Wikipedia:Reference desk/Archives/Science/2007 April 26

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.

April 26

Rainfall measurements

I'm tasked with making sense of the following: "Arica, Chile receives an average of .03 inches of rain per year. At that rate, it would take 100 years to fill a cup of coffee." But if rainfall is measured as a depth and not as a volume, how could the author of this fact arrive at this conclusion? Wolfgangus 04:04, 26 April 2007 (UTC) Z

Simple: the author is making an assumption, not only about the size, but about the shape of the coffee cup. --Anonymous, April 26, 2007, 04:16 (UTC).

I'm untrained in meteorology except for coverage on the Mr. Wizard TV show, but I understand that an inch of rain is literally one inch per square inch; in other words, it is depth. Mr. Wizard demonstrated making a rain gauge with an olive jar, which was a tall cylinder, with a larger funnel directing the rain into it. Thus by comparing the areas of the cylindrical tube and the funnel, the sensitivity was increased, as is done in some government weather gauges. A simpler rain gauge is a cylinder without the larger funnel. On the rainiest day I ever say, such a gauge collected 9 inches of rain and there was widespread flooding. I measured the nearest coffee cup, and the interior can be approximated by a cylinder 3.5 inches tall (I like a big cup of coffee). The diameter is irrelevant. At .03 inches per year in the location given, this cup would require 3.5/.03=116.7 years to fill if exposed to rainfall in that arid area and if evaporation were somehow prevented. The author must have a slightly shorter coffee cup. Edison 04:28, 26 April 2007 (UTC)

To clarify slightly, "one inch of rain" means one inch depth over any relevant (but local to the rain) surface area, not simply one inch per square inch ("inch per square inch" would also wreck your units). You are entirely correct about the relevance of the ratio of entrance plane surface area to measurement plane surface area, however. — Lomn 14:34, 26 April 2007 (UTC)

Then the author's original assumption is of a cylinder 3 inches tall. Got it. Thanks so much.Wolfgangus 04:40, 26 April 2007 (UTC)

How about "one inch of rain=one inch depth=one cubic inch of rain per square inch of area" to preserve the units? Thanks. Edison 15:55, 26 April 2007 (UTC)

Correct. --Anon, April 26, 2007, 23:15 (UTC).

There was a question not so long back similar to this one. It was pointed out that rainfall was always measured with a unit of length and not area or volume because of the following facts: In order to find the rainfall, you need to know the volume of water that has fallen (e.g. cm³), however, you also need to know over what area it fell (e.g. cm²). You then need to divide the volume by the area in order to find the concentration (more properly called the rainfall), giving you units like, for example: cm³/cm² = cm¹ or just cm. For more information, I suggest you take a look at the page on Dimensional analysis. --80.229.152.246 16:46, 26 April 2007 (UTC)

You can divide volume by area as described here, but you don't need to if you have a measurement of the depth of water in a rain gauge as described above. --Anon, April 26, 2007, 23:15 (UTC).

Yeah, but to increase sensitivity, the collecting area is usually way larger than the collection cylinder. 10 inches in the cylinder might equal 1 inch of rain if the funnel has 10 times the area. Edison 05:08, 27 April 2007 (UTC)

Gliese 581 and interstellar travel

Gliese 581 is said to be the first potentially habitable planet discovered. How much acceleration would be required from an ion engine to reach Gliese 581 in 200 years (assuming 100 years of acceleration and 100 years of deceleration if it is 20 light years away? I ran the numbers and it gets to a sufficient speed that relativistic effects intrude, so assume 200 Earth years (not spaceprobe years). How far beyond today's technology would such a spaceprobe be, given Deep Space 1 and Dawn Mission and the older technology of Voyager program and New Horizons, the latter two of which are destined for interstellar space? Edison 04:42, 26 April 2007 (UTC)

I can't give you all the technical details, but please note that Voyager was not designed to travel to a nearby star, and that even with 1970s technology and about the same budget, it would have been possible to target a spacecraft with a much faster speed out of the solar system.--Pharos 06:13, 26 April 2007 (UTC)

