Wikipedia:Reference desk/Archives/Science/2015 March 12

= March 12 =

Color-blindness problem
Are any of you familiar with the problem:

Look at this image. Most people should see a 74, but color-blind people should see a 21.

Do you think it is valid for a similar problem to occur with any two 2-digit numbers, with the only requirement is that each digit of the general number must be different from the corresponding digit of the color-blind number?? For example, 74-21, but nor 74-71 or 74-24. Georgia guy (talk) 01:36, 12 March 2015 (UTC)


 * There are many variations of the test - for example, with pictures for little kids who are too young to understand the numbers. (See tests G and H in this series) I don't see why other number choices wouldn't work. The critical part is the size, tones and shades of the dots.  SteveBaker (talk) 01:56, 12 March 2015 (UTC)


 * Mine must be really bad as I don't even see an image :/ --DHeyward (talk) 06:35, 12 March 2015 (UTC)
 * I had to zoom in to see it. G is a primitive sailboat, and H is a square and a circle. The rest of them are numbers. ←Baseball Bugs What's up, Doc? carrots→ 13:54, 12 March 2015 (UTC)

Is it possible to see solar flares during a total eclipse ?


...without any form of magnification ? StuRat (talk) 08:06, 12 March 2015 (UTC)


 * Original research here. I watched the August 1999 total eclipse in a part of France where there were two layers of broken clouds.  I hoped to see the eclipse through a gap in both layers, but couldn't maneuver myself under one in time and ended up in a position where a thin layer of cloud was in front of the sun.  Looking at the eclipsed sun with unaided eyes, I saw a ring of white light with several red spots, and was surprised to realize that the corona was bright enough to see right through the cloud layer&mdash;nothing I'd ever read had mentioned that that was possible.  I then looked through my binoculars and easily confirmed that I was seeing the corona, and that the red spots were prominences.  If a prominence can be seen in that way, even through a bit of cloud, it makes sense that the brightness of a flare could be also. --65.94.48.86 (talk) 13:39, 12 March 2015 (UTC)
 * The phenomenon of visible solar flare appears when charged particles accelerated in the corona hit the lower denser atmosphere of the Sun (lower chromosphere/photosphere). However during a full eclipse these lower layers are shielded by Moon. So, the answer is probably no. Ruslik_ Zero 20:37, 12 March 2015 (UTC)
 * I have seen a sunspot with my naked eyes. We had a bunch of wildfires near where i live and it cretaed a thick haze which was very uniform and it acted like a ND filter, i could look at the sun without any discomfort, (I still only did it for a few seconds because I am aware that invisible radiation might still get through and not cause "discomfort" but still damage my retina). However when I looked at the sun I could see a very distinct black spot, so I jumped on SOHO when I got to work and sure enough, there was a big balck sunspot there. Vespine (talk) 21:28, 12 March 2015 (UTC)
 * I, too, once saw sunspots with my naked eyes. I was living in Marin County, California, at the time, and there was an early morning fog of an exact thickness that filtered the sun in such a way that sunspots were clearly visible. I was driving when I first noticed and didn't trust my initial observation. I pulled my car to the side of the road and looked very carefully. I was certain I saw sunspots. Within a few minutes, the fog thickened a bit and it was over. Cullen328  Let's discuss it  23:24, 16 March 2015 (UTC)

Does alcohol affect appetite?
What it says on the tin, really. Does alcohol intake affect appetite? GoldenRing (talk) 10:28, 12 March 2015 (UTC)


 * You be the judge: Apéritif_and_digestif 196.213.35.146 (talk) 10:33, 12 March 2015 (UTC)


 * Chronic alcoholics often show greatly reduced appetite, but alcohol at moderate doses seems to increase both appetite and food intake -- see and .  There are however some complications; for a literture review see . Looie496 (talk) 14:45, 12 March 2015 (UTC)
 * Thanks, very helpful. GoldenRing (talk) 03:15, 16 March 2015 (UTC)
 * Note that alcohol itself provides calories, lessening the desire for calories from other sources. However, alcohol, of course, lacks many of the nutrients you need to survive.  (I wonder if an alcoholic drink could be made which contains all the nutrients a human needs.  Eggnog might be a good start.) StuRat (talk) 17:17, 12 March 2015 (UTC)
 * There used to be a semi-humorous assertion that one could live indefinitely and not unhealthily on 40 bottles of Guinness and a loaf of bread per week (or some vaguely similar figures). {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 14:26, 13 March 2015 (UTC)
 * A doctor I used to know said that stout and beetroot provide everything needed for the human body to live healthily. GoldenRing (talk) 03:15, 16 March 2015 (UTC)
 * I believed based from my family experience that drinking alcohol causes apetite to decrease, a reason why sometimes drinkers eat dinner well after sobers start eating. That's before I learned that it was true, though not always. Planet  Star  23:40, 17 March 2015 (UTC)

Is it possible to purify water from drinking alcohol?
In a situation where an individual has nothing but alcoholic beverages and the individual cannot detoxify aldehydes, is it possible to purify water from drinking alcohol rather than merely diluting alcohol in order to lower the alcoholic content in the water supply? Is 0.01% of alcohol/99.99% water still considered an alcoholic beverage? My first impulse is that the water supply must be distilled. The distillate is separated from the water vapor by differing boiling points, but the water vapor is kept. However, how can a container be made in order to hermetically seal the container collecting the pure water? 140.254.136.157 (talk) 14:41, 12 March 2015 (UTC)


 * You would lose some of the water in the process. Just leaving it out as the alcohol evaporates and drinking it before most of the water evaporates would be one method, but beware that when the alcohol level drops more bacteria can then survive in the water.  Heating it would speed up the process, but beware the alcohol fumes could ignite if you heat it with an open flame.


