Curious kids: Is time travel possible for human beings
I wish! In movies and books, characters use “time-turners,” treehouses, and other devices to travel back in time. In reality, this is not so easy. Why is this?
There are two kinds of “time-travel”: one is going backward in time, and the other is going forwards in time.
Harry and Hermione, the characters in Harry Potter and the Prisoner of Azkaban, use a time-turner. Warner Bros. Pictures
Traveling to the Past
We do not know how to travel back in time. It is hard to imagine that sending information backwards in time can alter events already occurring.
Imagine you broke your wrist, falling from the monkey bars. If you could go back in time, would you tell yourself not to get on the monkey bars? You would never break an arm if you succeeded. You would then have no reason to go back in time. What does this mean to your arm? Is it broken or not?
You’re not the only one who gets headaches when thinking about it.
Most people find the idea of time travel confusing. When we think of the passage of time, it’s as if we were moving in a straight-line, and that everything happens one after another.
We would change the order if we were able to travel back in history and change what happened. This would be a violation of a rule known as ” causality.”
The rule of Causality states that an “effect” is a result (of your actions) before a “cause.” In the monkey bar example, falling is the cause, while breaking your arm is the result.
The law of Causality is a universal rule that cannot be broken. It would be a terrible mistake for us and the universe to break this rule. The experts think that since the universe has this law, it must be impossible to travel back in time. Otherwise, the rule would be violated all the time.
Traveling to the Future
Can we move forward in time if going back to the past is not possible?
Technically, we are already moving forward in time because the time is passing. Each second, we move one second forward. This happens to everyone, so it isn’t really time travel.
You may be surprised to learn that two people experience time differently. If you are moving quickly, time passes at a different rate than if you are standing still. It is called “time-dilation”.
The time will pass faster for someone who is flying from Sydney or Melbourne than if they were waiting at the airport without moving. Why don’t you notice the difference?
You have to move much faster than a plane before you notice the time dilation. Even if you flew around the globe, it would feel like only a billionth second different than if someone stayed at home.
Read more: Curious Kids: Does space go on forever?
The only way scientists even know about time dilation is because of amazingly accurate experiments that have measured it.
This still won’t allow us to “time-travel.” Even if you flew around for four million years and a half, the people on the earth would have only experienced one second more than you.
How fast can you go?
If it all comes down to speed, then the answer is to go faster. You could travel for hundreds of years if you went fast enough and long enough.
Unfortunately, a fast enough speed to do this would be close to the speed of light, which is the fastest anything can go. The speed of light is about 1 billion km per hour.
NASA’s Parker Solar Probe is the fastest thing ever made by humans. It was a spaceship that was sent to the Sun on August 18, 2018. is, but it’s still only 0.064% faster than the speed of light. Light is 1,000 times faster than the speed of light!