• Flying Squid@lemmy.worldOP
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    1 month ago

    The speed of light in a vacuum unaffected by external forces such as gravity should be the same no matter what direction it is in. I’m not sure why it wouldn’t be. That’s like saying a kilometer is longer if you go East than if you go West.

    However, it’s actually far more complicated than that, and much of it beyond my understanding.

    https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/speed_of_light.html

    That said, direction should not matter.

    • vithigar@lemmy.ca
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      1 month ago

      There’s no reason it wouldn’t be. The point is that it’s impossible to prove that it is. There is no conceivable experiment that can be performed to prove the two-way speed of light is symmetric.

      • 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.

                  • 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.

              • 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.”

              • 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.