What would happen if you moved at twice the speed of light?
Einstein’s theory of relativity would seem to rule out the possibility, but what if it could be done?
As far as we know, it is impossible for a human to move at twice the speed of light. In fact, it is not possible for any object with the kind of mass that you or I have to move faster than the speed of light.
However, for some strange particles, it could travel at twice the speed of light and send those particles back in time.
A universal speed limit
One of our best physical theories at the moment is the theory of relativity developed by Albert Einstein. According to this theory, the speed of light is the universal speed limit for any object with mass.
Specifically, the theory of relativity tells us that anything with mass can be accelerated beyond the speed of light.
To accelerate an object with mass, we must add energy. The faster we want an object to move, the more energy we need.
The theory of relativity tells us that anything with mass, no matter how massive, requires an infinite amount of energy to accelerate to the speed of light.
But all energy sources, as we know them, are finite: they are finite in some way.
In fact, it makes sense that the universe contains only a finite amount of energy. This means that there is not enough energy in the universe to accelerate objects with mass to the speed of light.
Since you and I have mass, don’t expect to travel at twice the speed of light any time soon.
This general speed limit applies to everything we call “normal quality.”
This universal speed limit applies to anything with what we might call “ordinary mass.”
There is no evidence that tachyons exist. But according to the theory of relativity, the possibility of its existence cannot be ruled out.
If they exist, tachyons must always travel faster than the speed of light. Just as things of ordinary mass can’t be accelerated past the speed of light, tachyons can’t be slowed down below the speed of light.
Some physicists think that if tachyons exist, they are constantly moving backwards. This is why tachyons are associated with time travel in many science fiction books and movies.
There is an idea that one day we could use tachyons to build time machines. But for now, this remains a distant dream because we don’t have the ability to detect potential tachyons.
It’s disappointing that we can’t travel faster than the speed of light. Besides the sun, the closest star to us is 4.35 light-years away. So traveling at the speed of light, it would take over four years to get there.
The most distant star we have detected is 28 billion light-years away. So you can give up drawing diagrams of the entire universe.
In other words, the theory of relativity allows the existence of “wormholes”.
Wormholes are shortcuts between two points in space. While a star might be 4.5 light-years away under normal circumstances, it could be only a few hours away via a wormhole.
If true wormholes existed, they would allow us to travel vast distances in a very short time, allowing us to reach the farthest reaches of the universe in one lifetime.
Unfortunately, like tachyons, wormholes remain entirely hypothetical.
Even if we can’t actually go faster than light, we can still try to imagine what it would be like to do so.
By thinking this way, we are doing “counterfactual thinking.” We are thinking about how things would or could be if reality were somehow different.
We can consider many different possibilities, each with a different physics.
So we can’t be sure what would happen if we could travel faster than the speed of light. At best, we can guess what’s going on. Will we begin to travel in time as tachyons think some scientists?