Wikipedia:Reference desk/Archives/Science/2013 May 15

= May 15 =

Is this an artifact?
Could this rock be an artifact? Note the hole through it. It is almost 7cm long. Bubba73 You talkin' to me? 00:06, 15 May 2013 (UTC)

I'm absolutely not qualified to say, but look at kettle hole. I think you can have hydraulic drilling on a very small scale under certain circumstances, but certainly I cannot tell you this is the case here. Wnt (talk) 01:22, 15 May 2013 (UTC)


 * Holes caused by dripping are much wider than this due to splashing. μηδείς (talk) 01:57, 15 May 2013 (UTC)


 * The hole is about 3.5mm wide on one side and nearly 4mm on the other side. Bubba73 You talkin' to me? 02:03, 15 May 2013 (UTC)


 * The hole is through the thinner part of the rock and it is nearly 1 cm thick there. Bubba73 You talkin' to me? 01:27, 15 May 2013 (UTC)

I noticed that there are two small indentions on both sides next to the hole - those must be signs of how the hole was made by people. See File:Rock hole back.jpg and File:Rock hole front.jpg. Bubba73 You talkin' to me? 02:39, 15 May 2013 (UTC)


 * Where is it from? HiLo48 (talk) 02:50, 15 May 2013 (UTC)


 * I don't know. My wife found it but she doesn't remember where.  We live in the state of Georgia, so I asked her if it was in Georgia, but she doesn't remember.  Bubba73 You talkin' to me? 03:55, 15 May 2013 (UTC)


 * I'm no expert here, but I doubt the hole was created naturally. I'd lean towards something Native American, but that's a guess.  I found a similar item online here but the description given isn't helpful.  Have you contacted your local historic society, they'd probably have some better answers.    Hot Stop   04:05, 15 May 2013 (UTC)


 * I have not contacted a historical society. I ran across it cleaning out a box of stuff today.  I don't remember it, but my wife says that she found it.  I suspect native American too - there are such artifacts around here.  It looks like the hole was to put a cord through it.  So maybe it was worn, used as a toy, or a weapon.  Bubba73 You talkin' to me? 04:16, 15 May 2013 (UTC)
 * And she doesn't remember anything about where she found it. What state?  She doesn't remember if she found it in the ground or in a museum gift shop.  Bubba73 You talkin' to me? 05:30, 15 May 2013 (UTC)


 * Is there any darkening or discoloration around the hole (either side)? 64.235.97.146 (talk) 13:29, 15 May 2013 (UTC)


 * I think it may have been overlooked Hot Stop, but the similar holed object on that website is a weight. Maybe that's what this is? Thanks ツ Je no va  20  (email) 14:20, 15 May 2013 (UTC)


 * Perhaps there is a little darkening, but not much. See the close-up photos linked above.  The "weight" description has a question mark after it.  Bubba73 You talkin' to me? 16:44, 15 May 2013 (UTC)

Some molluscs will bore into rock. See Pebbles with holes made by sea creatures. Alansplodge (talk) 17:52, 15 May 2013 (UTC)


 * This is one small hole all of the way through the rock, and it was unlikely to have been in the ocean. Also there are two marks (slight indentions) on the sides of the hole on both sides of the rock that may be signs of a tool being used.  Bubba73 You talkin' to me? 18:03, 15 May 2013 (UTC)


 * If you put a string through it and hung it around your neck could it work as a stone gorget/throat armor ?  Sean.hoyland  - talk 18:30, 15 May 2013 (UTC)


 * If you wore it like a necklace it would be too low. If you tied it up higher - maybe.  Bubba73 You talkin' to me? 18:41, 15 May 2013 (UTC)


 * Wild guess here, but possibly a sinker used for fishing.  Hot Stop   00:32, 16 May 2013 (UTC)


 * It does look a lot like that. Bubba73 You talkin' to me? 02:34, 16 May 2013 (UTC)


