Wikipedia:Reference desk/Archives/Science/2014 January 7

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.

January 7

Records of variation in temperature

Does anyone know of any records (or interesting data) concerning wide variations in temperature readings? For example, (I am just making this up) ... On such-and-such a date, the temperature in such-and-such a city dropped (or rose) 75 degrees in a 24-hour period. Or that same type of data, perhaps in a one-hour period (or an even shorter interval). Another way to phrase this is that I am looking for the greatest temperature variation in the shortest amount of time. Thanks. Joseph A. Spadaro (talk) 03:44, 7 January 2014 (UTC)

See Chinook wind for one claimed record. Rmhermen (talk) 04:50, 7 January 2014 (UTC)

See heat burst for the extreme shorter time-period changes. StuRat (talk) 14:27, 7 January 2014 (UTC)

Spearfish, South Dakota and it's sourced. CambridgeBayWeather (talk) 18:21, 7 January 2014 (UTC)

And I now see that was also in the records section of Chinook wind.

Thanks, all. Yes, that was exactly the type of information that I was looking for. Thank you. Joseph A. Spadaro (talk) 19:36, 11 January 2014 (UTC)

Thermodynamics

Given the equation of state of a system (in the form of P=f(V,T)) can we find C_p, C_v and Joule-Thomson coefficient? I've been struggling to express these values in terms of derivatives of P, V and T with respect to each other and I've failed so far.--Irrational number (talk) 12:20, 7 January 2014 (UTC)

I think the equation of state alone doesn't give you enough information. For example the ideal gas equation can be a good aproximation for real gases and will give you Cv = Cp-nR, but you can't derive the heat capacity ratio from it, that will depend on the type of gas (on the degrees of freedom). Ssscienccce (talk) 05:27, 10 January 2014 (UTC)

NASA SDO sun photo

Hi all,

This photo shows a picture of the sun taken by NASA. Here gives an explanation of what it is showing. It says that it shows wavelengths of 5800 Angstroms to 94 Angstroms, which it sort of says is where the normal yellow and green sections come from (although I'm not sure about that). What are the ranges of wavelengths for the other sections, what types of EM radiation do they represent? Are these standard for an image like this? Bonus points: Why are the features in each of the sections like that (i.e. different from one another)? Thanks! 80.254.147.164 (talk) 12:20, 7 January 2014 (UTC)

Different temperatures produce different wavelengths of radiation. This is similar to how when you heat metal it goes from red hot to white hot. Thus, by looking at different wavelengths of radiation, we can focus on different temperature features. The surface is relatively cool compared with the interior and the corona. StuRat (talk) 14:24, 7 January 2014 (UTC)

See Ultraviolet and False color. As far as I know, there isn't a convention for depicting the ultraviolet region of the spectrum, but I may be wrong. Tevildo (talk) 23:09, 7 January 2014 (UTC)

Brittle due to cold

What is the term for the temperature at which it is so cold that a malleable metal becomes brittle? (I want to find a chart for the temperature but don't know the name for what I'm looking for.) RJFJR (talk) 14:34, 7 January 2014 (UTC)

Toughness, the property of a metal to absorb shock without fracturing, is a function of temperature. You might be able to find data in a materials handbook or by scouring our articles and linked references for each metal of interest.

I found this conference paper, Low Temperature Metals, on Brookhaven National Laboratory's website. It has data and charts for common metals, and some exotic metals useful for superconducting research. The entire conference website has loads of other interesting reading material, too. Nimur (talk) 14:43, 7 January 2014 (UTC)

(ec) Note that it doesn't happen instantly at a certain temperature. Metals, and other materials, become steadily more brittle the colder they get. StuRat (talk) 14:55, 7 January 2014 (UTC)

The article embrittlement calls such a transition temperature the embrittlement temperature, though it specifically references plastics and rubbers, rather than metals. (Perhaps because of the gradual transition that StuRat mentions.) -- 160.129.138.186 (talk) 16:22, 7 January 2014 (UTC)

During World War II, several ships broke in half in cold waters due to embrittlement, the article on Liberty ships describes the phenomenon. Widneymanor (talk) 18:48, 7 January 2014 (UTC)

The Titanic may have also had rather brittle metal and rivets, in part due to the cold, contributing to the sinking. StuRat (talk) 20:08, 7 January 2014 (UTC)

On the radio this morning they said that the railroads are keep extra crews on hand because they are worried about the train tracks breaking because of the cold snap. RJFJR (talk) 21:19, 7 January 2014 (UTC)

An additional risk there is the metal contracting due to it's coefficient of thermal expansion. Then there's also frost heaving on the underlying soil to worry about. StuRat (talk) 23:35, 7 January 2014 (UTC)

"Bolingo fruit"

In a documentary on bonobos, it said they like to eat "bolingo" fruit. What species of plant is this? Is there a Wikipedia article on it? Here's a photo: http://www.pri.kyoto-u.ac.jp/hope/reports/23-001/1.jpg —Keenan Pepper 21:23, 7 January 2014 (UTC)

Anonidium mannii --Dr Dima (talk) 21:35, 7 January 2014 (UTC)