Eli5: How come the universe is always expanding?

Question

Eli5: How come the universe is always expanding?

In: 1

Answer 1

We do not know. Answering that question would be a huge breakthrough in science.

We do know that since the Big Bang the universe has been expanding, though not always at the same rate. The initial expansion was incredibly rapid and lasted less than 375,000 years before expansion slowed down a lot. Then about 5-6 billion years ago expansion started accelerating again.