly removed before eating. Laïka 19:35, 16 September 2007 (UTC)
Note that the toxins in potatoes are less from aging than from exposure to sunlight, and that cooking does not necessarily inactivate them. See solanine, and always peel all the green bits off your spuds. --Sean 14:12, 17 September 2007 (UTC)
Frankg said eating beef with mad cow disease is bad. To my knowledge there is no proven connection between it and the similar disease that infects humans. Laïka said raw patatoes are poisonous. I've eaten them many times before and I don't think I ever got sick soon after. What's this for? Are you writing a story? Are you just curious? — Daniel 20:07, 16 September 2007 (UTC)
Variant Creutzfeldt-Jakob disease has been linked to eating nerve tissue from cattle infected with Mad Cow (which was caused by Scrapie prions the cows got from eating meal made from leftover sheep parts). -- Kesh —Preceding signed but undated comment was added at 20:31, 16 September 2007 (UTC)
The Spanish Blood Donation Service declined my offer on the grounds that I am English and had eaten British beef during the 90s, so they think there's a connection. Richard Avery 21:56, 16 September 2007 (UTC)
Ditto for the US Blood donation folks. Proving a causal link is very tricky indeed. However, the incidence of CJD in the UK spiked at exactly the time you'd expect from the incubation period starting at the time when BSE became prevelant. CJD and BSE are more or less identical diseases. Whilst this doesn't prove a link - it's enough to warrant a strong reaction and in my mind it shifts the onus from "prove that CJD is caused by BSE" to "prove that it isn't" - and there is no proof of the latter. SteveBaker 14:12, 18 September 2007 (UTC)
Humans ... not sure about the 'delicious' part though. --Duk 20:48, 16 September 2007 (UTC)
Pork, if not sufficiently cooked, can give you trichinosis. (In the US, this is less of a danger than it used to be.) Cardamon 03:50, 17 September 2007 (UTC)
Which might be part of the reasoning behind prohibiting the eating of pigs in the old testament. Which reminds me of an anecdote I read in Time about a famous Jewish scholar at a religious conference, waiting in line, who got frustrated and called out "I hope you all get trichinosis and come to believe in the god of Moses", wherin someone replied, "And if we don't get such diseases, will you believe in the god of Jesus?". Ah, witty religious scholars... (the article was about his book and how the Pope actually cared enough to write a rebuttal) Kuronue | Talk 23:01, 21 September 2007 (UTC)
Nutmeg in large quantity, if you consider it delicious. --antilivedT | C | G 04:40, 17 September 2007 (UTC)
Brain (as mentioned by Duk) is an interesting food stuff. It doesn't have much taste, but the texture is quite interesting. But as the article points out, there are some risks involved. DirkvdM 08:27, 17 September 2007 (UTC)
Nardoo accroding to this and this. Here is more information on Nardoo. Cardamon 09:22, 17 September 2007 (UTC)
Honey that is just fine for everyone else can be deadly to infants due to botulinum spores. --Sean 14:16, 17 September 2007 (UTC)
Condensed milk is supposed to be A Bad Thing to give to babies. I'm not sure why - but it tells you not to do so on the side of the tins. --Kurt Shaped Box 14:37, 17 September 2007 (UTC)

Chickpeas contain varying levels of antinutrients and can be dangerous in large quantities.

Atlant 14:28, 17 September 2007 (UTC)

Water will kill you if you drink enough of it. (Water intoxication) SteveBaker 14:54, 17 September 2007 (UTC)
Won't just about every single substance in existence kill you if you consume enough of it? --Kurt Shaped Box 15:04, 17 September 2007 (UTC)
Mr Creosote would be the best authority on that. "One little tiny wafer-thin mint..."
Atlant 18:15, 17 September 2007 (UTC)

KP, are you writing a murder mystery? —Tamfang 01:14, 18 September 2007 (UTC)

