drosse1meyer t1_j1e13q0 wrote
Reply to comment by nicuramar in Can we truly know the age of the universe? by Geodad478
Well, if you want to be pedantic, velocity is a rate too, is it not? Distance over time.
Anyway, there are countless articles / studies about this that can explain it far better than anyone on this thread. Suffice it to say, the size of the universe expanded from the planck length to a factor on the order of 10^28 in an extremely short amount of time
Existing radiation would simply be stretched and omnipresent given this massive change. That is why we have the CMB.
nicuramar t1_j1e7dhd wrote
> Well, if you want to be pedantic, velocity is a rate too, is it not?
Yes, but expansion is velocity over distance, so it’s not units of velocity and thus isn’t c or below or above c.
> Suffice it to say, the size of the universe expanded from the planck length to a factor on the order of 1028 in an extremely short amount of time
The observable universe. Maybe, yes, but that doesn’t make it expand at a certain velocity unless you measure over a certain distance. And at this distance, relative velocity wouldn’t be well defined due to the curvature of spacetime, and wouldn’t be constrained to c anyway.
See first answer to this: https://physics.stackexchange.com/questions/400457/what-does-general-relativity-say-about-the-relative-velocities-of-objects-that-a
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