How to build a real time machine
Queensland in Australia, said, “Something out there is having an ‘anti-gravity’ effect —it’s pushing rather than pulling. We don’t know what that is, but it makes up most of the Universe. We call it dark energy.”
A wormhole will only work for time travel if its ‘mouth’ can be held open for long enough that it allows something to travel through it.
That requires something called negative energy, which doesn’t really exist in the everyday world.
But the dark energy that permeates the cosmos fits the bill — if we can figure out what it is, we might be able to prop open a so rapidly that maybe space and time themselves are something that can come under our control.”
Wormholes exist at the more speculative end of physics, offering one approach to traveling in time. But Mallett has another.
He has drawn up plans for an actual time machine, and his concept was inspired by a book he read at age 12 about Albert Einstein’s equations.
Mallett has built a table-top device that illustrates principles he thinks could be used to build a real, working time machine.
First, lasers are used to generate a circulating beam of light. The space inside this ‘ring laser’ should become twisted, ‘like alter the normally linear timeline we all inhabit.
Mallett, said, “If space is being twisted strongly enough, this linear timeline is going to be twisted into a loop. If time all of a sudden is twisted into a loop that allows us the possibility of travelling into the past.”
However, in order to make it work, the concept would require vast amounts of power and a way of shrinking everything to a microscopic scale.
But once we have a time machine, using it successfully will require a detailed understanding of time itself.
The generally accepted view is that the Universe is an unchanging ‘block’ of spacetime; this idea arises directly from Einstein’s equations.
Dr. Kristie Miller, director of the Center for Time at the University of Sydney, Australia, said, “What’s important about the model is the idea that the past, present and future are all equally real.
“So you can think of everything that ever did exist, does exist or will exist as all somehow being out there in space-time.
“The dinosaurs are all out there somewhere in the past doing dinosaur stuff, we’re all here now and all of the future is out there somewhere in space-time too.”
One way to visualize the block model is to think of other places in time as being like other places in space.
Miller said, “We are here in Sydney, but there are other people located in Singapore and London. Those places are perfectly real, it’s just that we aren’t at them.
“This is good news for the budding time traveler, because it suggested there is nothing to stop us from swapping where we are now for some other place and time.
“But, importantly, it also implies that the past, present and the future are already written, so that if we were to travel back in time, we wouldn’t be able to alter it.”
To take an oft-quoted example, we shouldn’t be able to kill someone’s grandparent so that their descendant will cease to exist in the future.
The block model treats our everyday concept of time as an illusion, a way that humans rationalize reality.
But Prof. Lee Smolin, from the Perimeter Institute in Waterloo, Canada, disagrees.
He believes that the passage of time is a real and fundamental phenomenon.
He said, “Time travel is probably impossible. If what’s real is the present moment and the past is only real in the sense that there are memories and records of it in the present, and the future is still to exist… there’s nowhere to go.”
His colleague Prof. Neil Turok, director of the Perimeter Institute, thinks the weird world of quantum physics could be crucial to answering this question.
This area of physics emerges at very small scales, where the rules of classical physics we learnt about in our school textbooks break down. For example, in the quantum world, it might be possible for a particle to be in many places at once.
He said, “I think it’s clear to me that there is some probability of us going backwards in time.
“In quantum physics, nothing is impossible — particles travel through walls!”
Turok explained that time travel remains a distant hope because no one really has any plausible idea of how to go backwards in time right now.
But he added, “One should never say never, because some clever person will come along and tell you how to break the rule.”