Big Bang

Scientists believe that everything in the Universe began about 13 billion years ago in a giant explosion called the Big Bang. Over billions of years since the explosion, the Universe has expanded, and cooled, while matter formed into galaxies, stars, and planets. The observable Universe now measures 75 quintillion miles in all directions and continues to expand.

Image credits: main image illustration, Daryl Collins © AMNH; quote, © AMNH.