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by dguest20 hours ago |
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upvoteby 3form19 hours ago|
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This one feels less sinister than some other things at least to me, personally. You can reasonably doubt that the conservation of mass is violated and find out the truth based on that. But understanding more complex biology or historical context for some things? Granted, many of these things seem to be low stakes, but I'm sure there are some there are not (sex ed comes to mind).
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upvoteby zem19 hours ago|
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to be fair, fusion does violate conservation of mass, just not the way the teacher explained it. the loss of mass is where the energy comes from.
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upvoteby 3form18 hours ago|
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Yes, together with mass-energy equivalency it would form a coherent argument, and then also a correct one - but the thing is that if incomplete, it still might sound funky enough to you to research it if you care.

I think it helps that it's a very narrow field to look at, compared to fuzzy and big-picture view of social studies, for example. So much room to be confidently wrong... And sadly I can't think of a solution, LLMs or not.

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upvoteby mr_mitm17 hours ago|
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Yes, there is no law of conservation for mass like there is for energy. Fusion is a good example for why it's not conserved. The teacher was right.
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upvoteby dguest16 hours ago|
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He was right that it violates conservation of mass. He was completely wrong that it violated it by adding 2 atomic mass units when hydrogen fuses.

In reality heavier isotopes of hydrogen fuse, conserving the total number of nucleons, but the resulting hydrogen has a lower rest mass than the parent particles. The extra mass is released as energy and the total energy is conserved.

By his logic the system either violated energy conservation (by creating nucleons while releasing energy) or was endothermic (creating nucleons from the surrounding energy).

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upvoteby tardedmeme16 hours ago|
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There actually is a law of conservation of mass (it's the same law, because mass is energy) and it only appears violated if you forget about the particles that are zooming away at the speed of light. Of course the mass of a system changes if mass can flow in and out.
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upvoteby mr_mitm15 hours ago|
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Mass is not the same as energy. Mass can be converted to energy or has energy, but a photon, for example, is massless while carrying energy.
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upvoteby tardedmeme8 hours ago|
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That is incorrect. Photons have mass. They have no rest mass. They also cannot rest, so you might wonder how relevant that is.
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upvoteby mr_mitm8 hours ago|
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The concepts of rest mass and relativistic mass are considered outdated. In modern physics, "mass" means what they meant by "rest mass".

Here some indication I'm not making this up: https://hsm.stackexchange.com/questions/2465/when-and-why-di...

In any case, I never use those concepts, and I know no professional particle physicist that does. By "mass", I mean rest mass.

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upvoteby 10 hours ago|
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upvoteby bernds7419 hours ago|
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I had a chemistry teacher who told us that hydrogen reacts violently with oxygen, and this is how the hydrogen bomb works.
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upvoteby daymanstep18 hours ago|
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I had a chemistry teacher who insisted that the fissile isotope of Uranium was U-238 not U-235. I challenged him on this multiple times and he refused to budge on this. I get that it's a simple mistake to make (it seems like U-238 is bigger so intuitively ought to be less stable) but he could have just looked it up and he didn't, I guess he was just so confident about it that he thought there was no way he could have been wrong about it.
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upvoteby dguest16 hours ago|
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Hey it's a bomb made out of hydrogen! Also the deployment system for a thermonuclear bomb might involve that reaction in the rocket engine.
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upvoteby dreamcompiler15 hours ago|
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Well you can make a hydrogen "bomb" that way. Just not the hydrogen bomb.
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upvoteby 12 hours ago|
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upvoteby BobaFloutist10 hours ago|
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I mean fusion and fission do violate conservation of mass and conservation of energy, they just don't violate conservation of mass and energy, right? We thought mass was strictly conserved until Einstein, and then we updated our understanding.
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