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horsetuna t1_jaiipb4 wrote

Reply to comment by Ape_Togetha_Strong in Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science by AutoModerator

So how can this Hubble Horizon exist in a distance smaller than the observable universe? Everything outside that Horizon should not be visible because it's moving faster than light right

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mfb- t1_jak8660 wrote

Because of the way the expansion rate changed over time, as I discussed in my initial comment. The Hubble rate ("how much the universe expands in percent per year") decreased over time. A good analogy is the ant on a rubber rope problem where the rubber rope expands much faster than the speed of the ant, too - but the ant still makes progress on the rope and over time is less affected by its expansion. For the universe, this would be a perfect match in a scenario of constant expansion. That's not what we have, but it's reasonably close for the last 10 billion years.

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