Science desk
< March 31	<< Mar \| April \| May >>	April 2 >

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

April 1

Homeless public school students

According to [1] "homeless students rose from 59 in 2001 to 2,812 in the current school year" in Jefferson County, Colorado public schools. That caught my eye because that's where I went to public school, and lived for decades. Where can I find national statistics? 71.212.248.193 (talk) 04:49, 1 April 2013 (UTC)[reply]

That sounds so weird to a Brit (see Public School (United Kingdom)). Rojomoke (talk) 08:33, 1 April 2013 (UTC)[reply]

Not as weird as the British system seems to the rest of the World. Even without fagging. Floda 121.215.56.92 (talk) 09:25, 1 April 2013 (UTC)[reply]

It's tricky, since as the article on Homelessness in the United States points out, it's quite hard to do a comprehensive count of homeless people. However, some of the publications from the National Association for the Education of Homeless Children and Youth have estimates in them from previous years, such as this one that suggests there were just under a million in the 2008-09 school year - and a random "Did You Know" on one of their pages says in 2010-11 it was just over a million. You may want to try contacting them to see if they can point you to any more data. Confusing Manifestation(Say hi!) 00:37, 3 April 2013 (UTC)[reply]

Skinning a cat

How many ways are there to skin a cat? --Carnildo (talk) 09:50, 1 April 2013 (UTC)[reply]

Ask a taxidermist, and a butcher. They'll give different answers. Plasmic Physics (talk) 09:51, 1 April 2013 (UTC)[reply]

PP, you know very well that it's important we reference our answers here. Carnildo, there is more than one way. — Lomn 14:07, 1 April 2013 (UTC)[reply]

Indeed, it is a good thing then that I didn't give an answer. Plasmic Physics (talk) 21:28, 1 April 2013 (UTC)[reply]

Ti-4H producers

Who produces Ti-4H alloy? I'm not looking for chemical merchants. For clarity: Ti-4H is the most common commercially available titanium hydride. Plasmic Physics (talk) 09:59, 1 April 2013 (UTC)[reply]

Space tourism question

1) I want to know what is the cost to go to space right now.

2) Will one day space travel become cheaper enough so that a lot of people can visit space? Like low cost airline? --Huutoot (talk) 14:31, 1 April 2013 (UTC)[reply]

Around $40 million. Please see space tourism for details. Obviously no one can say how much it will cost in future, but given the conditions under which one has to travel, it's unlikely to become a mass market. If your funds are limited you might want to try the Vomit comet first, as this costs a mere $5000.--Shantavira|^{feed me} 14:50, 1 April 2013 (UTC)[reply]

The article you linked to put the figure at $20 million dollar to the ISS (not only suborbital trips). OsmanRF34 (talk) 18:15, 1 April 2013 (UTC)[reply]

I numbered your questions for ease of response:

2) Yes, the price will come down, but probably never as low as budget airlines, because far more energy is needed to go to space than to move around the Earth, and more energy means more cost. However, if we can find a way to more slowly move into space and back down (say with a space elevator), then we can eliminate much of that energy cost, as it's mainly due to the extreme air resistance when moving through the atmosphere at high speeds. Also, space is far more inhospitable than Earth, so additional protections must be put in place to protect the occupants, and that entails additional cost, too. For example, if an airplane develops a small hole into the interior, the occupants need to use oxygen masks and the plane needs to make an emergency landing. In a spaceship, those occupants would all need to wear spacesuits to survive, and the hole would need to be repaired before re-entry, or you could get a repeat of the Space Shuttle Columbia disaster. StuRat (talk) 14:55, 1 April 2013 (UTC)[reply]

I wonder if the recent successful Soyuz TMA-06M, which reached the ISS in 6 hours instead of 2 days, will decrease the price significantly. Take also into account that even to become a private astronaut, you'll also need to pass a screening process and months long training. OsmanRF34 (talk) 18:15, 1 April 2013 (UTC)[reply]

I think you meant to link to Soyuz TMA-08M Kram (talk) 21:10, 2 April 2013 (UTC)[reply]

That's the opposite direction we need to go. Faster doesn't help to reduce the energy cost of the drag from going through the atmosphere at high speeds. I suppose there's some savings in term of food, water, and air (and the addditional fuel needed to lift it), but that's quite minor over a few days. StuRat (talk) 22:48, 1 April 2013 (UTC)[reply]

I think they didn't moved faster in terms of miles/hour, but faster in terms of calculating better the route, and orbiting around the Earth less times to adjust to dock to the ISS. OsmanRF34 (talk) 01:40, 2 April 2013 (UTC)[reply]

Short answer: Right *NOW*, you can pay the Russians $40,000,000 to take you up to the ISS for a few days. In a year or so, Virgin Galactic will get you into space (briefly!) for $200,000. Eventually, I'd guess at a minimum of around $5,000....but who knows for sure?