While I can't answer the specific question, you might want to take a look at the somewhat similar question related to toxic foods a few weeks back. From memory amongst the things mentioned where tapioca (cassava), cashew nuts, bamboo shoots and various stuff containing Oxalic acid. Of these, the only one that may come close to a level of concern of something like fugu is probably tapioca. If we are speaking of specific people here, obviously you should consider allegies. Even a peanut shell could be deadly to someone who is severely allergic. There are of course various interactions e.g. grapefruit and some other fruit could be deadly to someone on certain medications as they inhibit the cytochrome P450 isoform CYP3A4 (which is also essential for the metabolism of these drugs and therefore you end up with a much higher level then you are supposed to have). There are also various other stuff relating to people with various conditions and a variety of food you could probably pick up from case reports in medical journals. E.g. someone who ended up with a potassium overdose from eating durian (I don't know but I suspect durian would be on a list of forbidden food for someone with a low potassium diet in SEA) Nil Einne 19:06, 18 September 2007 (UTC)

Chaya leaves are poisonous until cooked. Cardamon 09:12, 19 September 2007 (UTC)

ackee fruit. - Nunh-huh 21:25, 20 September 2007 (UTC)

[edit] Fusing vertebrae

When do vertebrae stop fusing in humans? ←BenB4 13:26, 16 September 2007 (UTC)

Well, I'm not sure I understand the question entirely. It is my understanding that vertebrae do not normally fuse in humans, except in abnormal circumstances. If vertebrae fused together - one to another - I assume that's what you mean, the spine would lose its flexibilty. There are a group of fused vertebrae at the lower end of the spine they are called the sacrum and they form the posterior part of the pelvic girdle, they show no flexibilty in adulthood although they are not completely fused in the prepuberty period. There is a pathological condition called ankylosing spondylitis(have a look) which causes the vertebrae to fuse together and this results in considerable mobility problems for sufferers.Richard Avery 21:50, 16 September 2007 (UTC)

Vertabrae#Sacral says those are "fused in maturity" but there is nothing in the ssociated article -- when do the sacral vertebrae usually fuse? ←BenB4 02:51, 17 September 2007 (UTC)
Uh, huh, I see what you mean. From my meagre knowledge of a twenty year nursing career I reckon they fuse at about the same time as the shafts of the long bones fuse with their extremities. This happens during puberty and a little after. It's a variable proces, depending on each individual. I think it is unlikely that there is much separation between the sacral bones in infancy, the spaces may show on a radiograph, but for general physical examination they would feel solid. Richard Avery 21:49, 17 September 2007 (UTC)

[edit] Re:The Sun and Moon

How does the Sun's gravity make stuff orbit around it? I only have a rough metaphor (made by me) for the phenomeneon, but I don't really understand it. Also, are there any pictures of the Moon's orbit around Earth? My sister asked me a question about the phase of the Moon and I need it to answer her. Zacharycrimsonwolf 14:06, 16 September 2007 (UTC)

Have you seen Orbit#Understanding orbits and Lunar phase#Names of lunar phases? --Wirbelwindヴィルヴェルヴィント (talk) 15:45, 16 September 2007 (UTC)
For the "how", are you starting from "gravity exists and pulls objects towards each other", or something else? If you start from there, then the link above to the Orbit article should be a reasonable explanation. Otherwise, you're looking at a slightly more complicated explanation. Confusing Manifestation 12:43, 17 September 2007 (UTC)
How gravity makes things orbit? Well, normally, an object (let's say a space ship) in deep space with no stars or planets nearby will travel in a straight line at constant speed (no friction) forever. When it's near a star (or a planet or something big and heavy like that), gravity will pull the spaceship towards the star. Now - imagine if the spaceship was already moving at right angles to the line between it and the star. It's tendancy to go in a straight line (in the absence of gravity) would make it gradually move further from the star. Now, if (by a amazing coincidence) the distance it would normally move away from the star in one second were EXACTLY equal to the amount it would fall towards the star in one second because of the gravity - then it would end up staying the exact same distance from the star...moving around it in a perfect circle forever. That's a perfect circular orbit. Now, it turns out that if things aren't exactly right for a circular orbit (for example if the gravity were a bit stronger or the spaceship were moving a bit slower) then you get an elliptical orbit...but the exact "why" of that is hard to explain in words without resorting to a lot of math.
The phases of the moon are something different. The moon moves in a roughly circular path around the earth - and the sun is a very long way away with the earth going around the sun in a roughly circular path with the moon constantly looping around it. The resulting path of the moon around the sun looks like a spirograph pattern. What this means is that as we watch the moon from the earth, the moon is being lit by the sun from all sorts of different directions - sometimes, the sun is on the opposite side of the earth from the moon - and the whole of the 'front' of the moon is lit up. Other times the sun is off to one side of the earth as the moon is overhead and the side of the moon nearest the sun is lit up. As the position of moon goes through this 'spirograph' pattern the relative position of sun, moon and earth changes gradually over a month or so and the moon is lit first from 'behind' (the moon looks dark because only the far side is lit), then from one side (a 'new' moon), then from in front (a 'full' moon), then from the other side (a 'waning' moon) and then from the back again. SteveBaker 14:46, 17 September 2007 (UTC)
Quibble: The Moon's path is always concave toward the Sun, because the Sun's gravity at that distance is 2.5 times Earth's. I don't know if it can be drawn with standard Spirograph parts. —Tamfang 01:12, 18 September 2007 (UTC)
I know - but let's keep the complexity of the answer commensurate with the complexity of the question. Someone who needs to ask this question isn't going to understand a more complex answer than the one I gave without another page of explanation. Hence spirograph rather than epicycloid. SteveBaker 14:05, 18 September 2007 (UTC)

