Reasons for the Existence of the Big Bang

The Big Bang is the theory that the universe was once much smaller and hotter than it is now, and it has been expanding and cooling over time. With an understanding of a few key pieces of evidence one can understand the basis of the theory. The strongest pieces of evidence for the Big Bang are the movement of distant galaxies, the expansion of space time, and the hydrogen and photons in the universe.

Measurements of the motion of distant galaxies reveal that they are all moving away from us, with farther galaxies moving away at higher speeds. The movement of distant galaxies is measured with a spectrometer, which can measure the brightness of the light, the type of atoms the light came from, and how much the light has been stretched or compressed. When scientists look at stars known as “Cepheid variables” the apparent brightness of the star changes based on its distance from the viewer. Using the brightness scientists can measure the distance of stars. If the galaxy is moving away, the wavelengths of the light will get longer, or red-shifted. Similarly, light from objects moving tow...