Longer answer:

Going slower to get into space makes sense if you only want to get above the atmosphere for a short while - but to get into orbit, you need to reach orbital velocity - so it's going to have to be pretty fast. To make the ride more comfortable, and more accessible to people who might not be healthy enough to endure 10g's of acceleration - you'd want to reduce the acceleration as much as possible.

The space shuttle only subjects you to 3g - which most people should be OK with. There are rollercoasters that briefly produce 6g. Apollo-era spacecraft subjected you to 7g - and for quite a long time...so that's more of a challenge. SpaceShipOne produces about 2g - and it made it into "space" (Defined as more than 100km altitude).

The space elevator might sound like an attractive way to get people into orbit cheaply - but there is a serious problem. The bands of intense radiation surrounding the Earth are lethal to humans if we stay close to the planet for too long. This isn't a problem for rocket launches because you only spend a minute or two in the danger zone...but a space elevator would take days to climb slowly past those regions - and human passengers would be fried. The space elevator is only ever going to be a freight elevator!

If you don't need to get into orbit - or to leave the earth and go someplace else - then something like SpaceShipOne (SpaceShipTwo, for example) should be able to get you there for relatively low cost. About 4,500lbs of rocket fuel and a re-usable spacecraft is required to get two people up there. SpaceShipTwo flight tickets can be bought right now for $200,000 each.

If the technology can be made to work, repeatably and reliably - then the fuel cost may limit how cheap this can be. A transatlantic flight in a 767 consumes 140,000 lbs (about $73,000 worth) of fuel. But that's for 300 passengers...so each person requires only about 500lbs of fuel...that's nine times less than Spaceship One. But it gives us a clue to the cost to get to space: If $250 of your $600 transatlantic ticket is fuel - then we can presume that $2,250 is your share of the fuel to get into space. Sure, there are lots of other costs - but the airlines can get those down to $350 per seat...so perhaps that's also possible for an efficient space-plane.

On that basis, I'd expect the cost to get into space to eventually settle down at around $5,000 per person - for a short, sub-orbital hop with a few minutes of zero gee and some amazing views of earth from space.

SteveBaker (talk) 15:09, 2 April 2013 (UTC)[reply]

On such occasions a prediction such as that is probably way off.--Arrogential (talk) 01:28, 3 April 2013 (UTC)[reply]

hydrocarbon ecology in a fossil fuel economy

There are oil eating microbes, and hydrocarbon seep communities, and studies that show that a large percentage of hydrocarbons on the surface are fossil derived. I am casually investigating the possibility that we are negatively affecting our organic fertility by over-harvesting fossil fuels. The "hypothesis" is that fossil fuels, while in the ground, are part of the "microbial food chain", which is in turn responsible for such aspects as soil fertility. The proposed issue is that by oil pumping, coal mining, and gas pumping (lately "fracking") are causing a loss in the ecological capabilities of harvested regions. So, fossil fuel harvesting might be contributing to desertification. As there is less food for life, there is less life. — Preceding unsigned comment added by 134.29.38.118 (talk) 20:14, 1 April 2013 (UTC)[reply]

An interesting proposition, but your entire post amounts to a statement. This Reference Desk is intended for asking questions to which responders can give (preferably referenced) factual answers: did you have a question? If so, please ask it explicitly. Conversely, this Reference Desk is not intended for hosting debates and discussions, or soliciting opinions, so if your post was an implied invitation for either of these, it is inappropriate here. {The poster formerly known as 87.81.230.195} 90.197.66.100 (talk) 21:23, 1 April 2013 (UTC)[reply]

I think the implicit question is reasonably clear, but I can't see how that could work out. Soil fertility is determined by the top few feet of soil (often much less), but hydrocarbons are found much farther down. Also some of the most fertile soils are found hundreds of miles from any known hydrocarbon deposits. Looie496 (talk) 21:46, 1 April 2013 (UTC)[reply]

Agreed. Also, fracking is a problem precisely because it contaminates the groundwater with hydrocarbons, which, under this theory, would be a good thing. StuRat (talk) 22:45, 1 April 2013 (UTC)[reply]