Many thanks all, especially to Steve. Well, since there isn't any straight explanation to the gravity question, then I'll just take what I understand. By the way, how far does the Sun's gravity go? I know comets go really far away, but they come back in an orbit aeons later. --Zacharycrimsonwolf 14:53, 20 September 2007 (UTC)

Well, strictly, gravity goes on for ever, but it gets weaker the further you go. It follows an inverse-square law, so if you go twice as far away, it's a quarter the strength, and if you go a thousand times as far away, it's a millionth of the strength. So your question doesn't really have an answer: it depends at what level you want to count it as negligible: one hundredth? one thousandth? one millionth? --ColinFine 20:14, 22 September 2007 (UTC)

[edit] Relative Age of Races

Is it true that the Negroid race is approxiamately 225,000 years, the Caucasoid race is approximately 110,000 years old and the Mongoloid race is about 40,000 years old? 4.242.18.225 14:37, 16 September 2007 (UTC)

There might be answers in our article on Race (although in an initial skim I didn't spot any). —Steve Summit (talk) 16:18, 16 September 2007 (UTC)
That doesn't really sound right to me. For one thing, it assumes a very old and now fairly discredited tripartite racial model. It also falsely assumes that the "older races" have not been differentiated at all in that time, which is not true in the slightest. That is, it sounds like a misunderstood interpretation of the recent single origin hypothesis. As an example of the falsity of this assumption, the Kennewick man, for example, looks very little like the "native" residents of that particular area that he was found in, even though very little time had passed between them. "Racial" characteristics are largely superficial and are fairly malleable as populations merge and separate. "Race" on a genetic level is a set of relatedness between various populations (at best—most of what we assign to "race" colloquially is culturally constructed mixed with a little bit of superficial biology), and are never static. --24.147.86.187 16:37, 16 September 2007 (UTC)
I have answered here: [1]. StuRat 01:29, 17 September 2007 (UTC)
Cute that you copied the question there so that you could disagree but not have people argue with you. Smooth move. Anyway, you really don't know what you are talking about, and the disparagement of the answers here as "politically correct" (and somehow tying affirmative action to that) is both insulting and intellectually dishonest. --24.147.86.187 14:40, 17 September 2007 (UTC)
You are certainly welcome to follow links to Wikiversity to leave information there. Personally I would appreciate it if you could leave your inter-personal squabbles from Wikipedia here at Wikipedia. They add little to Wikiversity. mirwin@wikiversity —Preceding unsigned comment added by 70.110.44.165 (talk) 03:45, 18 September 2007 (UTC)
I just responded there so it wouldn't be deleted by someone who disagrees. You are free to respond here, there or in both places, if you wish. I stand by my statement. StuRat 03:06, 18 September 2007 (UTC)
When you use terms such as 'Race' there are a lot of touchy concepts raised. There is no defined genetic definition of Race as is commonly used, it is simply a set of common characteristics in a population. Genetic studies have found that humans have an unusually low amount of variation between diverse populations. In fact, some studies have found that two people of the same "race" might differ, genetically, more than between two people of different "races". However, there has been speculation as to how humanity spread across the globe, and were subsequently isolated enough such that each subpopulation to develop independently, which you'll see in the Subspecies as clade section of the Race article. -- JSBillings 12:10, 17 September 2007 (UTC)

