Review

#01

Lack of walls or voids greater than about 300 Mpc in size.

#02

Essentially that there is no special viewing perspective of the universe. In other words the universe looks pretty much the same for all observers at all places.

#03

Olber's paradox is that if the universe is infinitely old and infinitely large, then there is no where one can look and not see a glowing source of some kind, hence the night sky should not be dark. But the night sky is dark. The easiest resolution is the implication that the universe has a finite age.

#04

Speed is distance over time. The Hubble law reads $v=Hd$. That means $H$, the Hubble constant, has units of ``per time''. So $1/H=d/v$ gives a rough estimate of the age of the universe.

#05

The universe is expanding equally at all locations. This means the universe appears to expand no matter where in the universe you observe it. In some sense it appears that every observer is at the center of the expansion, which can only mean that no one is at the center, and so there is no center.

#06

It is space itself which is expanding. The galaxies are not literally moving apart, just the space between them is growing. There is then the appearance that galaxies are in motion.

#07

Everywhere.

#09

The density of matter and of dark energy.

#11

No.

#15

The universe can not be younger than its contents.

#16

It was predicted before it was observed.