 * We need a petrologist here not an archeologist. To my eye, it looks like just sandstone or arkose. Both can contain iron oxides inclusions. Second: from its smooth appearance this stone is water tumbled  (iron oxide, water, dissolve...?) Third: man made holes are round (except in higher cultures). Fourth: the hole's diameter differs in stepwise in dimension  from face to obverse. Have not seen this in man fashioned  objects but in natural holes -frequently found.  Natural.--Aspro (talk) 00:36, 16 May 2013 (UTC)


 * I thought it was sandstone, but I'm not sure. It is smooth.  Bubba73 You talkin' to me? 02:34, 16 May 2013 (UTC)


 * Sandstone abrading sandstone of the same hardness will leave a smooth surface. Also, if you notice, that at the ten o'clock and four o'clock positions to the hole, there appears to be some iron staining. Testing for iron with what you have in the kitchen is not easy. Yet, if you have one of those super powerful  rare earth magnets. Then, by suspending the rock from a thread and after waiting for it to settle. The magnet may show that you have and iron rich river pebble.Aspro (talk) 14:28, 16 May 2013 (UTC)

FWIW, this rock File:Rock - another one.jpg was next to it in the box, but my wife doesn't remember if it has any relationship to the other one. Bubba73 You talkin' to me? 02:45, 16 May 2013 (UTC)

Office plant identification
A colleague has been looking after this plant for months in my office, and it is doing very well, but we have no idea what it is. It is not important at all, but if someone has 10 seconds to identify it for us, it would be great, we are very curious. I can provide a close up picture of a leaf if required. --Lgriot (talk) 10:12, 15 May 2013 (UTC)
 * Looks like Dieffenbachia possibly Dieffenbachia_seguine. Use Google images and search for 	Dieffenbachia. 196.214.78.114 (talk) 11:08, 15 May 2013 (UTC)


 * BTW FYI http://www.hoax-slayer.com/killer-house-plant-warning.shtml and Dieffenbachia 196.214.78.114 (talk) 11:15, 15 May 2013 (UTC)
 * Thank you very much, I think you are right.--Lgriot (talk) 13:42, 15 May 2013 (UTC)

Weak mixing angle
This image leads me to believe that a weak mixing angle that is a multiple of 90 degrees would leave the electroweak force unbroken. Is that correct? Am I mistaken in thinking that the weak mixing angle a free parameter? Baconmancer (talk) 17:08, 15 May 2013 (UTC)
 * A weak mixing angle that is a multiple of 90 degrees wouldn't be a mixing angle. Note that the weak mixing angle is determined by the position of the Higgs field labeled with an H at the picture. Note that the line connecting the origin to the Higgs field is perpendicular to the electric charge axis (labeled with a Q). The mixing angle is basically a measure of the ratio between the vertical scale (Labeled with a Y for weak hypercharge) and the horizontal scale (labeled with a T for weak isospin). You would need one these scales to be reduced to zero in order for the angle to be a multiple of 90 degrees. That can't be done without drastically changing the nature of the theory. Dauto (talk) 00:35, 16 May 2013 (UTC)

The number of microbes in the throat in case of cough
Hello, I have some questions about I have read (in one of my exercise in Math) that the pain in the throat is caused by found of 10^9 microbes (which is called "streptococcus"). First of all I would like to know if it truth. Second, I would like to know what to do if I want to check the air that I breath out of my mouth for looking for microorganisms like streptococcus what is the tool that I need for that? thank you :) {I hope that I've expressed myself properly... because English it's not my mother language}מוטיבציה (talk) 19:51, 15 May 2013 (UTC)
 * The tool you need to test for streptococcus in your throat is a physician or other medical professional. We don't have any of those at Wikipedia.  See Medical disclaimer.  -- Jayron  32  19:59, 15 May 2013 (UTC)


