If the entire mass of the universe was compressed into a single point, it would form a black hole.

What would be the radius of its event horizon?

 

I calculated this from a mass of the universe of 10^52 kg, and it came out as around 10 billion light years. Is this right?

If it is right then perhaps the whole universe is inside its own black hole. In which case where abouts is the singularity, and why aren't we sucked into it?

The size and total mass of the universe is unknown, and possibly infinite. It also does not have a center in which mass might congregate.

 

A black hole has its mass concentrated in a single point, the singularity. Obviously, that is not our situation, else we and everything else would be the singularity.

Edited February 14, 201015 yr by Sisyphus

You can make estimates of the mass in our observable universe. You could do this by counting stars and galaxies, however it is believed that this makes up only something like 5% of the mass. According to the latest models of cosmology the rest is made from dark matter and dark energy.

 

Anyway, you can guess the density of the Universe using the Lambda CDM model. This gives [math]\Omega_{total} \approx 10^{-26} kg \: m^{3}[/math]. The volume is something like (assuming flatness) [math] 3 \times 10^{80} m^{3}[/math].

 

From there you can work out the mass and so on...