The theory of general relativity that Albert Einstein published in 1915 establishes, among many other ideas that were revolutionary at the time, that no object with mass can move through the space-time continuum at a speed greater than that of light . To achieve this, very broadly speaking, you would need to have an infinite amount of energy, something that clearly is not possible.
But this is not all. In addition, during acceleration it would experience an increase in mass and a deformation resulting from the compression of the space that is unacceptable, among other effects that are not easy to fit (we explain this process in more detail in the article that I link here ). Even so, the barriers imposed by the laws of physics , fortunately, have not represented an obstacle for the writers of science fiction novels. And not for some filmmakers either. The barriers imposed by the laws of physics, fortunately, have not represented an obstacle for science fiction writers. And not for some filmmakers
And it is that in many of his works they describe a world in which space travel at hyperluminal speed is possible, which gives the human being the possibility of moving from one star system to another, and even from one galaxy to another. in a period of time perfectly acceptable to man. Science fiction fans have enjoyed this resource on many occasions both in film and literature.
Science fiction is often inspired by formal science to take it as a starting point and go a step (or several) further, but this formula works the other way, too. And it is that some scientists openly acknowledge having picked up the gauntlet that science fiction ideologues sometimes throw at them with the purpose of flirting with the possibility of putting their ideas into practice . The Mexican physicist Miguel Alcubierre is one of them, and his proposal is exciting. Promised.
Alcubierre’s proposal: propulsion by distortion of the space-time continuum
Before moving forward we must put the rules on the table. We are entering a purely speculative and conceptual terrain in which the most important thing is to respect the laws of physics and not break them. From there, the next challenge is to identify if our current technological development allows us to put into practice the theoretical proposal that we have devised as a starting point. This was precisely the path that Miguel Alcubierre entered in 1994.
He currently directs the Institute of Nuclear Sciences and the Department of Gravitation and Field Theory of the Faculty of Sciences of the National Autonomous University of Mexico. His specialty is black holes , gravitational waves , dark matter, and the theory of gravitation. And, in addition to all this, he confesses that he is passionate about science fiction. In fact, the ‘Alcubierre metric’ , which is the mathematical model he has developed to propose a way to travel through the space-time continuum faster than light, came to him while watching a chapter of ‘Star Trek’ .
The reason this physicist’s proposal is cited with some frequency by other researchers is that it does not violate Einstein’s general relativity . So how do you pose the possibility of traveling faster than light if, as we have seen, no object with mass can? The solution that Alcubierre proposes is very ingenious: deforming the space-time continuum. In fact, as he maintains, “the idea is not to travel through space; it is traveling with space .
In a way, his proposal describes what could be the effect of a curvature motor capable of propelling a spacecraft through the space-time continuum at hyperluminal speed . Of course, the concept of ‘curvature motor’ was not invented by Alcubierre; he’s borrowed it from science fiction, something he honestly acknowledges.
In any case, what distortion propulsion raises , which is what he calls his ingenious idea, is the possibility of expanding the space that is behind us, and, simultaneously, compressing the space that is ahead.
A space vehicle that incorporates the technology necessary to make this manipulation of space-time possible would, in effect, be able to travel gigantic distances at a speed greater than that of light .
And, furthermore, it would do it without breaking the laws of physics because, in reality, it would not be traveling faster than light; would be taking advantage of the same property of the space-time continuum that explains, without going into complicated details, that the expansion of the universe is caused by the creation of space between galaxies , and not because some are proactively moving away from the others.The premise that Alcubierre proposes is very ingenious: «the idea is not to travel through space; is traveling with space »
As you can see, this proposal sounds good. And it does so because there is no law of physics that prevents space from expanding faster than light . In fact, space can expand at an arbitrary speed. However, putting it into practice poses a number of challenges that are out of reach for the moment.