 * If you read about streptococcus in a math exercise, the biology was probably highly simplified, if not wrong. Likely, the people who wrote the exercise were just using bacteria as a way to introduce exponential growth. Anyway, testing for microbes in exhalation might be done for research purposes, but that is not how doctors test for strep throat. As our article explains, this is usually done via throat culture. And note that we have strict rules about requests for medical advice, so please don't ask us for medical advice, because we will not give it. However, I think you are looking for information and references, and your question passes Kainaw's criterion. SemanticMantis (talk) 20:34, 15 May 2013 (UTC)
 * There is a nice review article on diagnosis of respiratory infections (not precisely the same thing) here: ; unfortunately that does not directly address the OP's question about diagnosing Streptococcus pyogenes as a cause of pharyngitis; it does include Streptococcus pneumoniae as a cause of pneumonia. -- Scray (talk) 22:55, 15 May 2013 (UTC)


 * Tell me, what is the point of citing PUBMED articles here? Not only is a PUBMED article likely to be over the head of an OP asking a question like this, the article can only be accessed if you pay for it, or you are attched to a university of institution who has paid the subscription.  Wickwack 124.182.175.128 (talk) 00:22, 16 May 2013 (UTC)
 * While I could have taken time to summarize that article, as I said it doesn't directly answer the question. The point of citing (aside from it being an excellent practice for answering biomedical questions) is that for those interested, they can read the abstract for free, and (contrary to your assumption) a large number of Pubmed entries link to the free full text. For articles not available in full text for free, some questioners are students or otherwise have access. If you don't find any of that worthwhile, feel free to ignore my answer and cut my Wikipedia paycheck by 80%. -- Scray (talk) 01:24, 16 May 2013 (UTC)
 * You know, Wickwack, this is a reference desk. The last the we should be doing is berating someone for at least attempting to provide a high quality reference.  Too many times, we treat this as a "give an answer I pulled out of my ass desk" and Scray should be applauded for providing sources that the OP may be interested in.  -- Jayron  32  01:38, 16 May 2013 (UTC)
 * I agree that Ref Desk answers are better if they cite a relevant reference, preferably a creditable online reference, if not then a standard textbook. As far as I know, PUBMED, which is part of the Elsevier publishing empire, only makes articles available for free if they are judged to be of signifiant historical interest.  If you are able to access articles without charge, it's probably because your employer is an educational, research, or scientific organisation that has paid for access - just as I can access similar journals in my field.
 * Citing a source that the OP, and the rest of us, cannot access or are not likely to access because of the cost, or is likely to be above the OP's head, is not just as bad as not citing any source, it is worse. It is worse because it gives sense of authority which the source may or may nor support.
 * Too many Ref Desk posters seem to think that scattering a few hot links around, whether directly relavent or not, satisfies the Ref Desk policy. It only does that if the cited source is a) available, b) is directly relevant, and c) supports what the poster's answer, or answers the question.
 * More importantly, when answering questions, we should endevour to assess the OP's competence and educational level, and answer accordingly. Not always easy to do this, but we should always try, and mostly it is easy. I've been writing papers and technical manuals for decades - the first one learns is to write for your reader, and to help him/her, not to impress.
 * Incidentally, a Ref Desk answer is still a good answer without any citation if what it says is self evidently true, for example by using logical inference. E.g., if a question can be answere with some simple algebra, there's no need to cite an algebra source.  What I try to do as well, subject to Rule 1 Write For Your Audience, is use/explain the correct terminology, so that the OP and anyone else can google the terms and learn a lot more.  Wickwack 124.182.35.52 (talk) 03:32, 16 May 2013 (UTC)
 * No wonder you are so confused - Pubmed is a tool provided by the United States National Library of Medicine, specifically the National Center for Biotechnology Information. I suggest you take your poorly-informed criticism of my answers elsewhere. -- Scray (talk) 03:40, 16 May 2013 (UTC)
 * I'm not confused, you are. Public internet access to PUBMED articles is managed by Elsevier Science Direct, and has to be paid for - $31.50 in this case.  Log in as an ordinary private internet user and try it.  Check you facts before critising others.  Wickwack 124.182.156.152 (talk) 05:25, 16 May 2013 (UTC)
 * Let's continue this discussion in a more appropriate place. -- Scray (talk) 05:50, 16 May 2013 (UTC)


