Expanding Universe
No matter in what direction one observes galaxies, they are moving away from us. We need to understand how we determine that galaxies are in motion relative to us. The main indicator is the Doppler Effect on light. Objects that are moving away from us are red-shifted, and objects moving toward us are blue-shifted. If all the galaxies were moving around a universal center, then around half the galaxies that we can see should be moving toward us while the other half should be moving away from us. The fact that practically all of the galaxies that we can see are red-shifted suggest that there is an expansion.
