Why would'nt this work?
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It's pretty hand wavy. The question: why is the speed of sound so slow? (which is essentially isomorphic to this one) is pretty hard to answer. I can't do the the maths to derive it anymore haha.
There are similar things about light slowdown during refraction and stuff.
It's just much easier to view certain bulk phenomena as waves in homogeneous material but it can be very unsatisfactory. Hence all the bullshit artists in this thread talking about speed limits, the standard model, and time dilation. For some reason "it just be that way ok?" feels more satisfying if the thing you're asserting seems more fundamental, but it doesn't really make stuff clearer.
Not going to disagree with that, but you’re responding to somebody who obviously has no background in physics, and it strikes me as a reasonable balance between conceptual (“hand wavy”) and detailed enough.
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Alright now eli5? Everything is jelly?
Everything soft and slow like your brain yes.
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Not going to disagree with that, but you’re responding to somebody who obviously has no background in physics, and it strikes me as a reasonable balance between conceptual (“hand wavy”) and detailed enough.
I used to run physics labs at uni so I'd hope I was as alright teacher still. Never made it as a real physicist though ;_;
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It can look dumb, but I always had this question as a kid, what physical principles would prevent this?
Your push would travel at the speed of sound in the stick. You could think of hitting a pipe with a hammer, the sound of the hit would travel at the speed of sound, same is true for you pushing the stick.
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I used to run physics labs at uni so I'd hope I was as alright teacher still. Never made it as a real physicist though ;_;
Well, it made me feel smart. So either you're a good teacher, and helped me put into words and solidify something I already understood more abstractly. Or you're a terrible teacher, and have led me further astray.
Pretty rough dichotomy there. I would not want to be an educator.
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This is a nice example that also makes me think more questions.
- Will the hole punching be forward or backward?
- Assuming infinite deceleration, for an observer on the other end of the barn, will the barn be punched through, before or after the pole-pusher has stopped?
- For the pole-pusher, will the barn be punched through, before or after it has stopped?
Gets more interesting
The punching-through should start at the point of impact, since that end of the pole and that spot on the wall pole both know about the collision at that moment, and then the information travels back through the pole. So I think the front end of the pole would start breaking through the wall immediately, while the information about the impact is still traveling back through the pole. For that reason I think the front end of the pole might end up sticking farther out of the barn than the back end, because it has more time to so it. Would be interesting math, which I've never tried to figure out.
There can't be infinite deceleration, for the same reason that the back end of the pole can't instantly know the front end has run into the wall. Deceleration travels back through the length of the pole as its atoms squish up against the atoms in front of them and slow down.
Interesting for sure!
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Alright now eli5? Everything is jelly?
Everything bends when you move it, usually to such a small degree that you can't perceive it. It's impossible to have a truly "rigid" material that would be required for the original post because of this. The atoms in a solid object don't all move simultaneously, otherwise swinging a bat would be causing FTL propagation itself. The movement needs to propagate through the atoms, the more rigid the object the faster this happens, but it is never instantaneous. You can picture the atoms like a lattice of pool balls connected to each other with springs. The more rigid the material, the stiffer the springs, but there will always be at least a little flex, even if you need to zoom in and slow-mo to see it.
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Alright now eli5? Everything is jelly?
Sorta. I found this video a while back that helped me understand it. Pay attention to the clock hands part and how the movement is affected by how fast information is traveling in them. It’s basically the same idea as the stick but a different direction.
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It can look dumb, but I always had this question as a kid, what physical principles would prevent this?
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Okay for a thought experiment what if it’s a perfect element incapable of that?
"Ok, well, humans can't just teleport wherever they want, but what if they could?"
well, then they could, I guess.
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The punching-through should start at the point of impact, since that end of the pole and that spot on the wall pole both know about the collision at that moment, and then the information travels back through the pole. So I think the front end of the pole would start breaking through the wall immediately, while the information about the impact is still traveling back through the pole. For that reason I think the front end of the pole might end up sticking farther out of the barn than the back end, because it has more time to so it. Would be interesting math, which I've never tried to figure out.
There can't be infinite deceleration, for the same reason that the back end of the pole can't instantly know the front end has run into the wall. Deceleration travels back through the length of the pole as its atoms squish up against the atoms in front of them and slow down.
Interesting for sure!
There can’t be infinite deceleration,
I realise I should have been more specific.
Considering the pusher as a point object, deceleration of the pusher be infinite. Just another simplification so that you don't have to calculate what would happen to all the speeds in between. -
That's a great guess when you try to answer the problem with traditional (Newtonian) physics. However, space and time do not behave in a way we would expect when we go nearly at light speed. So Newtonian laws do not apply in the same sense anymore.
Hmmm. Is there an answer/solution to the problem?
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Nah, I prefer using quantum spookiness for that. Send a steady stream of entangled particles to the other person on the moon first. Any time you do something to the particles on Earth, the ones on the Moon are affected also. The catch is that this disentangles them, so you have only a few limited uses. This is why you want a constant stream of them being entangled.
Any time you do something to the particles on Earth, the ones on the Moon are affected also
The no-communication theorem already proves that manipulating one particle in an entangled pair has no impact at al on another. The proof uses the reduced density matrices of the particles which capture both their probabilities of showing up in a particular state as well as their coherence terms which capture their ability to exhibit interference effects. No change you can make to one particle in an entangled pair can possibly lead to an alteration of the reduced density matrix of the other particle.
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