Wikipedia:Reference desk/Archives/Science/2013 July 16

= July 16 =

Carbon emission
I've had no luck at Talk:Greenhouse gas, so I'm reposting the question here: carbon emission redirects to greenhouse gas, but the article doesn't clearly explain what "carbon emissions" mean. It doesn't seem to refer to emission of elemental carbon, but does it encompass emissions of all compounds of carbon, only gaseous compounds of carbon or some other still? — Kpalion(talk) 14:08, 16 July 2013 (UTC)


 * If editors agree on a definition, then the term and the definition can be added to "Glossary of environmental science".
 * —Wavelength (talk) 14:18, 16 July 2013 (UTC)


 * From my Google search of glossary environmental terms, I have checked most of the first 50 results and I have found the following.
 * http://www.epa.ie/irelandsenvironment/glossary/#C
 * "In the context of climate change, carbon dioxide released when substances, especially oil, gas, and coal, are burned by vehicles and planes, by factories and by homes."
 * http://www.bu.edu/sustainability/reference/glossary-of-terms/
 * "Polluting carbon substances released into atmosphere: carbon dioxide and carbon monoxide produced by motor vehicles and industrial processes and forming pollutants in the atmosphere"
 * —Wavelength (talk) 14:59, 16 July 2013 (UTC)


 * You might wish to consult List of online reference desks/Science.
 * —Wavelength (talk) 15:08, 16 July 2013 (UTC)


 * In the context of greenhouse gases, it mainly means CO2 but could also include methane, which is a very potent greenhouse gas but doesn't persist in the atmosphere for very long. Looie496 (talk) 15:11, 16 July 2013 (UTC)


 * Yes, "carbon emissions" is a little vague. You'll see it in press releases and such, but not usually in serious science writing (or if it is used, the scope is defined in the same article). I don't have time to check right now, but the authoritative/reliable bodies who might have a standard definition would be the IPCC and/or NOAA, who releases several freely-available white papers and technical documents that one could look into. When I'm at conferences that discuss this sort of thing, they usually present e.g. methane and CO2 (and others) in terms of Carbon_dioxide_equivalents. Basically, "tons of carbon" is not always meaningful, because different compounds have very different global warming potentials, even for the same amount of carbon per molecule. To my knowledge, solid carbon, (i.e. soot) is not ever considered an "emission" for the purposes of climate change studies. Soot particles will actually cool the atmosphere when in aerosol form, and when they settle, they become part of soil carbon (and hence are not emitted to the atmosphere). SemanticMantis (talk) 15:33, 16 July 2013 (UTC)

Totally off-topic, but I didn't find where to ask!
Some perpetual-motion believer(s) keep reverting Magnetic motor to represent it as aglorious future solution for humanity. What can be done, and how? Zarnivop (talk) 15:49, 16 July 2013 (UTC)


 * I have posted the article to the Fringe theories noticeboard, hopefully some editors will take a look at it to make it more neutral. You could also be bold and edit the article yourself! Mildly MadTC 17:36, 16 July 2013 (UTC)
 * \i did that, but mt edits were reverted. I do not enjoy edit-wars, and it seems in this case the article should be fixed and locked. Thanks for your help! 109.67.255.233 (talk) 20:36, 16 July 2013 (UTC)

When on H. sapiens' evolutionary timeline did the equivalent of the hallux ("thumb" on lower limbs) stop being opposable?
20.137.2.50 (talk) 16:43, 16 July 2013 (UTC)
 * I think it has not been fully opposable at least since Australopithecus afarensis appeared. Ruslik_ Zero 19:15, 16 July 2013 (UTC)


 * This article in Science says, regarding Ardipithecus ramidus, that "The foot has a widely abducent hallux, which was not propulsive during terrestrial bipedality. However, it lacks the highly derived tarsometatarsal laxity and inversion in extant African apes." I'll let you decide if that counts as "opposable". SemanticMantis (talk) 19:21, 16 July 2013 (UTC)


 * Yes, the transition seems gradual. See the images at the bottom of Australopithecus sediba. μηδείς (talk) 19:33, 16 July 2013 (UTC)

First embryonic stem cell transplantation in lab rats
I've been looking at the history of embryonic stem cells under the embryonic stem cell page; however it does not specify many of the details of the first transplant in mice which, I assume would have been recorded. Specifically I was wondering whether they transplanted the embryo into one of the two mice who actually parented it; or whether the receiving mouse was completely unrelated to the embryo. Also I am curious how long the scientists waited between the menstrual extraction and the transplantation; and whether prolonged culturing or cryonic freezing was involved in this process. I would say thank you for your assistance in clarifying this matter; however no one is going to answer this question. CensoredScribe (talk) 14:26, 17 July 2013 (UTC)

Energy into matter...
Inspired by the 'Why can't I run an electric heater in reverse to cool a room?' question above...

