Time is an illusion, albeit a very persistent one. It governs our lives but it is not what we believe. Time travel is generally thought to be impossible, but if you believe that you haven`t noticed you are doing it yourself. We are all time travellers : time’s arrow is pointing forward and we are hitching a ride, though it seems we are stuck in the present.
In the three-dimensional world the earth’s movement is used to measure time. We’ve divided this motion into hours, minutes and seconds, so most people have a simple view of time, feeling that it is identical for everyone. We all feel we know time intimately… until we have to describe it.
Newton’s vision was that it was immutable, changing always at the same pace, but although he used logic to conclude this, he was wrong. Time is not immutable, since it is affected both by movement and gravity. Time is elastic and speed affects the rate at which matter ages.
Take a slice of time. We are now reading this blog, but on the other side of the world someone is going to post a letter and at the North Pole a seal catches a fish. For the moving person holding the letter and the swimming seal time is moving more slowly than for us, sitting still. Einstein realised this by linking time to movement through space. The more you have of movement the less you have of time – which is why an intergalactic astronaut ages more slowly. At the speed of light time stops altogether.
As well as movement there is the effect of gravity : the stronger the gravity the slower time flows, as if gravity holds time back. On the top floor of a skyscraper time flows more quickly and near a black hole time slows down spectacularly.
Is it possible to stop time? Thoughts travel faster than light. If time stops at the speed of light, what happens at the speed of thought? What would happen if we repeated the thought I am growing younger for an hour during meditation? (see All the time in the world).
Before the big bang there was no time at all.