Recent comments in /f/askscience

Alert-Artichoke-2743 t1_ja14ppw wrote

Reply to Does the length of the fingers serve a purpose or could two fingers be the same length? by Hairy_Lengthiness_41

The common hand shapes were arrived at via evolution, meaning they are the shape that most encouraged survival, and doing well enough for oneself to get opportunities to reproduce.

If the longest fingers were on the outside, they could get bent back or hyperextended if the short middle finger couldn't provide support. With the shorter ones on the outside, a person losing their grip would lose it one finger at a time. When the long middle finger loses grip on something, you're only holding on with one side of your hand so there should be more room to wriggle free.

Also, the traditional ratio of finger lengths allows a person to make a fist comfortably. So, the digits are typicallly the correct length to be curled up comfortably into a closed hand.

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8NAL_LOVER t1_ja13g95 wrote

Reply to How old is the ISS REALLY? by gwplayer1

I don't think the satellites periodically reset their clocks. Rather, I think they are just programmed with formulas that constantly counter the relativistic effects. Otherwise the resets would have to happen quite frequently (literally every two minutes). They need to compensate for ~8000 nanoseconds per day, but need to stay within ~10 nanoseconds to work.

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vasopressin334 t1_ja10crm wrote

Reply to comment by katlian in Water on Earth is not Constant. Why ? by ItsDivyamGupta

While it is clearly true that the water is not “lost” and much of the water sequestered in this way is released through various degradation processes, some water is captured, much the way that some carbon is captured. This captured water makes up not only the organic molecules present in all fertile soil but also the bulk of all biomass.

However, since the entire biomass of every living thing on earth is about 10 million times less than the mass of all water on earth, the water captured in this way will never be more than a negligible amount.

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FellowConspirator t1_ja0zbrm wrote

Reply to How do scientists know where the mutation in a gene originated and how long ago the mutation occured? by goose966

Without getting into excessive detail: today we genotype or sequence DNA from many many people. We can cluster people into groups that have a higher than expected number of shared alleles (genetic variations). This happens when people share common ancestry because at some point their ancestors were isolated to an area, or had moved to a new area and founded a new settlement that grew, establishing a large group with common genetic history. This is effectively what the ancestry DNA companies do. You can plot that information on a map and to show where those people groups are most prevalent.

That same information can be used to make something like a pedigree of people groups, tracing the divergence and convergence of populations in time and geography.

Given that information, you can then ask where in that tree is the allele most common? Can you trace a line between people groups that carry the specific mutation? Sometimes you can, and you can estimate when and where the mutation first occurred. In some cases, you simply can’t — perhaps because the mutation is very common and doesn’t seem to have a strong correlation with any people group.

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