This problem does not actually yield significant errors with Newtonian mechanics: to reach a distance $d=10{\mbox{ ly}}$ from rest in time $t=100{\mbox{ y}}$, an acceleration $a={\frac {2d}{t^{2}}}=1.9{\frac {\mbox{cm}}{{\mbox{s}}^{2}}}$ is required, and the top speed is $v=at=0.2c$. To do it relativistically, see hyperbolic motion. Unfortunately, what we know is $x|_{t=10{\text{ ly}}}-x|_{t=0}=d-{\frac {c^{2}}{\alpha }}$ (where t's final value is unaltered because it is Earth time), so we must substitute $x=d+{\frac {c^{2}}{\alpha }}$ and get $\alpha ={\frac {2dc^{2}}{c^{2}t^{2}-d^{2}}}=1.92{\frac {\mbox{cm}}{{\mbox{s}}^{2}}}$ (slightly more than the Newtonian answer because we have less than 100 proper years in which to do the acceleration). However, because of the velocity addition going on, the top speed is actually lower: differentiating gives us $2xu-2c^{2}t=0$ or $u={\frac {c^{2}t}{x}}=0.198c$. I'm not enough of a space nerd to address the practicality of such a trip, but hopefully having the correct numbers will help. --Tardis 15:00, 26 April 2007 (UTC)

Thanks much. The acceleration required would thus be (.0192 meters/second^2)/9.8 meters/second^2)=.00196 G. Present Ion engines can produce .0098 m/sec^2 of acceleration for prolonged periods, about half that required for the hypothetical 200 year trip. In the Dawn Mission several engines wiill be used in sequence, for about 1 year each. I will post your reply in the talk page of the Gliese 581 c article, where there is an active debate about whether it is possible to send a probe to that planet. It looks like we are closer in 2007 to the capability to send a probe to a star 20 light years away than we were in say 1945 to be able to scale up V-2 rocket technology to reach the moon in 1969. We sent Pioneer 10 and 11 and Voyager 1 and 2 off into interstellar space. The latter 2 are still functioning and sending back data 30 years after launch. Other propulsion technologies should offer good prospects. One question is how wise it would be to run the risk of contact with extraterrestrials, should there be any at the target star, say 200 years from now, given the history of conquistadors on earth. Voyager 1 and 2 were in fact designed to reach several planets quickly, and a necessary and obvious consequence of its itinerary was that they reached escape velocity and are even now speeding into interstellar space, with Voyager 1 at 38,400 miles per hour relative to the Sun. However "message in a bottle" the prospect may be, it does carry messages to extraterrestrials in the form of Voyager Golden Record. In 40,000 years Voyager 1 will be within 1.7 light years of the star AC+793888 in the Camelopardis constellation. It might drift for millions of years, it might hit space junk and vaporize, it might be captured by some unknown planet of some unspecified star, or it might be brought back by our distant descendants and exhibited in the Smithsonian Air and Space Museum, since we have pretty good on its trajectory. Edison 15:05,

26 April 2007 (UTC)

The problem with an ion engine is, that it needs a lot of energy to work. You essentially have two options realized in current spacecraft technology: Solar panels and RTGs. Solar panels have a pathetic yield in interstellar space due to the low light influx and RTGs loose their power output with travel time because of decay. Current RTGs use Plutonium, which has a half life of about 80 years. So you need to factor in a power decay to by about 85% over 200 years. Maybe. Interesting Idea. —The preceding unsigned comment was added by 84.187.49.35 (talk) 17:33, 26 April 2007 (UTC).

What nuclear power source would maintain a more constant output over 200 years? How about 400 years? Edison 05:06, 27 April 2007 (UTC)

I would think you would actually want your nuclear power source to largely decay over the length of the mission, as that means you would get the most total energy out of it. If you select an energy source with a half-life which is the length of the mission, that means you only use half of the energy. If you have the ability to separate and eject the reaction products, that would also help by lowering the mass of the ship. StuRat 17:10, 28 April 2007 (UTC)

So what would be a suitable 200 year fuel, with a longer half-life than plutonium, which seems suitable to power Voyager 1 and 2 for 50 years or so? Edison 06:29, 29 April 2007 (UTC)

Torque horsepower, other concepts

Is it possible to reckon the torque of an engine if given horsepower and RPM? If not, what is required and what are the formulas? —The preceding unsigned comment was added by 69.178.134.34 (talk) 04:59, 26 April 2007 (UTC).

