These are notes on this Youtube video

Einstein added the cosmological constant to balance expansion-contraxion in his theory. "If you get rid of a quasi-static universe, then out with the cosmological constant"

Edwin Hubble discovered in 1929 that the universe is expanding, and things further away are fleeing faster.

Red shift tells us how fast they are retreating.

Since Hubble, we discovered that supernovae are of a consistent brightness.

Knowing this, we can figure out how far away they are from their apparent brightness.

We now know how far away things are and how fast they are retreating. This allows us to verify Hubble.

Because of virtual particles, there is another component of the massenergy of the universe.

90% of the mass of the proton is virtual particles, not quarks

Inspiring animation of the form of emptiness at 20:52

The amount of mass/gravity in the universe determines whether it is:

We can weigh the universe by the gravitational lensing effect of galactic clusters.

When we do this, 90% of the mass we find isn't stars; it's dark matter.

We find that there isn't enough mass to stop the universe being open

Dark matter is theorized to be everywhere. This is being searched for by checking its effects when it hits nuclei.

You can measure directly whether the universe is closed, flat or open by drawing a triangle and measuring the angles. They are 180 on a plane.

The universe cooled enough at some point after the big bang to form matter. Then the matter formed chunks. Gravity could only propagate at the speed of light, so only things 100,000 light years across had time to experience a gravitational effect to make them collapse.

Ourselves as observers and the two points 100,000 light years apart emerging from the heat before matter - this is the triangle.