21–30 of 125 posts
Earlier quoted context omitted.
That’s not an axiom, it’s an assumption. Anyway, it’s the assumption of isotropy.
An axiom is an assumption: https://en.wikipedia.org/wiki/Axiom
Earlier quoted context omitted.
Veritasium has a nice video about it on YouTube. We can only measure the average back and forth speed of light.
I'm not sure that claim is true. Take this experiment, where A sends B a message following two paths: /-->--B (/ and \ are mirrors) | | | | \-- with speeds: (assume lengths are all 1m) /--cr--B | | cu cu | | \--cl--A The time it takes for path 1 (left,up,right) is cl+cu+cr. The time it takes for path 2 is cu. B can measure the difference cl+cu+cr-cu = cl+cr. A can compare cl+cr to cu: if cl+cr != 2cu the velocity is…
The most eye-opening thing I've learned about relativity in the past few years is that the notion that space has no preferential direction is an axiom in the theory. There's nothing about the way we measure the speed of light that would disambiguate if light traveled instantaneously in one direction and at half the measured speed of light in the other. We just don't have a way to know, because time measurements requi…
That’s not an axiom, it’s an assumption. Anyway, it’s the assumption of isotropy.
Maybe a year ago, possibly here, I finally saw gyroscopic precession demonstrated in a way that didn’t invoke magic thinking. The person simply pointed out that the mistake is in thinking of the rotating mass as a stationary object, when in fact you are applying the lateral force to a different spot on the object at each time interval, leading to very strange vectors.
The most eye-opening thing I've learned about relativity in the past few years is that the notion that space has no preferential direction is an axiom in the theory. There's nothing about the way we measure the speed of light that would disambiguate if light traveled instantaneously in one direction and at half the measured speed of light in the other. We just don't have a way to know, because time measurements requi…
Could you not, at least theoretically, create two synchronized clocks and physically transport one of them to another location and then throw a beam of light from the location of the first clock and measure the time of arrival at the second clock? Am I missing something? Edit: What I was missing was time dilation. Physically transporting the clocks would mean that they are no longer synchronized.
The most eye-opening thing I've learned about relativity in the past few years is that the notion that space has no preferential direction is an axiom in the theory. There's nothing about the way we measure the speed of light that would disambiguate if light traveled instantaneously in one direction and at half the measured speed of light in the other. We just don't have a way to know, because time measurements requi…
If there's no such experiment, it just means that for all intents and purposes, light travels at the "same speed" in any direction for an observer inside our Universe, because the speed of light is how we measure time in the first place. If an outside observer could notice that our spacetime is non-uniform, it's a fun thing to contemplate, but it does not change anything for us inside.
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Wasn't that the whole idea behind Michelson-Morley ( https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_exper... )?
Yes, that is an example of a measurement of the two-way speed of light. What is impossible, however, is a measurement of the one-way speed of light.
The most eye-opening thing I've learned about relativity in the past few years is that the notion that space has no preferential direction is an axiom in the theory. There's nothing about the way we measure the speed of light that would disambiguate if light traveled instantaneously in one direction and at half the measured speed of light in the other. We just don't have a way to know, because time measurements requi…
> But it's an axiom. I don't agree. If light traveled instantaneously in one direction, then if we looked in the opposite direction (where such light originates from) we would be seeing stars and galaxies at much more recent time (now). Also, their light would have traveled a much longer distance (due to the ongoing expansion of space) and so would be redshifted much more. All in all what we see on the sky would look…
If the preferred/non-preferred directions were "toward you" and "away from you", then rotating yourself to look in the "opposite direction" wouldn't make a difference.
(Note: not a physicist)
Earlier quoted context omitted.
An axiom is an assumption: https://en.wikipedia.org/wiki/Axiom
It’s a matter of scope. Axioms are assumptions that undergird the formal edifice (those or mathematics or arithmetic) whereas assumptions are local to the theory. ‘Assumptions’ is a synonym of ‘postulates’. Axioms are foundational, such as m×n=m×n (which is true for scalars, but not true in general for matrices).
Maybe a year ago, possibly here, I finally saw gyroscopic precession demonstrated in a way that didn’t invoke magic thinking. The person simply pointed out that the mistake is in thinking of the rotating mass as a stationary object, when in fact you are applying the lateral force to a different spot on the object at each time interval, leading to very strange vectors.