Wikipedia:Reference desk/Archives/Science/2011 July 30

= July 30 =

Bone bruise, hairline fracture, or something else?
Sorry. APL (talk) 00:08, 30 July 2011 (UTC)
 * Just to go on the record here, I very heavily contest the fact that my question has been marked as a request for medical advice. The situation I am inquiring about occurred so long ago that I can't specifically remember when (probably 1-3 years ago), and the question requested information completely separate from advice (I've been around long enough that people should know by now I would be smarter than to ask for medical advice on Wikipedia)...it could have been answered with a simple link or explanation to the differences in symptoms between two conditions. In the interest of not going on an edit war I won't revert the deletion again (WP:BRD, if you will), but I strongly disagree with the question being considered a request for medical advice. Ks0stm (T•C•G) 01:11, 30 July 2011 (UTC)
 * I'd argue on your behalf, except ... I didn't know how to answer that question anyway. If it were easy to tell what happened by the difference in symptoms, there wouldn't be so many doctors sending people for X-rays. Wnt (talk) 07:05, 30 July 2011 (UTC)

Cloud phenomenon
Okay, I cave. I've watched several different videos of this phenomenon, so I'm fairly certain it's real, but I have absolutely no idea what's happening here or here. It seems like every time it shows up the person is behind the cloud from the sun, with the sun just below the lip of the top of the cloud, and the cloud has a diffuse, icy pileus around the top. Anyone care to speculate on what's causing these strange light "bouncing" phenomena? - Running On Brains (talk) 00:58, 30 July 2011 (UTC)
 * I don't know, but if I had to guess: it looks like a source of bright light sweeps across a cirrus cloud (which may be the anvil of a cumulonimbus cloud). The bright light appears to shift, with different "fronts" of light moving across the cirrus cloud quite quickly.  Assuming that the only source of bright light is the sun, and that the atmosphere above the cirrus cloud is pretty boring, the only possibility that I see is that the light is being reflected from below.  As it seems pretty sunny out, it doesn't seem like it could be reflecting from a lake with seiches or something - rather, my guess is that it's being reflected at an angle by ice crystals, perhaps in the cirrus cloud, more likely in the cumulonimbus formation just below it.  Presumably as the winds shift, or the temperature of the air changes, the light is reflected from a different point or refracted in a different direction, causing the rapidly changing lights.
 * There's a theorem in astronomy that no body can change brightness in a faster time than it takes light to cross it. I wonder if something similar applies to a situation like this involving the speed of sound.  Since the patterns seem to change within 0.5 to 1 seconds, I would picture that the reflecting feature should be less than about 150 to 300 meters in size.  But I don't know if that's really valid. Wnt (talk) 06:34, 30 July 2011 (UTC)


 * As Wnt suggests,its a form of Sun dog phenomena. The moving clouds are repeatedly occluding a patch of ice crystals in the higher parts. --Aspro (talk) 09:39, 30 July 2011 (UTC)

Bone tracheas
I was quite confused by the following passage:"One skeleton taken out of this part of the mound had the appearance of a very aged man; the point of the inferior maxillary was almost in two parts, while the trachea was bone all around. Quite a number showed indications of extreme age; seven or eight that I observed had bone tracheas."The context is a railroad official overseeing the excavation of a Glacial Kame archaeological site in the 1850s. So what's a bone trachea? I put this into Google and didn't find anything useful; most of the results were lists of body parts that happened to have "trachea" immediately following "bone". Nyttend (talk) 01:15, 30 July 2011 (UTC)


 * Cartilage tends to turn to bone over time. While some structures normally remain cartilaginous for life, ossification of tracheal cartilage can be a sign of advanced age. Ossification of tracheal cartilage in aged humans μηδείς (talk) 01:35, 30 July 2011 (UTC)


 * Try "trachea ossification" on google. Dauto (talk) 01:45, 30 July 2011 (UTC)


 * You will come up with the same paper I did above when I googled the same words. μηδείς (talk) 01:52, 30 July 2011 (UTC)
 * I always assumed that cartilage in childhood would normally remain cartilage throughout life, aside from issues such as arthritis; thanks for the help. I've now cited the linked PubMed article in a new article here about the site that was being excavated, the Ridgeway Site.  Nyttend (talk) 02:33, 30 July 2011 (UTC)

