Science desk
< May 11	<< Apr \| May \| Jun >>	May 13 >

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.

May 12

Rate data for dissociation & recombination reactions

For chemical reactions of the form A + A + M → A₂ + M and the reverse A₂ + M → A + A + M, there is a range of published rate parameters (ie values to insert into arrhenious and modified arrhenious reactions) for all sorts of elements A. But the published data is restricted to only a few element/molecules M (the bath gas in lab tests) Almost entirely, M in published data seems restricted to N₂ and the noble gasses Ar, He, and Xe (Noble gasses are not of course terribly useful). Sometimes, but not always, you see M set to A or A₂, which is most useful. Sometimes you see CO₂. Is there a usable way to predict approximate rate constants where M is A, A2 or even useful things like O, O₂, N, and N₂, given rate constants for published values of M? Ratbone121.215.159.87 (talk) 15:00, 12 May 2012 (UTC)[reply]

Have you tried http://kinetics.nist.gov/kinetics/ ? Ssscienccce (talk) 16:03, 12 May 2012 (UTC)[reply]

Yes, of course. I've used it enough to know that it has many inconsistencies, traps for young players, and some errors. It's main value is that for any reaction in the database, it gives a list of references to look up. It is no help whatsoever with the question I asked. Ratbone121.215.147.93 (talk) 03:17, 13 May 2012 (UTC)[reply]

You probably won't find data for M = O (oxygen atom), except for A = O, because the O will have a greater affinity for A than another A. In other words the rate for A + A + O → A₂ + O will be very much lower than the rate for A + A + O → A + AO, and the reaction A + O + O → A + O₂, making product from the first reaction insignificant and thereby difficult to measure before all the O is used up. Keit120.145.7.207 (talk) 12:37, 13 May 2012 (UTC)[reply]

Lift controls

What happens if you press the button for the floor, on which the lift is parked with closed doors? --84.61.181.19 (talk) 16:33, 12 May 2012 (UTC)[reply]

What happens if you press the button for the floor, on which the lift closes its doors? --84.61.181.19 (talk) 16:36, 12 May 2012 (UTC)[reply]

What is the difference between pressing the door open button, and pressing the button for the floor you are currently on? --84.61.181.19 (talk) 16:39, 12 May 2012 (UTC)[reply]

I would guess that the answers depend on the control software for that particular lift, and on whether you are inside or outside. Why not experiment on real lifts and report your findings here? Dbfirs 16:41, 12 May 2012 (UTC)[reply]

What is the difference between old and new lifts in respect of my questions? --84.61.181.19 (talk) 16:42, 12 May 2012 (UTC)[reply]

In really old lifts, you open the door yourself, pushing the current floor won't do anything since the door stays unlocked until you select another floor, or someone on another floor calls the lift. Ssscienccce (talk) 17:26, 12 May 2012 (UTC)[reply]

It certainly depends on the elevator, but in my experience, if you're on a floor and you push the button for that floor, nothing happens, the elevator just sits there. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:30, 12 May 2012 (UTC)[reply]

FYI, the OP here has been elevated to the block house. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:42, 13 May 2012 (UTC)[reply]

What do these presumably space related acronyms mean?

Take a look at File:Mission_control_center.jpg and specifically the map of the earth; there are a bunch of regions on it - I've worked out that SAA is the south atlantic anomaly, and am pretty sure that the biggest ovals are going to be to do with daylight/darkness, but am not sure what the other things are. Google doesn't seem to be of help. The acronyms from West to East, so far as I can make them out (although I encourage you to look at the image) are:

T???SW
HTSS
SAA (identified as South Atlantic Anomaly
ShLK
????
RDE
KiPA
ULDA
USKA
PPKA

Egg Centri c 19:07, 12 May 2012 (UTC)[reply]

I'll admit, I'm stumped. At first I thought they looked to be the orbits of various quasi-geostationary satellites relative to the ground. Yes, geostationary satellites aren't perfectly geostationary, they typically wobble([1]) though these seem a lot more extreme than the typical wobble. But I agree with your assessment of SAA being South-Atlantic Anomaly, which makes my theory less plausible. I can speculate that maybe HTSS is some Hawaiian high-altitude observing station, as would be the various circles over Russia. Unfortunately I can't find many references to the above acronyms that seem relevant. -RunningOnBrains^(talk) 20:28, 12 May 2012 (UTC)[reply]

The Kaena Point Satellite Tracking Station is the site of the Hawaii Tracking Station or HTS, but that doesn't explain the extra "S". -- ToE 20:58, 12 May 2012 (UTC)[reply]

I agree that the large oval-like light and dark regions are daylight. The shape and size looks like File:Daylight.png (the lede image at Daylight). Even the specific part that is daytime makes sense: the Mission Control clock ("GMT" display top just to the left-of-center) is "063:15:00:44+" (3pm in England), in keeping with the "becomes dark" line about 30° east of England (about 2 hours of daytime left). DMacks (talk) 21:50, 12 May 2012 (UTC)[reply]

