*I’m curious about what would happen if, hypothetically, someone was traveling at twice the speed of light? – Devanshi, age 13, Mumbai, India *
Hello Devanshi! Thank you for your question
As far as we know, it is impossible for a person to travel at twice the speed of light. In fact, it is impossible for any object with this type of mass to move faster than the speed of light.
However, for certain odd particles, traveling at twice the speed of light is possible – and possibly sending them back in time.
Universal speed limit
One of our best current theoretical physics is theory of relativity, which was developed by Albert Einstein. According to this theory, the speed of light operates as a universal speed limit for everything with mass.
In particular, relativity tells us that nothing with mass can accelerate beyond the speed of light.
To accelerate an object with mass, we must add energy. The faster we want it to go, the more energy we need.
The equations of relativity tell us that any object with mass – regardless of how much mass it has – would require an infinite amount of energy to be accelerated to the speed of light.
But all sources of energy that we know of are finite: they are limited in some ways.
Indeed, it makes sense that the universe has only a finite amount of energy. That means there isn’t enough energy in the universe to accelerate something with mass to the speed of light.
Since we have mass, don’t expect to travel at twice the speed of light any time soon.
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Tachyons
This universal speed limit applies to anything with what we call “ordinary mass”.
However, there is a hypothetical particle called tachyon with a special type of mass called “imaginary mass”.
There is no evidence that tachyon there is. But according to relativity, the possibility of their existence cannot be ruled out.
If there is, tachyon must always move faster than the speed of light. Just as something of ordinary mass cannot be accelerated past the speed of light, tachyon cannot be slowed down to below the speed of light.
Some physicists believe that if tachyon there, they will continue to move backwards in time. This is why tachyon associated with time travel in many science fiction books and films.
There is an idea that someday we can take advantage of tachyon for build a time machine. But for now it’s still a distant dream, because we don’t have the ability to detect potential tachyon.
Read more:
Curious Kids: is time travel possible for humans?
Shortcut?
It’s very disappointing that we can’t travel faster than the speed of light. Our closest star, apart from the Sun, is 4.35 light-years away. So, traveling at the speed of light, it would take more than four years to get there.
Farthest star we’ve detected is 28 billion light years away. So, we can give up on being able to map the entire universe.
Nonetheless, relativity allows the existence of “worm hole.
A wormhole is a shortcut between two points in space. While a star might be 4.5 light-years away normally, it might be just hours through a wormhole.
If there really were wormholes, they would let us travel great distances in a very short time – allowing us to reach the farthest reaches of the universe in a single lifetime.
Unfortunately, like tachyonthe wormhole remains completely hypothetical.
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Strange possibility
Despite the fact that we can’t actually travel faster than light, we can still try to imagine what it would be like to do so.
By thinking like this, we are involved in”counterfactual thinking“. We are invited to consider what would or might happen if reality were different in some respects.
There are many different possibilities we could consider, each with a different set of physical principles.
So we can’t say for sure what would happen if we could travel faster than light. At most, we can guess what maybe occur. Will we start traveling back in time, as some scientists think may be tachyon?
I’ll leave it to your imagination to come up with some ideas!
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Arina Apsarini from Binus University translated this article from English.
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