Okay, I need some discussion. I love love love reading about the universe and such. All the stars and planets out there, it’s amazing to me! But I’ve never been able to understand light years. Like, we could be looking at something in the sky and be all “Ooooh that’s a bright star!” But it’s 100 light years away and for all we know the star is actually dead and we are seeing the light as it had been traveling to us but died previously. This just goes right over my head. How do we just determine all these objects in the sky are so far… how do we know how far the light from thst object has been traveling? Please help lol! How do we also see planets so far away… I know we have amazing technology but damn… that’s insane to be able to see objects just so far away! I also think there must be some form of life out there. There’s no way we are the only planet with something living on it! Thanks for your input!
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It’s exactly as you said, pretty much all of the stars in our sky are light years away from us (besides the sun) and so the night sky we see is actually quite old.
The fact that light travels at a fixed speed through empty space is actually critical to how we determine how far away things are in there sky. All stars are made of mostly the same elements and they emit different frequencies of light in a very recognizable pattern called a spectrogram. As light travels through space, over very long periods of time, it actually gets stretched out slightly by the expansion of space. So, if we measure the spectrogram of light coming in from a distant star, and we look for those known patterns, we can estimate how far that light has traveled to reach us by seeing how much those patterns have stretched. If we know how far the light has traveled, we know how far away the star is.
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