"Time is not a line but a dimension, like the dimensions of space. If you can bend space you can bend time also, and if you knew enough and could move faster than light you could travel backwards in time and exist in two places at once.
It was my brother Stephen who told me that, when he wore his ravelling maroon sweater to study in and spent a lot of time standing on his head so that the blood would run down into his brain and nourish it. I didn't understand what he meant, but maybe he didn't explain it very well. He was already moving away from the imprecision of words.
But I began then to think of time as having a shape, something you could see, like a series of liquid transparencies, one laid on top of another. You don't look back along time but down through it, like water. Sometimes this comes to the surface, sometimes that, sometimes nothing. Nothing goes away.