HP=T*RPM/5252 in your antiquated units. Greglocock 08:33, 26 April 2007 (UTC)

Thanks for ponying up that answer. StuRat 04:37, 27 April 2007 (UTC)

Antiquated? I take it that's in Foot-Pounds? And how is a Newton meter different from a regular meter? Wasn't the metric system supposed to standardize all that? And the antiquated system is necessary for marketing. 454 cubic inches, 454 ft-lbs of torque and 454 horsepower. Try doing that with metric.  :) --Tbeatty 05:14, 27 April 2007 (UTC)

A newton metre is not a type of metre, but a unit made by multiplying a newton by a metre (just like the foot-pound is made by multiplying a pound-force by a foot). If the SI system gave a name to every single derived unit, it would be a very big system indeed! Laïka 15:18, 27 April 2007 (UTC)

But, of course, the Newton is itself a derived unit, a kilogram meter per second squared, I believe. StuRat 16:58, 28 April 2007 (UTC)

Christopher Lloyd's DeLorean

I don't know if this question should go on the science or entertainment desk, but one thing that's always bothered me about the Back to the Future films is how convenient it was that the mall parking lot was a flat farm field in 1955. What if it had been wooded? Would the car have blown up?

Yes, I know it's just a science-fiction movie. But I also know that the possibility of time travel into the past has not been completely ruled out. Our article on time travel gives several possible ways people could travel into the past (closed time-like curves, traversable wormholes, Roman rings, Tipler cylinders, etc.), none of which I understand. So let's say it is possible to travel back in time. What happens if the space you are occupying was occupied by something else in the past? -- Mwalcoff 05:08, 26 April 2007 (UTC)

Two things: you wanted to appear at the coordinates in space and time, then your atoms would appear exactly where they should. I don't see why they wouldn't just overlap. Even in a compound, it's almost entirely empty space. And wait a second, it isn't as if there wasn't anything there when the DeLorean appeared! There was most certainly air and dust and the farm field there. [Mαc Δαvιs] ❖ 05:27, 26 April 2007 (UTC)

For the record, I believe that originally the field was known as Twin Pines, and his DeLorean knocked a tree down on entry; consequently, when he returns to the 'future', it's known as something like Lone Pine. Wolfgangus 05:30, 26 April 2007 (UTC)

These movies just don't stand up to the rigors of scientific enquiry. The problem with a time machine that put you at exactly the same point in space - but sometime in the past or future is that the earth will have moved on its orbit in the meantime - so that you'll likely materialise a few million miles out into space. Hence, in truth, to be useful this machine would have to be able to put you somewhere different in space as well as moving you in time - so you wouldn't need to risk appearing at some inconvenient location. But if something nasty happens if you did happen to materialise in the middle of a solid object because of molecules at the same locations, etc - then the molecules in the air would be a major cause of problems. Then there is the question of how the time machines 'knows' how much stuff to push around in time/space. The wheels don't get left behind - but what about the road just beneath the wheels? SteveBaker 06:04, 26 April 2007 (UTC)

Suspend disbelief my friends and charge the flux capacitor.

Atlant 12:28, 26 April 2007 (UTC)

• In particular, there's no such thing as the "same point in space": it's all relative, y'know? So for fiction purposes we can simply assume that the point of reappearance is the same one in a reference frame that reflects the Earth's motion and gravity. --Anonymous, April 26, 2007, 23:28 (UTC).

Don't forget the plutonium required to deliver the necessary 1.21 jigawatts of power! It's allright though, if you're out you can use your prior knowledge of a lightning strike to precisely time the DeLorean's acceleration to contact a cable for the few hundred milliseconds or so that the bolt strikes... Even if your PRV engine dies and you're late by a few seconds... Ah, Hollywood. -- mattb 22:40, 26 April 2007 (UTC)

This plot point is particularly weak because the newspaper article only reported the time of the lightning bolt to the nearest minute. What the screenwriters needed to do was say that in 1955 Hill Valley had a streetcar system. Doc Brown could disconnect a section of overhead wire from the system and connect it to the clock tower, and fit the pole on the DeLorean with a trolley wheel. Simple and obvious! (Didn't they ever see Who Framed Roger Rabbit? Oh wait, they'd've had to go three years into the future for that.) --Anon, April 26, 2007, 23:283 (UTC).

