Time Travel, Anyone?

The Arrow of Time

Is time travel possible? What a great question, I’m glad you asked it. The initial problem we have to face is that there is still no consensus between philosophers and scientists of what constitutes time. There are a number of theories and many seem valid at a superficial level, but once we get to grips with the central problem and the concept of time, things start to become blurry around the edge. Something which appears simple, and everyday commonplace, is mired in complexity and apparent contradiction. I’ve had a tentative foray into this particular rabbit hole- check out my musings here and here. My pontifications on the matter are not definitive and I intend to visit the topic once again.

It could be argued that we all travel in time, eventually. But traveling through time as a consequence of getting older is not most folk’s idea/ideal of time travel: this only has meaning at the trivial and jocular level. The question we need to ask is- can we progress in time, both forward and backward, outside the normally accepted frame of time passage? Einstein’s theory of special relativity certainly allows for a form of future time travel due to the realisation that space and time are manifestations of the same thing; space-time. Thus, if you travel in a spaceship at 99.5% the speed of light for a period of 5 years, at least according to your time reference, folk on Earth would age a corresponding 50 years. If you left the Earth in 2020 and returned after a 5-year absence the date on Earth would be 2070 (the so-called, twin paradox). You could argue that this represents a form of time travel due to time dilation. What about the reverse- is it possible to travel back in time? If we consider the arrow of time inexorably moving forward without backward kinks, then the simple answer is an emphatic, probably not. This has not stopped science fiction writers, cosmologists, and theoretical physicists from exploring the possibility. However, just because we can advance a viable theoretical concept this does not necessarily relate to practical reality. Mathematical solutions to the equations of general relativity allow the possibility of backward time travel and several apparently practical solutions have been advanced. I’ll consider two, albeit briefly, of the most interesting ‘time machine’ solutions as there isn’t enough space-time to give an overall summary of all the conceptualised methodologies. Of course, going back in time would reveal a paradox, known as the ‘Grandfather Paradox’. Imagine returning to a time before your grandfather had met your grandmother. Now envisage killing your grandad. The paradox of such a scenario is obvious: now that good old granpappy is dead your father could not exist, and by extension, you would not have been born to go back in time to kill your grandad. There have been several attempts to resolve the paradox. To my mind, however, they raise more problems than they solve/resolve. 

The Tipler Cylinder solution: this possible solution involves rotating a very dense and very large cylinder at very high speeds (several billions of revolutions per minute). If this is possible then space-time adjacent to the cylinder will be warped resulting in a causal reality violation (wot dat den?). Any craft close to the cylinder would be in a time closed curve. According to the theory, this would allow the craft to travel back in time. There is one little problemette. I was being disingenuous when talking about the density of the cylinder and its length. The density of the cylinder would have to be stupendously dense: perhaps we could mine superdense neutron stars? Also, it would appear that the cylinder would have to be infinitely long. But, after all, we do exist in an infinite universe, perhaps…….

There have been other solutions based around wormholes. Wormholes are theoretical constructs allowing the connection of disparate regions of space-time. Wormholes could be natural (we have haven’t found one yet) or perhaps man-made. It appears however that for backward time travel exotic particles with negative energy and mass would be required. The artificial option would require huge amounts of energy and the great lamented physicist, Stephen Hawkin, reckoned such a contraption/contrivance inherently unstable and short-lived.

Wormhole of Doom

One thing rarely mentioned is how we would control these ‘contraptions’ (assuming of course that one of these 'machines' actually worked). There appears no dialing mechanism to set the backward leap in time to a specific period. And where on Earth would our intrepid traveler alight? Mayhap, they would end up in the vacuum of space or on Pluto? Remember both time and space are being warped. I can’t help wonder if clever theoretical physicists are engaged in a little ‘blue sky’ sophistry: perhaps they are using the concept of time travel simply as a means to exercise their intellectual muscle and to devise solutions to intricate and arcane mathematical formulae.

I would like to conclude with a little whimsy. On June 2009, Stephen Hawking (for it is he) set forth a unique party at Cambridge University. An open invitation was given but no one appeared at the allotted space and time. This should surprise no one as Prof. Hawking had sent his invitation after the party had finished (what a scamp!). The invitation, although universal, was particularly addressed to future time travelers. Hawking was not particularly surprised at the none attendance as he had postulated in 1992 that time travel into the past is fundamentally impossible. Nuff said, for now.

The cheap bastard served blue nun wine