The history and use of coal balls
The title says it all, pretty much. Does anyone know about the history of coal balls, and what they can be used for? -- Σ  talk contribs   01:36, 30 July 2011 (UTC)
 * The only reference I can find to anything called "coal balls" at Wikipedia is found at the disambiguation page Niggerhead which indicates they were deposits of Pyrite found in coal mines. I have no idea if this is the item you are looking for.  -- Jayron  32  03:43, 30 July 2011 (UTC)
 * I did find another reference to them, at Permineralization they seem to be small carbonate balls that represent the fossilized remains of microscopic plants. -- Jayron  32  03:51, 30 July 2011 (UTC)
 * A third possibility is the black fungus known as Daldinia concentrica. -- Jayron  32  03:53, 30 July 2011 (UTC)
 * I need information about the second possibility, about fossilised remains of plants. Thanks. -- Σ  talk contribs   04:03, 30 July 2011 (UTC)
 * How about the mixture of clay and coal dust which Marco Polo wrote of and is used as a fuel in China today?&mdash;eric 02:59, 31 July 2011 (UTC)
 * Clay + coal dust is called a pencil. -- Jayron  32  04:53, 31 July 2011 (UTC)

Sounds of Earth from the Voyager Golden Record: volcanoes, earthquake, whale song, tractor... ?
I came across this article: Contents of the Voyager Golden Record, and I found myself trying to recognize the different sounds listed in the "Sounds" section. There is also a list on the NASA website: http://voyager.jpl.nasa.gov/spacecraft/sounds.html You can hear these sounds here: http://www.youtube.com/watch?v=s-6CvmmcG0w

I have several questions:
 * Does the sound of volcanoes really start at 00:43?
 * Is it the sound of an earthquake we can hear around 01:05?
 * The list on the NASA website doesn't mention "Whale song"; but is it that sound that starts at 04:57?
 * According to the list, there are two sounds of tractor, one that starts at 07:32 and one another at 09:25. The first one doesn't really sound like a tractor to me, rather like a jackhammer. What do you think?
 * The list mentions "Thunder" before "Mud pots" and "Wind" just thereafter, but I can't hear them. Is it an error? You can hear the sound of the wind at 05:27.

Also, would it be a good idea to rearrange the list and to add the timing, like in the "Greetings" section? Thank you! --Glups (talk) 04:05, 30 July 2011 (UTC)


 * The 7:32 tractor sounds like it has Caterpiller treads and no muffler. Edison (talk) 20:01, 30 July 2011 (UTC)

orbit and mass
Is the mass of a planet related in any way to its orbit? --DeeperQA (talk) 08:17, 30 July 2011 (UTC)


 * Absolutely. Please see our article on orbit: "Newton showed that, for a pair of bodies, the orbits' sizes are in inverse proportion to their masses, and that the bodies revolve about their common center of mass. Where one body is much more massive than the other, it is a convenient approximation to take the center of mass as coinciding with the center of the more massive body."--Shantavira|feed me 12:17, 30 July 2011 (UTC)


 * How does that conflict with the fact that massive planets - Mars, Jupiter - are in the middle tier of the Solar System, but small planets are on its extremes? — Preceding unsigned comment added by 88.8.79.148 (talk) 13:16, 30 July 2011 (UTC)
 * Mars is not particularly massive. Dauto (talk) 14:05, 30 July 2011 (UTC)
 * You are right on that. I was thinking about Saturn. 88.8.79.148 (talk) 14:20, 30 July 2011 (UTC)


 * No Shantavira, that's completely wrong. Newton has not showed any such relationship which is not observed in practice either. Our specific solar system's history has lead to some patterns described by Csmiller bellow but exoplanets have been found that do not follow that pattern. Dauto (talk) 14:05, 30 July 2011 (UTC)


 * Huh? I am quoting our article. Maybe you could fix it if it's wrong.--Shantavira|feed me 15:55, 30 July 2011 (UTC)


 * The quotation is correct. Your interpretation of it is wrong. That quotation simply mean that the size of the orbit of the moon around the earth is much bigger than the size of the orbit of the earth around the moon because the earth's mass is much bigger than the moon's mass. It does not mean that if the earth had a second moon, than the size of the orbit of that moon would have to correlate in any way with its mass. Dauto (talk) 18:54, 30 July 2011 (UTC)


 * I said nothing about the size of the orbit, just that there is a relation between orbit and mass.--Shantavira|feed me 05:52, 31 July 2011 (UTC)


 * The question is clearly about the size of the orbit. what else would it be about? Inclination? right ascension? Dauto (talk) 20:28, 1 August 2011 (UTC)


 * See Formation and evolution of the Solar System. Basically for Mercury to Mars, the Sun is hot enough to boil off most of the hydrogen from the planet. Further out the surface of the planetary core (which would been rocky or metally) would be cold enough for the captured hydrogen (and helium) to be captured - the thermal velocity of the gas is less than the surface escape velocity. In the trans-Neptunian area, there is not much hydrogen to be captured. CS Miller (talk) 13:30, 30 July 2011 (UTC)

