• TheButtonJustSpins
    link
    fedilink
    English
    arrow-up
    2
    ·
    1 year ago

    Wait, why would you arrive one year after the flash if you’re heading at 0.5c? It would take you two years to travel the 1ly.

    • cynar@lemmy.world
      link
      fedilink
      English
      arrow-up
      4
      ·
      1 year ago

      The maths is wrong, though the idea is correct. At 0.5C, the length compression is approximately 86.6%. Basically, the star 1 ly away now appears to only be 0.866 ly away.

      From outside, you took 2 years to get there. By your ship’s clocks, you took 1.73 years to get there.

      The effect gets stronger as you approach C. At 0.99C, time passes at only 14% the speed it passes for an observer. The distance also shrinks to only 0.14 light years.

      This calculator lets you play with the numbers. https://www.omnicalculator.com/physics/time-dilation

      Time dilation and length contraction are fundamentally linked. The change is the same in both, so that C is always constant, at any speed.