 * An Agar plate containing blood agar can be used to culture streptococcus, but culturing dangerous micro-organisms probably should not be attempted by untrained/unqualified personnel. A sterile swab would generally be used to obtain a sample from the throat, rather than trying to get microorganisms from the breath. Edison (talk) 02:50, 16 May 2013 (UTC)
 * True, but that's not what the OP asked. They asked how to test their breath. While the title mentioned cough (and I now realize they might have meant to suggest tests of sputum rather than just breath), sputum culture is not a reliable test for pharyngitis (as you say, throat swabs are standard, and that's not what they were asking about). -- Scray (talk) 03:23, 16 May 2013 (UTC)

Nuclear reaction
If a really big asteroid smashed into Earth (like the one that is supposed to have finished off the dinosaurs, for instance) then would there be enough energy in the resulting explosion to cause any nuclear reactions (fission/fusion)? If not, how far away from the required energy would it be? Fairly close? Vastly too weak? 86.176.211.20 (talk) 20:29, 15 May 2013 (UTC)
 * No, but it has nothing to do with the energy involved. As a practical matter, only certain elements are capable of nuclear fission or nuclear fusion.  This section explains nicely how fusion can be accomplished outside of an active star, which is basically restricted to a small number of carefully controlled reactions involving a limited number of nuclei.  The earth is, by and large, not made of these nucleii, so forget that.  Likewise, nuclear fission requires highly concentrated collections of fissile material.  While that stuff does exist on earth, it doesn't exist in concentrations necessary to support nuclear fission; that's why we need to enrich it.  Basically, the only fissile nuclide native to earth in any sizable quantities is Uranium-235, any other fissile nuclide you'd need to make via other means, and there is nowhere on Earth where U-235 exist in anything except very trace amounts, many many many orders of magnitude too small to support sustained chain reactions.  So no, no impact is ever going to start a nuclear reaction of any sort.  -- Jayron  32  22:13, 15 May 2013 (UTC)
 * The above answer is a little hasty in dismissing fusion, as that happens often in hydrogen, of which there is plenty on the Earth's surface in the form of water. The question of whether we would get either fission or fusion does, of course, depend on both the energy dissipated in the impact and what materials are actually present at the impact site. I agree that there is very little chance that fission will occur, purely since the sort of materials that undergo fission at reasonable temperatures (uranium and plutonium)are incredibly rare. Fusion, on the other hand, we have plenty of hydrogen for. The question is then one of energy.
 * The asteroid which is thought to have killed off the dinosaurs was probably about 10km across. Doing some ballpark calculations, we find that a 10km sphere of rock falling onto the Earth's surface has to dissipate about 1024J of energy. If you assume that about 10% of that energy remains within that 10km across volume at impact and assuming it hits water, you would end up with a transfer to each water molecule of about 10-17J or, in units beloved of nuclear physicists, about 100 - 1000 electron Volts. Now, to get hydrogen to undergo fusion, you need to give each atom about 700,000 electron volts, so we find that we only have about 1000th of the energy density required to cause hydrogen to undergo fusion. Of course, this is a very approximate calculation, but 1000 times the energy is still a long way off. So probably no nuclear reactions, I'm afraid. Eaglehaslanded (talk) 22:20, 15 May 2013 (UTC)
 * My question was kind of based on the premise that any nucleus could potentially disintegrate (and/or fuse) if you smashed something into it hard enough. However, clearly if the most easily fusible / fissile nuclei won't do that at the relevant energies then the more difficult ones won't either. 86.176.211.20 (talk) 23:08, 15 May 2013 (UTC)
 * The problem is sustainable fusion or fission as well. While, hypothetically, you can "force" any two nuclei to collide and do something, given enough energy, practically only those reactions which are highly exothermic will be self-sustaining.  And known self-sustaining fusion and fission reactions are very limited in number, and cannot occur using random bits of the Earth, but rather require certain very carefully controlled types of matter and environments which simply do not exist naturally on earth.  -- Jayron  32  23:34, 15 May 2013 (UTC)
 * I wasn't suggesting that such an event could trigger any kind of self-sustaining nuclear reaction, but wondering whether it could cause any nuclear reactions to happen due to the energy of the impact itself. 86.176.211.20 (talk) 00:23, 16 May 2013 (UTC)
 * Assuming that the calculations of Eaglehaslanded are plausible, that "1000th of the required energy density" would be on average, and actual energies of individual atoms would be higher or lower, right? Given this distribution of energy, is it possible that some atoms could still undergo fusion? 86.176.211.20 (talk) 00:47, 16 May 2013 (UTC)
 * No, even on the long tail of the Maxwell–Boltzmann distribution, I'd expect to find no measurable number of atoms with enough energy. -- Jayron  32  00:56, 16 May 2013 (UTC)
 * XKCD's "what if" section is very keen on suggesting that the pressure wave in front of a sufficiently fast moving object could be enough to cause fusion in the atmosphere (e.g. what-if.xkcd.com/1/‎ and what-if.xkcd.com/12/ ) Much as the examples are probably well beyond any practical asteroid (well, at lest one that we're likely to be abel to comment on afterwards), is there actually any possibility of this? MChesterMC (talk) 09:31, 16 May 2013 (UTC)
 * Depends on what the definition of "is" is. Seriously.  It is, of course, quite trivial in any of these cases to mathematically calculate exactly how much energy is needed to do whatever it is you want to do.  The math is easy, trivial, and can be done by anyone with a calculator.  The difficulty is in envisioning a real scenario where such events could occur.  So, when you ask if some bizarre scenario is possible, my first inkling is not merely to do the trivial math, but to try to envision a scenario in the real, physical universe where such math would come into play.  I simply can't see it.  -- Jayron  32  12:02, 16 May 2013 (UTC)


