Recent comments in /f/askscience

d4m1ty t1_jdrqngm wrote

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

Elephant wasn't galloping in the vid. A gallop requires the animal to have all 4 feet off of the ground at the same time. Animal must be fully airborne. Gallop has nothing to do with speed, it is a terminology that defines 4 suspended feet while running.

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acfox13 t1_jdrpt6c wrote

Reply to comment by dukesdj 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

>"99% of the universe is fluids, the remaining 1% is just details"

I like that. I live somewhere with huge tides, whirlpools, microclimates, and the fluid dynamics here is stunning to witness.

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Coomb t1_jdrprjg wrote

Reply to comment by Global_Lavishness_88 in How did Vladmir Markovnikov actually come to what we know as Markovnikovs Rule? by aquaticlorax

Can you give a complete physical description of why Lego blocks fit together in particular ways? What's the fundamental physical interaction(s), in detail, then make it so some Legos can fit with other Legos, and some Legos can't?

You can't. Actually, nobody can, because we don't have a coherent theory that is known correctly predict all of the interactions, at all of the scales, which are involved in two Legos sticking together. However, that doesn't prevent you from experimenting with Legos and observing that Legos come in a variety of sizes and shapes, and some of them can stick to other Legos in one particular way and some of them can stick in different ways. This is how people discovered things through experimental chemistry: they had atomic theory, which helped provide insight at an important level into the structure of everyday substances, but they didn't need quantum chemistry to experiment with bonding and breaking bonds and draw logical conclusions from experimental results.

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adventuringraw t1_jdrnbmp wrote

Reply to comment by Fenrisvitnir 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

Um no (we have to keep the comment chain going).

You're actually being overly dismissive of what they're saying I think. The key word they used was 'inspired'. I tried to dig up the origin of convolutional image kernels, and while I couldn't find much in five minutes of digging, I'm sure you're right, that they predate deep learning certainly, and possibly even digital computing entirely given that their historical origin was probably in signal processing.

Their comment though wasn't whether or not CNNs directly imitate biology, or that the way they did it was entirely novel... They were just pointing out that biology was an inspiration for trying it this way, and that part's unambiguously true. To my knowledge, the first paper introducing the phrase 'convolutional neural network' was from Yann LeCun. This one I believe, from 1989. If you look at the references, you'll note Hubel and Wiesel's 1962 paper introducing a crude model of biological vision processing is in the references. More importantly, Fukushima, 1980 is referenced (and mentioned in the text as a direct inspiration). This 'Neocognitron' is generally accepted to be the first proto-CNN. The architecture is a bit different than we're used to, but it's where things started... And as the author puts it in the abstract:

> A neural network model for a mechanism of visual pattern recognition is proposed in this paper. The network is self-organized by "learning without a teacher", and acquires an ability to recognize stimulus patterns based on the geometrical similarity (Gestalt) of their shapes without affected by their positions. This network is given a nickname "neocognitron". After completion of self-organization, the network has a structure similar to the hierarchy model of the visual nervous system proposed by Hubel and Wiesel.

So... Yes. CNNs weren't inspired by cow vision or something... Hubel and Wiesel's most famous work involved experiments on kittens. but CNN origins are unambiguously tied into Hubel and Wiesel's work in biological visual processing, so the person you're responding to is actually the one that was right. I just noticed even, some of the papers referenced from Wikipedia that you said didn't show biological inspiration are the same ones I mentioned even, so they were the correct papers to cite.

If I may be a bit rude for my own Sunday morning amusement: 'Thanks for being interested, but there is a lot of fluffery in ML discussions.'

Seriously though, it's an interesting topic for sure, and historical image processing techniques are certainly equally important to the history of CNNs... They were the tool reached for given the biological inspiration, so in all seriousness you're not entirely wrong from another perspective, even if you're not justified in shooting down a biological inspiration.

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DDWingert t1_jdrkc41 wrote

Reply to 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

Fascinating. I'd always assumed that the magnetic field was a combination of the chemistry of the particulates recombining, and the density of the mass accumulated. I had no idea that it fluctuated.

I think what you are looking for is the theory of geodynamo, which is referred to in the article you shared:

"Earth’s magnetic field is generated in its outer core, where swirling liquid iron causes electric currents, driving a phenomenon called the geodynamo that produces the magnetic field.
"Because of the magnetic field’s relationship to Earth’s core, scientists have been trying for decades to determine how Earth’s magnetic field and core have changed throughout our planet’s history. They cannot directly measure the magnetic field due to the location and extreme temperatures of materials in the core. Fortunately, minerals that rise to Earth’s surface contain tiny magnetic particles that lock in the direction and intensity of the magnetic field at the time the minerals cool from their molten state."

https://websites.pmc.ucsc.edu/~glatz/geodynamo.html

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