Question

What does Hubble's constant represent?

Answer 1

It represents the ratio between the recessional velocity of a galaxy (`km` `s^-1`) and the distance to the galaxy (`"Mpc"`), `km` `s^-1` `Mpc^-1`, or sometimes converted to `s^-1`. When given in terms of `s^-1`, `1/H_0="approximate age of the universe"`

Explanation:

Based on observations, we know that `vproptod` with `v` being recessional velocity(`km` `s^-1`) and `d` being distance `(`Mpc#)

A graph of `v` against `d` produces a rough straight line with gradient `H_0`, using this we can work out the recessional velocity or distance to a galaxy given the other.

`"time"="distance"/"velocity"=1/H_0`

When `H_0` is given as `s^-1` the reciprocal can give the approximate age of the universe.