ELi5: How does the whole light year thing work? How does something happen a long time ago that we know of yet we can still see it and have to wait for it to happen again (like those exploding star things on tt)
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Hi /u/chimmy_w!
The speed at which light (and information) can travel is finite. In fact, on cosmic scales, the speed of light is fairly slow. Thus, when a star goes supernova very far away, it takes the light emitted in this event considerable time to reach us.
If the star is, say 100 light years away from us, it takes the light 100 years to reach us. If it is 1000 light years away, it takes 1000 years to reach us and so on.
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