"In spite of the fact that we call it the Big Bang theory, it really says absolutely nothing about the Big Bang. Ah, it doesn't tell us what banged, why it banged, what caused it to bang. Ah, it doesn't even describe, it doesn't really allow us to predict what conditions are immediately after this bang."
"The fundamental problem of Cosmology is that the laws of physics, as we know them, break down at the instant of the Big Bang. Well, some people say what's wrong with that, what's wrong with having the laws of physics collapse. Well, for a physicist this is a disaster. All our lives we dedicated to the proposition that the universe obeys knowable laws, laws that can be written down in the language of mathematics. And here we have the center piece of the universe itself, a missing piece beyond physical law."
The very beginning of the Big Bang was the single, biggest mystery in all of Cosmology. It was called the Singularity.
"When you extrapolate Einstein' general theory relativity back to the beginning, you discover what would be called Singularity, the Cosmic Singularity which is to say that the equations blow up."