Hawking: The Beginning of Time
Quantum theory introduces a new idea, that of imaginary time. Imaginary time may sound like science fiction, and it has been brought into Doctor Who. But nevertheless, it is a genuine scientific concept. One can picture it in the following way. One can think of ordinary, real, time as a horizontal line. On the left, one has the past, and on the right, the future. But there’s another kind of time in the vertical direction. This is called imaginary time, because it is not the kind of time we normally experience. But in a sense, it is just as real, as what we call real time. – Hawking
The no boundary proposal, predicts that the universe would start at a single point, like the North Pole of the Earth. But this point wouldn’t be a singularity, like the Big Bang. Instead, it would be an ordinary point of space and time, like the North Pole is an ordinary point on the Earth, or so I’m told. I have not been there myself.
According to the no boundary proposal, the universe would have expanded in a smooth way from a single point. As it expanded, it would have borrowed energy from the gravitational field, to create matter. As any economist could have predicted, the result of all that borrowing, was inflation. The universe expanded and borrowed at an ever-increasing rate. Fortunately, the debt of gravitational energy will not have to be repaid until the end of the universe.
Someone is going to have to help me out on this one. To borrow energy from the gravitational field to create matter? Wow. I admit, I never thought of the E=MC2 equation in terms of matter being created out of pure energy. We are all familiar with the energy that is bound up in matter and the result of releasing that energy (nuclear explosion), but I never consider the force that did the reverse: to suck the contents of that explosion and compress it into the nucleus.
But that is another story. This post is about two things: imaginary time and how inflation creates space. “The universe expanded and borrowed…” Another way of saying the universe expanded is to say more space was created. From where does this space come from?
If I am following correctly, Hawking is saying that gravity itself is the source of matter! What a reversal! I thought gravity was a property of matter, not its source. Can you conceive of gravity without matter? Interesting. Perhaps this “borrowing” explains why gravity is so weak?