Question

How did scientists originally view the idea of an expanding universe?

Answer 1

By using and testing Einstein's theory of General Relativity, scientists have observed galaxies moving away from Earth. A few years after Albert Einstein had developed his famous (and by now very well tested!) theory of General Relativity (GR) in 1915 he applied it to the entire universe and found something remarkable. The theory predicts that the whole universe is either expanding or contracting. There really isn't any other alternative. To have the universe staying static is like a pencil balanced on its point... possible, but very, very unlikely and not liable to last for very long. Since the time of Hubble we have observed millions of galaxies with better equipment and verified his results. With the exception of a small handful of galaxies close to us, every galaxy is moving away from us. And in fact, the farther away a galaxy is the faster it is moving away from us. This fits in very well with Einstein's predictions. The galaxies seem to be receding from us because the entire universe is getting larger. The space in between the galaxies is stretching! And the farther away a galaxy is the more space there is to stretch so the faster the galaxy appears to move away from us.