The Museum of Natural History in Turin is a beautiful structure, built as a hospital in the 17th century to create a centre for the emerging discipline of practical, scientific, evidence-based medicine. On 14 October, however, it’s being turned into the “Time Machine Factory”. A number of eminent physicists are coming together to make the case – to each other, at least – that time travel is possible.
Time is certainly slippery. Our best model for getting to grips with it is Einstein’s special theory of relativity, which says there is no such thing as absolute, objective time. It ticks one way for you and differently for someone accelerating towards or away from you. After six months on the orbiting International Space Station, for instance, the astronauts return to earth seven milliseconds younger than they would have been if they had remained with the rest of us.
We know this to be correct because our GPS works. The GPS satellites, which orbit the earth at 14,000 kilometres an hour, are also subject to this “time dilation” and their signals have to be put forward by seven microseconds a day to compensate.
But, confusingly, we also know relativity must be wrong. That’s because we have a deeper theory governing processes in the universe – quantum theory – and the two don’t mesh well.
The mismatch is largely because quantum theory doesn’t require a concept of time at all. Though that seems ridiculous, experiments have shown that many of the fundamental subatomic particles pay no attention to time; they are as happy travelling forward in time (from our perspective) as backward. Expanding on this, the Oxfordshire-based physicist Julian Barbour, who is participating in the Turin conference, has repeatedly claimed that time is an illusion.
The universe, he says, is static in time, with no past and no future: that is, there is no such thing as time. Barbour, it’s worth pointing out, is taken very seriously.
All this is fascinating, but there is almost no practical benefit to researching time travel. Some physicists like to argue that GPS wouldn’t work without our understanding of relativity but it would –we would observe the signals going awry and program in a correction. It’s fair to say that understanding the human grasp of time might have some benefit for those whose brain signals tend to go wrong. Attention deficit hyperactivity disorder, for instance, has been linked to misfiring time perception circuitry in the brain’s frontal lobe, basal ganglia and cerebellum. It is difficult, though, to make the case that hyperactive children will benefit from our attempts to build a time machine.
Time out of mind
Yet the attempts will continue – because we are human. As a species, we are slaves to time and clearly enjoy escaping it, even if only in our imagination.
As Stephen Hawking said when excusing himself for researching cosmic engineering projects born from ideas in science fiction: “To confine our attention to terrestrial matters would be to limit the human spirit.”