Time and black holes?

Question

I was reading this article about black holes and I came across a concept I don't completely understand.

"However, there's a snag in this intergalactic transportation

scheme. The baby universes, that take the particles that fell

into the hole, occur in what is called, imaginary time. Imaginary

time may sound like science fiction, but it is a well defined

mathematical concept. It seems essential, in order to formulate

Quantum Mechanics, and the Uncertainty Principle properly.

However, it is not our subjective sense of time, in which we feel

ourselves as getting older, with more gray hairs. Rather, it can

be thought of as a direction of time, that is at right angles to

what we call, `real', time."

From this article http://www.totse.com/en/technology/space_astronomy_nasa/hawking2.html

Could someone explain this real and imaginary time in a simple way? I am not scientifically inclined.

Answer 1

I don't think this is refering to time as it is subjectively experienced by humans. I believe it relates more to the example of how if you were falling into a black hole, to outside observers you would appear to be slowing down and moving slowly. But to you, (if you were still alive somehow), everything would appear normal and if you could see someone on the outside, they would appear to be moving like as if time had slowed down for them. Both people, if they had an accurate clock with them would measure time as if it were moving properly. The effects of the black hole distort time in a strange and complicated way far beyond my limited understanding.

I don't think I really answered your question at all. Although when you quote: "it can be thought of as a direction of time, that is at right angles to what we call, `real', time". It was this that made me think of that.  

Answer 2

It's time that is measured by imaginary numbers. Imaginary numbers are sort of like what you get when you try and find the square root of a negative number, but that really isn't important here if you just want to understand the concept.

When you measure time in imaginary numbers, you get what's called Euclidean Space-Time. In Euclidean space-time, there is absolutely no distinction between direction in space and direction in time. In real time, events come one after another and happen at different locations in space whereas with imaginary time, there are no boundaries for when or where events happen. They just happen.

However, Euclidean space-time is regarded more as a mathematical trick rather than an applicable concept. With imaginary time, we can solve problems and calculate what unfamiliar events (such as singularities) might look like, but that's all it does.