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