im a major fan of this movie. if you noticed in the begining before marty went back in time, he asked how he knows he wont run into something in the past, he said cause it was all farm. in other words he did research on the place before he decided to go there. =) anyways as wolfgangus stated he did run into something it was a scarecrow then a barn(then from running away from the owner, a pine) now i know this isnt what you wanted to hear but it clarifies why he didnt run into a forest. the samething happend in part 3. really in order to travel back in time a person has to do reasearch on that area before they travel. it would be foolish if they didnt. User:Maverick423 If It Looks Good Nuke It 13:51, 26 April 2007 (UTC)

Alternatively, you could use the Novikov self-consistency principle, which says that the probability of an event can change to prevent a time parodox. Since a car occupying the same space-time as a tree would be a strange occurrence indeed and probably cause a major explosion (even merely occupying the same space as some air and dust could cause catastrophic damage to the electronics), which, since car is nuclear powered, would result in a massive nuclear disaster. Such an event would easily change the course of history quite dramatically, violating the principle. Therefore, no matter how improbable, the car just happened to arrive in an area of space containing a DeLorean-shaped vacuum. Of course, this probably wouldn't work in BTTF's universe (BTTF takes place in a Type 2.2 universe, where the timeline is easy to change; the Novikov principle only works in Type 1 and 3 universes). —The preceding unsigned comment was added by Smurrayinchester (talk • contribs) 17:16, 26 April 2007 (UTC).

Tuber or corm?

Does Equisetum have tubers or corms? In Equisetum palustre, I wrote "tuber" because that's the word used in Equisetum diffusum. On second thought, it seems that "corm" is correct. Does it need to be changed in both articles? — Sebastian 05:15, 26 April 2007 (UTC)

airborne radio direction finder

list the merits and demerits of airborne radio detection finding at medium,high and very high frequencies?please help —The preceding unsigned comment was added by Ambuj0542 (talk • contribs) 06:33, 26 April 2007 (UTC).

We don't do homework. And if you'll look back a week or two in the Reference Desk archives, you'll find a very similar question.

Atlant 12:31, 26 April 2007 (UTC)

At least not with great frequency. Clarityfiend 16:44, 26 April 2007 (UTC)

"We don't do homework...." not even our own homework : ) Nimur 05:14, 27 April 2007 (UTC)

well area of influence

What is the radius of influence of a residential well with and without irrigation in sandy soil. ( 5 gpm without and 20 gpm with) What is the name of the formula that would be used to calculate it? I would like to see the calculations. If the Theis Equation can be used without field data that would be OK. Otherwise any normally used formula. —The preceding unsigned comment was added by Bonanza77 (talk • contribs) 06:57, 26 April 2007 (UTC).

Acne!

Hi people, I understand that this is not exactly a health help page but i am curious to hear any and everyones suggestions as to what is the best cure for acne. Suggestions ranging form natural to nuclear will be greatly appreciated. Thanks so much

Acne vulgaris#Treatments is pretty comprehensive. Rockpocket 07:03, 26 April 2007 (UTC)

I find Paula Begoun's website very helpful for skincare problems. Here's a list of her articles giving advice about skincare. Here's one about acne specifically. Paula Begoun is a consumer advocate who researches the cosmetics industry. She has her own brand of skincare products as well, but her website isn't just advertising; she gives general advice that will help you pick out products that will do what you want, and avoid the ones that could cause problems for skin. (I do use the Paula's Choice products and I really like them, though I don't have acne myself.) Finally, Makeup Alley is a website that has reviews for all kinds of body products, not just makeup. Don't be put off by the name - it might look a bit frivolous but the advice is sound and it's helped me discover some really good products. --Grace 11:47, 26 April 2007 (UTC)

The best cure for acne depends a lot on the severity and persistence of the acne. I was treated with Isotretinoin as a teenager, which probably would score in as "nuclear" on your scale. —The preceding unsigned comment was added by 84.187.49.35 (talk) 16:45, 26 April 2007 (UTC).

