Recent comments in /f/askscience

Fenrisvitnir t1_jdsp8nn wrote

Reply to comment by Coomb in The two retinas are tied/linked together in the brain. Are they tied 1:1, so that each retinal point corresponds to the same retinal point in the other eye? I.e., each retinal point from one eye shares the same binocular neuron with its counterpoint in the other eye? by ch1214ch

https://glassboxmedicine.com/2019/04/13/a-short-history-of-convolutional-neural-networks/

"The popular press often talks about how neural network models are “directly inspired by the human brain.” In some sense, this is true, as both CNNs and the human visual system follow a “simple-to-complex” hierarchical structure. However, the actual implementation is totally different; brains are built using cells, and neural networks are built using mathematical operations."

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dukesdj t1_jdsowp3 wrote

Reply to comment by Ganondorf_Is_God in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

Depends on exactly what you want to know more about.

Fluid dynamics in general An Introduction to Fluid Dynamics by Batchelor is good. Hydrodynamic and hydromagnetic stability is a classic book on fluid instabilities by Chandrasekhar which includes convective instabilities. Introduction to Modeling Convection in Planets and Stars: Magnetic Field, Density Stratification, Rotation by Glatzmaier is good for the more numerical modelling side but also includes theory. Internally Heated Convection and Rayleigh-Bénard Convection by Goluskin is a good book on convection. An Introduction to Magnetohydrodynamics by Davidson is great for some dynamo theory. Self-Exciting Fluid Dynamos by Moffatt and Dormy is a tough read but focused on all kinds of dynamo theory. Chris Jones lecture notes on Dynamo theory are also great.

For double diffusive convection Pascals notes in the previous post are an excellent place to start.

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Clearchus76 t1_jdsmrvs wrote

Reply to Humans experienced a massive population expansion in a very small amount of time. What are the evolutionary consequences and benefits of such an event, massive popular of a species in a small amount of time? by bent_over_life

I feel like we are about to find out. We are a global economy that is about to become regional and a lot of people are going to starve. Africa is going to be in a very bad place soon and if China doesn’t pivot into something else soon they are going to be in a bad place as well.

So we will have to evaluate what is left over in the coming decades.

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ronflair t1_jdskzk1 wrote

Reply to comment by Octavus in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

You still would get a net increase in surface ionizing radiation, which would increase as a positive feedback loop the longer the magnetosphere was “off”.

According to NASA, a prolonged loss of the magnetosphere could erode the protective layers of the atmosphere. More cosmic rays would reach the surface as well.

https://science.nasa.gov/science-news/news-articles/earths-magnetosphere

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LastLapPodcast t1_jdsk7ig wrote

Reply to Can elephants canter or gallop? by [deleted]

Elephants don't have ankles, it's why they can't jump. To be able to gallop you'd need to spring off your feet. Try running (or even fast walking) without bending your ankles at all keeping you feet directly 90 degrees to your shin bone whist also never bending your toes. Then imagine being 20 tons and trying to do the same.

Edit: they also have 4 forward facing knees which also precludes galloping. Added for completeness.

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Octavus t1_jdsj58i wrote

Reply to comment by ronflair in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

You are forgetting that the atmosphere is responsible for the bulk of Earth's radiation shielding and is equal to about 10 meters of water.

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ronflair t1_jdsiy99 wrote

Reply to comment by zanderkerbal in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

As a molecular biologist, It just seemed like an obvious connection to me given the time frame. I have not googled the hypothesis but if geologists have noted years ago that the magnetic field was severely weakened during that geologic era, I would be surprised if no evolutionary biologist noted the connection. That said, I don’t see that mentioned as a hypothesis for the Cambrian explosion on wikipedia.

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GforceDz t1_jdsfj7d wrote

Reply to Can elephants canter or gallop? by [deleted]

Elephant run, but not often. They also charge at threats. I've seen them run to waterhole.

It looks like a elderly person doing a quick shuffle.

There's a lot of body rolling as they shift their weight. And of course they don't lift thier legs very high.

Babies Elephants are always charging and running around but nothing like the graceful gallop of a horse.

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ronflair t1_jdscqhs wrote

Reply to comment by PolymerPolitics in Around 550 million years ago the earth's magnetic field almost collapsed, but then strengthened a few million years later. Scientists say this may have been due to the formation of the inner core. But why exactly would that cause the magnetic field to get stronger? by somethingX

Depends on the depth. According to this site, a water layer 7cm thick reduces ionizing radiation dosage by about half.

https://space.stackexchange.com/questions/1336/what-thickness-depth-of-water-would-be-required-to-provide-radiation-shielding-i

If correct, means that cyanobacterial mats inhabiting the top layers of oceans will still be receiving significantly more ionizing radiation than normal. We’re not talking about enough radiation to sterilize the planet, just enough to significantly increase the rate of mutagenesis.

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