13.8 billion years ago, what we know as our Universe began with the hot Big Bang. The Universe was filled with matter, antimatter, radiation, and existed in an ultra-hot, ultra-dense, but expanding-and-cooling state.
- The limits to which we can observe the Universe are set by three things: the rate of expansion, the time since the Big Bang, and the speed of light.
- But beyond our visibility limit, there ought to be more Universe out there, and no one knows how far it goes on for.
- Is it finite or is it infinite? Although we don't know for certain, many have their suspicions, and scientists are working to find out as much as possible.