Wikipedia:Reference desk/Archives/Science/2017 April 12

= April 12 =

If a person eats an apple seed, then will an apple seedling grow inside him?
What about a watermelon seed or an orange seed or a cherry pit? If an apple, watermelon, orange, or cherry is part of a person's last meal, then will the seed grow inside the person's dead body? 50.4.236.254 (talk) 00:12, 12 April 2017 (UTC)


 * The digestive system is a rather hostile place for seeds, and they normally would only spend a day or two in there anyway. I suppose a dead person might make it possible for the seed to grow a bit, if it made it past the acidic environment intact, but it would probably die before it made it out.  Tree roots have grown into coffins and taken the shape of a corpse, as they grew through it and absorbed it. StuRat (talk) 00:15, 12 April 2017 (UTC)


 * Many seeds are designed to be defecated alive which is why they're placed at the center of delicious fruits. You're the seed's taxicab. Sagittarian Milky Way (talk) 00:25, 12 April 2017 (UTC)


 * A main problem there is that the seed basically contains cotyledons (two since apples are a eudicot). The seed splits open and delicate seed leaves come out on a short stalk.  Depending on the size of the seed they may have stored energy resources to fall back on, but to grow out through a significant amount of flesh, perhaps clothing, let alone a coffin seems like too much to ask.  The seed can certainly survive a short bath in acid, as pointed out above, so if the body is left on the surface it is possible that scavengers tear it apart and the seed drops on fertile ground. Wnt (talk) 01:28, 12 April 2017 (UTC)


 * A slight tangent, tomato seeds can certainly make it through the human gut and remain viable, as can be seen on railway tracks and in sewage plants. An example here. DuncanHill (talk) 01:32, 12 April 2017 (UTC)


 * A somewhat famous example would be Surtsey Nil Einne (talk) 10:22, 12 April 2017 (UTC)


 * What nobody has clarified is that germination requires a variety of cues, most of which are not met inside the human digestive tract. SemanticMantis (talk) 19:18, 12 April 2017 (UTC)


 * I'm not sure this is the case of this scenario. The OP wants to know what if the person dies with the seed in the stomach, would the body decompose and leave a viable seed behind? At a first glance this look realistic to me. Seeds are resilient. Hofhof (talk) 22:51, 12 April 2017 (UTC)


 * It appears that placing apple seeds in a very cold environment (a fridge) for a prolonged period of time is required for them to germinate (e.g. (http://www.instructables.com/id/Growing-Apple-trees-from-seed/]). Basic plant biology is that, once germinated, light is required for growth to continue.  So, I think the answer depends on several questions about the body and how it is treated after death. DrChrissy (talk) 23:41, 12 April 2017 (UTC)

Windows in highrise buildings
So, as I sit here with the sun going down over Anaheim, on the eleventh floor of a hotel, my windows are cracking and spluttering and creaking with the sun moving into obscuration. Are there any examples of high-rise buildings whose windows simply smashed with the temperature differentials, or did they get it right, straight off the bat, when making such shiny buildings? The Rambling Man (talk) 02:18, 12 April 2017 (UTC)


 * Breaking windows is nothing. A Twin Towers-ish sized building was built such that sub-hurricane wind would blow it over like a tree being cut down and this wasn't discovered till some undergraduate told the structural engineer. Its city was hours away from hurricane evacuation and repairs were only half done, the police had a plan to evacuate a mile wide circle of the New York City CBD so the building and any debris didn't fall on people and the existence of the poor design was kind of covered up for 20 years cause the hurricane veered away. Sagittarian Milky Way (talk) 07:56, 12 April 2017 (UTC)


