How can we witness a galaxy’s death as it’s happening when the galaxy is 9 billion light years away?
In: Physics
We can’t. But if we get really lucky and are looking in the right direction at the right moment we can see something amazing. 9 billion years ago some event happened. The light from that event traveled at light speed for the entire 9 billion years until it was 9 billion light years away from it’s starting point. That is how far away we are from it. So that is when we finally get to see it happen.
We can’t. We’re witnessing it 9 billion years later. It takes 9 billion year for the visual of that galaxy’s death to reach us. What you see when you see a galaxy dying is the image of what happened eons ago. Funnily enough, it mean that a dead galaxy still impact many other billion years after its death.
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