The foundation of Special Relativity –enunciated more than a hundred years ago by the ‘most important person of the 20th century’, Albert Einstein-, is that nothing can travel faster than light: the speed of light is a maximum limit, situated at almost 300,000 kilometers per second (km / s).
The speed of light is considered a fundamental constant of nature. In the famous equation of Relativity, E = mc2 , the speed of light (c) serves as a constant of proportionality, linking the previously very disparate concepts of mass (m) and energy (E).
But how are we so sure that nothing can travel faster than light? What would happen to us if we tried?
The problem of time dilation
The universe is a space-time fabric; In other words, when it comes to traveling great distances, not only space, but also time comes into play. It takes four years for light to travel the distance that separates us from the closest star to our solar system, Proxima Centauri. And the speed of light is always the same; it always moves at the same speed with respect to us, no matter how fast we travel. It is absolute, while the rest of the speeds in the universe are always relative.
The absolute speed of light has a consequence: temporal dilation , that is, space and time are also relative. Time dilation is the ‘deceleration’ of a clock determined by an observer who is moving relative to that clock.
To see it more clearly, let’s imagine that we are accelerating in space at an increasing speed. As we reach the speed of light, we will perceive that ‘our clock’ is slowing down: we would be freezing in time little by little, as if traveling ‘in slow motion’, and we would never be able to reach 300,000 m / s of the light. This is the basic structure of Relativity.
So how could we travel faster than light?
However; If nothing can travel faster than light, you may wonder if the headline of this article is mere clickbait . But not. Physics contemplates some ways to travel great distances in less time without violating the law of the absolute speed of light, even in its theoretical aspects.
Theoretical physicist Miguel Alcubierre, during his conference at the 2018 Future Congress, captured before the public two ways of traveling ‘faster than light’.
1. A wormhole
Without violating Einstein’s Relativity (more precisely, using it) we find the first of the ways to travel ‘faster’ than light (rather, in less time).
A wormhole is a hypothetical cosmic object, but one that is based on one of the principles of Relativity: that space can curve. A faster way to travel from point A to point B in the universe, far from each other, is to ‘fold’ the space to create a tunnel between the two, as shown in the image below.
If light travels from point A to point B in a straight line (in red), it would take much longer than us through the shortcut (in green). Of course, if the light took the same shortcut as us, it would always beat us.
But the bad news is that, on a practical level, no scientist yet has a clue how to build these shortcuts.
These wormholes are also known as Einstein-Rosen tunnels, and they would come to be a kind of cosmic ‘shortcut’ . Both scientists, Einstein and Rosen, already developed the hypothetical idea of wormholes in 1936.
2. Distortion drive
This is another way to ‘warp’ the space to use it at our convenience. According to Alcubierre, it would consist of doubling the space to propel us with it; that is to say, it would be about traveling ‘with space’.
Assuming that space is expanding, that is, it is ‘stretched’, we could hypothetically make the space behind us stretch, and contract in front of us . If we can get the space from point A to point B to contract, in theory we could travel this same distance faster than light would under normal circumstances.
Alcubierre adds that, for both forms of space travel to be carried out, we would need enormous amounts of energy, the equivalent of entire stars; and, on the other hand, we would also require what we call negative energy (mass) . And, as far as we know, we have never detected negative energy, a kind of antigravity; but luckily the laws of physics do not prevent it from existing.
