• Flying Squid@lemmy.worldOP
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    1 month ago

    That’s not how anything works. It’s impossible to prove that the universe wasn’t created last Thursday with everything in place as it is now. There’s no point in assuming anything that can’t be proven has validity.

    • Got_Bent@lemmy.world
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      1 month ago

      It’s just a thought exercise. There are several reputable YouTube videos on this topic. None of them claim that the speed of light isn’t the speed of light. They’re just demonstrating that we can’t prove it with current technology. Similar to the difficulty it took to finally prove that one plus one equals two. We know that’s correct, but it took years to prove it.

    • vithigar@lemmy.ca
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      1 month ago

      …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.

      • Flying Squid@lemmy.worldOP
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        1 month ago

        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.

        • InnerScientist@lemmy.world
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          1 month ago

          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

          • Munkisquisher@lemmy.nz
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            1 month ago

            With a detector and very accurate clocks, it would be easy to say “I’m going to send a pulse at 2pm, record when you receive it” that’s measuring it in one direction

            • InnerScientist@lemmy.world
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              1 month ago

              The very accurate clock needed in this case is physically impossible as far as we know, there’s no way to measure it as far as our current understanding of physics goes.

              Though if you can figure out a way you should publish a paper about it.

              • Richard@lemmy.world
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                1 month ago

                Can you cite some literature to back up that claim? Stating that something like acceptable clock synchronisation (a well established and appreciated method in the measurements of physical effects) is impossible in and of itself is something so bold that no one can just take your word for it.

                • InnerScientist@lemmy.world
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                  1 month ago

                  It is impossible to synchronize the clocks in such a way that you can actually measure the speed of light with it due to time dilation unless you define beforehand how fast the speed of light is to calculate that time dilation.

                  See also This or, more accessibly “Synchronization conventions”

              • Munkisquisher@lemmy.nz
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                1 month ago

                The clocks involved in gps are accurate enough that they have to take relatively into account for gps to be accurate. That’s far more accurate than you need to measure the speed of light.

                • InnerScientist@lemmy.world
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                  1 month ago

                  And to calculate the offset needed to get them all synced up involves calculating time dilation, which involves knowing/assuming the speed of light. These synchronizations work just as well if the two way speed of light is different than the one way speed of light.

                  To know the speed of light you assume the speed of light is c, but you’re trying to calculate c so all those clocks aren’t verified synced.

                  Just read through the wiki or Harvard’s books if you’d like, this is an unsolved “problem” in physics for a reason or do you think no one cares about how fast c is?

                  See also This or, more accessibly “Synchronization conventions”

                  • Munkisquisher@lemmy.nz
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                    1 month ago

                    I read all those and every test has reduced the amount that the speed of light could be anisotropic. From “it could be twice as fast in this direction to the other” to “it could be a small fraction of the relativistic effect of moving a clock through space.” Every improvement in measurement trends towards isotropic.

          • Flying Squid@lemmy.worldOP
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            1 month ago

            Why would the one-way speed be different? For what reason? Just because you think it’s possible?

            • vithigar@lemmy.ca
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              1 month ago

              For no reason. No one is saying that it is different, only that it’s impossible to prove one way or the other. Light traveling the same speed in all directions, and light traveling at 2x c away from an observer and instantaneously on the return, and every other alternative that averages out to c for the round trip, are indistinguishable to any experiment we can conduct.

              • Flying Squid@lemmy.worldOP
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                1 month ago

                And it’s impossible to prove that just the exact right type of orange will double the speed of light.

                But there’s no reason to speculate either thing without a reason for the speculation. Your reason seems to be “I think it would be cool.”

                I don’t think you realize it, but this is a very similar argument to “you can’t prove God doesn’t exist.”

                • vithigar@lemmy.ca
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                  1 month ago

                  Take 30 seconds to at least glance at the article the other user posted. It’s not just myself, there are plenty of very interested physicists who also find the unprovability of the one-way speed of light interesting.

                  I’m also not sure what your point about orange is supposed to be. Are you suggesting that there is a particular spectra of light that we cannot test?

                  My reason for being interested isn’t just that I think it’s “cool”. I think it’s fascinating that a fundamental underpinning of physics has such a gap in its experimental verifiability.

          • Richard@lemmy.world
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            1 month ago

            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.

              • Munkisquisher@lemmy.nz
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                1 month ago

                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.

                • Tavi@lemmy.blahaj.zone
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                  1 month ago

                  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.

                  • Richard@lemmy.world
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                    1 month ago

                    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