A professor of theoretical physics at the University of Connecticut believes he has found a way to build a time machine using light. He thinks that a circulating beam of light, slowed down almost to a snail’s pace, might be the answer. ?With this device,? says Mallett, ?time travel may become a practical possibility.?
It?s not simple, since slowing down light requires temperatures close to absolute zero, but if it works the way it should, this device would provide time travelers from the future with their first gateway into our history…and given the strides that are being made in slowing light, some of us may actually be among the travelers.
?People forget that light, even though it has no mass, causes space to bend,? says Mallett. Light that has been reflected or refracted to follow a circular path has particularly strange effects. Last year Mallett published a paper showing how a circulating beam of laser light would create a vortex in space within its circle. Then, he says, ?I realized that time, as well as space, might be twisted by circulating light beams.?
To twist time into a loop, Mallett worked out that he would have to add a second light beam, circulating in the opposite direction. If you increase the intensity of the light enough, space and time switch roles. Inside the circulating light beam, time runs in circles, while what looks to an outsider like time becomes like an ordinary dimension of space. A person walking in the right direction could actually be walking backwards in time, meaning that you could eventually leave the circle and meet yourself before you entered it.
As the the principle of least action (the same principle of physics that makes it certain that water will always seek the lowest possible way to flow, for example) will prevent you changing your own past in such a way that it violates the ‘grandfather paradox,’ however, you will never be able to kill your own past self…or, unfortunately, give him stock market information, or indeed do anything that will change present reality…or so we now believe.
Slowing down light has just become a practical possibility. Lene Hau of Harvard has slowed light from the usual 300,000 kilometers per second to just a few meters a second?and even to a standstill. ?Prior to this, I wouldn?t have thought time travel this way was a practical possibility,? says Mallett. ?But the slow light opens up a domain we just haven?t had before.?
To slow light down, Hau uses an ultra-cold bath of atoms known as a Bose-Einstein condensate. ?All you need is to have the light circulate in one of these media,? says Mallett. ?It?s a technological problem. I?m not saying it?s easy, but we?re not talking about exotic technology here; we?re not talking about creating wormholes in space.?
Mallett and his team have planned their first experiment, which will be to observe the twisting of space by looking for its effect on the spin of a particle trapped in the light circle. If they can then add a second beam, Mallett believes that evidence of time travel will eventually appear.
He?s not sure how time travel will manifest itself. What starts out as a single trapped particle may acquire a partner?the same particle visiting itself from the future.
William Stwalley, who leads the team of cold-atom researchers that will be working with Mallett, remains skeptical about the possibilities of time travel. ?A time machine certainly seems like a distant probability at best,? he says.
Astrophysicist Fred Adams, of the University of Michigan, accepts that the theoretical side of Mallett?s work stands up to scrutiny. He invited Mallett to speak and found that ?the reception was cautious and skeptical, but there were no holes punched in it, either. The solution is probably valid.?
But even Mallett isn?t certain that time travel is within reach. ?Whether it will do what I predict is something that one will only know by performing the actual experiment,? he says. There is the problem of getting on and off the loop of time without destroying it?or yourself. ?I really don?t know whether you could use this in the sense of H.G. Wells?s time machine,? he says.
If we enter an era when time travel is possible, all kinds of strange situations, things and people may visit us from the future. One thing to remember is that Mallett?s circle of light won?t allow anyone to travel back to a time before it was set up. ?A later person could only travel back to the time when the machine is turned on,? he says. This means that once we do turn it on, we will be inviting visits from the future.
It could be that the setting up of the machine will, in effect, open a gate that will allow future time travelers with far more sophisticated abilities to reach us.
NOTE: This news story, previously published on our old site, will have any links removed.
Subscribers, to watch the subscriber version of the video, first log in then click on Dreamland Subscriber-Only Video Podcast link.