The Big Bang Theory
In the 20th century, scientists came up with the idea that the universe was made billions of years ago. It started from a teeny, tiny piece of matter the size of an atom! From there, it exploded and the universe was formed. It kept growing and growing and growing until it became the size it is today. Although, there still are many uncertainties about this theory and scientists continue to research it every day until they are absolutely positive of what happened.