Compute a numerical value (in units of protons/m3 ) for the critical density of our Universe. How does it compare to the density of hydrogen gas at standard temperature and pressure?

With the aid of a diagram, explain the physical origin of cosmological redshift in an expanding universe, and how this differs from the Doppler shift due to relative motion. Observations of distantgalaxies indicate that their recession velocities, v, and their distances, d, follow a Hubble Law:v = H0d, where H0 is a constant. Using the analogy of an expanding grid or ruler, demonstratethat Hubble’s Law indicates that the Universe is undergoing uniform expansion.

Calculate the Hubble constant for a universe which is 10 billion years old.

The Universe is approximately 13.8 Billion years old. What is the volume of the visible universe in m3?

Estimate the critical density of the universe if the Hubble's constant was 100 km/s/Mpc.

What is the estimated age of the Universe (in years) if the Hubble constant is 60 km/s/Mpc?