Question: Is the universe expanding or contracting or staying the same and how do you know and if its expanding or contracting how fast is it expanding or contracting?

William O'Connor answered on 27 Feb 2018:

The universe is expanding.
That was a very big discovery over the last half century, as this became more and more certain.
It is one of the reasons for believing it all began in the Big Bang. Because, if it is expanding, and you imagine what would happen if you ran the clock backwards, you would end up with everything in the whole universe at a point.
Will the expansion slow down, and perhaps stop and reverse?
Or will it go on expanding.
The latest thinking is that it is expanding at a faster and faster rate, so it will go on expanding for ever, or for as long as we can predict.

How fast? I don’t know how you could measure this.
But we can say that it has reached the size it is at in about 13.8 billion years, from the Big Bang.