...assuming that the other chemicals associated with fracking are OK. Of course, having seen what happens to plants when they are exposed to crude oil, I have my doubts about this whole concept. --Guy Macon (talk) 00:09, 2 April 2013 (UTC)[reply]

In response, pollution is unnatural. Natural hydrogeological blah blah would run the hydrocarbons through bacteria, and each step would take them through some modification very slowly, but very steadily. Pollution just puts refined and broken hydrocarbons where they weren't before. There certainly are bacteria all the way up and down, we've got a lot of articles on it over the last decade or so. There are also hydrocarbon seep communities, which are unique, but then food for passing life, and what I'm talking about is basically hydrocarbon seep, but rather than through a hole or fault, just slowly via osmosis. — Preceding unsigned comment added by 66.188.222.186 (talk) 01:52, 2 April 2013 (UTC)[reply]

It takes a very special class of organisms to use hydrocarbons as their main source of food; most other organisms (including all multicellular plants and animals) not only cannot use hydrocarbons in this way, but are positively harmed by them, either directly (acute toxicity, sunlight deprivation for aquatic plants, clogging of gills in fish and of feathers in birds, etc.) or indirectly (increased BOD caused by proliferating extremophile bacteria, possible infection by same, etc.) So, in other words, an oil spill is a VERY bad thing -- and in fact, for some of the same reasons that phosphate runoff is a bad thing (which would have been a "good thing" by the OP's reasoning, too). 24.23.196.85 (talk) 01:02, 3 April 2013 (UTC)[reply]

Ok, so it does indeed take a very special class of organisms to use hydrocarbons. The place we originally found them was in the reserves or in hydrocarbon seeps. I'm ballparking. When there has been an oil spill, probably (I recall) microbes then did also proliferate in these locals, and utilize these hydrocarbons. modern science has made strains that are more rapid in their use of the hydrocarbons. rewinding, and commenting also on the soil fertility. it's true, we measure fertility in the first few feet of soil, but the hydro-logical cycle of the subterranean environment means that much more of the earth has an impact on the small region which is this few feet. If there is a water table 60 feet below the surface (Depending on other geological formations) it will have an impact on the soils conditions. I am suggesting that likewise, having gas shale (such as in minnesota) 60 feet below the surface would also have an effect, and here's why. Naturally occurring within the shale are hydrocarbon "eating" microbes, which then convert the hydrocarbons into other forms of organic matter. Through osmosis, and other hydro-logical activity, some of the contents of the shale would be released towards the surface. Although this would occur very slowly, and very little at any given time, it would be like the growth of any other permanent, fixed organic community, and very continuous. My QUESTION is mostly is this accepted as common understanding, and why or why not, and what science supports our common understanding? btw, I am the original poster... thanks!

The methods scientist use to predict if Earth will get eaten up

There is another paper said few scientist actually saw Earth got eaten up by their host star, but I wonder how they figure that out. Can scientist actually use a strong telescope and expect a well-done resolution, or they use the computer and throw in variables to calculate. Is solar model done by computer or astronomer can see things from a extra-strong telescope. Can solar model trace the history, telling how old is the star and what happened to the planets when they get eaten up. I will thought astronomers use strong telescope and try to scale down the variables manually from telescope. --69.226.42.134 (talk) 23:18, 1 April 2013 (UTC)[reply]

First of all, let's get that link right: "Fried planets". What it says is that astronomers detected signs that a rocky planet (not necessarily "earth-like") was "devoured" by it's sun. The way they did that was by detecting chemical traces in the star's atmosphere that shouldn't normally be there. You can take the light from a distant star and feed it into a spectrometer that measures the colors present in the light. Some chemicals absorb light of very specific colors so instead of getting pure white light from the star, you get white - but with a few specific colors missing from it. If you spread that light out into a "rainbow" - you can see gaps where those colors are missing.

To give an example of this kind of observation, in the picture (at right here) you can see that the light from that star is passing is though the atmosphere of a nearby planet. The "rainbow" spectrum of that light is clearly missing two bands of orangey-yellow light - the black lines on that spread-out light mean that something is absorbing light from the star. In this case, it's because the planet has lots of sodium in it's atmosphere - and sodium is well known to absorb those two specific shades of orange.

