Wikipedia:Reference desk/Archives/Science/2013 August 21

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.

August 21

Carbon Footprint Q: Whose foot is that, then?

In Sydney, Dick Smith, environmentalist, businessman and aviator, recently hosted a very interesting TV doco on renewable energy. In it, he noted that Australia has one of the largest carbon footprints(per capita)in the world, mainly in consequence of the massive amounts of coal we mine and export.

But that made me think: which party incurs the responsibility for the carbon release: the exporter, or the importer, which in our case is China. If it is the exporter – us – then China is virtually blameless for any carbon debt, as all the nations that sell them coal, iron and the rest are the ones who are fitted up as the guilty parties. But I have read that they too have a very big carbon footprint. Is there some rather shonky bookkeeping going on here, where carbon emissions are being counted twice? Myles325a (talk) 06:22, 21 August 2013 (UTC)

Environmentalists generally prefer alarmism so they would prefer doing the calcs to make the numbers appear worse for everyone. That being said, you could also argue - since the Chinese use the coal they buy from Australia to generate power to manufacture goods which they export to other countries - that those countries should bear the carbon footprint. So the US, which consumes much of the stuff manufactured in China, should have the CO2 from the coal mined in Oz in their footprint. Otherwise see Carbon footprint. In reality the system is quite perverse with everyone pointing to other people's CO2 emmissions to justify themselves not doing enough to cut down their own emmissions. 163.202.48.125 (talk) 08:40, 21 August 2013 (UTC)

That's a bit glib. Acquiring resources, using resources, and obtaining the results are all different activities. You could count the mining operations footprint against Australia, the production using those resources against China, and the shipping of their output against the US.Phoenixia1177 (talk) 10:39, 21 August 2013 (UTC)

The question makes it clear that’s not the case, though. The carbon released from the coal mined in Australia is contributing to Australia’s carbon footprint. Or at least that’s how I interpret the question. 163.202.48.125 (talk) 11:37, 21 August 2013 (UTC)

No, the question expresses confusion about how the accounting is done, and some guesses that things might not be accounted for in the way that we might expect. There are indeed many ways such things can be calculated, but it is wrong to assume that emissions made in CN by burning coal mined in AU are counted as AU emission, merely because the OP is unsure of what's going on. SemanticMantis (talk) 15:27, 21 August 2013 (UTC)

Myles, can you give us a link to any specific reports? We can't really say how the carbon accounting was done unless we can see the original documents (And I can't find/watch the show right now). I will say that coal mining is a major source of emissions, even not counting any emissions from the burning of coal. Consider: all the gasoline to power trucks, electricity for lights, not to mention heavy digging equipment, manufacture of specific tools, etc. All that goes into the life cycle analysis of mining coal, and much of that energy is derived from fossil fuels. So it could be that Smith was basically correct that mining coal is a big part of AU's carbon footprint, even if the burning of said coal in CN is not. SemanticMantis (talk) 15:27, 21 August 2013 (UTC)

Many parties are involved. See "Environmental impact of the coal industry" and "Environmental impact of shipping" and, more generally, Category:Environmental impact by source. Sellers are enticed by high profits, and buyers are enticed by low prices, and often the natural environment (our natural life support system) pays a price. See "Environmental full cost accounting" and "Ecological debt". The natural environment can be affected negatively by resource extraction and processing; commodity distribution, use, and misuse; and waste disposal. A responsible person can do a limited amount of good without community support, but we can all do much more if everyone takes individual responsibility.

—Wavelength (talk) 16:33, 21 August 2013 (UTC)

The point here is "does it matter?" - this is a global problem. If Australia didn't mine the coal, China couldn't burn it. If China didn't burn coal, Australia wouldn't mine it. Who cares which of the two countries is responsible? Either one of them could choose to end it - so in any useful sense, they are both equally at fault. The naive statistic of "National Carbon Footprint" glosses over so many details in a dynamic, interconnected world as to be almost useless. Any simplistic view of the situation has to be viewed as a very general indication of a problem - and the specifics have to be examined before deciding on some course of action. If the world decided that this trade between Australia and China was unacceptable, political pressure would likely be exerted at both ends of the supply chain.

If China was pressured into not buying the coal - probably the Australian mining industry would sell it somewhere else. The sudden glut of coal would result in a dramatically falling price of the stuff on the open market - which would likely result in more Australian power generators burning it instead - and other countries would probably step in to buy Australian coal at this lower price point.

If Australia was pressured into not mining the stuff - the Chinese would buy it from some other country - a shortage of coal on the open market would push up the prices and encourage other countries to step up their production rate accordingly.

No single "fix" for this problem will work. It requires a global perspective. You need ALL coal mines around the world to reduce production and ALL coal fired power plants in every country to reduce their consumption. That kind of global cooperation has proven elusive...which is a very depressing situation.

SteveBaker (talk) 14:10, 22 August 2013 (UTC)

OP myles325a back live. It matters to me Steve coz while I am an environmentalist I despise the Green’s natural position that they can lie thru their teeth whenever they feel the end is worth it, while becoming holier than thou whenever they spot a fib that doesn’t suit their purposes. Activist literature is full of colossal exaggerations and outright falsehoods, and in the end it does their causes much harm, as the public founds out eventually and becomes cynical.