 * I'd like to put this into some sort of context. Consider an Apollo Capsule re-entering Earth's atmosphere at a horrendous rate of knots. The plasma created at  the shock-front is only a few inches thick. The temperature only gets up to about 5,000 degrees in this instance, because the kinetic energy that is converted into heat, get radiated away at the speed of light. The OP is speaking about a ruddy great lump of cosmic material of much greater mass (and thus kinetic energy) than this. As the OP question's: This issue about whether the   'dynamic' confinement time at X Kelvin at Y density for Z seconds is enough to trigger enough fusion reactions to account for what is observed in meteor encounters.  Re: The nuclear and aerial dynamics of the Tunguska event. S. J. D. D’Alessio and A. A. Harms McMaster University, Hamilton, Ontario, Canada : and  Natural low energy nuclear fusion reaction. Boris A. Andrianov. National Research South Ural State University, Chelyabinsk. What is interesting, is that numerous  (an as yet, anecdotal)  reports from witness of the of the latest big Russian meteor, is that they experienced radiant heat in excess of what Newtonian physics can account for. Aspro (talk) 13:38, 16 May 2013 (UTC)


 * As an aside: Found a non pay-wall reference to Natural low energy nuclear fusion reaction by Boris A. Andrianov,  here at  >  http://www.google.com/url?q=http://www.intellectualarchive.com/getfile.php%3Ffile%3DHvKjaN0om65%26orig_file%3DAndrianov.pdf&sa=U&ei=6eKUUbn2As6KhQeT74CIBQ&ved=0CBgQFjAA&usg=AFQjCNHLlNCPO-302RDitKKzu3JEmO4R-g  < .  Why can't science (that we pay for in our taxes)  be free for anyone to access?''Aspro (talk) 14:00, 16 May 2013 (UTC)