So in the case reported in the "Fried planet" article, they looked at the light from that star and found that the light was missing specific colors that match the colors that "lithium" absorbs. Lithium is commonly found in vaporized rock...and since lithium doesn't naturally occur in stars of that age and size, they can deduce that a very, very large chunk of rock must have fallen into it fairly recently...a planet in fact. A rocky planet - which might (maybe) be "Earth-like".

SteveBaker (talk) 14:39, 2 April 2013 (UTC)[reply]

Well, Smith and Schroder carefully calculated, I don't know what did he do in his calculation [2] [3] they created the most detailed model to date of the Sun's transition to a red giant, based on observations of six nearby red giant stars. from [4] They are trying to bet anybody Earth's chance to get away from being eaten up is fat chance. Did they use the computer to do the calculation? How did Smith find out the Earth existed have been swallowed up?--69.226.42.134 (talk) 00:08, 3 April 2013 (UTC)[reply]

Lots of questions!

I'm sure they used a computer to do the calculation. Hardly anyone uses a slide-rule or does arithmetic on paper anymore.
They know that a "rocky planet" (let's not call it "earth" - much less, "Earth") existed around that star because the telltail traces of the lithium from its rocks could be found in the atmosphere of that star.
We've long known that our sun will one day run out of hydrogen fuel and soon after will grow to gigantic size. The question has always been whether it'll grow large enough to engulf the earth, or whether it'll fall a little short and just toast us to a crisp. It's known for sure that Mercury and Venus will eventually be swallowed up as the sun expands...but the earth was right on the edge of where the calculations suggested the sun might expand out to. I suppose that these new calculations, based on new data and a better mathematical model have actually answered the question...but it would take close reading of the actual paper to know how sure they are about that.

There is absolutely no doubt that the sun will ultimately grow into a red giant. We know that from the mass of the sun. All stars must ultimately run out of fuel - and when that happens, either they are large enough to have sufficient gravity to collapse into a neutron star or a black hole - or they grow into a red dwarf - or simply fizzle out into a brown dwarf. Since our sun is in the right size range, it'll become a red dwarf for sure. We've known that for decades. The only question was exactly how big it would get. For the Earth, this means that we might burn up and continue to orbit the sun as a lifeless molten blob...or we'll crash into the sun as it expands and be vaporized. One or the other...there is no other escape.

SteveBaker (talk) 14:39, 3 April 2013 (UTC)[reply]

Red giant, for Spock's sake. On top of that, a Brown Dwarf is usually a type of celestial body of near-stellar mass (in the 1/100 to 1/15 solar mass ballpark) but not enough to fuse even hydrogen. Old stars which aren't massive enough to degenerate into White Dwarfs are usually not called this - but mainly because these stars burn so slowly that none of them have exhausted their hydrogen yet.

Even if the Sun won't physically touch planet Earth, it could melt and ultimately vaporize the planet, and then devour the gas. Or if the Sun expands rapidly enough (but just short of far enough), the friction of the Sun's atmosphere could slow Earth, causing its orbit to decay. Simply put, Earth would then spiral in.

- ¡Ouch! (^{hurt me} / _{more pain}) 07:22, 5 April 2013 (UTC)[reply]

How Find A Persons E-Mail Address

If I have 1 e-mail. Address from someone. How do I find all their other. E-mail accounts is there a way. — Preceding unsigned comment added by 216.125.251.254 (talk) 23:40, 1 April 2013 (UTC)[reply]

See the computing reference desk. PCHS-NJROTC ^(Messages) 00:05, 2 April 2013 (UTC)[reply]

No. Not unless the person has left a trail that you can follow. The links between e-mail addresses are supposed to be confidential (unless the person has deliberately or accidentally revealed them), though hacking the servers of some e-mail providers might reveal them. Dbfirs 07:04, 2 April 2013 (UTC)[reply]

Which is, of course, illegal. Evanh2008 ^{(talk|contribs)} 11:30, 2 April 2013 (UTC)[reply]

...in most jurisdictions, and even then law enforcement usually has a way to do it legally. --Guy Macon (talk) 16:39, 2 April 2013 (UTC)[reply]

...only with a warrant, for example through the FISA court. 24.23.196.85 (talk) 04:31, 3 April 2013 (UTC)[reply]

I was going to repeat my "in most jurisdictions" comment (this is the English (language) Wikipedia, not the USA Wikipedia), but even in the USA, "only with a warrant" went away with most of the rest of the Bill of Rights long ago. Now all it takes is a US government agency issuing a national security letter -- no pesky judicial oversight required. --Guy Macon (talk) 05:20, 3 April 2013 (UTC)[reply]