Let’s imagine a world where time machines are invented.

Hypothetically, what’s stopping anyone from travelling to the past, where the dollar is much more valuable, and buying things at a much lower price? What if you then go back to the present, sell those things at a higher price and repeat the cycle? And wtf would happen if everyone there started doing that?

  • WoodScientist@lemmy.world
    1·
    7 hours ago

    https://en.wikipedia.org/wiki/Relativity_of_simultaneity

    The present does not exist. From the previous link:

    It can be argued that special relativity eliminates the concept of absolute simultaneity and a universal present: according to the relativity of simultaneity, observers in different frames of reference can have different measurements of whether a given pair of events happened at the same time or at different times, with there being no physical basis for preferring one frame’s judgments over those of another. However, there are events that may be non-simultaneous in all frames of reference: when one event is within the light cone of another—its causal past or causal future—then observers in all frames of reference show that one event preceded the other. The causal past and causal future are consistent within all frames of reference, but any other time is “elsewhere”, and within it there is no present, past, or future. There is no physical basis for a set of events that represents the present.

    Many philosophers have argued that relativity implies eternalism.[6] Philosopher of science Dean Rickles says that, "the consensus among philosophers seems to be that special and general relativity are incompatible with presentism.

    If two observers will disagree on which events happened in “the present,” then “the present” cannot exist as a real universal entity. “The present” only makes any physical sense in classical, pre-20th century Newtonian mechanics.

    This is why the block universe or eternalism makes more sense.

    • Buffalox@lemmy.world
      1·
      7 hours ago

      It can be argued that special relativity eliminates the concept of absolute simultaneity

      That’s not the same thing. Obviously all experiences are delayed, and therefore about the past, even if it is merely picoseconds.
      In that way we can only experience the past, that is obvious, and not relevant to the existence of an objective present.

      Although we can only experience the present with some delay depending on circumstances, (can be billions of years astronomically) there is zero doubt that there is an objective “present” we all experience and act according to.

      • WoodScientist@lemmy.world
        1·
        7 hours ago

        You’re still imagining that there is some fixed universe playing out at constant time, and that we all just experience the echoes of this present in different orders. This isn’t what relativity says. Clocks traveling near the speed of light don’t just appear to slow down, they actually slow down.

        Different regions of the universe don’t even experience the same flow rate of time. Someone living on a mountaintop experiences time faster than someone at sea level. And yet you cling to this fantasy of their being some universal “present.” You cannot have a universal present in a universe composed of different flow rates of time!

        • Buffalox@lemmy.world
          1·
          7 hours ago

          Clocks traveling near the speed of light don’t just appear to slow down, they actually slow down.

          Which is EXACTLY the ONLY thing I said you can actually do.
          You can slow down time locally. And for a photon it’s slowed down to a standstill.

          That does not contradict ANYTHING I’ve claimed.

          • WoodScientist@lemmy.world
            1·
            6 hours ago

            Yes, you recognize the fact, but you haven’t internalized its implications. You can only have a universal present in a universe of shared time. Ultimately, “the present” is something applicable to and that exists within the mind of a single observer.

            One of the hallmarks of science is that different people can independently measure something and confirm its existence. If no two observers can ever agree on what constitutes “the present,” then how can “the present” be said to exist at all? It’s a fundamentally unscientific concept.

            • Buffalox@lemmy.world
              1·
              6 hours ago

              Ultimately, “the present” is something applicable to and that exists within the mind of a single observer.

              No, it’s an objective thing. No observation can be exactly “at the present”, I clearly explained that earlier, there are always delays, that doesn’t change the fact that like a photo is not the past being real, so it is far all observations. That doesn’t change the fact that there is an objective “present”.

              One of the hallmarks of science is that different people can independently measure something and confirm its existence. If no two observers can ever agree on what constitutes “the present,” then how can “the present” be said to exist at all? It’s a fundamentally unscientific concept.

              Oh boy, yes I know that argument, and it’s a flawed argument IMO. It’s about definition. If we agree to meet somewhere at the same time, then when we meet we are at the present. There is no sane argument about that IMO. We perceive each other with a slight latency, but that does not prevent us from being together in the present.

              To argue the present doesn’t exist is nonsense, and no more than a philosophical curiosity. Scientists absolutely work with a present too, and obviously compensate for latency.

              I could ask the same question reversed: How can scientists compensate for latency to a degree they can measure gravitational waves, without an objective time frame, that requires acknowledgement of a present?