 * The Hancock building in Boston springs to mind. 200_Clarendon_Street. It famously had many of its windows replaced with plywood while engineers tried to figure out the problem.
 * Sadly, the Spontaneous glass breakage article does not have a list of notable historical examples. ApLundell (talk) 02:33, 12 April 2017 (UTC)
 * Indeed, nor does it have single reference.  But thanks for your reply. The Rambling Man (talk) 02:49, 12 April 2017 (UTC)
 * Generally according to the Coefficient of thermal expansion (Glass 8.5, Iron or Steel 11.1, Concrete 12, Aluminum 23) neither the glass nor the height are cause but glass is the most brittle of the common building materials. So these tension brakes in glass are the result but the cause lies in the construction/design of the glass or window frames which are usually made of or themselves framed up in the other mentioned materials. In any good construction there are always spare spaces or gaps to cope with the differences of termal material expansions. So the closest conclusion likely is a bad construction/design. --Kharon (talk) 03:29, 12 April 2017 (UTC)
 * Yes, but that doesn't answer my question. The Rambling Man (talk) 03:34, 12 April 2017 (UTC)
 * It's very unlikely that a window pane would "simply smash" due to temperature difference. Sure, it might crack, probably at one corner, but shatter? No. Plenty of examples of high-rise panes falling around the world because of high winds, but we never know whether they cracked due to high temp before falling because the evidence is destroyed on impact. All googleable crack links that I've found are associated with high winds. Of course, any cracks that appear in panes are unlikely to be publicized, because of confidentiality clauses. They're not as publicly conspicuous as panes that actually fall. Akld guy (talk) 05:52, 12 April 2017 (UTC)


 * I'm not sure, but I remember reading something about the Seagram Building's windows breaking over time because of thermal expansion-related stresses (which is probably why it has two-colored (black and orange) glass now instead of the original all-black glass). 2601:646:8E01:7E0B:89D0:8453:4885:B526 (talk) 06:49, 12 April 2017 (UTC)


 * It's perhaps helpful to first get an idea of what we're talking about. which seems to be from an expert suggests that failures due to thermal stress are normall called thermal? stress cracks. It does however suggest that care needs to be taken in diagnosis since cracks arising from thermal stresses after edge damage may look the same.  suggests (I think, didn't read that well, it's a very long story full of heart string elements) that a fallen window fragment from the CNA Center that killed someone was a result of stress cracking and failed remedial work. One thing does sources sort of suggest as does, is that actually determing the precise reason for failure can get complicated, particularly once lawyers get involved. Nil Einne (talk) 10:17, 12 April 2017 (UTC)


 * This seems related to the current questions. -- Jayron 32 10:44, 12 April 2017 (UTC)

Thanks all. I'll look forward to tonight's sunset and another orchestra of bangs, cracks and pings, and not get too stressed about it! The Rambling Man (talk) 14:42, 12 April 2017 (UTC)
 * Anecdote: ever since we replaced the windows in our house with double-pane windows, they audibly make such noises at morning and evening. Our previous cheap single-pane windows didn't. I presume the double-pane construction amplifies the noises from thermal contraction/expansion, with the gas-filled cavity between the panes acting as a resonator. The hotel windows are likely double-pane, since places like hotels care about energy savings since it costs them a lot of money. If you don't have double-pane windows at home, you're presumably not used to the noises. --47.138.161.183 (talk) 05:23, 13 April 2017 (UTC)