This is just my observation, but whenever I eat trans-fats, I get acne, and when I don't eat them, I don't have acne. KFC is the worst offender in selling trans-fat filled foods, so I'd avoid them entirely, but all fast foods are a risk. I'd check out the labels on foods you buy (if you're in the US, anyway, as they aren't listed in many other countries). Go to web sites for other fast food places and check out their nutritional info for trans-fats. StuRat 04:29, 27 April 2007 (UTC)

Aging generally cures acne. And it's all natural. --Tbeatty 06:12, 27 April 2007 (UTC)

Multiple pivots

Was in the bus looking at the metal bar people use to hold on to while standing, could anyone point me to a good resourse to learn how to calculate the forces and the moments experienced by the structure?Bastard Soap 10:15, 26 April 2007 (UTC)

You might want to see Four bar linkage.

Atlant 12:33, 26 April 2007 (UTC)

Zinc amino acid chelate

I was looking at zinc supplements in the store today. One brand says on the label that it contains zinc amino acid chelate 125 mg, equivalent to zinc 25 mg. Another brand contains zinc amino acid chelate 220 mg, equivalent to zinc 22 mg. First of all, why are the proportions different in those figures - are there different kinds of zinc amino acid chelate? Also, do you have any idea why the second brand might have been 2.5 times the price of the first? Thanks in advance. --Grace 11:12, 26 April 2007 (UTC)

• Unfortunately our article on Zinc proteinate is a somewhat neglected stub, so you won't find much there, perhaps some of the external links might be useful? As far as the difference in price, I wouldn't attribute that to the chemical composition at all, rather to the various marketing strategies of the different companies --VectorPotential^Talk 11:21, 26 April 2007 (UTC)

The use of different amino acids would lead to varying zinc content. --Stone 13:16, 26 April 2007 (UTC)

Human studies seem to be very limited. "A number of zinc supplements are available, including zinc acetate, zinc gluconate, zinc picolinate, and zinc sulfate. Zinc picolinate has been promoted as a more absorbable form of zinc, but there is little data to support this idea in humans. Limited work in animals suggests that increased intestinal absorption of zinc picolinate may be offset by increased elimination (source). See also
--JWSchmidt 15:43, 26 April 2007 (UTC)

Before deciding whether and how to take supplements of anything, please consider that almost anything becomes harmful if taken in excess. Regarding zinc specifically, see Zinc#Zinc_toxicity. --mglg_(talk) 16:38, 26 April 2007 (UTC)

How to spend a trillion dollars

The U.S. has spent almost a trillion dollars on wars in the middle east since 911 [1]. How much could we reduce our dependency on foreign oil if that money had been spent in other ways?

For example - incentives to install alternative energy, manufacture electric cars, design competitions for industry that have huge lotteries (you bring a 70mpg car to market, you get a billion). Could a 100 billion in incentives spur a trillion dollars worth of solar and wind farm installations? Any analyses out there like this already? Thanks PatriotSurvivor 18:11, 26 April 2007 (UTC)

The costs of ITER are only 10 billions and if successfull could solve our energy problems for the next few thousand years. 84.160.254.114 20:43, 26 April 2007 (UTC)

Oil is used for car fuel. Fusion reactors produce electrical power. Cars seldom run on electric energy. —The preceding unsigned comment was added by 84.187.65.189 (talk) 21:17, 26 April 2007 (UTC).

No point. With enough cheap electrical power you can crack and distill oil from any organic wastes. (See Syngas et al.) 84.160.254.114 21:45, 26 April 2007 (UTC)

ITER is still very much an experimental (though at massive scale) reactor. It is hoped that it will facilitate development of technologies that enable wide scale fusion power generation, but the feasibility of this is still at least a generation behind ITER (their website estimates the earliest date at 2050 [2]). You can understand skepticism at dumping enormous amounts of money into a technology that is at least half a century away from being a viable energy source.

