In the new Disney Pixar Lightyear movie, time is running out

At the beginning of Disney Pixar’s new film, Lightyear, Buzz Lightyear is trapped on a dangerous distant planet with his commander and crew. Their only hope of leaving the planet is to test a special fuel. To do this, Buzz must fly into space and repeatedly try to jump to hyper-speed. But every experience he makes is worth a terrible price.

Each time Buzz takes off for a four-minute test flight into space, he lands back on the planet to find that many years have passed. The people Buzz cares about the most fall in love, have children and even grandchildren. Time is becoming his greatest enemy.

What’s happening? Is this just science fiction or can what really happened to Buzz really happen? Time is relative: Einstein’s great idea. Buzz is experiencing a real phenomenon known as time delay. Time delay is a prediction of one of the most famous scientific theories ever developed: Albert Einstein’s theory of relativity.

The mechanics of Isaac Newton

Before the theory of relativity, the best theory of motion we had was the mechanics of Isaac Newton. Newton’s theory was incredibly powerful, providing stunning predictions of the motion of the planets in our solar system. In Newton’s theory, time is like a giant clock that strikes seconds in the same way for everyone. No matter where you are in the universe, the main clock will show the same time.

Einstein’s theory of relativity broke the main clock into many clocks – one for each person and object in motion. In Einstein’s picture of the universe, everyone carries their own watch. One consequence of this is that there is no guarantee that the clocks will tick at the same speed. In fact, many watches will tick at different speeds.

What’s worse is that the faster you travel relative to someone else, the slower your watch will tick compared to theirs. This means that if you travel very fast in a spaceship – as Buzz does – it may take a few minutes for you, but it may take years for someone on the planet you left behind.

Time traveling forward – but not backward

In a sense, time delay can be seen as a type of time travel. It provides a way to jump into someone else’s future. Unfortunately, there is no way to use time delay to travel back in time, to the past (as one important character says later in the film). It is also not possible to use time delay to travel to your own future.

This means that there is no known way to travel into the future and meet your older self just by walking very fast.

Traveling in time over Earth right now

Time lag may seem like science fiction, but it is actually a measurable phenomenon. In fact, scientists have conducted a number of experiments to confirm that clocks tick at different speeds, depending on how they move.

For example, astronauts on the International Space Station travel at very high speeds compared to their friends and family on Earth. (You can watch the space station pass from above if you know when to look up.) This means that these astronauts are aging a little slower. In fact, the American astronaut Buzz Aldrin, from whom Buzz in Leiter got its name, would experience a slight time delay during his voyage to the moon in the 1960s.

Don’t worry, however, astronauts on the International Space Station will not notice or notice any time delay. It’s not like the extreme time jumps seen in Leiter. Aldrin managed to return safely to his family, and astronauts in space will do the same.

To infinity – and beyond It is clear that delaying time can come at a serious cost. But not everything is bad news. One day delaying time can help us travel to the stars. The universe is a massive place. The nearest star is 40,208,000,000,000 km. Getting there is like traveling around the world a billion times. Traveling at normal speed, no one would ever survive long enough to make the journey.

However, the delay in time is accompanied by another phenomenon: shrinking in length. When a person travels very fast to an object, the distance between your spacecraft and that object will appear shrunken. Very rough, at high speeds everything is closer. This means that someone traveling at high speed can reach the nearest star in a few days.

But the time delay will still be in effect. Your watch will slow down compared to someone on Earth. So you can take a round trip to the nearest star for a few days, but by the time you get home, everyone you know will be gone. This is both the promise and the tragedy of interstellar travel.

Sam Barron, Associate Professor, Australian Catholic University

Posted on

June 20, 2022

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