At the start of the new Disney Pixar movie, Lightyear, Buzz Lightyear is stranded on a remote and dangerous planet with his captain and crew.
Their only hope of getting off the planet is a special fuel test. To do this, Buzz has to fly into space and repeatedly attempt to jump to extra speed. But every attempt he makes comes at a heavy cost.
Each time Buzz takes a four-minute test flight into space, he returns to the planet to find that many years have passed. The people Buzz cares about falling in love with, they have children and even grandchildren. Time becomes his biggest enemy.
What’s going on? Is this just science fiction, or could what happened to Buzz really happen? Time is Relative: Einstein’s Great Idea Buzz tests a real phenomenon known as time dilation. Time dilation is a prediction of one of the most famous scientific theories ever developed: Albert Einstein’s theory of relativity.
Before relativity, our best theory of motion was Isaac Newton’s mechanics.
Newton’s theory was incredibly powerful, and it made amazing predictions about the motion of the planets in our solar system.
In Newton’s theory, time is like one giant clock that cuts seconds in the same way for everyone. No matter where you are in the universe, the master clock will display at the same time.
Einstein’s theory of relativity broke the master clock into many hours – one for each person and one moving object. In Einstein’s picture of the universe, everyone carries their own watch with them.
One consequence of this is that there is no guarantee that the clocks will tick at the same rate. In fact, many clocks tick at different rates.
Even worse, the faster you travel compared to someone else’s, the slower your watch will be compared to theirs.
This means that if you travel very fast in a spacecraft – as Buzz does – a few minutes may pass for you, but years may pass for someone on the planet you left behind.
Time traveling forward – but not backward In a sense, time dilation can be thought of as a kind of time travel. It provides a way to jump into someone else’s future.
Unfortunately, there is no way to use time dilation to travel backward through time, to the past (as one of the important characters talks later in the movie).
It is also not possible to use time dilation to travel into your future.
This means that there is no known way for you to travel into the future and meet your older self, simply by going too fast.
Time-Travelers Above Earth Right now time dilation may sound like science fiction, but it’s actually a measurable phenomenon. In fact, scientists have conducted a number of experiments to make sure that the clocks tick at different rates, depending on how they are moving.
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 overhead if you know when to look for it.) This means astronauts are aging at a slightly slower rate. In fact, American astronaut Buzz Aldrin, who gets his name from Buzz in Lightyear, experienced quite a bit of time dilation during his voyage to the Moon in the 1960s.
Don’t worry, though, astronauts on the International Space Station won’t feel or notice any time dilation. It’s nothing like the extreme jumps seen at Lightyear.
Aldrin was able to safely return to his family, and the astronauts will now be back in space as well.
To infinity — and beyond, it’s clear that time dilation can have a serious cost. But it’s not all bad news. Time dilation could one day help us travel to the stars.
The universe is a huge place. The nearest star is 40,208,000,000 km. Getting there is like traveling around the world a billion times. Traveling at a normal speed, no one will survive long enough to make the journey.
However, time dilation is also accompanied by another phenomenon: length contraction. When one travels at great speed towards an object, the distance between your spaceship and that object will appear to shrink.
Roughly, at higher speeds, everything is closer together. This means that for someone traveling at high speed, they can reach the nearest star in a matter of days.
But the time extension is still in effect. Your clock will slow relative to the clock of someone on Earth. So, you can make a round trip to the nearest star in a few days, but by the time you get home, everyone you know is gone.
This is the promise and tragedy at the same time of interstellar travel.
(This story has not been edited by the Devdiscourse staff and is automatically generated from a shared feed.)