It's a generation behind only with their current funding, the more money you have, the less time you can spend doing things.Bastard Soap 00:21, 28 April 2007 (UTC)

There are plenty of viable alternatives that exist right now; I'm thinking of ethanol (look at Brazil) and photovoltaics. PV is theoretically roughly cost competitive with fossil fuel now, but unfortunately we have the wrong power infrastructure to make it so (distributed rather than central points of power generation). Ethanol's lowish net return on energy investment can probably be improved with technological and manufacturing developments. There are promising alternatives out there, the problem is largely that oil still remains a bit cheaper (though this won't always be the case). -- mattb 22:03, 26 April 2007 (UTC)

It's a utility question that offers a false choice. First, even without the war, the U.S. could spend a trillion dollars on alternative energy. It's just not the best utilization of the money. If the war ended tomorrow, that money would not be diverted to alternative energy. 2). Subsidizing energy is an ongoing cost, not a one time hit. 3). the cost of collecting, transporting and refining organic matter is prohibitively expensive. Energy density is simply not high enough. The energy market ensures that refined gasoline is the cheapest/highest density energy product on the market. So if ethanol becomes cheaper to produce, gasoline will become cheaper simply due to supply and demand. Therefore ethanol will never be cheaper because the market won't allow it. As an example, consider that there are trillions of gallons of fuel locked up in shale. Opec will always make it cheaper to buy oil from their field than to manufacture it from shale. As an aside, if you think the Arab world is angry at the West now, dry up their supply of money and you will see much more poverty and despair. Oil pays for their food. If the West is willing to go to war to keep gas in their SUV's, what do you think the Arab world would do to keep food on their table? --Tbeatty 04:59, 27 April 2007 (UTC)

Cancer

Moved from here Rockpocket 18:42, 26 April 2007 (UTC)

Hi there

Someone has been diagnosed with cancer and they have an operation to remove the cancer. After surgery the person does not live very long. It is said they did not get all of cancer. Also they say "When air hits cancer it grows faster". Is it true about cancer growing faster when it is exposed to air? Please tell me why most people die not too long after surgery.

Pamela Grant --143.111.22.28 14:06, 26 April 2007 (UTC)

I had never heard that saying, but it is discussed and debunked on this Mayo Clinic page (about halfway down the page). That section also some other factors that might affect mortality rates after surgery. --LarryMac 19:15, 26 April 2007 (UTC)

One thing that can happen is that the cancer mass is punctured during surgery, allowing cancerous cells to escape into the body and later metastasize. To avoid this, it is common to take lots of extra tissue around the cancer mass to make this less likely. Another option is to also follow up with radiation or chemotherapy. Radiation therapy is especially effective in the case of thyroid cancer, since thyroid tissue (even escaped cells) absorbs radioactive iodine. StuRat 20:16, 26 April 2007 (UTC)

Strange eye problem, long term watering

I've read the medical disclaimer, so please feel free to answer the question on my promise that I won't sue, or follow any of your advice %D. For over a year now, my left eye has persistantly watered, with no rhyme nor reason to do so. The amount of fluid released can vary, but is genarally at least enough to allow a tear (or more) to run down my fact. Does anyone have any ideas as to what may be causing this, and any sort of potential remedies which, erm, I could think about using if I were so inclined to take your advice, which, of course, I would never do.... —The preceding unsigned comment was added by 81.159.227.103 (talk) 19:45, 26 April 2007 (UTC).

Tearing in one eye is often the result of obstruction, but could also result from other unilateral eye problems. There's nothing you can do about this at home; you need to see an eye doctor both for accurate diagnosis (probably involving fluorescein dye) and treatment. - Nunh-huh 19:56, 26 April 2007 (UTC)

About 9+ months ago, I had a grommet put in my left ear to deal with repeated ear infections. Although the grommet is still in place, my hearing feels off balance from left to right, and I was wondering if the two issues could rbe related (eustachian tube and tear duct...) —The preceding unsigned comment was added by 81.159.227.103 (talk) 20:34, 26 April 2007 (UTC).

The tear duct and the eustachian tube both drain into the nose and are closely related. Repeated infections could affect either or both: again, to determine which, or if an obstruction exists, or to treat it, would require you to seek medical attention. - Nunh-huh 21:11, 26 April 2007 (UTC)

"my left eye has persistently watered" <-- please go to a doctor. There might be a simple fix or there might be a more serious problem like a growing tumor (rare) that is blocking a tube. --JWSchmidt 17:36, 27 April 2007 (UTC)

Near earth Astroids and empty space

hey guys ok im back again and amazingly this question isnt about nukes or radiation!! Would finding near earth astroids be alot easier if we had a computer operated Observitory on mars (or a astroid itself for that matter)? Using that observitory to find astroids by a system of trangulation? i think this will be faster and more accurate (assuming it hasnt been proposed) as it will give us a 3d veiw of where the astriods are in space. Also for the empty space thing, if you leave the solar system or galaxy for that matter is there a risk of running into a astroid? and just to not leave you all sad cause i didnt ask a radiation question here it is =) for all of you that like awnsering my radiation questions would radiation effect a observitory on mars in a harmful way (electrical coponites)?