What's standing in the way of us creating a device that could (just for example) gather the energy from sunlight and convert it into gold? Per Einstein, this should theoretically be possible, correct? Matter can be converted into energy and energy can be converted into matter? --Kurt Shaped Box (talk) 21:14, 16 July 2013 (UTC)


 * "What's standing in the way"? Entropy !--Aspro (talk) 21:28, 16 July 2013 (UTC)


 * Well you can collect sunlight and turn it into useful energy in the form of electricity see solar electricity. The next stage of making matter or antimatter can be done in particle accelerators. But note these are very expensive and inefficient. Actually producing gold will need you to assemble protons and neutrons into a nucleus. There is a high level of electric charge in the nucleus that repels other protons, and the nucleus is very small, so it makes it hard to fuse your proton into a smaller nucleus. See synthesis of precious metals and nuclear transmutation. Chrysopoeia is the production of gold, but there is not much content in this article. Graeme Bartlett (talk) 21:30, 16 July 2013 (UTC)


 * What's standing in the way is the prohibitive cost and extreme inefficiency of such a device. Anyone who can afford to build the device can build a gold mine and get gold much more quickly, at much lower cost.  Anyone who can harness huge amounts of solar power can sell it to the grid, instead of using it to produce a few atoms of gold at a time.  If gold ever runs out on Earth, mining the asteroids would still be a more economic option.  If even the asteroids run out, and humans still haven't colonized other planets, gold would hold the same status as the rare earth elements do today.  In other words, the extreme difficulty of obtaining gold would make it useless as a store of value, and nobody would try to obtain gold for economic purposes.  --Bowlhover (talk) 23:41, 16 July 2013 (UTC)


 * Let's run some numbers on this... E=mc^2, so to get 1kg of gold, you need about (3x10^8)^2 =~ 10^17 J of energy, =3x10^10 kWh. A quick googling shows that electricity in the US is about $0.12 per kWh, so this will cost a bit shy of $4x10^9.  The price of 1kg of gold on the open market is about $40,000 a kilogram, so around a hundred thousand times less.  And that's befor considering the inefficiencies everyone else has highlighted. MChesterMC (talk) 08:11, 17 July 2013 (UTC)


 * Not a thing stands in the way. Why would you want to create such a device? Plasmic Physics (talk) 08:24, 17 July 2013 (UTC)


 * Taking the original calculation back to the original 'solar powered' version, it's also worth noting that the mean insolation at the sunniest places on Earth (like the Sahara) is only about 2500 kWh per square meter year&mdash;and much less at those places further from the Equator and/or subject to those inconvenient 'cloud' thingies. If you were able to wring every single joule out of every solar photon striking the Earth and apply it to this process with perfect efficiency (it is to laugh), you would still need completely cover 12 square kilometers to get that kilogram of gold in a year.  In reality, of course, even the best commercial solar panels are only about 20% efficient at converting sunlight to electricity, so multiply the area required by five.  And then note that the nuclear transmutation processes described above will be vastly less energy-efficient than that, since real life isn't always like Star Trek.
 * Worse still, in 2011, about 2700 tons of gold were mined. At 60 square kilometers per kilogram of gold, that would require 160 million square km of solar panels (all located in the Sahara desert....)  The total land surface area of the Earth is only about 149 million square km, much of which is located in less-than-ideal-for-solar-energy locations. TenOfAllTrades(talk) 13:19, 17 July 2013 (UTC)


 * I didn't focus on the example of generating gold, but matter in general. Plasmic Physics (talk) 13:55, 17 July 2013 (UTC)

Thanks for all the informative answers so far, folks. --Kurt Shaped Box (talk) 18:47, 17 July 2013 (UTC)


 * So you certainly could do it with enough fancy equipment - but by *FAR* the most efficient way to turn sunlight into gold is to turn sunlight into electricity, sell the electricity to people who need it - and use the resulting cash to buy gold. SteveBaker (talk) 20:24, 17 July 2013 (UTC)
 * Along those lines (and possibly more efficiently), you could also plant crops, which turn sunlight into food, and sell the food to raise cash for gold. Farmers are ultimately in the solar energy business ;) SemanticMantis (talk) 23:12, 17 July 2013 (UTC)
 * It is possible to transmute lead into gold, but it's not worth the cost. CS Miller (talk) 21:24, 17 July 2013 (UTC)


 * This Humpty Dumpty cartoon demonstrates a similar folly, though the device used is far more primitive. And (in case I need to say this), it is only very loosely based on actual science. InedibleHulk (talk) 23:30, 17 July 2013 (UTC)

Sorry to be the party pooper but actually, the question doesn't make sense. Einstein never, ever said that energy could be converted to matter or vice versa. What he did say was there is mass-energy equivalence as denoted by E=MC2 and that mass and energy are always conserved. The difference is subtle but important. Typps (talk) 01:36, 21 July 2013 (UTC)