New York (USA) In science fiction literature a warp drive is a technology that allows travel faster than the speed of light by warping space-time to beat the speed of light barrier. This is also not entirely impossible in reality. Einstein’s theory of general relativity says you can’t accelerate objects from below to above the speed of light, because that would take an infinite amount of energy, however this restriction only applies to objects in space-time not to space-time itself. Space-time can bend expand or warp at any speed and even physicists think, that the universe expanded faster than the speed of light. So on the spectrum from fiction to science, warp drives are on the more scientific end.
Recently two researchers at Applied Physics have created a new model for a warp drive. They describe it as a model for a space craft that could travel faster than the speed of light, without breaking the laws of physics. The researchers Alexey Bobrick, and Gianni Martire say, that this is the first general model for a real warp drive. Together they have written and published a paper titled “Introducing physical warp drives, Classical and Quantum Gravity (2021)” (DOI: 10.1088/1361-6382/abdf6e).
Every time someone mentions warp drives, the first thing that comes to mind is of course the TV series “Star Trek”, where the warp drive enabled the crew to travel vast distances in space much faster than the speed of light. However in real life many physicists have problems to accept the idea of a warp drive, as the theory would break the laws of physics.
The concept behind a warp drive engine would basically create a “warp bubble” in front of a ship to bend space time. One approach to such a system is the so called Alcubierre drive. It is an idea based on a solution of Einstein’s field equations in general relativity. It was created by theoretical physicist Miguel Alcubierre. In his theory a spacecraft could achieve faster than light travel, if a configurable energy-density field lower than that of vacuum (negative mass) could be created. Rather than exceeding the speed of light, a spaceship would move by contracting space in front of it and expanding space behind it, which should allow it to travel with faster than light speeds. Objects can’t accelerate to the speed of light within the normal space time, so instead the Alcubierre drive shifts space around an object so that the object would travel faster than light would in normal space, without breaking the laws of physics.
Although the metric proposed by Alcubierre is consistent with the Einstein field equations, construction of such a drive is not really possible with our current understanding. The system of the Alcubierre drive requires a negative energy density and therefore it needs exotic matter or manipulation of dark energy. If exotic matter with the correct properties does not exist, then also the drive can’t be constructed. In his original article Alcubierre argued that the “Casimir vacuum” between parallel plates could fulfill the negative-energy requirement for the Alcubierre drive.
In this new effort to develop a working warp drive, the researchers have taken previous ideas based on warping space-time a step further. Bobrick and Martire created a model which they believe could be feasible in the future. Based on the Alcubierre warp drive idea, both scientists suggest that instead a massive gravitational force could be used to bend space time. The trick to accomplish this is to find a way to compress a planet-sized mass to a much smaller spaceship size to use its gravity. These problems still make it impossible to construct a working warp drive today, however the model is not impossible and suggest that someday in the future it might be possible to create a working drive.
“Many people in the field of science are aware of the Alcubierre Drive and believe that warp drives are unphysical because of the need for negative energy,” says Alexey Bobrick. “This, however, is no longer correct; we went in a different direction than NASA and others and our research has shown there are actually several other classes of warp drives in general relativity. In particular, we have formulated new classes of warp drive solutions that do not require negative energy and, thus, become physical.”
“While we still can’t break the speed of light, we don’t need to in order to become an interstellar species,” says Gianni Martire, “Our warp drive research has the potential to unite us all.”