Is human time travel truly possible?

I read an article recently which was indicative of time travel is theoretically possible, that scientists have said there is no mathematical reason why a time travel machine could not be able to disrupt the spacetime continuum enough to go backwards in time, they suggested.

The study, published in the journal Classical and Quantum Gravity, is titled “Traversable acausal retrograde domains in spacetime”, which spells TARDIS – the name of Doctor Who’s famous police box time machine.

Gravitational waves find could let scientists build a ‘time machine’.

In the paper, mathematicians from the University of British Columbia and the University of Maryland proposed a mathematical model for a viable time machine, presenting geometry which has been designed to fit a layperson’s description of a ‘time machine’”, they wrote.

“It is a box which allows those within it to travel backwards and forwards through time and space, as interpreted by an external observer.”

One of the researchers, Ben Tippett, said: “People think of time travel as something fictional and we tend to think it’s not possible because we don’t actually do it. But, mathematically, it is possible.”

Any time travel machine would probably need to be able to warp spacetime – the connection between time and physical dimensions such as width, depth and height.

The subject fascinated me and I recently purchased a book called ‘Your brain is a time machine’ by Dean Buonomano, where he describes ‘Time’ as the most common noun in the English language. Buonomano states on the first page of his fabulous new book, despite fixation with time, and its obvious centrality in our lives, we still struggle to fully understand it.

Dean Buonomano, “Your Brain is a Time Machine”

Neuroscientist Dean Buonomano explains our sense of time in relation to physics. He’s in conversation with Ted Chiang, writer of “Story of Your Life”.

Could our theories about physics be informed by the very architecture of our brain?

From a psychology perspective, for instance, time seems to flow by, sometimes slowly like when we are stuck in line at the a supermarket and sometimes quickly like when we are lost in an engrossing novel. But from a physics perspective, time may be simply another dimension in the universe, like length, height, or width.

The human brain, Buonomano stated, is a time machine that allows us to mentally travel backward and forward, to plan for the future and agonisingly regret that past like no other animal. And, he argues, our brains are time machines like clocks are time machines: constantly tracking the passage of time, whether it’s circadian rhythms that tell us when to go to sleep, or microsecond calculations that allow us to the hear the difference between “They gave her cat-food” and “They gave her cat food.”

In an interview with Science of Us, Buonomano spoke about planning for the future as a basic human activity, the limits of be-here-now mindfulness, and the inherent incompatibility between physicists’ and neuroscientists’ understanding of the nature of time.

Why are humans unique in our ability to grasp the concept of time for the short- and long-term?

Let’s indulge in a little science fiction for a moment. Time travel movies often feature a vast, energy-hungry machine. The machine creates a path through the fourth dimension, a tunnel through time. A time traveller, a brave, perhaps foolhardy individual, prepared for who knows what, steps into the time tunnel and emerges who knows when. The concept may be far-fetched, and the reality may be very different from this, but the idea itself is not so crazy.

Physicists have been thinking about tunnels in time too, but we come at it from a different angle. They wonder if portals to the past or the future could ever be possible within the laws of nature. As it turns out, they think they are. What’s more, they have even given them a name: wormholes. The truth is that wormholes are all around us, only they are too small to see. Wormholes are very tiny. They occur in nooks and crannies in space and time.

Nothing is flat or solid. If you look closely enough at anything you’ll find holes and wrinkles in it. It is a basic physical principle, and it even applies to time. Even something as smooth as a pool ball has tiny crevices, wrinkles and voids. Now it’s easy to show that this is true in the first three dimensions. There are tiny crevices, wrinkles and voids in time. Down at the smallest of scales, smaller even than molecules, smaller than atoms, we get to a place called the quantum foam. This is where wormholes exist. Tiny tunnels or shortcuts through space and time constantly form, disappear, and reform within this quantum world. And they actually link two separate places and two different times.

Unfortunately, these real-life time tunnels are just a billion-trillion-trillionths of a centimeter across. Way too small for a human to pass through – but here is where the notion of wormhole time machines is leading. Some scientists think it may be possible to capture a wormhole and enlarge it many trillions of times to make it big enough for a human or even a spaceship to enter.

Given enough power and advanced technology, perhaps a giant wormhole could even be constructed in space. I’m not saying it can be done, but if it could be, it would be a truly remarkable device. One end could be here near Earth, and the other far, far away, near some distant planet.

So, in conclusion and in theory, a time tunnel or wormhole could do even more than take us to other planets. If both ends were in the same place, and separated by time instead of distance, a ship could fly in and come out still near Earth, but in the distant past. Maybe dinosaurs would witness the ship coming in for a landing.

To physicists, time is what is measured by clocks. Using this definition, we can manipulate time by changing the rate of clocks, which changes the rate at which events occur. Einstein showed that time is affected by motion, and his theories have been demonstrated experimentally by comparing time on an atomic clock that has traveled around the earth on a jet. It is slower than a clock on earth.

Although the jet-flying clock regained its normal pace when it landed, it never caught up with earth clocks – which means that we have a time traveller from the past among us already, even though it thinks it’s in the future.

Some people show concern over time traveling, although Mallett – an advocate of the Parallel Universes theory – assures us that time machines will not present any danger.

As HG Wells said in ‘The Time Machine’:

“The time traveller proceeded, “any real body must have extension in four directions: it must have Length, Breadth, Thickness and Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimentions, three which we call the three planes of Space, and a fourth, Time.”