Is warp drive possible?
Ever since we broke the sound barrier, people have turned their attention to something else. How we can break the light speed barrier! But any term for faster-than-light travel still remains science fiction.
The the bulk of scientific knowledge concludes that it’s impossible to do so. Especially when considering Einstein’s Theory of Relativity. There are some credible concepts in scientific literature, but, it’s too soon to know if they are viable.
One of these is the warp drive. Follow me to get to know more about it! We know Relativity puts a limit on the speed at which matter and information can move in space-time. This limit is the constant c or the speed of light in a vacuum. It is about 300,000 kilometers per second. But then there isn't any opportunity to overcome this obstacle and to move quickly? Or is there any chance for us to travel faster than the speed of light? Well, there may be loopholes (at least on a theoretical level).
Star Trek Warp drive
One of the ideas that have received more attention in the past years is something that looks a lot like the star trek warp drive. In this article, I want to try to explain to you what it is like. Relativity shows in a pretty clear way that the interactions and causal signals of any kind cannot propagate in space faster than light. We've already told you about that in some other videos (which we recommend watching!). Then how is it possible to even theoretically imagine that we do can move rapidly in the universe? Well, this could be one of the solutions: general relativity. This is the best theory we have at the moment to describe the severity of space-time, admits solutions that would allow you to travel in space through the so-called wormholes. If a wormhole did exist, you might enter one embouchure and find yourself almost instantly in a very distant point of space.
In theory, for an outside observer, your journey would have occurred at a speed greater than c. Because of this, wormholes are one of the most favorite means of transportation used by science fiction writers. Sci-fi authors imagined overcoming the light-speed barrier to allow interstellar travel. But, It is unlikely that wormholes exist (or that we can build them). But, from the theoretical point of view, a wormhole does not violate any known physical law. So, it is compatible with relativity.
The general theory of relativity
The point is that general relativity introduces one more possibility. In fact, in special relativity space and time are not absolute, yet they depend on the speed of the observer. In general relativity space and time can warp in a way that depends on the distribution and type of matter present in a certain region. Space curves itself and gravity is a manifestation of this curvature. Thus, relativity doesn't prevent deforming space so that distant points are approached (or separated) at very high speeds and maybe even higher than the speed of light.
We already know for example that the expansion of the universe can do so! Two very distant galaxies can move away from each other at a speed that, from the point of view of an observer in one of the two galaxies, is greater than 'c'. But the galaxies are not actually moving in space! It's space that is dilating itself, and the fact that this dilation occurs at a higher than c speed is quite compatible with relativity! For example, in the inside of a black hole, beyond the event horizon - the curvature becomes huge! And space gets stretched at a crazy higher speed than that of light, which also explains how light can never go out of a black hole once entered. It can't keep up the stretching of space. This is where the idea of the warp drive was born.
A spaceship equipped with such a warp drive would be able to control and alter the geometry of space. And to take advantage of this effect to move quickly in the universe without violating relativity. The idea is a lot simple: one should expand the space behind the spaceship and at the same time should contact the space ahead of it. In other words, the spaceship stays in a bubble of space, but this bubble moves quickly in the universe, due to contraction and the expansion of the surrounding space. It is pretty much the same thing that happens when a surfer rides a wave: the board does not move relative to the water, but the wave pushes the board forward. In short, the spaceship is not moving faster than the speed of light in its local reference frame. But due to the distortion of space around the bubble, it would come to its destination sooner than light would take. In 1994 the theoretical physicist Miguel Alcubierre, inspired by stars trek published an article in which he describes the way which – hypothetically – it could be obtained such a thing, starting from Einsteins' equations.
Alcubierre warp drive
The article became very popular (especially among fans of science fiction). In fact, nowadays we talk about the “Alcubierre warp drive”. All we're saying, yet, is that Alcubierre didn't invent a new engine. He proved that the relativity equations allow (in theory) to describe a geometry of spacetime that can allow us to travel faster than light. Alcubierre used math that is very like the one we use to describe the expansion of space during inflation. Inflation is an event that many cosmologists think happened in the very first moments of the history of our universe. But what kind of physical conditions should be fulfilled to shift from mathematics to physical reality?
Since matter distribution causes the curvature of space matter distribution, we must ask ourselves what kind of matter we would need to run such a warp drive. The answer is: we need a kind of matter with negative mass! (Also, this is the same kind of exotic matter that we need to create a traversable worm-hole). But the problem is that we don't know such a matter! We don't know any object with a negative mass! Of course, we know antimatter but antimatter is not a type of negative mass! Its mass and its gravitational properties are identical to those of normal matter. That's why we can't use antimatter to curve the space, as required by the warp engine. There is something that might have the right properties: dark energy. Dark energy is the energy of empty space, and it could explain the fact that the expansion rate of the universe is increasing. According to current data, dark energy makes up about 70 percent of the energy density of the universe! Dark energy in its simplest form is not negative, but in some particular models, it might have (from a gravitational point of view) some suitable features useful to run a warp drive.
It's too good to be true, what's the catch?
Anyway, it is needless to say that for the moment there isn't any concrete idea. And, most of all, we are not even sure that dark energy exists! In any case, how much energy or negative mass will we need to get a working warp drive? "Before answering, don’t forget to share this article with your friends"
Well...calculations produce mixed results. According to Alcubierre's initial estimates, it seemed that we needed way more negative energy than all the mass contained in the entire observable universe! Yes, you read it right! More negative energy than all mass of the Universe! Later studies showed smaller results, but the fact remains for the moment the amount of negative energy available is 0. There are many other potentials problems. Some studies have shown that to build warp drives, the exotic material that will be used to push the bubble should move in space faster than light. In other words, you should first have a warp drive to build one! Then we would be back to nothing.
Another problem is that not the spaceship could not send messages out of its bubble and also it could not even alter the trajectory of the bubble, because, to do it, it should send information out of the bubble faster than light which, as we already know, is impossible. In short, the spaceship would be disconnected from the rest of the universe! Furthermore, other studies have shown that there may be high levels of radiation in the bubble. That would be lethal to the occupants and would destabilize the bubble itself, leading to its own destruction in a very short amount of time.
The idea of Alcubierre is based just on general relativity and we know general relativity is unable to take into account quantum effects. A theory of quantum gravity could so change things completely, and it could show that the idea of the warp drive actually is wrong (or right!). Yet, at least theoretically, the warp drive does not violate any known physical law, and it is not a completely absurd idea! Maybe, in the distant future, someone will find a way to put it into practice. So far, there is nothing wrong to use this idea to understand a little better how the universe works: sometimes it is good to fly your imagination thanks to some good science fiction opera as star trek. But, Science fiction writers have given us many images of interstellar travel, but traveling at the speed of light is simply imaginary at present.
In the meantime, science moves forward. And while NASA is not pursuing interstellar flight, scientists here continue to advance ion propulsion for missions to deep space and beyond using solar electric power. This form of propulsion is the fastest and most efficient to date. There are many “absurd” theories that have become reality over the years of scientific research. But for the near future, warp drive remains a dream! "Did you find this content interesting? Do you think it will be possible to build such a warp drive? Do you have any questions for us?
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