Hypothesize This: Is Time Travel Really Possible?
Hypothesize This is a monthly series looking into trends, buzzwords and other phenomena with the curiosity of science. In the early 2000s, an individual by the name of John Titor made appearances onto bulletin boards claiming to be a time traveller from the future and making outlandish political and technological predictions, none of which came true. Almost a decade later, private investigators linked Titor to two brothers, a computer programmer and lawyer, concluding the mystery as a hoax. But what do we know scientifically about the ability to traverse through time? How would our bodies respond to travelling at such speed and distance? What if the first time traveller was a message? We sat down with Youth Program Specialist, Parker McLean, to discuss some theories on travelling forwards and backwards in time.
What's the best way to wrap our heads around the physics of time travel?
On a very baseline level, we are currently travelling through time. More surprising, observations on how light moves introduced the physical possibility for time travel to the distant future. Light is often observed as a wave and researchers wanted to learn more about the medium it was travelling through so they conducted a series of experiments. The most famous is the Michelson–Morley experiment. They shone light in different directions, and based on the Earth’s rotation, the experiment predicted that light should be affected by “aether winds”, a current in the invisible medium that light is moving through. The thing was, at that time, they didn’t know whether the aether even existed or not. The experiment showed that it didn’t matter which direction the light was going in, it always maintained the same speed. That, among other experimental findings, debunked the aether hypothesis. Which means that light is a wave propagating through nothing. But these findings also led to something else: that light appears to move at the same speed in a vacuum no matter how we look at it, which is very, very weird.
Why is that weird?
What we experience in regular Galilean relativity is this: if you’re in a car at 100km/hr and you take a speedometre and you shine it on the road, you’ll see that you’re traveling at 100km/hr. But if you see another car beside you and you shine a speedometre at them, you’ll see that they’re going at 0km/hr because they’re moving in the same speed as you. And if they go against you and you shine a speedometre at them, you would see that they're going at 200km/hr. Whereas light, is weird and different. If you were to go the speed of light at about 300,000km/sec and you measured the speed of a beam going by you, you would still detect it as the speed of light as it normally is. And if it moved against you, you’d detect it as the same speed of light. Because of this strange phenomena, where light always moves at the same speed and is always measured to go at the same speed, it means that weird things happen when you start moving near the speed of light.
Let's say we did have the ability to move at the speed of light, what weirdness could we possibly experience?
Einstein created a thought experiment now known as the ‘twin paradox’. One twin stays on earth and the other goes into a rocket ship at near the speed of light away from earth and returns home. Because Velocity = Distance / Time, and the speed of light has to stay constant, Einstein’s theory of special relativity notes that when objects move, their length and time as measured by an outside observer, have to contract. This effect only becomes noticeable to us when things move near the speed of light. All that means is that the time and biological clock of the twin in the rocket ship would slow down during their near light-speed travel. So, when the twin returns, let's say in this scenario that they could return having aged 5 years or even 5 days, whereas their twin on Earth aged 30 years. That kind of time travel is mathematically discovered to be possible, which is pretty cool. The film Interstellar shows that really well with the time dilation that occurs due to gravity.
Could we do that same experiment and go back in time?
We know that time travel is possible going into the future. But going back in time? Not really. It’s been theorized. As you speed up and get closer to the speed of light, time slows down. If you go at the speed of light, according to these equations, time would stop. But physicists suggest that if you were to try to match the speed of light you couldn’t actually reach it. It’s because the closer you get, the more energy that you add to speed up would also increase your mass. When your mass gets bigger, it makes it much harder to speed up. Basically, the equation says that it’s impossible to accelerate to the speed of light if you have mass. Then there are fun ideas such as hypothetical particles, ‘tachyons’, always moving faster than light and backwards in time. As well, there are some weird things in quantum electro-dynamics, where some particles are treated mathematically as if they are moving backwards in time. There are all sorts of funny ways to skirt around infinitely increasing mass but so far we have not seen things travel backwards in time.
What if we were to take mass out of this? Instead of sending a person back in time, could we send a message?
You would need something to travel faster than the speed of light for something to go theoretically backwards. Radio waves are just another colour of light, which means if you were to send a message it could travel at the speed of light but there still isn’t something that we’ve seen that would go faster than that. The speed limit of the universe is the speed of light.
What the biggest misconception about time travel?
I guess, the biggest misconception people have about time travel is that it's a thing of science fiction. People are experiencing time travel right now, we are moving through time. Humans have discovered and invented things that have, in a way, allowed us to travel in time. Science, for example, creates methods to predict what will happen in the future. Mathematical relations discovered through experiment by scientists such as Newton, Kepler, and many others allow us to say, “Halley's Comet will be flying over that horizon in 41 years 9 months and 10 days.” That ability to predict the future and know what’s going to happen is a pretty cool thing that we’ve developed. Similarly art, literature, paintings and cultural traditions are ways for us as a consciously aware species to travel back in time. We see that with the oral histories of First Nation peoples, particularly in the West Coast of BC. They talk about a great flood happening and the receding ice. Those are events that occurred 10,000 years ago, which we can now verify through observation. Fossils are also a way in which we can travel back in time and can get a sense of geological phenomena that existed. So we might not be physically be able to time travel but there are ways in which we can bring our imagination back in time to see what life was like and how it was lived.