• Synapse@lemmy.world
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    1 month ago

    If I understand that right, gravity also moves in space at the speed of light, therefore Earth will keep on orbiting for 8min around nothing?

    • vithigar@lemmy.ca
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      1 month ago

      Kind of. The concept of simultaneity breaks down at distances where the speed of light matters. If we base it on what we currently observe and call “now” on the Sun the eight minute old state we currently observe then what does “now” on earth look like from the point of view of the Sun at that same moment? You can’t reconcile a single “now” for observers in both locations.

      An alternative take which is also consistent with observable physics is that the speed of light is infinite but it’s causality itself that propagates at c.

      Thinking in those terms also makes a number of relativistic effects more intuitive. You need infinite energy to reach the speed of light simply because it’s infinitely fast. Time dilates when moving because you’re encountering approaching causality earlier than you otherwise would have. Time “stops” for anything traveling at the speed of light because at infinite speed it just experiences literally everything in its line of travel at once and the concept of “after” becomes meaningless, encountering all future oncoming causality in a single instant.

      This was a bit of a tangent but it’s something that has fascinated me for a long time.