How many trees need to be planted in order to reverse global climate change?
Yeah, I know carbon dioxide is a greenhouse gas. But trees need it to photosynthesize. So, how many trees and other types of flora need to be planted in order to reverse global climate change? Is it possible to fill up an entire city with lots and lots of indoor plants, with plants in every room and in every story? Can ballparks and farms and schoolyards become thick, dense forests? 50.4.236.254 (talk) 03:59, 12 April 2017 (UTC)
 * No, and for two reasons. First, there is an excess of about a trillion tonnes of carbon dioxide in the atmosphere as a result of industry . Such a quantity contains a similar amount of carbon to the entire biomass of all living eukaryotes on the Earth (see Biomass (ecology) and be careful converting the numbers, as this article considers the mass of carbon alone, whereas my first link is talking about carbon dioxide). So you would have to plant so many trees you'd double the biomass of the planet, which is a pretty tall order. Second reason, though, is that trees only cause a net reduction of carbon dioxide in the atmosphere when they are growing. In a thriving ecosystem, plants are born, consume CO2, grow, and then die. When they die, their decomposition results in much of that carbon simply being returned to the atmosphere, unless it gets sequestered. You'd eventually reach the Earth's capacity for plants, and then would be helpless to get rid of any new carbon dioxide being released to the atmosphere from fossil fuels. Now, if your plan was to grow an absurd number of trees, then cut them down and store them in such a way that their carbon never re-entered the carbon cycle, that would theoretically work. As you can read at the sequestration article I linked, this is something people have been thinking about for a very long time. Someguy1221 (talk) 04:08, 12 April 2017 (UTC)
 * But fossil fuels will eventually be depleted. So, will that put a limit in the amount of carbon dioxide in the atmosphere? 50.4.236.254 (talk) 04:17, 12 April 2017 (UTC)
 * It depends (as always ;-). Putting on my theoretical logician's hat, yes, the amount of carbon and oxygen on Earth and in its future light cone is finite (assuming current models of the universe), so there is an upper limit on the CO2 in the atmosphere (and there are other such theoretical arguments - if you add too much CO2, the Earth will turn into a black hole), but these are not very relevant, because the upper limits are gross overestimates of what humans (as a species) are likely to experience. Going back to human time scales, this paper in Nature Climate Change claims that five trillion tonnes of carbon ("5 exagram") is an accepted lower estimate for economically feasible reserves. Burning those under a "business as usual" scenario might lead to a temperature increase of about 10K by 2300. I'm not a climate scientist, but if they say 5egC is an accepted lower bound, the real value might be within one order of magnitude, so maybe 50egC. That would set a an upper bound under realistic assumptions. Now, going back into insufferable "knows-it-all"-mode, most of the carbon on (as opposed to in) Earth is ultimately released from carbon-bearing rocks, and that process continues. So even if we burn all current fossil fuels, over geologic periods, more may form, and I think that in the long run (many many millions of years) the amount of carbon available on and near the surface will very slowly increase. --Stephan Schulz (talk) 07:39, 12 April 2017 (UTC)
 * I read a 40 year old tree may arrogate roughly 1 ton of carbon dioxide. So we would have to plant 1 trillion trees, according Someguy1221's reference about the exess of carbon dioxide. Its most likely less because, as these trees produce an exess of oxygene, our atmosphere would expand and thus in some part get lost into space in addition to changing the mixture by filling it up with oxygene.
 * Unfortunately there is not enough suitable land on earth to grow that many additional(!!) trees and it is needed for farming at the same time. Also even if it would be achievable to plant that many trees, it would take 40 years to let them grow enough to bind all the exess co2 into biomass (wood) and ofcourse we would have to stop burning stuff aka produce more and more CO2, which already seems impossible to get done on this planet, nomatter it seems to be the easier part of such a plan. --Kharon (talk) 10:48, 12 April 2017 (UTC)
 * (1) as these trees produce an [excess] of [oxygen], our atmosphere would expand and thus in some part get lost - but they also "destroy" some carbon dioxide, so the net effect on the total atmospheric volume that gets out in space is not as obvious as your reasoning makes it seem. (2) there is not enough suitable land on earth to grow [1 trillion] [additional] trees - need some numbers on that: assuming 1 to 100 m^2 are needed for each tree, the area is 10^12 to 10^14 m^2. Earth physical characteristics tables says the emerged landmass on Earth is 149.10^12 m^2, so an argument about the area is not sufficient. Of course, it will only happen if we assume away economics (humans suddenly transformed into a slave species of treeplanters) and physics (humans irrigate the whole Sahara and design a giant greenhouse for Antartica), so it is not going to happen.