It's not well understood at this time. Count Iblis (talk) 15:00, 30 July 2011 (UTC)
 * There are many satellites at altitude 35,786 km above the equator that have exactly 24 hours orbital period, see the article Geostationary orbit. Geostationary orbit is independent of the mass of the satellite. The orbital periods of planets about the Sun are similarly independent of their masses. Wikipedia has a long List of satellites in geosynchronous orbit that have a wide range of different masses. Cuddlyable3 (talk) 00:28, 31 July 2011 (UTC)
 * That is only true because the masses of satellites are much smaller than the mass of the earth. The relation between radius, orbital period and mass is Kepler's third law. Unfortunately, the article does not give the general form: M is actually the sum of the masses of the primary (earth) and secondary (satellite). See e.g. the fourth equation in the German article. The geostationary orbit for a more massive satellite is slightly higher than for a less massive satellite. In practice, of course, this mass dependence is buried among parturbations and in all likelihood not measurable.--Wrongfilter (talk) 08:46, 31 July 2011 (UTC)

Does anyone know what this plant is, please?
A plant grew in my garden, and I've no idea what it is. Or was, as it grew on a long stem and looked temptingly like a cat toy, so my kitten attacked it, and it is no more. Here are a couple of photos: The entire plant: http://www.flickr.com/photos/63456161@N07/5990829659/in/photostream Close up of the head: http://www.flickr.com/photos/63456161@N07/5990829243/in/photostream/ Thanks for any information!Snorgle (talk) 19:23, 30 July 2011 (UTC)
 * Allium canadense --Digrpat (talk) 20:11, 30 July 2011 (UTC)
 * Thanks - that looks right(although I'm in the UK I suppose it could have been introduced), and it did smell garlicky too. The wiki entry suggests that it's edible AND poisonous, which is confusing, though.Snorgle (talk) 20:26, 30 July 2011 (UTC)
 * maybe Allium vineale my 1st guess anyway--Digrpat (talk) 20:33, 30 July 2011 (UTC)
 * That looks EXACTLY like it, thanks!Snorgle (talk) 23:24, 30 July 2011 (UTC)

Funny Science Video Clips
Can anyone suggest funny science clips like the one here Thanks! Barbaricslav (talk) 20:23, 30 July 2011 (UTC)


 * Turboencabulator. Cuddlyable3 (talk) 00:02, 31 July 2011 (UTC)


 * Unintentionally funny, but hilarious to me. - Running On Brains (talk) 01:03, 31 July 2011 (UTC)


 * The "Duck and Cover" routine is probably not as useless as a lot of people seem to think. Obviously if you're within a certain radius of the bomb, you're going to die regardless. The point of "duck and cover" is to save people who are further away from the blast.--Srleffler (talk) 04:39, 31 July 2011 (UTC)


 * I think the funny (or perhaps appalling) part is using a cartoon with a turtle and a jingle, instead of a serious discussion of thermonuclear war. I picture a series of these videos, where being raped and murdered is treated to a cartoon and jingle, then maybe having your school bus catch fire as everyone inside slowly burns to death. StuRat (talk) 04:44, 31 July 2011 (UTC)


 * I always figured that it was largely to protect you from structural damage - i.e. if the school roof collapses, it's probably a good idea to be under a desk. Sturdy buildings, even near the epicenter of an atomic blast, can survive, and may retain enough of their integrity to keep the people inside alive.  A book that I recommend reading for those interested in first and second hand accounts of the explosion is John Hersey's Hiroshima.  Several of the survivors detailed were within a mile of the bomb blast. Buddy432 (talk) 19:46, 31 July 2011 (UTC)


 * A human is a lot sturdier than a building. A steel-framed building will pretty much always collapse when it's subjected to 5 PSI (a miniscule force).  A human can survive a lot more than that (5 PSI is roughly equivalent to being punched hard in the gut). Whoop whoop pull up Bitching Betty 20:51, 31 July 2011 (UTC)
 * PSI is not a measure of force, it is a measure of pressure. Assuming your numbers are correct, you should consider what would happen if you were hit with the same force as a punch but over your entire body, just as the building is subjected to the force over it's entire cross-section. If you were standing in the open, you would probably be thrown backwards rather than crushed, but if you were standing against a wall, say, you could easily be crushed against it. How well buildings survive such forces depends a lot of how rigid they are. If they can't move, then they will break. If they can move (by swaying, primarily) then they'll survive in the same way you would if thrown backwards. --Tango (talk) 23:15, 31 July 2011 (UTC)
 * Thinking about force and cross section is also part of the logic behind "duck and cover". By curling up into a ball at ground level, even if you aren't under any kind of shelter, you reduce your cross-section to the blast. Better than nothing...--Srleffler (talk) 02:40, 1 August 2011 (UTC)
 * How about a bit of Police Squad!? Also, not science-related, I'm afraid - but I was reminded of the late, great Stanley Unwin, and more recent Fry and Laurie . Sorry...I'm sure everyone can think of their favourite 'funny clips'... but I couldn't resist mentioning those.  Chzz  ►  06:46, 1 August 2011 (UTC)