If Hubble’s law proves correct for the entire universe, it will help us estimate the age and size of the universe.
In fact, the radius of the measurable universe is called the Hubble radius. There is one problem, however.
The galaxies in the outer reaches of the universe move faster and faster.
Astronomers have detected galaxies moving around 90,000 miles per second, or half the speed of light.
At some greater distance, the galaxies will be moving at the speed of light.
That would be the limit to what we can see of the universe, because light from a galaxy traveling at the speed of light could not reach Earth.
This means that we could not see it even though it is there.