Searching [2] sniffs out a link at NASA, but I don't know what kind of file it is. (I dunno... lot of random noise when viewed as text... I might be Helen Keller reading the stucco wall here) Wnt (talk) 23:36, 12 May 2012 (UTC)[reply]

Searching for things related to the "PPKA" site, two interesting similars are "PKA" (acronym for the Russian Federal Space Agency) and Petropavlovsk-Kamchatsky, which is definitely in the correct location for that label. But this is definitely my WP:OR here. DMacks (talk) 03:22, 13 May 2012 (UTC)[reply]

Alright, found some more concrete information. ISS Ground Stations and Capabilities lists a bunch of Russian space-tracking installations, including things with identifiers "ULD", "PPK" (agrees with the lead I found by an unrelated search method), and "KLD". Soviet/Russian OKIK Ground Station Sites lists more sites with less information about them. DMacks (talk) 07:20, 13 May 2012 (UTC)[reply]

I suppose it goes without saying that "ShLK" is a Russian acronym of some sort (Sh is a single letter in Russian, Ш). --Mr.98 (talk) 15:13, 13 May 2012 (UTC)[reply]

The yellow circles with yellow letters in the upper right are indeed Russian ground stations. HTSS is a ground station in Hawaii. SAA is indeed the South Atlantic Anomaly. The blue letters in the center left are T171W, which is a TDRS satellite located at 171 degrees west. There are yellow letters over South America for TDRS 46 as well. anonymous6494 18:49, 14 May 2012 (UTC)[reply]

Herschel and life on the Moon, etc

Mormon cosmology says "Such beliefs were common in the nineteenth century and were even considered to be "scientific fact" by many at the time. For example, William Herschel, the discoverer of the planet Uranus, argued "[w]ho can say that it is not extremely probable, nay beyond doubt, that there must be inhabitants on the Moon of some kind or another?" Furthermore, "he thought it possible that there was a region below the Sun's fiery surface where men might live, and he regarded the existence of life on the Moon as 'an absolute certainty.'"

William Herschel says "Despite his numerous important scientific discoveries, Herschel was not averse to wild speculation. In particular, he believed every planet was inhabited,[16] even the Sun..."

So the first says that it was considered scientific fact by many. The second says that it was a wild speculation. Which is more accurate? And will someone correct one of the articles? Bubba73 ^{You talkin' to me?} 19:12, 12 May 2012 (UTC)[reply]

Those can both be true. Consider that today, the Earth having been created a few thousand years ago is "considered scientific fact by many". They are completely wrong, of course, and this belief has nothing whatsoever to do with science. StuRat (talk) 22:08, 12 May 2012 (UTC)[reply]

Did many scientists consider it a scientific fact that there was life on the Moon, etc? That seems to be what it is implying. Bubba73 ^{You talkin' to me?} 23:25, 12 May 2012 (UTC)[reply]

Note that the phrase "scientific fact" was in quotation marks. Anonymous.translator (talk) 01:44, 13 May 2012 (UTC)[reply]

I suspect "scientific fact" is too strong a phrase, quotation marks or none. It would have likely been considered speculation. Perhaps not "wild" speculation. It would have been considered likely that other worlds had life — as it is considered likely today, though we now know that the parameters for life on a planet are considerably more specific than they would have known in the 19th century. But even as late as the mid-20th century, the idea that Mars might be populated with plants (if not intelligent life) was considered not an impossible prospect. (Today, of course, the possibilities of life on Mars are reduced to looking for bacteria-like organisms.) Anyway, both the scare-quoted "scientific fact" and the "wild" seem like things worth demanding a reference for. "Wild" is not neutral in any case; and I would want to see someone asserting the "fact" that there was life on the Moon. --Mr.98 (talk) 15:01, 13 May 2012 (UTC)[reply]

I agree with you. Bubba73 ^{You talkin' to me?} 18:46, 13 May 2012 (UTC)[reply]

The Herschel quote technically belongs to the 18th Century - it was made in a letter to the Astronomer Royal Nevil Maskelyne according to this. However the idea of Cosmic pluralism wasn't a fringe idea in the 19th Century. Not that his writings quite live up to scientific rigour perhaps, but one writer that does spring to mind in the 19th Century is Thomas Dick, who I came across in the Great Moon Hoax article. His 1826 book The Christian Philosopher, or the Connexion of Science and Philosophy with Religion suggesting life on the Moon was widely known, in both Britain and the United States; whether it had any influence on Joseph Smith, I don't know. In another book published in 1837, Celestial scenery: or, The wonders of the planetary system displayed; illustrating the perfections of the deity and a plurality of world, basing his estimates on the population density of Britain and scaling accordingly, he estimated the population of the Moon to be 4,200,000,000, the population of Saturn's rings to be 8 trillion and the population of the Solar System as a whole to be 21 billion (give or take). (These figures taken from this book). FlowerpotmaN·(t) 23:17, 13 May 2012 (UTC)[reply]