Scientists claim to have reversed time

Timey wimey: In theory, wormholes could allow us to jump through vast chasms of time and space. © Fred Mantel

Is time travel really possible? For centuries, humans have dreamed of leaping into the deep past or distant future. Will we ever do it? The answer lies in one of Einstein’s strangest theories.

When scientists said they had reversed the flow of time in a quantum computer last week, the news made headlines around the world.

According to the Technology Review, it’s not quite as historic as it sounds. What the scientists did was closer to pressing rewind on a video. However, it’s a step in the right direction towards a goal that has captivated the human imagination for generations.

Will Tardis-style time travel ever be possible?

“We can jump forward into the future as much as we want. It’s only a matter of going really, really fast,” says Paul Sutter, an astrophysicist at Ohio State University.

But the closer you get to the speed of light, the slower you travel through time. Scientists have already observed the effect, using ultra-precise atomic clocks travelling on jet planes.

But going backwards in time is much harder.

According to Einstein, time passes more slowly the closer you are to fields of gravity. This means that strange things can happen to time near black holes, which have huge gravitational pulls.

Theoretically, it is possible, Sutter said. “But all of these scenarios end up violating other known physics, like requiring negative mass or infinitely long rotating cylinders.”

Will we ever be able to time travel?

Back to the future

Backward time travel is physically impossible, says physicist Richard Muller. And as for the future, we will never be able to travel to there because it “does not yet exist”. It is being created in the now.

But others are more hopeful. According to Stephen Hawking, while time travel would seem to be impossible according to 20th-century classical physics, it might be possible as we understand quantum mechanics better. One day we could build a traversable wormhole and hop through time. It’s far-fetched, but it might just work.

You Decide

  1. Could a time machine do more harm than good?


  1. Choose the moment in time that you would most like to visit. Write a few sentences explaining why.

Some People Say...

“People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.”

Albert Einstein (1879-1955), German-born physicist

What do you think?

Q & A

What do we know?
That Newsweek and other media outlets might have got a bit overexcited when they ran the headline: “Scientists Have Reversed Time in a Quantum Computer”.
What do we not know?
If we did build a time machine, could you travel back in time and kill your own grandfather. This is known as the Grandfather Paradox. It’s really a question about how changing the past might affect the present — like in the film, Back to the Future.

Word Watch

Quantum computer
A relatively new field of computing that uses the principles of quantum mechanics to do strange things with data.
A fictional time machine in Doctor Who. The name stands for Time And Relative Dimension In Space.
Speed of light
When we talk about light years, we are saying how long it would take to get somewhere if you were travelling at the speed of light.
Atomic clocks
Clocks that use measurements of time far, far smaller than seconds.
Negative mass
Physicists believe that matter can have negative mass in the same way a particle can have a positive or negative charge.
Rotating cylinders
In 1974, Frank Tipler theorised that you could use a rotating cylinder to warp space time.
Stephen Hawking
Famous physicist who wrote A Brief History of Time.
Able to be travelled through.

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