 * The atmospheric heating is never going to be enough to cause nuclear reactions - there are only a very few materials that remain solid at more 5,000 degC and that don't boil at more than 6,000 degc. As soon it gets hot enough they boil or melt, they carry the heat away and the object doesn't get much hotter from that point onwards.  So temperatures just don't get high enough to get nuclear effects during entry into the atmosphere.  Any effect that might happen would most likely have to be on impact with the ground or ocean. SteveBaker (talk) 19:10, 16 May 2013 (UTC)
 * Don't follow your reasoning. An atom  bomb (the uranium/plutonium type)  fission-fire-ball lasts for a about two seconds (the device itself vaporises after some micro-seconds).  A hydrogen devise continues to undergo fusion for many more seconds. Whether it is solid, molten gaseous or plasmic doesn’t matter. It is the density, temperature and confinement  time that matters. An as the OP points out... A very large object travelling a miles per second is imputing a lot of energy in a very small time frame. True: expansion of the plasma allows it to cool .... but  the fire ball expands whilst heat is being generated and  until it reaches normal atmospheric pressure. After that, the only way it can cool further, is to ascend  - upwards - hence the sudden rush of wind in the opposite direction of the blast wave.  As my reference pointed out; it may not be hydrogen fusion but  fusion of  magnesium and silicon. Newtonian physic alone, can not explain why these lumps of rock suddenly go poof and radiate more energy than Newtonian physics can account for  before the fragments hit the ground. At these speeds and time frames, it happen too quick for thermal conductivity to account for fragmentation and energy output. Hence the interest in other possibilities - such as fusion of the meteoric mass.Aspro (talk) 00:00, 18 May 2013 (UTC)

I'm not entirely clear on whether the question is, would there be any noticeable incidence of fusion (answer is clearly no), or would there be likely to be even a single fusion reaction? I suspect the answer to the latter question is still "no", but it's not quite as trivially disposed of.

The biggest problem with Eaglehaslanded's analysis is that ordinary hydrogen cannot fuse in a two-body collision, except in the very rare case that the resulting diproton decays to deuterium (see proton–proton chain reaction). I don't know how rare "very rare" is, but let's suppose it's so rare that we wouldn't expect it to happen even once in this scenario (anyone know if that's true?). I can't find out much about proton-deuteron reactions in a quick search, but I gather that they're not very likely either. (Three-particle collisions are so unlikely that I feel pretty confident that we can exclude them, though I haven't tried to calculate it.) So probably we'd need to get lucky and have, at least, two deuterons collide, or a deuteron and a Helium-3, or a proton and a Lithium-6, or a proton and a Boron-11. All of these involve species that are much much less abundant than ordinary hydrogen.

Anyone feel like putting these things together and estimating the probability of even a single fusion reaction in the scenario described? My guess is it's going to be negligible &mdash; but I haven't done the math. --Trovatore (talk) 02:26, 17 May 2013 (UTC)

Explosions...IN SPACE!
How big would an explosion on Earth have to be to be visible to the naked eye in space? How much TNT/how big a nuke would this equate to? --iamajpeg (talk) 22:17, 15 May 2013 (UTC)


 * You would have to specify how far away in space. Possibly you are thinking of low earth orbit? 86.176.211.20 (talk) 23:09, 15 May 2013 (UTC)
 * Brightness matters, too. It doesn't have to be big so much as bright. Mingmingla (talk) 23:13, 15 May 2013 (UTC)
 * In fact, an explosion doesn't have to be very big at all to be seen from LEO. One of the early ISS occupants reports that he could clearly see American ordnance from space during the 2001 invasion of Afghanistan. "One night, I looked down on Afghanistan and I saw these big, bright explosions ... I was witnessing the invasion of Afghanistan in pursuit of Osama bin Laden and the Taliban." The article states that he, "was able to identify what he saw as explosions from cruise missiles and bombs being dropped from B-52s." Evanh2008 (talk&#124;contribs) 00:42, 16 May 2013 (UTC)


