# Tag Info

## Hot answers tagged speed-of-light

7

http://en.wikipedia.org/wiki/Light_cone It simply says that some parts of the space-time are not accessible to us. For example I assume :-) you are on (Earth, Now). No matter what you do (Moon, Now) is not accessible to you. (Moon, Now + 1 second) is also not accessible to you, because the Moon is 1.28 light seconds away from Earth. Some events from the ...

7

It's tempting to think of gravity as some kind of interaction between the two bodies involved - maybe some form of signal (gravity wave?) sent between the two bodies. If this were the case then you would indeed have to allow for a propagation delay as the signals were sent between the two bodies. However this is not how gravity works. A massive object ...

5

I don't think I can rigorously prove that simulation engines don't need to worry about the (possibly? I don't know if there's a reliable measurement) finite speed of gravity, but I can offer some lines of thought that point in that direction. I'll start with your question 3. Suppose that gravity does have finite speed equal to $c$. Your question seems to be ...

4

The way to do problems like this is always to use the Lorentz transformations. Choose some sensible spacetime points in the rest frame $S$ and use the transformations to see what those points look like in the moving frame $S'$. In this case this is what the points look like in $S$: The spacetime points are labelled as $(t, x, y)$ - we'll ignore $z$ since ...

3

If I understand you correctly, your two points about apparent slowness of speeds is related to scale, and disappears when you quantify it using a common unit. ie: We think of 10m/s as relatively slow because the average human is 1.8 metres in height, and we can imagine that 10 metres per second, or 36 kilometer/hour as an achievable speed using a machine ...

2

Relativistic effects like time dilation only depend on how close you are to the speed of light in vacuum. This may make it sound like relativistic effects have something to do with the light itself, but that's not the case. What it means is that there is a speed, c, to which no mass can be accelerate, no matter how much energy you dump into it. Light ...

2

Leaving aside for a moment the comments made by dmckee et al, what matters is the angle of the measurement to the direction of motion. If an ether exists and you make a measurement along the direction of motion then you would get a different result to a measurement made at right angles to the direction of motion. It doesn't matter whether the right angle ...

1

The important thing is that all speeds seem to change: If you would look at the universe, in this case the two protons, from the perception of a man shrunk to the size of a proton, not only would the particles appear much faster, but so would the speed of light. So if you shrunk yourself to a trillionth of what you are now, one proton would have a diameter ...

1

There is certainly an interaction there between the optical medium and the photon. Actually, there are two photons in the interaction: the incoming one is absorbed by an electron in the material so that the latter fantastically fleetingly rises to an excited state. A fantastically short time later, another, outgoing, photon is emitted and the electron ...

1

Not sure if you're still looking for an explanation about this since was posted 4 months ago. The animation posted by Alfred Centauri is a great example. In fact, this is the illustration that Einstein used in his thought experiment. If you look at the light beam, imagine that every time the light beam reaches one side (mirror or origin/flash light), you ...

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