CanadaPlus

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A backup account for !CanadaPlus, and formerly /u/CanadaPlus101 on Reddit.

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CanadaPlus , to Ask Science in Could non-Newtonian fluids be used in the future as a kind of percussive ear protection?

It’s a bit oversimplified, actually. Sound bounces off of discontinuities in the medium, which is why foam works. You just have to control scattering somehow.

The big problem with using oobleck or whatever is it responds to shear, and shear can’t travel through air. You could use it for earthquake protection, though, or if you could channel compressive waves from the air into shear form using a fancy bridge like in OP.

Also, shear-thinning fluid is a thing too.

CanadaPlus , (edited ) to Ask Science in Is the "Tromatz" bioelectric wave toothbrush legit, or snake oil?

Based just on the name even, snake oil. WTF is a “bioelectric wave”?

CanadaPlus , to Ask Science in Has a vaccuum chamber ever been used for desalination?

Yeah, OP didn’t even phrase it like nobody else could have thought of it, which is a frequent pitfall for these kinds of questions. The experts that can give the best answers hate that. It’s implicitly saying their years of study aren’t worth much.

CanadaPlus , to Ask Science in Would a mechanical counter pressure suit make you poop?

In terms of engineering, it does. Micro meteorite protection and heat management can both be provided by normal garments. UV protection is obviously easy enough too. Breathing gas is a bit less convenient, but still not as tricky as making a suit that’s both rigid enough to reliably hold several PSI in and flexible enough to comfortably work in. That’s why the elastic suits are being researched like they are.

CanadaPlus , (edited ) to Ask Science in Would a mechanical counter pressure suit make you poop?

… That’s actually a good point. I’m guessing since the digestive tract is flexible and isn’t held open to the outside all the time, it wouldn’t cause problems with things deep inside. I also think it’s inevitable that if you did shit yourself in it, suction would kick in at some point and make it all a bit more dramatic. And then it would boil-freeze off into space, and be icy cold. That might still be better than pooping a sealed space suit, though.

CanadaPlus , to Ask Science in Would a mechanical counter pressure suit make you poop?

I think it’s like a third of an atmosphere or something. Enough to comfortably achieve the same partial pressure of oxygen as normal Earth air, by providing it pure.

CanadaPlus , to Ask Science in Why do many microwave ovens hum in an interval of a minor 7th?

Wow. This question is a good but very specific observation, and I did not expect an actual answer.

CanadaPlus , (edited ) to Ask Science in Why are we so concerned with oxygen production yet we never hear about nitrogen production, though we actually need 78% nitrogen vs 21% oxygen to survive?

Atmospheric nitrogen is useless to most life, as it’s extremely hard to break down into other nitrogen compounds. Certain bacteria are the exception, and they’re very important both to ecology and human agriculture (although less so since the Haber process was invented and artificial fertilisers became available). The other natural source of nitrogen compounds is lightning strikes.

Oxygen is completely the opposite. It’s unstable in an Earth-like environment (which is why fires happen), and if you find it in such an environment there must be something special producing it continuously. It’s not the only biomarker astronomers look for, either. There was a planet with insane amounts of a chemical called DMS found recently, and that’s just as eye-catching, if weirder.

Deep sea divers also use a nitrogen mix (nitrox) to stay alive and help prevent the bends

You’ve actually got that somewhat backwards. To go really deep you switch to heliox or similar. Nitrox is for intermediate depths where you need less oxygen than in the normal nitrogen-oxygen atmosphere, but nitrogen narcosis isn’t an issue yet.

CanadaPlus , (edited ) to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

No, it’s not worth it. Honestly that’s great all on it’s own. I guess they never had a reason to update it, then, since anybody that needs a more accurate value would just measure it themselves.

It looks like they went back to the original litre definition a few decades later. I’m not sure why they thought defining volume by mass rather than geometry was better in 1901, anyway. Some fun facts about the kilogram itself, since I never get to talk about this stuff:

Since 2019 the kilogram has been based on a “Kibble balance”, which is a contraption that precisely measures the force produced by electromagnetism. The necessary electricity is provided by circuit with a material that has quantised resistance near absolute zero, and a superconducting junction which produces oscillation exactly tied to the current flowing through, which is itself timed by atomic clock. This allows you to measure it out using just the new fixed value of Plank’s constant.

Before 2019 there was just a chunk of metal the was the kilogram, which is hilariously low-tech.

CanadaPlus , to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

It also depends on latitude, and local geology and…

Maybe it is just weighted by surface area, you’re right, and that’s what I meant by “surface average”.

CanadaPlus , (edited ) to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

G is also fixed in GR, although it’s not guaranteed to manifest in a neat relation like that in every situation because spacetime curvature has a lot of components at every point, and they interact super nonlinearly.

CanadaPlus , (edited ) to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

F=Gm1m2/r^2^

G is the gravitational constant, the m’s are the masses in question, and F is the force generated. The r is radius from the center of one body to the other; that is, height. If it didn’t decrease, orbits wouldn’t exist the same way and astronomers would have laughed Newton out of the room.

I could give you a link if you really want, but it’s the Newtonian gravity equation, so it’s probably just going to be “Gravity” on Wikipedia.

CanadaPlus , to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

Is that so? I wonder what the story behind that is. Maybe it’s a surface average?

Most people would probably guess this, but meters and seconds are defined independently of Earth’s gravity, so it doesn’t have a true value, just apparently a standard nominal one.

CanadaPlus , to Ask Science in Does everyone learn the same gravity in school or is it different everywhere?

Newtonian physics also has gravity decreasing with height, no need to get out the big guns.

CanadaPlus , (edited ) to Ask Science in [Solved] Trees supposedly take 30 years *before* they absorb CO₂. Why?

Young trees of many species also grow faster, though, and if the old tree dies and decays all that carbon returns to circulation. Forestry, done right, actually is carbon negative. However, it’s also incompatible with the critters that need old-growth forests (and old growth itself soaks up carbon fairly slowly). Environmentalism needs to get better at appreciating tradeoffs IMO.

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