[edit] Dacryocystorhinostomy in the UK

In the UK (England, in fact), does the NHS tend towards the use of external or endoscopic dacryocystorhinostomies, or do they use both procedures in equal preference to eachother? I found a NICE document from 2005 (ish), saying that it was basically "ok" to use the endoscopic method, but I was wondering if anyone here had any experience of the same? Martinp23 16:25, 16 September 2007 (UTC)

[edit] Science blog

Hello. Could you recommend a daily science blog or news site? Someone pointed me to gizmag.com but they seem to be mainly interrested in cars and phones. Any recomendation for a general science news site? Thank you 81.242.81.35 16:30, 16 September 2007 (UTC)

Nature News —Keenan Pepper 17:38, 16 September 2007 (UTC)
http://www.sciencedaily.com/ - they are just an aggregator, but they do a great job. ←BenB4 18:01, 16 September 2007 (UTC)
http://www.scienceblogs.com - Several blogs by various scientists and academics hosted by Seed Magazine. PZ Meyers has a very good one called "Pharyngula." -- Kesh 20:54, 16 September 2007 (UTC)
Scientific American has a good blog and they cover the gamut of science & technology. — Scientizzle 15:37, 17 September 2007 (UTC)
In a similar vein, New Scientist also has several blogs [2] Nil Einne 21:25, 19 September 2007 (UTC)

[edit] Radio brightness of this or other earths

Looking at the radio rather than the visible spectrum,

1) how bright is the earth compared to stars (including the sun)? I vaguely remember hearing it would be very bright due to the great amount of radio transmision.

2) If there was another earth identical to ours in 2007, but placed near the hub of our galaxy the milky way would it stand out and be easily spotted? (So either the answer will be "no" or we are alone at least in this galaxy).

3) Would the radio spectra of earth be different in quality from stars and stand out?

4) Are there any objects in the sky which have a similar radio spectrum? (Presumably answer will be "no".)

5) How far away from earth could you be and still (if you were very clever and had unlimited resources) watch tv or listen to the radio?

80.0.135.165 18:12, 16 September 2007 (UTC)

1) Not sure. 2) and 5) I'm often told that a typical high power radio transmitter can transmit far enough that a very sensitive radio receiver could pick it up from 4 light years away (well, that's all very general isn't it, so a good deal of range depending on how good equipment you're talking about). However, if you're using this baby as your radio receiver or transmitter, that thing can reach far. Not sure how far, but easily many thousands of light years. 3) The radio spectra of the Earth would noticably different from those of any star, so informs me a planetary scientist. 4) He also tells me that no radio signals have ever been detected not-of-earth-origin that were undoubtably intelligent communication. Further, only a handful of radio signals have ever been detected that have not been explained by natural phenomena presently understood. Someguy1221 19:43, 16 September 2007 (UTC)
Also, detecting Earth from a distance would be difficult except within around 70 light-years or so. Much more than that and there'd be no radio signals from here at all. Richard B 23:04, 16 September 2007 (UTC)

Thanks for answers so far. Its the first question that particular interests me - ignoring the fact that radio started about 80 years ago, are we a bright beacon in space that would stand out in the radio spectrum sky? Perhaps this could be estimated by adding the total amount of radio and tv transmitter power and taking away the proprtion absobed by the earth. Would this be greater than the radio power of the sun? 80.3.42.129 13:53, 17 September 2007 (UTC)