== Feynman Lectures. Lecture 52. Ch.52-4, Ch.52-5, Ch.52-6 Reflection symmetry ==

I don't understand why does Feynman in reflected world use right-hand screw rule but not left-hand screw (e.g. Fig. 52–3). And why do both the result and the vector product change sign in reflected world? It contradicts first statement. Username160611000000 (talk) 10:56, 12 April 2017 (UTC)

Are humans only concerned about climate change because they know they will be affected negatively?
While it is true that many species of flora and fauna are dying, other species seem to be thriving... just not in a way that would be favorable to humans. Many bacterial species may be completely harmless for the average human with a healthy immune system, but they can easily attack an immunocompromised human, the very young, the very old, and the unborn of pregnant women. Plants that humans don't want are interpreted as "weeds", and animals that humans don't want are interpreted as "pests", and those must be exterminated or removed from the food supply. But plants, animals, and bacteria can become resistant to the chemical treatments, so a new chemical must be developed. In the end, isn't nature winning, and humans are always struggling to keep alive and their populations up? 50.4.236.254 (talk) 13:09, 12 April 2017 (UTC)
 * There are lots of organizations around for conserving plants and animals that some people would consider pests. So the answer to you is no. Try thinking for yourself of things against something you think as well as things which confirm it, well anyway try doing that if you aren't interested in going into religion or politics ;-). Dmcq (talk) 13:55, 12 April 2017 (UTC)
 * But wouldn't elimination of the entire human species be the ultimate way of conservation of other species? 50.4.236.254 (talk) 14:02, 12 April 2017 (UTC)
 * Only ones that can survive in the new climate. In the past, sudden climate changes have resulted in all kinds of extinctions. Every schoolchild knows about the Cretaceous–Paleogene_extinction_event that killed all of the dinosaurs (but happily, not all the birds.), but there have been others. The Permian–Triassic extinction event was pretty devastating. With the benefit of hind-site we can say these were all "good" because they set into motion the events that eventually birthed our species, but from the perspective of the species that were killed, or the species that might have evolved from them but never got the chances, it was a disaster of the highest possible order. ApLundell (talk) 14:36, 12 April 2017 (UTC)
 * Even if that is true, it's irrelevant. You seem to be thinking people can only have one goal and must do everything possible to achieve it. In reality plenty of people may have many different genuine goals and these can sometimes come into conflict. There are plenty of people who may genuinely support conservation. The vast majority of them by far, for a variety of reasons, don't support the elimination of the human species. A larger but still small number may support a drastic reduction of the human population numbers (in a completely voluntary fashion). More commonly conflict comes in other ways. For example, when is the development of land or the mining of resources acceptable despite a negative effect on conservation. Or predator-human interactions. There is perhaps legitimate question over whether people have a tendency to push others to conserve but then fail to do so themselves (particularly in the developing-developed world context). And also even where people do conserve, how reasonable it is to demand others conserve at the possible expense of their development when you've already developed at the expense of conservation. But an argument people need to support the elimination of the human species if they are genuine about conservation doesn't tend to get much traction. Nil Einne (talk) 09:51, 13 April 2017 (UTC)
 * The Voluntary Human Extinction Movement is one group that proposes that the human species should allow itself to go extinct. Mitch Ames (talk) 08:41, 17 April 2017 (UTC)


 * "Only"? No. But that's a big part of it. Effects_of_global_warming_on_humans could be pretty devastating to our civilization. ApLundell (talk) 14:36, 12 April 2017 (UTC)
 * So, climate change is only devastating to species who are adapted in the former environment and rewarding to species who are adapted in the new environment, especially in the environment devoid of the previous species, including humans, which means how "good" or "bad" something is depends on what point-of-view you are looking at. So, if humans don't do any sort of "environmental protection", then they will be essentially living in their own filth and die. Bad for humans, great for the microbes or anything that can live at the expense of humanity. 50.4.236.254 (talk) 15:15, 12 April 2017 (UTC)
 * Sure, if you want to look at the "big picture".
 * If you want to look at the really big picture, Earth life in general is doomed unless a spacefaring species comes along in the next five billion years. (Sun)
 * ApLundell (talk) 16:12, 12 April 2017 (UTC)
 * We might only be a hundred years from being able to terraform planets around other suns and put humans there using robots for the spacefaring, we already have most of the required basic technology. People doing spacefaring though would take a lot more work. Dmcq (talk) 20:31, 12 April 2017 (UTC)
 * I guess that's kind of my point. This is veering into soapboxing and theorizing, but briefly, if the question is "does it matter to other Earth life if humanity goes extinct?", then I think part of the answer is that deap-space spacefaring is required for super-long-term survival. It's tough to say if humanity is earth life's best chance of that, or if something better might develop after we're gone. Five billion years is a long time. Perhaps it's vanity to think our extinction means no more spaceships.
 * ApLundell (talk) 21:41, 12 April 2017 (UTC)
 * We'll be able to do that soon enough anyway. What people will do is another question though. And I suppose it is life, but that view of life is like a child bashing things to make noise compared to music. The glory of life on earth is being pushed into pitiful enclaves on the edge of our civilization. Dmcq (talk) 09:16, 13 April 2017 (UTC)
 * Yeah, so it's a question of what it means for something to "matter". without defining a goal, it's a naive question wildly different valid answers. ("Humanity should go extinct." or "Humanity should push to the stars as hard as possible.") ApLundell (talk) 18:00, 13 April 2017 (UTC)

