Answer:
The evidence that the universe is expanding comes with something called the red-shift of light. Light travels to Earth from other galaxies. As the light from that galaxy gets closer to Earth, the distance between Earth and the galaxy increases, which causes the wavelength of that light to get longer. Distant galaxies are getting further away hinting at a point of origin. The composition of all observed matter in this universe points at a common origin point for all matter in the universe.