No, I don't think we are a large radio beacon at all. I read someplace (I think it was on the SETI web site) that the amount of normal radio/TV/radar we humans emit is less than we could detect with our most sensitive radio telescopes at a distance of 4 lightyears (the distance to the nearest star). So it's very, very feeble indeed. The thing with radio waves is that their energy decreases as the square of the distance. Remember that your local radio or TV station starts to fade out at maybe 100 miles from the source - at 200 miles, it would be 1/4th as loud, at 400 miles, 1/16th as loud, at 800 miles, 1/256th as loud...at 4 light years...it's too feint to detect, even with our most sensitive devices. This is one of the problems with SETI (looking for alien civilisations by listening for their radio transmissions) - it's only going to work if the aliens have some INSANELY powerful radio transmitters. So it would take aliens quite close by (cosmologically speaking) with much more advanced radio telescopes than we have to be picking up "I love Lucy" (1951) out at 50 lightyears. SteveBaker 14:26, 17 September 2007 (UTC)
And of course, we point our power towards earth-bound receivers using directional antennas and the skywave effect. The vast majority of our transmitted radio frequency signals never leave our planet. Nimur 01:04, 18 September 2007 (UTC)

So nobody knows the answer to 1). ;-( 80.0.122.151 21:39, 18 September 2007 (UTC)

Nope, but I can look it up. ;-) The problem is, "radio" is a big place. It covers a lot of frequencies, and you can look either at broad-band emission, or narrow lines. Here are a few references to start you off. Check out figure 1 of Man-made radio noise: Part I [3] It's on page 23. You can find the definition of Fa in the introduction. This shows man-made radio noise in various environments is comparable to the galactic center around 10-200 MHz. The galactic center's radio emission is strongest around 1-104 GHz [4], at about 1 Jansky. The sun is much louder, about 105-107 Janskys in the range 1-1000 GHz. (Be careful about comparing spectra in Fa with spectra in Janskys, I think there must be a factor of λ2 to give a different frequency dependence). Remember that all of these are as seen from earth. I conclude that the Sun and the galactic center are intrinsically *much louder* above 10 MHz or so, and probably at lower frequencies too. However, man-made radio signals aren't a continuous spectrum. I believe it is true that the Earth outshines the sun at certain radio frequencies, and that you could see these from ~a few light years away. As far as I can tell, you would not see the Earth next to the galactic center. --Reuben 23:14, 18 September 2007 (UTC)

[edit] The colour of Light

Further to the above question on 'Green', I am a bit confused about all this colour being to do with light waves that are reflected. If I was to switch on a red lamp, surely it is giving red light off, not absorbing green and blue light inwardly and reflecting magenta out? How does this work? Is it something to do with the red glass absorbing the green and blue light energy? --russ 19:07, 16 September 2007 (UTC)

Precisely. Red glass only permits red light to pass through (for visible light, anyway). Other colors are absorbed. However, you can have a light emitting diode or a laser that only emits one color (a narrow band of wavelengths). An important distinction from the above question is that the lamp is generating its own light, and not simply reflecting light from another source. Someguy1221 19:26, 16 September 2007 (UTC)
Also, neon lamps emit an orange light, and many other types of lights emit a characteristic color. StuRat 23:08, 16 September 2007 (UTC)
What's the colour of love? —Bromskloss 19:28, 16 September 2007 (UTC)
You can have a red lamp - that emits red light. If you look directly at the lamp, it looks red because it's EMITTING red light. But things that are not light sources (a table or something) are only visible by the light they reflect. When you see objects illuminated by that light, you see the light reflected by that object. White light (which is the normal thing we experience - from the sun or 'white' lamps) contains all of the colours. When lit by white light, the colours of objects depends on the colours they reflect. A green object reflects green light and absorbs everything else - so we see green light reflected off of it. However, if you were to view the world in light from a red lamp, the green object would absorb the red light and reflect...nothing...there is no green light there to reflect. So a green object will look black when lit with red light. In actual fact, it's rare for a green surface to literally only reflect green light - it'll usually reflect a little red and blue also...but nowhere near as much as it does green. So when you actually use a red light, green objects will just be very dark - not literally black. If you go out at night into a street that's lit with orange 'sodium' lights, you'll see that everything is in shades of orange depending on how much orange light they reflect. Some objects that are really bright colours in daylight will look very dark indeed if they aren't reflecting orange light. SteveBaker 14:14, 17 September 2007 (UTC)

[edit] And Energy, too

At school, we were always told that energy took several different forms: potential, kinetic, light, sound, nuclear and so on. My question is that if light has something to do with moving photons, sound to do with moving atoms bouncing on the eardrum, nuclear to do with emitted particles and so on then surely they are varieties of kinetic energy and not forms in their own right? Furthermore, if you are deaf, then does sound energy exist? If there are other forms of energy that our senses are not able to detect then how would we ever know to look for them? russ 19:13, 16 September 2007 (UTC)

