Comment by joecarrot | Hacker News Reader

Comment by joecarrot | Hacker News Reader

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I read a book about particle physics and understood a very small amount of it. My understanding is that you cannot have faster than light anything because nothing can travel faster than light. For instance, the gravitational field of this coffee cup in my hand spans the entire universe. The cup is gravitationally attracting me, the Earth, the Sun, and every other atom in the universe (albeit at a remarkably low level of power). Even this gravitational field is not FTL though, because some particle exists that does the work of attracting. My cup is emitting gravitons or something like that, and those gravitons travel at the speed of light. A graviton leaves my cup, travels at the speed of light to Mars, and when it hits Mars, it attracts it.

What I am saying is that, in my understanding, there is no action that can occur without a particle that acts, and since no particle can travel FTL, nothing can happen FTL.

In the case of Quantum entanglement, mustn't some particle travel from the first quantum thing to the entangled quantum thing in order to have an effect?

I believe that my understanding is flawed! I don't know how to get a clearer view though. Any advice?

The issue that is misunderstood is that entangled particles cannot be used for FTL communication, which has to do with being unable to control the outcome of the measurement rather than transportation speed limits. Entangle two particles, ship one off to the Sun by whatever less-than-FTL speed you like, perform a measurement there, and in theory measurement of the particle that remained here will be instantaneously affected. ie: without waiting 8 minutes for the initial measurement to “propagate at light speed”.

Photons, like everything else, travel along the curvature of spacetime (though a physicist has told me that they do have some mass and thus warp spacetime themselves, too), and the speed of light is just how fast spacetime can curve. The faster you go, the more curved it is, and the harder it is to bend it further, but there's a point where you can't bend it any faster than you are because it doesn't go faster.

I always imagined it as everything always moved at the speed of light in spacetime, like 4d motion vectors that were always the same length. Acceleration is changing the angle of the vector to move through more space and less time. Space curvature causes motion on stationary objects (gravity) because of some of the time motion becomes space motion.

I kind of assume this is incorrect because it seems like a simple explanation and explanations of this stuff tend to not be simple

The "speed of light" is actually a somewhat poor common name for the limitation.

It should be called the "speed of information."

If the sun somehow magically disappeared, we would continue to orbit that empty space for about 8 minutes.

or the speed of causality

Hence, "c".

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