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What is the Rh = ct cosmology?

  1. Nov 20, 2015 #1
    I have been looking at several articles recently about the Rh = ct cosmology, but none of them have explained the meaning of the equation. They just assume than anyone looking at such an article will already know what it means. I guess that (1) h is the Hubble "constant", and (2) c is the speed of light, and (3) t is some kind of time. But R is a mystery. R must be a units like m s, but i can't think of what such a variable might be.

    Will someone please explain this?
  2. jcsd
  3. Nov 20, 2015 #2


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    Coasting cosmology. This would be an accurate picture of our universe if the universe was perfectly empty. All objects within such a universe would move at constant velocity.

    The "[itex]R_h = ct[/itex]" description is because in such a universe, the Hubble radius (given by [itex]R_h = c / H_0[/itex]) increases with time as [itex]ct[/itex].

    People talk about this universe because it rather coincidentally comes somewhat close to matching observations (it completely fails to describe our universe at very early times, however).
  4. Nov 20, 2015 #3
    Hi Chalnoth:

    Thank you very much for your post completely answering my question. I also apperciate your not mentioning the dumb mistake I made regarding Rh having units m s.

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