 * (EC) Where in space? The Kármán line?  The lower boundary of the exosphere?  Geosynchronous orbit?  Half way to Proxima Centauri?  Red Act (talk) 23:15, 15 May 2013 (UTC)


 * The human eye has a visual acuity of about one arc-minute. If you're looking from the International Space Station (about 400km above the Earth's surface) during the daytime, that corresponds to being able to distinguish things about 120 meters across.  That's a dust plume from a reasonably large controlled demolition, or blasting in an open-pit mine or construction project.


 * If you're looking at night, it's a different matter. You're looking for the flash of the initial explosion, so the size of the explosion doesn't matter, it's the brightness that determines if you can see it or not.  If your eyes are fully dark-adapted and you know where to look, you can see amazingly dim things. --Carnildo (talk) 00:43, 16 May 2013 (UTC)
 * I just want to add, for the sake of factual data and whatnot, that the fireball from even just a nominal-size nuclear explosion (say, a few tens of kilotons) is on the order of 400 meters across. For a 1 megaton explosion, it's almost 2 kilometers across. For a 10 Mt explosion, it is about 3 kilometers across. So they are pretty big. They release the majority of their thermal energy (and thus light) over the course of a few seconds (nominal yield explosions take about a second; much larger ones can take longer than that). --Mr.98 (talk) 22:01, 17 May 2013 (UTC)


 * The distance is only part of the picture here. The ISS orbits at about 250 miles up.  That's around ten times further than the distance to the horizon when you're standing on the top of the Empire State Building...so things look ten times smaller.  That's really tiny!  However, when you look out at the horizon from a tall building, there's lots of air and mist and pollution between you and what you're looking at.  But the vertical view from the ISS is looking though only maybe 20 or so miles of that 'stuff' - so unless there is a cloud in the way, the view is actually clearer even than looking at the horizon from the top of the Empire State building.  Better still is that the shimmering of the air is present only in the lower altitudes - and you're looking though a lot of that when you're on top of that building - but hardly any of it from the ISS.  So this winds up being a trade-off between size and optical clarity.  For small objects that don't have much contrast against the landscape, the view from the ISS would make them hard to see.  For large objects or things that are very bright or very dark compared to the rest of the landscape, they are likely to be easier to see from the ISS than from the top of a tall building.  Fires and explosions at night should be easily visible from space - even if they are quite small - but a cloud of smoke drifting over the landscape would be much harder to see.  So for a modest daylight explosion that produces much smoke - I doubt you'd see it from orbit - but even a fairly small one should be clearly visible at night. SteveBaker (talk) 16:38, 16 May 2013 (UTC)


 * Where an explosion makes a visible flash, Carnildo is on the money, SteveBaker is close. Some idea of the visibility of visible flashes at night can be obtained by considering aircraft navigation lights. Nav lights don't flash one a and go out, but their power will give us a rough guide. Nav lights for light aircraft have generally been incandescent globes (LEDS are taking over) about 25 mm diameter rated at 28V about 5 to 6 W.  Max altitude for unpressurised light aircraft is about 4000 m, where the distance to horizon is 225 km.  The nav lights in airliners are usually rated at 26 W.  Airliners can reach ~13,000 m, at which the horizon is 412 km away.  In both cases on clear nights (and for ailiner altitudes all nights are clear) pilots can see the nav lights of other aircraft when they come over the horizon, commercial aircraft very noticably.  Wickwack 120.145.81.185 (talk) 00:02, 17 May 2013 (UTC)
 * Saw this article, thought it was relevant to the discussion. It concerns a meteoroid that made impact with the moon recently. The article states that the explosion was equivalent to roughly five tons of TNT, and that it would have been visible to the naked eye from earth. I find that very hard to believe, but there you go. Evanh2008 (talk&#124;contribs) 23:25, 17 May 2013 (UTC)

