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why is space dark? that is because there is no atmosphere to scatter the light. why are we pretending that if we have had enough visible light from all those distant start, the space would light up. i mean it still wouldn't? does the space around sun lights up? no can someone explain this, please? i feel like i am missing something completely obvious.

aniesa
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Imagine the universe would be truly infinite in both space and time, and it would not grow or shrink. In this case, no matter where you look, a beam of light from a star would eventually reach you.

Think taking an image of a piece of space with a digital camera: each pixel would be hit by photons, as no matter where you look, there would eventually be a star that has sent it (unless there's some object that obscures the light).

Because of this, the night sky would appear bright if these assumptions were true. Since it's not bright, we know the assumptions to be false. We only see a few bright spots from stars and galaxies that are near enough so their light can reach us.

In particular, the expansion of space plays a vital role and results in the Cosmic Microwave Background. So in a sense, there is some light in most directions but it has lost so much energy that it's no longer visible to us as it's shifted into the microwave region.

DarkDust
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    "unless there's some object that obscures the light" and if there were such an object, it would be heated up until it was the same temperature as the star, and would glow as bright. – James K Nov 23 '23 at 23:49
  • Worth adding that stars don’t get dimmer with distance, as people intuitively suppose they do. Thus in every direction not only do you see a star, you see a star which is as bright as the surface of the Sun… though smaller. – Martin Kochanski Nov 24 '23 at 08:00