←back to thread

The Universe Within 12.5 Light Years

(www.atlasoftheuniverse.com)
266 points algorithmista | 1 comments | 05 Sep 25 22:20 UTC | HN request time: 0.202s | source
Show context
jader201 ◴[06 Sep 25 01:47 UTC] No.45145848[source]▶
Tangential comment, but it’s crazy to think about how, when we look up at the stars in the sky, we’re seeing light in wildly varying degrees of age.

For example, when we look at the sun, that’s 8-minutes-old light. When we look at Polaris (the North Star), that light is 447 years old.

When we look at Andromeda?

Yeah, that light is 2.5 million years old.

replies(3): >>45145857 #>>45145869 #>>45146125 #
SoftTalker ◴[06 Sep 25 02:34 UTC] No.45146125[source]▶
Light doesn’t age. From its perspective it hit your retina the moment it left the star.
replies(3): >>45146273 #>>45146753 #>>45147652 #
jb1991 ◴[06 Sep 25 03:05 UTC] No.45146273[source]▶
You are saying, from the perspective of light, whether it travels 1 mile or a trillion miles, that journey takes the same amount of time?
replies(4): >>45146482 #>>45146866 #>>45147661 #>>45150109 #
1. sh-run ◴[06 Sep 25 03:59 UTC] No.45146482[source]▶
I'm not a physicist, but I believe that's the exact insight that led to special relativity. It goes something like: If your moving at 1,000kmh next to a jet moving at 1,100kmh then the jet is moving at 100kmh relative to you. Eventually people realized those wasn't the case with light. No matter how fast the observer is, light still moves at 299,792,458m/s. Einstein figured out that if the speed of light is fixed despite relative motion, then time must slow down as you move faster. So from the perspective of a photon no time has passed since its departure.