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Due to the huge number of stars in the universe, will there ever be a time that the night sky is filled up completely with stars such that the night sky is as bright as it is in the daytime?

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  • $\begingroup$ This is related to Olbers's paradox. Google that one -- there are some subtleties. In short: The universe is finite in size and stars' lives are finite in time, so no, the night sky will not fill up. $\endgroup$ – bernander Aug 4 '18 at 12:42
  • $\begingroup$ More on Olbers’ paradox. $\endgroup$ – Qmechanic Aug 4 '18 at 13:08
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No.

The fact that the night sky is not currently filled up with stars is due to the finite speed of light, so that the light of very distant stars hasn't reached Earth yet. However, the universe is expanding, and that expansion is accelerating. This expansion is not bound by the cosmic speed limit of the speed of light and can, in fact, expand faster than light. Thus as the universe continues to accelerate its expansion, at some point the expansion of the regions of space occupied by very distant galaxies will, relative to us, be faster than light and thus the light from those galaxies will never reach us.

Your question is very much along the lines of Olbers' Paradox, and I encourage you to research that further (and specifically the paradox's resolutions) if you want to know more.

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  • $\begingroup$ Down voters, what don't you like about this answer? $\endgroup$ – NeutronStar Aug 7 '18 at 19:01
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I think the best answer as far as we know, is dissipation of light energy. The electromagnetic phenomena known as light, is a wave of alternating electric and magnetic fields. It is a 3 dimensional wave, so if you have a point source the wave travels outwards like ever increasing spheres. The surface of the spherical wave gets larger and larger. The light loses its intensity over distance, eventually becoming weak enough it is no longer detectable. Imagine how intense the sun appears from mercury compared to Saturn or Pluto.

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  • $\begingroup$ Maxwell's equations describe how intensity of light falls off with distance, which agrees with experience. It is also abundantly clear we can not see an infinite spectrum of ever weakening light. So unless at some point this fall off abruptly stops at a visible level it's quite expected that the night sky be black. Also it seems the temporal and spatial size of the universe is completely independent. $\endgroup$ – marshal craft Aug 6 '18 at 10:06

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