Clams, Oysters, Pearls in Freshwater ??
Are there any types of clam or oyster that lives in freshwater, and can pearls from such living organisms appear in freshwater? Most likely not, I should think...

Well, I found one, at least. The Freshwater Mollusc — Preceding unsigned comment added by 84.211.184.66 (talk) 15:04, 12 April 2017 (UTC)

84.211.184.66 (talk) 14:59, 12 April 2017 (UTC)
 * In the U.S., one of the largest cultured pearl regions is Tennessee where the Megalonaias nervosa or "Washboard Mussel" is farmed for pearl cultivation. See here for example.  Wikipedia has articles on Cultured freshwater pearls.  The Freshwater pearl mussel is a different species as well.  -- Jayron 32 16:06, 12 April 2017 (UTC)

Thanks, Jayron. Much appreciated. 84.211.184.66 (talk) 16:27, 12 April 2017 (UTC)

Distance estimate to the outside objects in driverless cars
I wonder how they do it? Do they use lasers or what? It seems lasers are ill suited for this. I also wonder if they measure the distance or estimate the distance. There is a difference. Any ideas? Thanks, - --AboutFace 22 (talk) 15:00, 12 April 2017 (UTC)
 * Many techniques exist; the most famous robot cars use LIDAR and other sensors, and then use complicated software algorithms to combine data (sensor fusion) and make high-level planning decisions.
 * Here's a great review of Stanley, the original 2005 automobile robot. They used a LIDAR to create a point cloud model of the surroundings, and had a special algorithm to estimate obstacle positions from point cloud data.  They also used cameras and RADARs.  That technology is decades old - newer cars use lots of other hardware and software methods - but you might as well start with the basics...
 * Nimur (talk) 15:35, 12 April 2017 (UTC)

Thank you. Helpful. --AboutFace 22 (talk) 20:22, 12 April 2017 (UTC)
 * Another link: (see in particular the section behind "goal #2").  Tigraan Click here to contact me 16:43, 12 April 2017 (UTC)


 * This story shows an animation which illustrates the information a Google self-driving car has about other road users - a world build up from the information fusion of its various sensors. It's a pretty rich picture - certainly better than the mental model a person would have of the same situation. The animation also shows the limits of the technology - look at the vehicles in the opposite lane: as they pass through the intersection, where they are densely occluded by other vehicles, the Google car has difficulty tracking the individual cars, so they flicker about. One goal self-driving vehicle makers have for the future is "swarming", where a given vehicle can also use sensor information from other vehicles to built its unified world view. -- Finlay McWalter··–·Talk 13:33, 13 April 2017 (UTC)

Could future fossil fuels be dying now?
Where might these plants be? (sentients would have to not harvest them while they're still peat or pre-oil, dismantle the Earth in a technological singularity or otherwise disturb them for millions of years) Sagittarian Milky Way (talk) 17:15, 12 April 2017 (UTC)
 * Oil mostly comes from water based microorganisms. So presumably they're still in the ocean doing whatever they do. Petroleum
 * Coal is a tricker question. It's believed to come from forests and land-based plants that become buried. Coal
 * But when we think about the time frames involved I don't think we're necessarily talking about a continual process. Perhaps a small forest gets buried every couple centuries. ApLundell (talk) 17:53, 12 April 2017 (UTC)