Amateur (or professional) mycologist wanted
Unfortunately, I don't have a picture, but perhaps someone can put me in the right ballpark as to what I have seen. While watering the impatiens and petunias this evening, I noticed that in some specific patches of mulch, when I hit it with the hose, a puff of what looked like dust or smoke would appear. Upon investigating one of these spots, I found, buried just under the top layer of mulch, a very fine orange-tan powder, roughly the color of my wife's foundation powder (this color) and what looked like smallish blisters just underneath it (maybe the size and shape of the tip of my pinky finger), which were very sensitive, even a gentle prod with a stick caused the blisters to burst, and spread a fine cloud of what I assume were mold spores of some sort. A few pokes, and the patch dissipated entirely, leaving almost no evidence of its prior existence. If it helps, I live in Raleigh, North Carolina. Any clues? -- Jayron  32  22:57, 15 May 2013 (UTC)
 * Certainly sounds like a puffball, but you probably know about those and want the genus/species. I wonder whether you might have missed the rest of the spore sac (the "blisters" being the tip; though perhaps they were the entire spore sac), and an example that can grow low to the ground in decaying matter is Geastrum triplex, fairly ubiquitous in distribution. The puffball mode of spreading spores is pretty common, and not monophyletic (has probably arisen more than once in fungal evolution). -- Scray (talk) 23:21, 15 May 2013 (UTC)
 * No, I'm familiar with puffballs. This wasn't them.  These were clusters of small blisters, not large fruiting bodies like puffballs.  Immature puffballs are firm as well, unless these were a very different type of puffball.  The ones we have around here tend to grow into largish (baseball-or-orange sized) balls which send off purple-black clouds of spores, and until they mature, are fairly firm, and even when mature, aren't this fragile.  This stuff literally almost evaporated at the slightest provocation.  I'm not denying this might have been some very different kind of puffball-type fungus than I am used to, but it definitely didn't look anything like Geastrum triplex or any puffball I am familiar with.  After the spores dissipated, I looked around in the mulch, and nothing particularly stood out: no residual stalks or scraps of the bodies left over, as I usually see when I run over a puffball with the lawnmower.-- Jayron  32  23:29, 15 May 2013 (UTC)


 * Going purely from the habit and location, you may be the proud owner of a slime mold! See, and our page on Fuligo_septica (of course not necessarily that species) The so called "dog vomit" need not be so bright as the picture in our article, see the 10th pic here , which is pretty close to your makeup photo. I believe the slime mold genus Fuligo matches all your characteristics, down to the color, growing in mulch, and the powdery spores. SemanticMantis (talk) 23:37, 15 May 2013 (UTC)
 * I did not realize the slime molds could produce such a puff - thanks for the well-crafted answer. -- Scray (talk) 23:53, 15 May 2013 (UTC)
 * Ooh, I like this! I'll go with this.  Does this present any sort of problem for my garden, or is it just a harmless annoyance?  -- Jayron  32  00:20, 16 May 2013 (UTC)
 * The one complaint I'm aware of is that some spores may try to take hold on your house. I've heard the little dots/failed colonies can be tough to scrub off of vinyl or aluminum siding. Of course they won't do much there but leave a tiny dot. You'd think it might conceivably try to eat wood siding, but I've never heard of that, and you can google around these issues if you're concerned. I suppose paint and other sealants keep them out pretty well. As for your garden, I wouldn't worry. It's just a decomposer of sorts that does well in mulch. Me, I'd be more interested in putting some under my microscope, or seeing if I could get it to solve steiner trees or rail networks! (see, or google /slime mold city planning/ for videos and other fun stuff). SemanticMantis (talk) 02:04, 16 May 2013 (UTC)