Memory Game The Big Bang Theory - EvidenceOnline version Match the piece of evidence to the information it tells us about space and the history of the universe. by Natalie Smith Cosmic Background Radiation Radioactive Decay The universe was once very hot, and has cooled off over time. Stellar Formation and Evolution The universe is expanding - so, at one time, it was very small. Knowing how fast light travels allows us to determine how far apart things in the universe are, and how old they are. Based of half-lives of radioactive elements, we can determine the relative ages of things within our solar system. Knowing the life cycles of stars gives us an understanding of the formation of solar systems, and how long this takes. The Red Shift Quasars Hubble's Law Speed of Light Galaxies were forming 10-15 billion years ago. This shows when objects are moving away from you, because of the changes to the color of light.