Why don’t we constantly see new stars in the sky as an increase of light travels to us?

Question

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.

In: 515

Answer 1

Light intensity decreases as a square of distance. this is because the light is spreading out as a sphere. light passing through one square unit of area on that sphere will be spread over 100 square units of area after passing ten units of distance from the source. Same idea as the shock from an explosion, in a way: up close, it is intense, but far enough away and you wouldn’t even notice it; don’t even hear it.

So, although there is lots of light coming from everywhere, most of it is just too faint to see. That is, if you go away in a straight line from here, you will eventually hit a star, because even though stars are pretty sparse in space, you have basically forever you can go, so eventually, odds are that your line of sight would hit a star. The sky would by bright everywhere if we could see it all.

But we cannot. We only see stars that are reasonably close (really close, mostly, although telescopes and other detection devices can “see” light at levels much lower than our eyes). Everything else is too faint to see.

If distant stars only sent light directly toward the earth, so the light was a straight beam and did not decrease intensity with distance (working like a laser, sort of), then sure, we could read at night using that starlight. But stars do not send all their light in one thin line directly toward the earth. Only the tiny part of the output of a star follows that super-thin line from there to here; the rest ends up somewhere else. We will never see most (essentially all) of the light from most stars, for this reason. We only get a tiny, tiny, tiny, tiny portion of their light. Not enough for our eyes to see. And the further away it comes from, the way lower amount we will ever get. Still some, though.