What do the American scientists mean that after a long time the galaxies will recede?

Answer

What we see today is the galaxies moving away from each other. The interpretation is actually that the space itself is getting bigger. It is sometimes compared to dots on a balloon: when you inflate the balloon, the dots move away from each other, but on the balloon they all stand still. So there is no such thing as a point from which everything originated, each point has an equal or equal right to claim to be the center of the universe.

We can’t really ‘prove’ why the universe is expanding. We’re just establishing it. We also try to interpret this theoretically, and come to the conclusion that a universe that gets bigger or smaller is actually more normal than a universe that doesn’t change! But it could also have contracted. Some argue that one day it will start to shrink again.

Based on what we see today, we don’t really expect the universe to ever stop expanding. It moves so fast that the pull of matter is too small to stop it. But the future is still long, and it would be an exaggeration to make statements with absolute certainty now.