with how light works and the constant expansion of what we term the “observable universe” why don’t we constantly see new stars appearing in the night sky as the observable part expands and stars/galaxies light reaches us for the first time?
The night sky has stayed relatively the same (accounting for changing postions over time, stella phenom, supernovas etc.) for all of humans written history.
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It takes millions of years for stars to form and die. In order for us to even be able to see most stars, they need to already be inside of our galaxy, so its not like a new star forms or dies in our galaxy every day. When you get further out, there are distant galaxies that you can really only see with high-tech telescopes. We can see supernovae all the time from those distant galaxies, but not with the naked eye.
When the Hubble Telescope first started taking pictures of deep space, we just pointed it at an empty patch of sky to see what would happen, and we were amazed by the number distant galaxies we could see that we would never be able to see from Earth.
There are a couple of recorded supernovae that happened in our galaxy, though. It would appear in the sky as a very bright “new” star for a few days/weeks. About a dozen in the last 2000 years.
The sky also does change as the stars move around the galaxy, but not much over the last few thousand years (when humans started recording the positions of stars in the sky). About 10000 years ago, the North Star was actually Thuban, not Polaris.
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