I don’t like propaganda, and I don’t like crappy statistics. I like to know the truth, and if some fanatic is counting carbon footprints twice, then I wanna know about it, and I want the lie exposed. Call me an old fuddy duddy but I’ve had an absolute gut full of the mealy mouthed post modernist view that “there is no such thing as truth”, and it’s all just a matter of what suits you, sir. Myles325a (talk) 05:27, 23 August 2013 (UTC)

Transmission of light through transparent medium

Okay, so in a transparent medium with a refractive index greater than 1, light is propogated with a velocity that is less than c. I understand the wave explanation of this in terms of electromagnetic radiation, distinction between group velcoity and phase velocity etc. But what actually happens at the level of individual photons ? Does each individual photon travel at a speed less than c ? Or do individual photons travel at c but the slowing down is a bulk effect because photons are absorbed and re-emitted by electrons ? Or is the slowing down the result of some complicated interaction involving virtual photons ? I've read the articles on refractive index, speed of light, slow light and transparency and translucency, but they don't seem to answer this question. Gandalf61 (talk) 08:54, 21 August 2013 (UTC)

The Photon article under Photons in Matter goes into it. It mentions scattering and interaction with quasi particles.Phoenixia1177 (talk) 10:53, 21 August 2013 (UTC)

Thank you. Yes, photon says the slowing down is due to "blending of the photon with quantum excitation of the matter (quasi-particles such as phonons and excitons) to form a polariton; this polariton has a nonzero effective mass". So in short, it's quantum weirdness. Gandalf61 (talk) 13:31, 21 August 2013 (UTC)

Or just consider that the photon is itself an excited state of the electromagnetic field, the field in the medium is, of course, described by the free field plus the interactions with the medium and quantizing that will lead to a different beast than quantizing the free electromagnetic field. You can then intepret what you get in terms of free photons that mix with quasi-particles, but then given any Hamiltonian, you can always write that as a sum of two different Hamiltonians, so these intuive pictures are not always unambiguous. Count Iblis (talk) 14:22, 21 August 2013 (UTC)

The wave picture is just as correct as the particle picture. They are different ways of calculating the same thing, mathematically. The particle picture works classically too—loop-free Feynman diagrams give you classical electromagnetism, and the diagrams with loops are quantum "corrections". The phenomenon you're describing is classical, and the quantum explanation isn't fundamentally any different however it's phrased. -- BenRG (talk) 16:06, 21 August 2013 (UTC)

Yes, I understand that the wave model and the particle model are equivalent in the classical limit, when there are a large number of photons. However, the intensity of the incoming light can, in principle, be reduced until only a single photon at a time is transmitted. So the particle model must explain the behaviour of individual photons in a way that replicates the wave model in the limit of large numbers of photons. And any description of the behaviour of individual photons must be a quantum physics model, not a classical model. So I was looking for a description of the mechanism by which an individual photon is refracted and slowed down (or, indeed, speeded up if refractive index is less than 1) as it passes through a transparent medium. Gandalf61 (talk) 09:00, 22 August 2013 (UTC)

What you have to understand is that a photon in vacuum and a photon in a medium are not the same object. In a medium, the normal modes of oscillation which will be quantized in order to obtain photons are not the same as the normal modes of a free field in vacuum. That fundamentally changes the Dispersion relation of the wave function. We chose to call it a photon just the same, but that choice really is arbitrary since the two objects have fundamentally different natures and properties. Dauto (talk) 13:21, 22 August 2013 (UTC)

I imagine that a lot of people have wondered at this, having been told that we can only observe light travel at the same speed c, we are then told that it can “slow down” when travelling thru a medium. How is that possible? I think the simple answer is that when light is travelling, it cannot be seen to move at any other speed than c, regardless of whether it is moving through empty space or honey. When a photon moves thru material, it can be briefly trapped by an electron in an atom’s shells. That excites the atom as it absorbs the photon, and then the atom sheds the photon (or another exactly the same) and returns to its previous state of energy. This procedure takes some little time. The photon ALWAYS travels at the same speed, but if we count these times when it is being absorbed and re-emitted, then it appears to travel at a lower speed than c. Myles325a (talk) 07:49, 23 August 2013 (UTC)

The problem with that explanation is that it is completely wrong. There is no absorption and re-emission going on. What you do have is that the normal modes of vibration that are being quantized are different because the electrons also vibrate back and forth along with the electromagnetic fields and must be included in the proper calculations of the dispersion relation. A photon in a medium is partially a matter vibration phenomenon. We still call it a photon, but it is not the same thing as a photon propagating in vacuum. Dauto (talk) 19:04, 23 August 2013 (UTC)

Yeah, well that's what I said more or less, except in language that is not full of obscurantist voodoo talk..."Vibration phenomenon"? Next you will be talking about crystal power and auras and we will all be told to get coffee enemas. Not for this little black duck! I like my science neat and my coffee in a cup, thank you all the same. Myles325a (talk) 04:07, 24 August 2013 (UTC)

Not to be rude, but what are you talking about? I don't see any new agey junk science terms, nor anything obscurantist; it's a pretty clear answer about a complex phenomena. Moreover, if you look at the relevant section of Wiki's own article on photons, you see something to the same effect.Phoenixia1177 (talk) 03:59, 25 August 2013 (UTC)

Is there any organ that made of only one tissue?

