The main evidence for the expansion of the universe is something called redshift. Redshift is the tendency for the light of far away objects to be composed of wavelengths at the red end of the spectrum.
Redshift
The Hubble Constant
Sir Edwin Hubble was one of the first to suggest that the apparent red shift of stellar objects is caused by the doppler effect as the universe expands and the stars become further and further away.
Everlasting Light
We're told that the new heaven and new Earth, where we'll life for eternity, is a place of perpetual light. We're making the case that this permanent physical separation of light from darkness is the purpose of creation.
Voyager Found the Firmament
The Voyager spacecraft have been on their missions since 1977 and have flown far past the orbits of the planets in our solar system. They took a solar system family portrait and found the firmament.