Wikipedia:Reference desk/Archives/Science/2020 May 11

= May 11 =

Hatchlings of olive ridley turtles
When they come out, within one second they know they have to move towards the sea. https://www.youtube.com/watch?v=Ipf0fehg5os

How do they decide with one second age that they should move towards the sea, not towards the land? — Preceding unsigned comment added by Lordracktry (talk • contribs) 04:55, 11 May 2020 (UTC)


 * They look for light on the water, usually brighter than looking inland. In the Threats sub-section of our article Olive ridley sea turtle it tells us "...coastal development also threatens newly hatched turtles through the effects of light pollution. Hatchlings which use light cues to orient themselves to the sea are now misled into moving towards land, and die from dehydration or exhaustion, or are killed on roads." HiLo48 (talk) 05:50, 11 May 2020 (UTC)


 * They don't decide; it's instinct.--Shantavira|feed me 09:39, 11 May 2020 (UTC)

Sulfuric acid
The infobox at sulfuric acid conforms what I saw elsewhere: its melting point is about 10 °C or 50 °F. Question: how do car batteries manage to work in cold weather? I somehow thought the acid/water mix had a much lower freezing point than plain water. What's the deal? Thanks. 2602:24A:DE47:B270:DDD2:63E0:FE3B:596C (talk) 08:04, 11 May 2020 (UTC)
 * Freezing-point depression of the acid/water solution sounds right. Sulfuric acid has a useful datapoint. DMacks (talk) 08:46, 11 May 2020 (UTC)
 * The sulfuric acid concentration in car batteries is about 37%, which is to say that it is still mostly water. The freezing point of that solution will depend on the relative concentration of two liquids, calculating the freezing point of a mixture of two liquids is fiendishly difficult, but it will be generally lower than the freezing point of either one in isolation.  -- Jayron 32 13:34, 11 May 2020 (UTC)
 * Re: "Calculating the freezing point of a mixture of 2 liquids is fiendishly difficult." Well what if you had a diagram of freezing point of percentage, for example, the middle point being 50/50 water/H2SO4, from 0 to 100. What would the curve look like, linear? Asymptoptic? 67.175.224.138 (talk) 18:54, 11 May 2020 (UTC).
 * Calculating the values is fiendishly difficult. Where do you get such a diagram from?  Diagrams are not handed down from God to be used whenever someone needs them.  Someone has to make such a diagram somehow.  Freezing point behavior for sulfuric acid solutions have been experimentally determined, see here, and as you can see the behavior is relatively well behaved up to about a 40 percent solution, and after that the behavior begins to behave rather chaotically depending on the exact measurement conditions and theoretical assumptions.  Remember, diagrams you may use still need to be created by someone, and in this case the behavior of sulfuric acid solutions is complex and messy and if you observe the diagram there, you can see that (from the solid line) does not indicate a nice relationship between concentration and freezing point.  -- Jayron 32 19:21, 11 May 2020 (UTC)
 * Okay, clearly the curve is not linear, or asymptotic. Are there any solutions by concentration, where the curve is? 67.175.224.138 (talk) 22:10, 11 May 2020 (UTC).
 * page 7 also has a nice unified graph, cited to 10.1021/ja01160a005 that has several different graph sections. DMacks (talk) 04:47, 12 May 2020 (UTC)
 * Thanks everyone. It looks like at 40% concentration (as found in car batteries) the freezing point gets as low as –60 °C.  Maybe that concentration was chosen to make the freezing point as low as possible.  2602:24A:DE47:B270:DDD2:63E0:FE3B:596C (talk) 21:57, 11 May 2020 (UTC)