3. The Time-Traveller’s Almanac

I got this book for Christmas — a great book about time travel, and all the implications of it. I won’t review it here, but I recommend it. I just want to jump off it to a thought about time-travel in fiction generally. This is something I see in this anthology — and indeed nearly all stories I can think of (including Doctor Who, Philip K. Dick etc.).

The more I think about time travel the more I think the common version used in fiction is not science fiction but science fantasy. Now, first off: you might think it’s a fantasy anyway. Time travel is not a serious possibility. Yet, many physicists have argued that there is a solution of relativistic physics which allows something like time-travel or, at least, causal loops.

A chain of causation is a sequence of causes and effects: I throw a stone (cause) breaking a window (effect); breaking the window (cause) draws the barking daschund (effect). The barking daschund(cause) wakes up the neighbour’s donkey which starts braying (effects), etc.

A causal loop is a chain of causation where an effect is also a cause of the chain. It is a form of time-travel because something done now causes something in the past to happen. It is also a form of backwards causation. This is causation in which one event causes an earlier event to happen.

In the above example, there’d be a loop if the braying donkey (effect) sets off a twist-y spacetime vortex which causes an earlier event (i.e.. backwards causation). This, in turn, causes me to misunderstand my girlfriend’s point about washing up (effect), sending me out grumpily down the street (effect) where I eventually do carry out the cause above — throwing a rock through a window (effect).

So should we take causal loops seriously? Well, so far as I know, it is not generally taken seriously that there is time travel. But, given the opportunity, one might want to say that there is time travel and/or have no problem saying there are causal loops.

First, arising from a challenge by Carl Sagan, Kip Thorne in the 80s developed a solution to relativistic physics which allows causal loops (through using wormholes etc. — I get this from John Gribbin’s In Search of the Edge of Time).

Second, the philosopher of physics Huw Price has argued that we can solve problems of quantum mechanics with backwards causation. Just listen to him talk about it on this Philosopher’s Zone podcast (‘The New Great Time War’, October 2013).

But this doesn’t get us the scifi time travel. Time travel in stories looks to me to be this: much more free than physics’ description of causal loops etc. It’s more than the equivalent of spatial travel. It’s teleportation.

The idea that we could ever be free to travel to any time comes of the Wellsian idea that  travel through time is travel through a fourth dimension — time — which is as freely traversable as the other three dimensions of space. But there is also this in most of the fiction: people who travel tend to do so either instantaneously or near-instantaneously. A person twiddles their chronic hat and …….whach they are are somewhere else.

This is time travel? I think public transport and traffic jams have slipped these writers’ minds. Stephen Hawking has said that time travel is likely to be impossible because, otherwise, there would be loads of time-travellers around here, visiting as tourists. I think Hawkings might presume too much freedom about time travel.

First, perhaps there is no way to get back here to certain times, including this one. It doesn’t mean that we can’t travel to others — and at least one wildly speculative physicist has tried to explain how  that might be so. A Tipler time machine only allows travel in to the future of its creation — (wikipedia entry here; P.S., I have not read this wikipedia entry; I got my original source from Gribbin above. So….it’s a wikipedia page, no idea what it says exactly).

Second, maybe technically one could get back to this time. The problem is everyone or a lot of people wants to get back here (I mean look at all the great tv!). And future time travel is completely unregulated. As a result, the paths through time (‘Timeways’, maybe? Hmm) are stuck in eternal traffic jams.

Perhaps there is this: Just beyond the edge of the fourth dimension is an eternal Friday afternoon of a long weekend, with an infinity of people from all of future history sitting there, sighing as their passengers cry in multiple dialects:

“Are we then yet?”