## Wednesday, March 11, 2015

### mass content of the Universe

can you estimate and quote an error on the estimate of the total mass inside the Hubble-volume? what assumptions do you make and which measurements are needed?

2. thanks a lot, Phillip, for your answer. with a measurement of $\Omega_m$ (from e.g. supernovae) and of $H_0$ (from Cepheid stars) one could estimate the mass to be $m=\Omega_m\rho_\mathrm{crit}\times 4\pi\chi_H^3/3$, with $\chi_H=c/H_0$ and $\rho_\mathrm{crit}=3H_0^2/(8\pi G)$. numerically, this yields $M\simeq 10^{52}~\mathrm{kg}/h$ or $10^{22}M_\odot/h$.