 * As for what counts as an alcoholic beverage, see near beer for some legal defs. StuRat (talk) 17:14, 12 March 2015 (UTC)


 * You can't completely separate the ethanol from the water by simple distillation. Water and ethanol form an azeotrope.  There are methods for completely separating azeotropes, though, you can read about them in the Wikipedia article.  -- Jayron 32 19:49, 12 March 2015 (UTC)

Hottest natural Lake (without vulkanism/hot springs)
E.G. Lake Natron gets up to 40°C - but hot springs are feeding the lake. Where can conditions be found (maybe salt lake, maybe high humidity in warm climate) where water naturally can reach temperatures above 30(?)°C ?  GEEZER nil nisi bene 14:48, 12 March 2015 (UTC)


 * The hottest lake is the aptly named Frying Pan Lake. The lake is also a hot spring. A place without a lake would be likely a hot and dry desert, like the Sahara Desert, which was once an ocean. 140.254.136.157 (talk) 15:08, 12 March 2015 (UTC)


 * Wikipedia has a hot spring article. However, that may not be very useful to you, as it seems to focus on averages of "hot springs", "warm springs", and regular "springs". There are significant overlaps with "hot springs" and "warm springs", so the linguistic distinction is not very useful. Perhaps, a rule of thumb may be looking for a body of water that is at most at 20 degrees Celsius, since that number seems to be a good cut-off point. At that point, it's pretty much saying "water at room temperature". 140.254.136.157 (talk) 15:27, 12 March 2015 (UTC)


 * Some more reading on hot spring suggests that cold springs just link directly to Spring (hydrology), which may hint that a body of water at 20 degrees Celsius is considered "a cold spring", and you want to find the warmest cold spring? 140.254.136.157 (talk) 15:31, 12 March 2015 (UTC)


 * One type might be a shallow lake which gets lots of direct sunlight, with dark water to absorb that sunlight. This could occur due to lots of tannins, for example, from decomposing leaves.  However, cooling from the surface limits the max temp.


 * Lakes with a salinity gradient, with cool, fresh water on top and hot, salty water at depth, can theoretically reach up to boiling (100°C) in the lower level:  (that article is on man-made solar ponds, but they also occur naturally).  StuRat (talk) 15:45, 12 March 2015 (UTC)


 * In our article on The Dead Sea is the text (my bolding):
 * "Until the winter of 1978–79, when a major mixing event took place, the Dead Sea was composed of two stratified layers of water that differed in temperature, density, age, and salinity. The topmost 35 meters (115 ft) or so of the Dead Sea had an average salinity of 342 parts per thousand (in 2002), and a temperature that swung between 19 °C (66 °F) and 37 °C (99 °F)"
 * Similar bodies of water may also meet the OP's specification of above 30°C. {The poster formerly known as 87.81.230.1`95} 212.95.237.92 (talk) 17:52, 13 March 2015 (UTC)

Phosphate buffered saline role
Am I correct in assuming that when phosphate buffered saline is added to Trypsin or other enzymes, it dilutes the enzyme and also acts as a cleaning agent? So it has a double role when added to a cell culture flask? 194.66.246.87 (talk) 20:03, 12 March 2015 (UTC)

Are high-speed trains easier to drive?
In comparison to cargo trains, is it easy to drive a high-speed train running on a dedicated track? --Fend 83 (talk) 21:55, 12 March 2015 (UTC)
 * Cargo trains also drive along a dedicated track, as all trains do. That's what trains do. I'm sure that if you go to your local station and ask, they can give you some information on how to get a license to drive one.  KägeTorä - ( 影 虎 )  ( Chin Wag )  22:20, 12 March 2015 (UTC)
 * I am pretty sure you could do such jokes at another place, like yahoo answers. It's obvious that I was asking about a dedicated high-speed railway line. Fend 83 (talk) 22:41, 12 March 2015 (UTC)
 * Knowing what you mean by easy might help. What sort of reference or objective data are you looking for?  You seem to be comparing apples and oranges, a slow train with a heavy load, and a fast train with mostly passengers and limited carry on luggage. μηδείς (talk) 00:29, 13 March 2015 (UTC)
 * High speed trains use the latest technology, whereas freight trains tend to use older locomotive stock requiring more work and skill in, say, starting and stopping and handling gradients, so I think its probably self-evident that high speed trains are "easier" on the driver. However, high speed drivers must pass more rigorous tests as they have a much greater responsibility, so in that sense they are not so easy.--Shantavira|feed me 09:23, 13 March 2015 (UTC)
 * I would imagine much of the process is going to be similar. If you look at videos of people driving modern trains a lot of the time is spend operating the Dead man's switch to check the driver is still awake, there also the Block signaling systems and something like the Automatic Warning System which will need continuous attention. I'm sure you going to have similar safety feature for dedicated tracks. I'm not really a train buff and you might get a batter answer on the Miscellaneous desk.--Salix alba (talk): 09:43, 13 March 2015 (UTC)

Counting cells suspended in liquid
Are there currently any machines that can count cells and place a specific number of cells in a tube rather than measuring the average number of cells per volume of liquid and having to put that volume in? 194.66.246.87 (talk) 23:28, 12 March 2015 (UTC)


 * Flow cytometers do what you're asking about. - Nunh-huh 00:19, 13 March 2015 (UTC)
 * As do Coulter counters. Hematology analysers may use both detection principles |(reference) . --NorwegianBluetalk 10:08, 14 March 2015 (UTC)