eli5 Is it correct to think of events happening on the far side of the universe or in a different galaxy as occurring “at the same time”?
In: Physics
Kind of. The speed of light is the speed in which that information travels.
Take our sun for example. It is around 8 light minutes away, meaning that it takes light about 8 minutes to travel from the sun to the Earth. Let’s say that the sun quit shining at exactly 3:00, and at that exact time, you sneezed. The sun going out and you sneezing would have happened at the same time. But it would take 8 minutes for the information that the sun went dark to get to you. So from your perspective, you sneezed at 3:00 and the sun went out at 3:08.
Now, if someone was twice at far from the sun as you and could somehow see you sneeze, from their perspective, you sneezed at 3:08 and the sun went out at 3:16, even though both events happened at the same time at 3:00. That’s why there are theories of Relativity. Because the time in which events are noticed are relative to where the observer is and how fast the observer is moving
On a cosmic scale, time and distances are enormous. So a lot of the stars that you see at night have blown up or burnt out hundreds or thousands of years ago, it’s just that the light of those explosions haven’t reached your eyes yet.
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