And on a last note this is assuming that one day we have the time tech and cash to fund a observitory on mars. User:Maverick423 If It Looks Good Nuke It 20:11, 26 April 2007 (UTC)

As far as we know, Asteroids are usually the remnants of moons or planets that have been pulled apart for some reason, maybe gravitational shear, we dunno yet. As such, you're probably much more likely to find one deep in the gravity well of a star than in interstellar space. This is not to say that they aren't out there, it's just the difference between counting how many cars there are in a block of a metropolitan down-town versus in the same length of road in the middle of Nevada, far away from a house. In regards to other laboratories, sure, the more the merrier, but there's no special reason to put them at other planets. We can triangulate without that much parallax these days, two observatories orbiting earth photographing a suspect rock would be able to very quickly figure out where it is and how fast it's moving. In fact, putting an observatory ON mars would be problematic because you lose resolution to atmospheric distortion and have to deal with sandstorms and tripods and whatnot. So, eh, sure, more observatories are great, and spreading them around the solar system, why not? Absolutely necessary for seeing where/howfast asteroids are? Not so much. - CHAIRBOY (☎) 20:21, 26 April 2007 (UTC)

The origin of asteroids is pretty nicely explained in Asteroid belt. The gravitational "sheer" (let's call it tidal forces) you might find in our own solar system wouldn't be strong enough to pull apart anything sufficiently solid. Interplanetary/moon/planetesimal collisions are a much much more likely source of debris, however this is impossible when you reach earth sized planets, given that earth colliding with another earth at a good 50,000 kph has less than 1 millionth the energy needed to break either apart (some debris would escape, but the planets would still be there). Someguy1221 09:10, 27 April 2007 (UTC)

ah i see thats good info =) so then basicly a observitory in another planet would be a waste of cash =) User:Maverick423 If It Looks Good Nuke It 20:28, 26 April 2007 (UTC)

Yes, it would be far more expensive and less useful than an Earth orbiting observatory which we could service regularly. I believe radiation is a factor, but they can design to handle that, with electrical shielding on wires, for example. I would expect the chances that you would be hit by an asteroid outside of any solar system, while "stationary", to be less than the chance you will be hit standing where you are. On the other hand, if you're traveling at near light speed, then a speck of dust could destroy a massive spaceship at those relative speeds, so that changes the calculations. StuRat 20:41, 26 April 2007 (UTC)

A small point, but maybe you're confusing finding asteroids with determining their velocity (and so future path) once found? The latter isn't too hard, as we can (usually) watch them zoom around for years on end. But finding near Earth asteroids is hard because they're a) really small, b) really far away, and c) really dark. Putting observatories on other planets might help if they happen to go nearer that body, but you'd get more searching done for your [insert unit of currency here] by having more and bigger telescopes scanning more of space from where you already are. Spiral Wave 22:50, 26 April 2007 (UTC)

actually now that i think of it from playing Hegemonia, they have a probe there that scans about 10000 miles using what appears to be light. why cant we create something the same? use light like a sonar system that creates a 3d map of space and the obsticles around it. i know you all will prob say that was just a game but think of it. what if we can acctually do something like this. wouldnt mapping space be faster? or would light just be too weak to create a sonar like effect?User:Maverick423 If It Looks Good Nuke It 20:39, 26 April 2007 (UTC)

I don't see any reason why you couldn't use LIDAR just like SONAR or RADAR, but it would have a very limited range. 10,000 miles is extremely small on the scale of the solar system. Pluto orbits up to 4.6 billion miles from the Sun, giving the inner Solar System a diameter around 9.2 billion miles (there's quite a bit of stuff farther out, too, though). So, to do a linear scan just a bit bigger (10 billion miles) than the diameter of the inner Solar System would take a million scans. To do a cube with that diameter would take a quintillion scans. How long does it take to do a scan and move to the next position ? An hour ? Now multiply that by a quintillion. You say "why not have a thousand such probes" ? Then it would only take a quadrillion scans each and could be completed in a quadrillion hours. That's some 40 trillion days, or over 100 billion years. Also, don't forget that the meteors are always moving, so you may miss them because they weren't at the same location where you were doing your scans. StuRat 20:57, 26 April 2007 (UTC)

