I'm about halfway through Paul Davies' How to Build a Time Machine. Starting from an application of Einstein's general theory of relativity (GTR), Davies talks about how it's possible to move forward and backward in time, and to some extent not just in theory but in practice.


I'd known that moving forward in time is actually pretty easy. All you have to do is accelerate yourself to near the speed of light so that you sort of hide out in a little fold in spacetime. Then let the world go about its business. Then pop out of your little fold and voila you've time traveled forward. You're still young and smooth while everyone else has grown back hair. And contrary to popular belief you don't have to go out into space to do it. You can just drive around the block really fast. Really, really, really fast.


The harder trick is going backward. But according to Davies that too is possible. This I didn't know. It takes wormholes and the looping of light around spinning cylinders, but can be done.


What I like most about the GTR and its effects on space, is that it turns out that time is not singular. There is a measurable difference in the spacetime at the bottom of a skyscraper as compared with the top. When you fly on a plane you travel through time a couple of nanoseconds faster than people on the ground.

This means that even our bodies exist in a range of time spaces rather than at a point in time. Your head and feet experience time in slight disjunction with each other. And of course, as is well known, matter itself is only a kind of energy. This means that our bodies are fuzzy coincidences of energy inhabiting ambiguous space in ambiguous time.

I had forgotten how much I dig hard science.