Is there any organ that made of only ONE tissue? (I have not found information about on Wiki) 46.210.138.154 (talk) 17:48, 21 August 2013 (UTC)

Well, to get an absolutely solid answer you'd have to first explain what you mean by a "tissue", but using the common meaning I'd say no, because every organ contains blood vessels, which are a distinct type of tissue. Looie496 (talk) 18:37, 21 August 2013 (UTC)

what do you think about the nail or hair, are they not organs or do they contain blood vessels? 46.210.138.154 (talk) 18:46, 21 August 2013 (UTC)

I've never seen nails or hair referred to as organs. (I regard these kinds of things as totally unimportant -- I'm just giving my impression of how most people say things.) Looie496 (talk) 18:50, 21 August 2013 (UTC)

Would the heart not count as this, being entirely composed of cardiac muscle? --TammyMoet (talk) 21:26, 21 August 2013 (UTC)

Epicardium, cardiac muscle, fibrous pericardium, serous pericardium, .... Reaper Eternal (talk) 21:33, 21 August 2013 (UTC)

Liver? Count Iblis (talk) 23:26, 21 August 2013 (UTC)

Blood vessels, also bile ducts (arguably there's a common origin to that cell type, but they look really different under a scope, and heck, there's a common origin to every cell type...) Wnt (talk) 06:17, 22 August 2013 (UTC)

Hmmm, I suppose the lens of the eye is one tissue type ... but it's not really an organ. Wnt (talk) 06:21, 22 August 2013 (UTC)

"the lens of the eye is one tissue type".^{[citation needed]} Have a look (ha!) at Lens (anatomy)#Lens structure and function. DMacks (talk) 14:38, 22 August 2013 (UTC)

I'd argue that the lens fibers and lens epithelium are the "same tissue type" at different stages of differentiation. I mean, if we hold the same standard to the liver, then we say there are three different tissue types because there are zone I, zone II, zone III hepatocytes. But even that is probably an incomplete description of the levels of differentiation involved... ultimately every cell is unique, and to some extent or other all the differences matter. Wnt (talk) 20:18, 22 August 2013 (UTC)

Absorbtion of non-soluble medicine.

Can non-soluble medicine pills be absorbed into the body through the mouth? This applies to the whole world. Pubserv (talk) 17:59, 21 August 2013 (UTC)

Not unless they are broken down by saliva. Otherwise the pill would just sit there forever. Looie496 (talk) 18:41, 21 August 2013 (UTC)

I mean pills that turn into powder when you crush them. Pubserv (talk) 19:58, 21 August 2013 (UTC)

I'm not an expert in medicine, but there are medications that don't dissolve in water, but dissolve with fats. Vitamin D, while not really a medicine, is one of the cases. --Wirbelwind(ヴィルヴェルヴィント) 00:23, 22 August 2013 (UTC)

Also, solubility isn't a 100% yes or no thing. A material might not be very soluble in water, but several hours churning in the digestive system, with water, fats, and acid thrown into the mix, might tend to break it down rather effectively. For example, calcium carbonate, present in many antacid tablets, isn't very soluble in water, but will react with the acid in the stomach and dissolve that way. StuRat (talk) 08:19, 22 August 2013 (UTC)

nervus cells called neurons?

why all cells of the body are called "cyties" (in example: osteocyties is of bone tissue, miocyties is of muscle tissue) while the nerves cells called neurons without 'cyties'? and second, how are called the cells of connective tissue? (see about the names of the cells of the other tissues in the first qustion). thank you. 46.210.138.154 (talk) 18:40, 21 August 2013 (UTC)

The term is "cytes", not "cyties" (no "i"). It's simply a synonym for "cell". As to why neurons are not called "neurocytes", the answer is simply tradition. Looie496 (talk) 18:45, 21 August 2013 (UTC)

thank you for the answer on the first qustion. what about the second question on the name of the cells of the connective tissue? Is it called conneccytes? :) 46.210.138.154 (talk) 18:54, 21 August 2013 (UTC)

Fibrocytes and fibroblasts. Icek (talk) 19:35, 21 August 2013 (UTC)

Sorry, fibrocyte is just not the general name of the cells which incloud all the connective tissues. A fibrocyte is only ONE of kinds of the the cells which build the connective tissue. There are some kinds of cells of connective tissues like adipocyte, chondrocyte, endothelium, and so on. So, you can not say that the name of all cells of connective tissue called "fibrocytes" like you can say that the miocyte is general name of all kinds of muccels tissues cells. It's intresting for me to know if there is a general term for connective tissue cells. 176.13.166.201 (talk) 20:51, 21 August 2013 (UTC)

Why are you deliberately messing up the spelling of "muscle"? 89.241.229.123 (talk) 15:04, 24 August 2013 (UTC)