(edit conflict) - Am i getting predictible already?? heh i was about to suggest a thousand probes. i know its diffrent from a game but the making of a probe was quite cheap and you can make them reletivly fast there too. to reduce launch cost we can launch them in groups of 10 or so it would be a awsome site to see on the news. also instead of 1000 we should make about 100000 or so that might cut the time shorter. ( i just saw 100 bil years) wow ok then 1 mil probes, of course at this time im talking in the relm of impossablilty. but if the scanner was perhaps expanded to make it scan 100k miles it would reduce the time alot no? User:Maverick423 If It Looks Good Nuke It 21:08, 26 April 2007 (UTC)

Let's increase it to scan 10 million miles, while we're at it. Then we would only need 1000 scans to do the diameter of the inner solar system. However, that would still be a billion scans required for the entire volume of the inner solar system. Since each scanner now needs to move 10 million miles between scans, we probably need to allow at least a day for that (and that's a really fast ship, some 40x as fast as current ships), so we have a million days, total. Make it 1000 scanners, and you can scan the entire inner solar system in 1000 days, or a bit under 3 years. We finally made it workable, but only by making some rather absurd assumptions. If you lower the range to just 1 million miles per scan (but keep the time between scans at 1 day), that would change it to just under 3000 years. So, then we would be back to needing a million scanners to get it back down to under 3 years. StuRat 23:37, 26 April 2007 (UTC)

I suppose I should have said this at the beginning, but humanity has far more serious things to worry about than giant asteroids. After all, the one that killed the dinos hit 65 million years ago, so the chances that one that size will hit anytime soon are incredibly small. More serious threats are global epidemics and nuclear warfare, so it might be wise to invest all this scanner money into preventing those. StuRat 23:43, 26 April 2007 (UTC)

you do know i wouldnt mind much nuclear warfare sturat XD. anyways wow thats a big diffrence for just one million miles. and i did hear that there is ganna be a really really near earth astroid in the year 2026 or something like that User:Maverick423 If It Looks Good Nuke It 01:46, 27 April 2007 (UTC)

Check out our Near-Earth asteroid article. StuRat 04:21, 27 April 2007 (UTC)

neutralizing

what does a chemical such as phosphoric acid combined with magnesium hydroxide create? i can't seem to make an accurate outcome. —The preceding unsigned comment was added by 76.188.176.32 (talk) 21:42, 26 April 2007 (UTC).

For a hint, phosphoric acid is H3PO4, and magnesium hydroxide is Mg(OH)2, which is one of the simplest bases you can get. Remember what the old "acid plus base" reaction gives, and try balancing the reaction to get that result. Confusing Manifestation 22:26, 26 April 2007 (UTC)

Looks like you're going to generate some dihydrogen monoxide, which readily evaporates at room temp, so don't inhale any vapors ! :-) StuRat 23:26, 26 April 2007 (UTC)

I'm not aware of any health warning about inhaling gaseous dihydrogen monoxide - it's the liquid form that you've got to watch out for. Aaadddaaammm 07:19, 27 April 2007 (UTC)

Eye watering in response to reading about eye watering...?

Very interesting this - as I was reading the question above about watery eyes, my own eyes began to water. What the hell just happened? --Kurt Shaped Box 22:35, 26 April 2007 (UTC)

Just like I itch all day after I see some spiders. StuRat 23:23, 26 April 2007 (UTC)

If I ever see an animal being skinned on TV, I can actually feel my own skin prickle a little... --Kurt Shaped Box 23:58, 26 April 2007 (UTC)

Jsut what kind of TV do you watch, anyway ? StuRat 17:35, 28 April 2007 (UTC)

See also: mirror neurons. [Mαc Δαvιs] ❖ 04:07, 27 April 2007 (UTC)

I once read a series of accounts of people dying, miserably, of thirst: in lifeboats, in the desert, and in the Black Hole of Calcutta. When I finished, I could not drink enough cold water to satisfy my thirst. Edison 06:31, 29 April 2007 (UTC)