The Big Bang happened 13.8 billion years ago, and is generally regarded as the start of the Universe as we know it. The Universe we see is expanding, cooling, and gravitating into an ever-clumpier state, which means earlier on it must have been denser, hotter, and more uniform.
In the earliest moments that we can imagine, there must have been matter, antimatter, radiation, and any-and-all types of particles that there was enough energy to create. All the matter and energy presently visible in our Universe today was contained in a volume of space no bigger than a city block, and has since expanded to extend for more than 46 billion light-years in all directions.
Still, all of that energy had to come from somewhere, and that’s the big question of what put the “bang” in the Big Bang? Fortunately, science already has given us a tremendously successful answer. It’s time for the rest of the world to learn about it, too.
The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.