this post was submitted on 15 Jun 2024
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...but that's exactly what you're doing. The fact that light travels at the same speed in all directions cannot be proven. You're the one insisting that it does.
I'm not insisting anything. I'm saying that, based on everything we know, the direction of light has no bearing on its speed.
Suggesting that it does just because we don't have evidence that it doesn't is no different, as I said, as claiming the universe was created last Thursday.
Maybe the speed of light doubles when it goes through the exact right type of orange. You can't prove it doesn't.
This is slighlty different though, we only know the two-way speed of light, not the one way speed of light.
We only know that this trip, to and back, takes x seconds. We cannot prove that the trip to the mirror takes the same length of time as the way back.
The special theory of relativity for example does not depend on the one way speed of light to be the same as the two way speed of light.
Wiki
Synchronise two high-precision clocks at different locations. Transmit the signal from A to a receiver at B and then send a signal back (or reflect the initial signal) from B to A. Both locations will record the synchronised time that their sensors picked up the transmission. Then, compare their clocks.
How would you sync them... ? Seems to beg the premise.
Sync them right next to each other, then move one of them. The other way you could test this theory is to have one clock tell the other the time over an optical link and then have the other do the same. If the speed of light was different in different directions. Each would measure a different lag.
Well, moving them is out of the question, since, you know, motion will change the clocks time. If you re-sync them, you bake the "error" into your framework. If you try a timer, the timer is offset. If you try and propagate a signal, the signal is offset. And eventually, you have to compare the two times, which muddies the waters by introducing a third clock.
Basically, there is no way to sync two clocks without checking both clocks, ergo, no way of proving or disproving. That's the premise.
In practicality, I assume it is constant, but it's like N=NP. You can't prove it within the framework, even if you really, really want to believe one thing.
If you move one clock very slowly away from the other, the error is minimised, perhaps even to a degree that allows for statistically significant measurements.
To cite the Wikipedia entry that one of the other commenters linked:
"The clocks can remain synchronized to an arbitrary accuracy by moving them sufficiently slowly. If it is taken that, if moved slowly, the clocks remain synchronized at all times, even when separated, this method can be used to synchronize two spatially separated clocks."
One-Way Speed of Light
Except if you continue reading beyond your Quote, it goes on to explain why that actually doesn't help.