Proof that you can travel faster is the so-called Cerenkov radiation , that bluish glow that can be seen in the pools where the fuel used in nuclear power plants is stored. Named after the Russian scientist Pavel Alekseyevich Cerenkov , who characterized it precisely and for which it received the Nobel Prize in 1958 , it is produced when charged particles pass through a material – in the case of power plants, it is water – at a speed that is superior to that of light in that medium. This is what is important and for the sentence at the beginning of this paragraph to be correct, a tagline must be added: nothing can travel faster than light in a vacuum . At no time is it forbidden to go faster than her in water, air, glass, plastic…
Although this statement is as valid now as it was when Einstein made it more than a century ago, the problem is what the word void means , because there are many kinds of voids. The one that we know, the one that is achieved on a daily basis in our laboratories and that we can find in space, is not the only one that can exist. In fact, the vacuum is not what we all imagine, absence of energy and matter . If we make use of the laws of quantum mechanics , we find that the vacuum has an energy known, for example, as vacuum energy . If we manage to lower it in some way, we will get light to travel faster than those mythical 300,000 km/s. This is what happens when we place two sheets of metal well burnished and separated by barely the diameter of an atom. This is the Casimir vacuum and the theory is that in this ultra-tiny space light must travel faster, but we don’t yet have the technology to test this prediction.
To understand the impact that results from researching at hyperluminal speeds, we must know that any object with mass, be it us, a few pellets or an electron, if it wants to reach the speed of light, we must supply it with an infinite amount of energy. Even more important is that no information can travel faster than light because that would violate the ubiquitous principle of causality: cause must precede effect. This is clear with hypothetical particles that were imagined more than half a century ago.
In 1967 the physicist Feinberg postulated the existence of particles capable of traveling at speeds greater than that of light , tachyons . Four years later Bendford, Book and Newcomb studied the consequences of this fact from the so-called Tolman paradox -enunciated in 1917- where it is shown that sending signals faster than light implies communicating with the past. Why?
Let’s imagine that we play with a tachyon frisbee . We see how our friend makes the movement of throwing it to us and seconds later, as the image of the frisbee travels towards us, we find it in our hands! This is so because by going faster than light, which is what brings us its image to the retina after colliding with the frisbee, it goes before it. Even more. The sequence of images that we would see would be: first, obviously, the one that the photons bring us when the frisbee is 5 meters from us, then the 15, followed by 30, 45… until the last one would be the one of the frisbee leaving hand in hand with our friend. In other words: the frisbee reaches our hand before we see it leave.
This, of course, implies serious paradoxes, such as that which arises if we deal with events dependent on one another. Imagine that Mamen and Esther have inherited two tachyon phones so that they can send a message to the past that arrives only one hour apart: if a message is sent at 3, it will be received at 2. They both decide that Mamen will send a message at 3 o’clock if she hasn’t received Esther’s at 1 o’clock earlier. On the other hand, Esther will send hers a little after 2 o’clock if she has received Mamen’s at 2 o’clock. Will Esther send the message? Whether Esther sends her message at 2 o’clock depends on Mamen sending hers at 3 o’clock, but (and here is the most paradoxical thing) Mamen will do so if she does not receive Esther’s: the communication will take place if it is not carried out.
The idea of hyperluminal velocities was nothing more than a theoretical diversion until at Bell Laboratories, first in 1970 Goffrey Garrett and Dean McCumber, and then in 1982 Steven Chu and Stephen Wong brought them back to the fore, showing that they could be obtained . empirically .
In recent decades, superluminal effects have jumped onto the pages of scientific journals thanks to a rather ghostly phenomenon in quantum theory: tunneling . We all know that when throwing a ball up a hill, if we don’t throw it with enough energy it will stop and come back down. Now, according to the rules of quantum mechanics, this doesn’t have to happen every time: there’s a certain probability that the ball will pop up like magic on the other side. This does not mean that the ball can appear inside the hill, because there is no place where it can be placed; it’s like tunneling to the other side, where you do have room to stay. It is this step that is verified at a speed greater than light. And that is what the group led by German Günter Nimtz did in 1994: transmitting Mozart’s 40th symphony through a barrier 11.4 cm wide. According to his rather controversial interpretation, this was done at a speed of 4.7 times the speed of light.
On the other hand, in 2001 the Chinese physicist Ni Guangjiong of the Fudan University in Shanghai published several articles in which he stated that the neutrino could be a superluminal particle . In 2007, the North American MINOS experiment, designed to study the oscillation of the neutrino by sending a jet of these particles from Fermilab in Chicago to Minnesotta, 724 km away, observed certain indications that Ni could be right, but the error in the measurement could not guarantee it. In 2011, the Italians of the OPERA experiment (acronym for the English Oscillation Project with Emulsion-tRacking Apparatus), also aimed at studying the oscillation of the neutrino, said they had shown it.
This time jets of neutrinos were sent from the CERN facilities in Geneva to the Gran Sasso tunnels in central Italy. This 730-kilometre journey was made in less than 3 milliseconds, so one can imagine how precisely the measurements must be made. According to the Italian team, the neutrinos arrived 60 nanoseconds -60 billionths of a second- earlier than light would. And not only that, but they claimed that their results were statistically significant at 6-sigma. To get an idea: a value of 5-sigma is enough to accept an experimental result and 6-sigma is enough to break champagne bottles.
The scientific community received these results with a tactic that is always good advice, wait and see. In the end, on July 12, 2012, OPERA included the new sources of error in their calculations: they found that the speed of neutrinos coincided with the speed of light. So we still don’t know if the speed of light is really unbeatable.
