So I heard that, possibly, two super massive black holes could be merging by the end of this or next year. My question is this, and essentially trying to get my head around, if it takes x amount of time for light to reach us, has this event already happened? And we are just seeing it in its past?
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Yes, we are viewing “the past.”
The fun bit is when you realize that *everything* you observe is *necessarily* already in the past, just by different degrees.
In the case of interstellar events, the distance is so great that the age of the event is dramatic by the time the light we use to observe it reaches us.
When astronomers say the black holes are going to mere at some time in the future, what they mean is that the merge will be observable at some time in the future. From our earthly perspective, it is simply that we don’t have a compelling reason to distibguish that the event happened X years ago and we will be observing it Y years from now. It’s an excessive mouthful and everyone serriously studying the event already knows that such a caveat is being assumed.
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