Cosmology is the scientific study of the entire universe. It asks questions about how the universe began, how it has evolved, and what its ultimate fate will be.

The Big Bang Theory is our best explanation for how the universe started. It states that the universe began as an extremely hot, dense point about 13.8 billion years ago and has been expanding and cooling ever since.

These are the two biggest mysteries in cosmology. Dark matter is an invisible substance that provides extra gravity to hold galaxies together. Dark energy is a mysterious force that is causing the expansion of the universe to accelerate.

Because light takes time to travel, looking at distant galaxies is like looking back in time. Telescopes like Hubble and James Webb allow us to see galaxies as they were billions of years ago, giving us clues about the early universe.