The truth is that we are all travelling in time at every moment! And we do it at a constant rhythm of 1 second per second.
At first, you might think that this is totally different than travelling through one of the three spatial dimensions at, say, one metre per second. However, according to Einstein’s theory of relativity, we live in a four-dimensional universe, in which there are three dimensions of space, and one of time, which are closely related.
Einstein discovered that the faster an object moves through space, the slower it experiences time.
This was a complete revolution in science, because until that moment it was thought time was uniform throughout the universe. We now know that time is experienced differently by each object, and this has been experimentally verified on various occasions.
One of the most known experiments is the following: two atomic clocks (the most precise that exist on Earth) configured at the same time were used. One of the clocks remained on the Earth’s surface, while the other flew on a plane around the Earth. The result was that the clock on the plane (that moved more quickly) was slightly behind the one that didn’t leave the surface. So, the clock on the plane was travelling slightly slower in time than 1 second per second.
This effect is known as time dilation.
Travelling to the future
Obviously, when we talk about travelling to the future we normally refer to travels as the ones in movies, tens of thousands of years into the future. Are these travels possible? The answer is yes.
At the speeds we achieve in our everyday lives, the effects of time travel aren’t noticeable. For these effects to be perceptible we would need to travel at near-light speeds (300.000 km/s).
For example, travelling at 80% of the speed of light, one year to us would represent 1 year and 240 days on Earth. And this effect doesn’t evolve proportionally, but it is exponential.
- At 90% of the speed of light, one year in the spacecraft would correspond to more than 2 years on the Earth.
- Travelling for a year at 99.9% of the speed of light, on the Earth 31 years would have gone by.
- One year travelling at 99.99% of the speed of light would correspond to 100 years on the Earth!
However, acquiring such speeds presents an infinity of technical problems. Nowadays, the spacecraft that has achieved the highest speed is the Parker Solar Probe, which got to 163 km/s when it approached the Sun.
It is important to mention that a person inside the spacecraft doesn’t have the feeling that the time he experiences is slower. Only an external observer situated, for example, on the Earth, will see that the time on the rocket is slower than his.
As you can see, time travel to the future is totally possible, the problem is that extremely high speeds need to be achieved in order for it to be noticeable.