# Belief that the universe can't be infinite seems to contradict simple logic

Physics professors I have had (including Dr. Feynman in 1962) contend that an infinite universe would produce a fairly uniform "glow" from our point of view, which is not present. This seems to be contradicted by a few simple factors:

1. The light from a star reaching the earth decreases as the cube of the distance, so light from sufficiently distant stars would have an ever decreasing probability of reaching us and as the distance increases approach zero.
2. As the distance from earth increases, there is an ever increasing probability that light producing objects would be blocked by non light producing objects (planets, etc.).
3. The light from some distant stars can also be blocked by nearer stars.
4. Some light from distant stars can be absorbed by nearer black holes or scattered by gravitation effects and not reach us.
• Welcome Steve! Are you by any chance referring to what is known as Olbers' paradox? If so, perhaps that linked article can help you with your question.
– Amit
Jun 7 at 23:01
• The light from a star reaching the earth decreases as the cube of the distance. The cube? Jun 7 at 23:20
• More on Olbers' paradox Jun 8 at 2:09

As has been mentioned in the comments, this is Olbers' paradox. As we are fairly certain that the Big Bang really happened (and does not preclude an infinite universe), the paradox can be resolved by the expansion of the universe. Stars that are far enough away from us will be moving away at more than lightspeed, and hence invisible to us. In other words, an infinite universe is possible.

Now I'll explain why your arguments are wrong.

1. Light from stars decreases as the square of the distance (the inverse square law).
2. If objects like planets absorb light from stars, those objects will heat up. If the entire sky were covered in stars, all planets would have the same temperature as the stars, and would appear equally bright.
3. Same as for the previous problem, except now the blocking object is already as bright as a star - because it is a star.
4. This is correct. Black holes would block light. However, it would appear that there are far more stars than black holes. Hence, with the observed star/BH ratio, the sky would still be uniformly bright.