Time Travel (Part 1)

What time machines look like without production designers (although they went to town on the interior).

(If you're reading the FB version, you may not see the picture.)

The thing about time travel and time machine stories is that the reality is actually much more interesting than the fiction. The reality of time, that is.

You don't 'travel' in time, because there is no such thing as time in the first place. There's nothing to travel 'in'. The 'in' is very interesting though, because it's a spatial term - we nearly always describe time in terms of space, and space in terms of time. More on that in a bit.

One of our measures of time is days and nights. Our days and nights pass us by, we think. It's one of the main ways we think of time. But you don't need to have done much science at all to know that days and nights themselves are mostly caused by the Earth spinning on its axis. If you stopped the Earth spinning and orbiting, you'd have either permanent day or permanent night, depending on where you were on the planet before it ground to a halt. So one part of what we usually feel as time passing, the passing of days and nights, would simply stop happening. That rotating and orbiting Earth was the only reason night-follows-day even existed in the first place. There is no mystery thing called 'time' that causes the day to pass into night and then into day again, etc. Just a spinning planet.

The other most obvious reason we think time passes is the fact that things age. I wrote something about aging here, come to think of it. It's true that what we call aging happens, we see the results of it. But as that earlier post of mine went on about, what we see there is not necessarily what we think we see. Aging is something ordered becoming disordered, which in our bodies we normally think of as our bodies falling apart or breaking down as we get older. But that disorder is really the birth of a new order or orders, the same as a dead animal will decay and from its remains new bacteria and plants and other living things will grow. One thing's order is another's disorder. And vice versa.

Time and space are very difficult to tell apart, when you look at them closely. That's because there is no separate thing called space and a separate thing called time, separate again to some thing called matter/stuff. Say something is 'far away' - what does that mean? It's a phrase that suggests distance i.e. space. But try to define 'far away' without using time, it's not easy. 'Far' means a place that will take a long time to get to. Far and near are relative terms, if you could travel at the speed of light for example a lot of things that seem far away now to you, like the other side of the country, would be less than a second away. But the important thing is that 'far' is defined in terms of the time it would take for you to get somewhere. As Henri Bergson once said, space defines time and time defines space. Also what Einstein discovered (after Bergson, and other philosophers).

Space and time aren't things, they're relationships between things. There aren't things (objects, cups and saucers, us, trees, whatever) and then space and time as containers that these things sit 'inside'. You can't be 'in' time any more than you can be 'in' space, it makes us much sense as saying you can be 'in married' or 'in cold'.

The relationships which constitute time and space aren't that difficult to follow - if things interact in some seemingly irreversible way, you have time. If it's reversible, you have space. For example, human aging is pretty much irreversible, at least given our current state of knowledge, so when something ages we think of it as 'time passing' i.e. as time at work. On the other hand where something seems to remain unchanged (we can experience it again as it was before, so it's therefore reversible), then we'd call it space - it's that aspect of things that remains (or seems to) unchanged. If I walk away from a house and see it disappear into the distance, then walk back towards it and there it is again, growing bigger and there in front of me, then the house is 'in space' because it's still there, looking as it did before. That's what space as we usually think of it is - what is just 'there'.

If you apply this to the example above of days and nights, you can see how it works. Because days start with a dawn and end with a sunset, and you can't reverse those without reversing the spin of the planet, we end up with something relatively irreversible, and therefore we think that 'time has passed'. Similarly because seasons change throughout the year we also feel that time is passing. But days and nights and seasons all derive from the position and motion of the planet, not some mysterious thing called time which the planet sits in. Some might say that all the Earth movement is taking place 'in time', but again as Einstein realised, what is time except for those movements? How would you define it or measure it? If the Earth stopped moving and you had either a permanent day or night, depending on which side of the planet you lived, and the seasons never changed, that sort of time would stop passing.

Matter, and What's with the "In"?

Tied up with misunderstandings about time and space are misunderstandings about matter. There was an earlier blog entry about that here. Space and time aren't containers other things sit inside, they're just matter behaving in different ways. Sometimes matter behaves in relatively irreversible ways and we have time, and sometimes in reversible ways and we have space. But it's always relative, nothing is absolutely reversible or absolutely irreversible. So for example we started to think tuberculosis was a thing of the past, but suddenly it's back. What we thought was an irreversible march of progress forwards thanks to medical science wasn't that at all. History has been reversed, TB is now here with us again, 'in space'.

We're just matter behaving in various ways. For most of our lives if we injure ourselves our body reversibly heals the injury so we're pretty much as good as new. So it's not as simple as everything falling apart and decaying, your own body defies time all the time - it does lots of reversible as well as irreversible things. (Some living things such as bacteria don't age at all, they're immortal provided their environment is favourable to them - see here.)

And what would it even mean to be "in" time or space? Is it like being in a boat, or in a room? How can you be in time or space like that? Where are these containers - look around you and see if you can see anything called space or time, separate to the things that apparently sit inside them. It's backwards, in a way Einstein's revolution was the simplest of things - he noticed that time and space are only some constructs derived from clocks and rulers. If I measure out a square metre with a ruler and some chalk, and ask you to stand inside the square for 30 seconds measured by a stopwatch, where's the space separate to the chalk or the time separate to the hands of the watch? The scene is as it was before, I've just drawn with a bit of chalk and looked at the hands or numbers on a watch. For some bizarre reason we've turned simple measurements into some whole other world outside this world that we apparently sit inside.

Next time a few examples.