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It seems to me like this is only true if you assume space is perfectly transparent, which seems like by far the weakest assumption. Introducing any tiny amount
by Tomminn 6y ago
It seems to me like this is only true if you assume space is perfectly transparent, which seems like by far the weakest assumption.
Introducing any tiny amount of absorption in space would fix this, even in an infinite size, infinitely old universe.
- saagarjha 6y agoWell, no, the paradox accounts for this. In an eternal universe any intervening dust would have steadily absorbed radiation by the stars behind it until it glowed at the same temperature. Therefore, the sky should still look uniformly bright.
- Tomminn 6y agoAhh, so we're assuming eternal universe implies that the entire universe is in thermal equilibrium. This makes some sense, but it feels like cheating. Because then the paradox is broader: "how can anything be at a different temperature to anything else in an eternally old universe?". Nothing really to do with night skies.