Recent comments in /f/askscience

thisoldmould t1_j2ceo3p wrote

Reply to Do nerve endings closer to the brain / spinal cord take less time to transmit signals because there is less distance to travel? by ssinatra3

This depends on the sensation being transmitted to the brain. Some nerves travel at hundreds of metres per second (A-delta fibres), others travel at only 2 m/s (C-fibres).

The distance to the brain will impact the time taken for the sensation to be delivered to the brain. But it’s usually imperceptible because the signals are so quick.

Nociception (noxious stimulus) carried by C-fibres, are integrated in the thalamus and modulated by pro and anti-nociceptive areas of the brain, which can delay your perception of pain.

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matticitt t1_j2cej5s wrote

Reply to Do nerve endings closer to the brain / spinal cord take less time to transmit signals because there is less distance to travel? by ssinatra3

Yes, it takes longer for information from your toe for example to reach your brain that information from your eye. Your brain actually synchronizes all those inputs and so there's a delay for you and the information which got to your brain first has to "wait" to get synced with the one which got there last. You're always living slightly in the past.

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Xyver t1_j2ce9ur wrote

Reply to Do nerve endings closer to the brain / spinal cord take less time to transmit signals because there is less distance to travel? by ssinatra3

Semi related answer, yes I know there is a noticable time delay for sending signals for the brain to your feet/hands, something in the range of 50-100ms. I assume that since it's an actual electrical signal travelling through the nerves, further things take longer.

But the exciting thing is, that is way slower than the speed of a signal through a wire. So for someone with a prosthetic leg, if you get the signals from the brain stem and send them through wires (or other digital means) to muscles/actuators in a robot leg, you would make faster reflexes and response times.

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Shadowkiller00 t1_j2ce2ap wrote

Reply to Why is Mitochondrial Eve dated to 150-170,000 years go? by jayhovian

We know how fast genetic changes occur. If we look at all mitochondrial dna and count the number of genetic differences between all we have cataloged, we can follow backwards to they would all effectively be the same. Depending on fastest estimates and slowest estimates of genetic drift, it's roughly 150k-170k years ago.

And basically this means that we only know of one female at that point. We can see nobody else beyond her because we have no mitochondria that show genetic differences that come out older than that. Either they all died out, or they were bred out of the population.

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_AlreadyTaken_ t1_j2cdktk wrote

Reply to comment by theCumCatcher in How much does the liquid magma of the Earth affect it's surface temperature? by tripperfunster

We wouldn't lose our atmosphere, Venus barely has a magnetic field and it has a very thick one. It helps us hold onto lighter elements. Water vapor could be photodissociated into oxygen and hydrogen and the hydrogen stripped away. We could also lose the ozone layer. There is even a weak spot in the magnetic field, the South Atlantic Anomaly.

You don't absolutely need it but it definitely helps.

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keithatcpt t1_j2cdfjr wrote

Reply to I live in New Hampshire, USA. How come it continues to get colder here after the Winter solstice? by WayneHudsonIII

With anything that’s warmed by a heat source, there is a “thermal lag time” where the temperature of what’s being warmed doesn’t start increasing right away. The bigger the system, the longer the lag time, and the earth is a pretty big system. Also, the energy provided by the sun generally is the same a week after the winter solstice as it is a week before, when the northern hemisphere is still cooling off on average. That’s why the coldest month tends to be January. When things start warming up in late February into March, the weather patterns tend to be windy and stormy as more energy is heating the northern hemisphere, causing evaporation from the oceans which runs into the cold air over the continents.

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Pegajace t1_j2cd5zl wrote

Reply to comment by jayhovian in Why is Mitochondrial Eve dated to 150-170,000 years go? by jayhovian

The title of "Mitochondrial Eve" is defined as the most recent matrilineal common ancestor of all living humans. If we trace the ancestry of all living humans through their mother's side, all lineages pass through M.E. before they get to any generations further back, and once you're past M.E. all the lineages look identical.

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ccdy t1_j2cb5ky wrote

Reply to can brass be broken down into it's original metals? by s33761

Not by any practical or economic means. In principle you could distill brass to separate copper and zinc by boiling point but this obviously poses significant technical challenges. The more realistic way is through hydrometallurgy, where the brass is dissolved in an aqueous solution and the two component metals separated by chemical or electrochemical means. This includes selective leaching of zinc from brass, which should be possible although I have not looked up any specific references for this. In practice the energy required is too great and it is far easier to just remelt scrap brass to make new brass.

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