Time machines may seem better suited to science fiction than the physics lab, but experts say this futuristic technology could become a reality.
Researchers have revealed how time travel could really work by using the laws of quantum physics.
While their method won’t let you hop back to the time of the dinosaurs, scientists say it could be possible to send messages into the past.
The researchers even say this mind–bending technique would work just like in Christopher Nolan‘s sci–fi epic, Interstellar.
In the movie, an astronaut played by Matthew McConaughey sends a message to his daughter in the past by moving the hands on her watch.
Although the reality wouldn’t be so cinematic, the researchers argue that this ‘causal loop’ resembles the way real time travel would work.
Co–author Dr Kaiyuan Ji, a researcher at Cornell University, told New Scientist: ‘The father remembers how the daughter decodes his future message.
‘So he can instruct himself on what is the best way to encode the message.’
Scientists have uncovered a way to send messages backwards in time, and they say it works just like a scene from Christopher Nolan’s sci–fi epic Interstellar
It might seem surprising, but there is actually nothing in the laws of physics as we understand them that makes time travel impossible.
According to the laws of general relativity, which are the best description of the universe we have, everything moves through the fabric of space and time on a set path.
One possible path that something can follow is known as a closed time–like curve (CTC).
Something travelling on a CTC moves into the future before looping back on itself via the past to end up exactly where it started.
The laws of physics allow for these loops to form, but actually making one on a large scale requires twisting spacetime with a literally infinite amount of energy.
However, on the very, very small scale, structures like CTCs might form naturally through the laws of quantum physics.
On the quantum level, two particles can become ‘entangled’, which means that what happens to one particle affects the other even if they are light–years apart.
One possible way to explain this effect, which Einstein called ‘spooky action at a distance’, is to say that one particle is actually sending messages backwards in time to the other.
The laws of physics allow for the creation of ‘closed time–like curves’, structures in spacetime like wormholes that loop backwards in time. On the quantum scale, scientists say these can be created using entangled particles
Rather than assuming that they are part of one massive system or that they are sending information faster than light speed, the particles’ ‘sensitivity’ is explained by their receiving messages in the past that tell them how to react later.
That might sound absolutely mad, but in 2010, scientists actually came up with a way of mimicking closed time–like curves using entangled particles.
Professor Seth Lloyd, a quantum physicist from the Massachusetts Institute of Technology, says: ‘It was the equivalent of sending a photon a few nanoseconds backwards in time, and having it try to kill its former self.’
What this creates is a bit like a telephone with a direct connection to another device a few moments earlier.
In theory, you could use something like this to pass messages back to yourself in the past.
Just like a real phone line, the connection on a CTC isn’t always going to be perfect, and noise or disruption will make it hard to pass information with 100 per cent accuracy.
Professor Lloyd says: ‘Nobody’s built an actual physical, closed time–like curve, and there are reasons to think it’s very hard to make one. But all channels are noisy.’
This is where an insight from Matthew McConaughey in Interstellar comes in handy.
In Interstellar, an astronaut played by Matthew McConaughey sends a message to his daughter in the past by moving the hands on her watch. Since he knows how his daughter decodes the message, he can encode it in a way that makes the information legible
In their new paper, accepted for publication in Physical Review Letters, Professor Lloyd and his co–authors write: ‘The father, who is in the future, may retrieve his memory of past events he has witnessed, even including the daughter’s decoding of the message which he is about to send!
‘It would thus not be surprising that he will consult his memory of the daughter’s decoding when encoding his message, so as to maximize the efficiency of the communication.’
Essentially, if you’ve already watched someone struggle to piece together your garbled message, you should know how to send it so that it’s easier for them to decode.
Even if the connection is very noisy, a backwards time–travelling message would still be legible.
The slightly weird conclusion of this is that sending messages backwards in time is likely to be clearer than sending a message in normal time.
Although no one has built a real closed time–like curve, Professor Lloyd says it should be fairly easy to turn this new idea into an experiment on the quantum level.
That could let scientists investigate how information is transmitted through ‘noisy channels’ and even improve real–life communication methods.