When developing the Alcubierre postulate using the equations of general relativity, what we would obtain is that the deformation that we need to introduce into space to expand it behind us and compress it in front requires the use of a huge amount of energy . As much as the one that contains a star. Or, perhaps, even more than one.
And, furthermore, it is not just any kind of energy; to bend space we would need negative energy, and this form of energy is closely linked, again according to general relativity, to negative mass . The problem is that at the moment we have no indication that this kind of mass actually exists.
Of course, it is not prohibited by the laws of physics, so, as Alcubierre argues, “we have a small ray of hope.” Before moving on to the next section of the article, I leave you an 18-minute video in which this physicist explains his proposal in a very didactic and entertaining way. It is very worth seeing.
Harold ‘Sonny’ White’s ploy is based on the ‘Casimir effect’
The propulsion by distortion of the space-time continuum proposed by Miguel Alcubierre in the mid-1990s has inspired many scientists. To serious scientists who have taken it as a stimulus to feed on to develop original ideas . One of them is the American physicist and mechanical and aerospace engineer Harold ‘Sonny’ White, whose career has largely been at NASA.
In 2011 this scientist published an article entitled ‘Warp Field Mechanics 101’ that takes Alcubierre’s ideas as a starting point and in which he proposes, among other interesting concepts, a strategy to drastically reduce the energy needed to trigger the distortion of space that it would make it possible to travel faster than light.
According to White, if the bubble that confines the spacecraft and induces deformation were not spherical in shape and were a torus (it is a geometric figure shaped like a donut), the energy required to carry out this operation would be much lower.
At the end of July Harold White published an article in which he claims to have identified a nanostructure that predicts the existence of negative energy
Obviously, even assuming that White is right, there are still many other a priori unsolvable problems to avoid, such as, for example, the need to use negative energy . Even so, this technician has not given up and has continued investigating.
His most ambitious project is the interferometer he is working on at the Advanced Propulsion Laboratory housed at NASA’s Johnson Space Center to try to identify the distortion of space-time introduced by a theoretical warp engine coupled to a conventional propulsion system. (All this is developed in the article that I linked in the previous paragraph).
The most interesting discovery White has made, however, came this year. And it is that at the end of last July he published an article together with other researchers in which he claims to have identified a nanostructure that predicts the existence of negative energy . His experiment on this occasion has been supported by DARPA, which is the Advanced Research Projects Agency of the United States Department of Defense (it is the same organization that financed the creation of ARPANET, the forerunner of the internet, in 1969).
Initially, White’s experiment aimed to analyze the structure of the energy density present inside a cavity in which two parallel metal plates reside that are separated by a tiny distance (much smaller than any of the dimensions of the sheets).
The surprising thing is that under these circumstances an attractive force appears between the plates predicted by quantum field theory and derived from the properties of the quantum vacuum (investigating it would excessively complicate this article, but we explore it in some depth in the article I link right here ).
The attractive force that arises between the plates due to the ‘Casimir effect’ is caused by fluctuations in the quantum vacuum
This phenomenon is known as the Casimir effect , and the attractive force that arises between the plates is caused by fluctuations in the quantum vacuum; It is not the result of electromagnetic or gravitational interaction.
What White probably did not expect to find when he started working on this experiment is that his measurements were going to predict the existence of a negative energy distribution . And this brings us, again, to Miguel Alcubierre’s proposal: the propulsion by distortion of the space-time continuum and its dependence on negative energy and mass.
This discovery has yet to be reproduced, verified and developed; in fact, it is only a small thread in a large and complex tapestry. Harold White, who is involved in the project for DARPA that I mentioned above, has encouraged other scientists to continue working in the line of research that he has started.
Possibly no one knows better than he the enormous effort that still needs to be undertaken for this little spark to flourish . Still, there is no doubt that the work of Miguel Alcubierre, Harold White, and many other scientists as well, is exciting. And hopeful. A breath of fresh air for those of us who love science and science fiction alike.
Cover image | Matheus Bertelli