Why would'nt this work?
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But will it fold?
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That’s the thing. The math says they’re both correct, and that it depends on the viewpoint of the observer.
I’m inside a car moving at 60 mph. I throw the ball forward (let’s ignore air resistance) at 30 mph.
Me, who’s inside the car, sees the ball move forward at 30 mph.
You, who’s outside the car, sees the ball move at the car’s speed PLUS the throw speed (60 + 30 =90 mph)
So, the ball is moving both at 30 mph and 90 mph. How can that be? It depends entirely upon your reference frame (inside the car? Outside the car? Inside another car moving at 40 mph?). The ball moves at all these speeds, and they are all “correct” within universal terms.
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The photons move from laser to moon and it takes time of light's speed. FTL is not possible in that case. Also the information is transmittes from earth to moon and not from one side of moon to other side of moon
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I was definitely talking about the first scenario, as is mostly everyone else. I know not everyone admits gravity (gravitational attraction) might travel faster than light as in the "sun moving" thought experiment.
I'm not confused, I'm discussing like everybody else.
You linked an article about gravitational waves which must transmit through some sort of gravitational field and they might transmit at approximately c as predicted in general relativity.
What I believe is that gravitational attraction, so the general effect of the field will be felt as if it acts almost instantly, and that does not contradict anything about the waves in that field. Because the waves in that field are not responsible for the attraction. This is similar to how photons do not mediate the magnetic attraction in magnets even though they are electromagnetic waves.
The current theories (which you are pulling from) manage to mathematically explain that in our moving sun thought experiment, the gravitational force coming from the sun appears to "update" instantly as if it's acting from it's actual position without the lag, because of (to my understanding) the curvature of space-time. So I personally can't fight that on mathematical grounds because that's above my understanding. But in the end it doesn't change much of anything to our discussion, because the force of gravity still updates "as if" it was mostly instantaneous and that's the standard model. Meanwhile, gravitational waves do travel at c but are kind of unrelated to the continous force. They are merely fluctuations in that force.
Please keep poking and challenging me at that, I'm still wrapping my head around it and will need better and better sources while I'm hyper focusing on it until I move on lol -
The motion of the stick will actually only propagate to the other end at the speed of sound in the material the stick is made of.
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Here's a video that actually kinda answers the question:
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If your stick is unbreakable and unavoidable you have already broken laws of physics anyway
You have it backwards: if your stick is unavoidable, NOT HAVING IT is the impossible thing.
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It would stretch like a rubber band stretches just a lot less. Wood, metal, whatever is slightly flexible. The stick would either get slightly thinner or slightly less dense as you pulled it. Also, you won't be able to pull it much because there's so much stick.
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Seems likely. The most rigid materially known, (or at least theorized) is nuclear pasta.. Nuclear pasta only forms inside neutron stars, stellar objects that are the last stage of matter before matter gives up entirely and collapses into a black hole.
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Very well put.
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You're not creating more stick, but you're making the stick longer. The pressure wave in the stick will travel at the speed of sound in the stick which will be faster than sound in air, but orders of magnitude slower than light.
Everything has some elasticity. Rigidity is an illusion . Things that feel rigid to us are rigid in human terms only.
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How does that work?
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I get it. Elasticity isn't something you think about in the every day so it all seems rigid.
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This is hard to truly eli5, so I'll have a go too, in case the others haven't cleared it up for you.
The spot on the moon that moves isn't a real thing, it's the effect of photons hitting the left side, then other photons hitting the right side. The 'reason' or 'cause' for those photons comes from earth very much at light speed. But the left side of the moon can't cause an effect in the right side, that fast. It just experiences a thing right before the right side experiences something similar.
Like if two cars drive from London to Manchester and Liverpool, arriving within seconds of each other. It doesn't mean you can drive from Manchester to Liverpool in seconds.
There's an SMBC I love on this: "The shadows of reality go as fast as they like." https://www.smbc-comics.com/comic/superluminal
Bonus: IIRC, any two events that are too close in time for light to travel from one to the other, can be viewed from a different "inertial reference frame" (someone else moving fast and analysing things with the same physics) as being the other way round. I.e. the right observer could see the right hand side of the moon get lit up before the left hand side. But the chap on earth wiggling the laser pointer is still wiggling it slower than the speed of light, so this observer would still see the laser pointer move from left to right. How does that work?
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Autocorrected from unfoldable. This is what I get for occasionally browsing on a shitty Amazon tablet. At least it was cheap to the point of being almost free.
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Also, even if you could somehow pull the stick, Newton’s Second Law (F = ma) tells us that the force required to move it depends on its mass and desired acceleration. If the stick were made of steel with a 1 cm radius, it would have a mass of approximately 754x10^6kg due to its enormous length. Now, if you tried to give it just a tiny acceleration of 0.01 m/s² (barely noticeable movement), the required force would be:
F = (754×10^6) × (0.01) = 7.54×10^6 N
That’s 7.54 MN, equivalent to the thrust of a Saturn V rocket, just to make it move at all! And that’s not even considering internal stresses, gravity differences, or the fact that the force wouldn’t propagate instantly through the stick.
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As it so happens the way the atoms push each other is electromagnetism, in other words sending photons (same thing light is made of) to each other but these photons are not at visible wavelengths so you don't see them as light.
Wat? I strongly believe you are not correct. Which is to say, I think you are talking out of your arse entirely. If you push on a thing you peturb the electron structure of the material. These peturbations propagate as vibratory modes modeled as phonons.
While technically some of this energy is emitted as thermal radiation that is not primarily where it goes.
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There are multiple forces at work in a rocket nozzle:
- The exhaust is pushed outward, giving the rocket thrust
- The exhaust hits the wall of the nozzle as it gets thinner, braking the rocket
These two effectively cancel out, which is why the actual effect of making the nozzle thinner/converge is that it increases the back pressure within the engine (constricted space, smaller hole), essentially (idk how) increasing the efficiency of the fuel burning.
However, when the nozzle gets too thin, the exhaust becomes faster than its speed of sound. Since the pressure travels at the speed of sound, it can now not actually get back into the engine anymore. So that's the limit of how thin you can make the nozzle. The pressure has to get back into the engine to have its effect, so you can't make the exhaust travel faster than its speed of sound.
If any of this sounds wrong to anyone, let me know, I'm not an expert in this.
