It’s a theory. Like the theory of gravity or the theory of evolution. So it has not been proven. Red shift is a theory that they used to interpret data from humble to come to that conclusion. But I don’t believe any of their theories, the wisdom of man is foolishness to godThe "if it is expanding now.." was my text. I did not mean to imply that we're not sure it's expanding because we are. Hubble proved the universe is expanding through observation of the doppler shift of stars - they are all moving away from us. That was back when astronomers did astronomy through observation and not just theoretical mathematics.