 * Modern geologists would all broadly agree the answer to the question is an unqualified "yes". Starting with James Hutton and Charles Lyell in the early 1800s, the principle of uniformitarianism has been a central tenet of geology for almost 2 centuries; the notion that processes that are going on now have been going on in broadly the same manner for a few billion years, and will continue to happen under roughly the same mechanisms for the forseeable future.  We have no reason to suppose that the principles of geology are expected to change in the future, or have stopped working.  -- Jayron 32 18:28, 12 April 2017 (UTC)


 * So there's no currently non-existing requirement like oil needs calcite seas to form or only certain configurations of continents can cause current microorganisms to be crushed into oil or anything like that? Sagittarian Milky Way (talk) 22:42, 12 April 2017 (UTC)


 * Right, fossil fuels are forming even as we speak -- only very slowly! 2601:646:8E01:7E0B:4C74:BE2F:701E:8F7E (talk) 04:40, 13 April 2017 (UTC)


 * The cycles that led to the formation of fossil fuels in the past are expected to repeat in the future as well. Uniformitarianism isn't an expectation that the earth remain identical, merely that for any arbitrarily long time period, there is no reason to presume any past process would not have similar conditions in the future which could recreate it.  -- Jayron 32 14:54, 13 April 2017 (UTC)


 * Until stellar evolution vaporizes the water and melts the world. Uniformitarianism's days are numbered. Sagittarian Milky Way (talk) 18:08, 14 April 2017 (UTC)


 * Coal is the exception here. Coal formed on Earth after the first trees evolved. It took a very long time before microbes evolved the capability to break down wood from dead trees. Huge amounts of dead trees from the Carboniferous era were converted to coal as a result. Count Iblis (talk) 19:47, 12 April 2017 (UTC)


 * Actually, coal formed under anaerobic conditions which would preclude microbial decomposition even today -- so coal could still form today under the right conditions, just not on such a yuge scale. 2601:646:8E01:7E0B:4C74:BE2F:701E:8F7E (talk) 04:40, 13 April 2017 (UTC)


 * What was the soil profile like at the end of the Carboniferous? Dead trees merging into lignite or something over hundreds of meters? Sagittarian Milky Way (talk) 20:52, 12 April 2017 (UTC)


 * A paradise for all those people who today pollute the air with their wood stoves. Count Iblis (talk) 21:11, 12 April 2017 (UTC)


 * Unless we get to something like the world of Soylent Green where nothing and nobody will have the chance to become a fossil. ;-) Dmcq (talk) 20:14, 12 April 2017 (UTC)


 * Peat is itself a fuel, and was used as such long before lignite or coal were perceived as resources. I am less clear on whether dried sphagnum moss (before becoming compacted) was or is used as a fuel in any significant amount.   There are indeed ecological issues - peat moss bogs straddle the line between a renewable ecosystem and a fossil fuel.  Wnt (talk) 11:33, 13 April 2017 (UTC)
 * It's all about supply rate compared to extraction rate. Sustainability essentially means that the extraction rate is at or below the supply rate. Oil is renewable if you're willing to wait 65 million* years for the next batch (*made up). Timber is renewable if you're willing to wait a few decades. Peat is formed more slowly than trees grow. Most of it formed around 4,000-8,000 years ago, but some is much older. We have lots of info on how many board feet we can sustainably harvest from a Loblolly pine plantation, but I am not aware of any comparable work for peat (or oil!). There is a decent amount of research in to accurately dating peat deposits, and so presumably there are some people working on establishing site-based estimates of supply rate. This Slate article has a fairly credible person saying that we'll run out of peat in a bout 2k years if use stays constant, but would never run out if peat were only used for Scotch production. Of course, use is not constant, and in fact more peat is used each year, as its use as fuel  becomes more attractive. SemanticMantis (talk) 16:10, 13 April 2017 (UTC)
 * Yes, and notice that peat very slowly turns into coal -- which debunks Count Iblis's statement on the subject. 2601:646:8E01:7E0B:889F:C54C:B6C4:1C77 (talk) 22:23, 14 April 2017 (UTC)