Wednesday, December 23, 2015


can you show that the density inside a sphere which contracts according to a Hubble-law $\upsilon(r)\propto -r$ remains homogeneous? what's the relation between density $\rho$ and time $t$?

we wish all our readers and followers merry x-mas and a happy and successful year 2016. we hope to see you again in january.

1 comment:

  1. I'll leave the answer as an exercise for the readers, but offer the following related comment: The Robertson-Walker metric contains no physics. A homogeneous and isotropic universe must have this metric, which is completely independent of any physics.