Sound energy (the energy stored in sound waves, which is really just the kinetic and elecrostatic potential energy of the particles carrying the wave) exists whether or not you can sense it. Further, there are forms of energy we are incapable of sensing on our own. Nuclear energy was unknown until the discovery of radioactive materials, and not understood until quantum mechanics existed. Gravitational waves carry energy, but were themselves unknown to exist until the theory of relativity. However, scientists still came up with ways to try to detect them, and might actually succeed one day. Someguy1221 19:35, 16 September 2007 (UTC)
(edit conflict) Nuclear energy is a form of potential energy. Other than that, all of your examples are forms of kinetic energy (although I think it might be arguable with light). Every particle is energy, although only massless ones (such as photons) can be considered kinetic energy. Sound energy exists whether or not you can hear it. People can't detect most forms of energy directly. One way to know to look for a form of energy is if the energy in a system doesn't appear to be constant, such as the sun radiating more energy than can be explained by chemical energy (this was noticed before nuclear energy was discovered). — Daniel 19:44, 16 September 2007 (UTC)
Sound waves can be detected by the deaf. Low frequency waves can be felt as vibrations and higher frequencies will cause waves to form on water. And, of course, they can see the volume meter move on an amplifier. So, there are other forms of energy (like dark energy) which are much harder to detect than sound is for the deaf. StuRat 22:18, 16 September 2007 (UTC)
Sound is just vibrations. The vibrations are there whether you are deaf or not - and deaf people can still feel very low frequency sounds vibrating in their stomaches or if their fingertips are resting lightly on a flexible surface...just like hearing people can. So the energy is still there - even if it's not being heard. SteveBaker 14:16, 17 September 2007 (UTC)
If you're technical enough about it, thermal energy in opaque electrical insulators tends to travel as sound, as well. It's inaudible, but it heats up your skin, which allows you to sense this form of energy indirectly. Of course, it's indistinguishable from heat energy which has traveled as light or as diffusing electrons. Also note that sound is quantized; a particle of sound is called, unsurprisingly, a phonon. —Preceding unsigned comment added by 128.115.27.10 (talk) 17:56, 17 September 2007 (UTC)

[edit] Ozone effects

If the ozone layer disappeared, would blacks have a better chance of surviving than whites? I remember hearing somewhere that white people have a higher chance of UV poisoning.--130.126.67.144 21:33, 16 September 2007 (UTC)

If I recall correctly, blacks have an almost-nil incidence of skin cancer, so yes, I would think that might be the case. Vranak 21:56, 16 September 2007 (UTC)
  • This document says whites have about 10 times the chance as blacks of getting melanoma, so not quite nil, but still a pretty good adaptation for spending time in Africa. --Sean 14:26, 17 September 2007 (UTC)
But don't forget that sunscreen exists. This would mean that those living in poverty (who couldn't afford it) would likely fare worse. StuRat 22:11, 16 September 2007 (UTC)
And also don't forget those living within a couple thousand miles of the poles; not much sunlight reaches there anyway, comparitively. Someguy1221 23:08, 16 September 2007 (UTC)
See this about biological effects. If the ozone layer disappeared completely, there could be a breakdown in the entire foodweb, and getting skin cancer may be the least of our worries while we starve to death. --jjron 07:09, 17 September 2007 (UTC)

[edit] Diagram

Do you know of any scientific diagram shaped roughly like some kind of bird, perhaps a bat? Would probably be named after the man who invented it. Thanks. —Preceding unsigned comment added by 88.111.107.4 (talk) 21:51, 16 September 2007 (UTC)

Rorschach inkblot test? -Arch dude 22:50, 16 September 2007 (UTC)
Penguin diagram? Half on the ball :-) Someguy1221 23:07, 16 September 2007 (UTC)
Butterfly diagram? Relates to Fast Fourier transforms. SteveBaker 14:00, 17 September 2007 (UTC)
Smith chart? The diagram itself is circular, but the patterns inside always struck me as sort of Thunderbird-like. Saturn 5 20:44, 20 September 2007 (UTC)