About 60 years ago, the original Star Trek series featured a technology called a “warp drive,” which allowed space travel at speeds much faster than light. Theoretical physicist and philosopher Albert Einstein, through his theory of special relativity, established that no object with mass can be accelerated to the speed of light, which is 3108 meters per second, often called the “cosmic speed limit.” At first glance, this might immediately seem to make real-life warp drives impossible because of their ability to release a spaceship at an extraordinary speed. However, the enormous energy required to make a warp drive is the real problem, not the speed of the spaceship you are traveling in. Even so, some physicists say creating real warp drive technology is not outside the realm of possibility.
In science fiction, a warp drive is a propulsion system that creates a bubble of spacetime around a spaceship. That bubble is then accelerated to move faster than the speed of light, with the spaceship remaining stationary relative to its local space within the bubble. Spacetime, the fundamental concept that fuses time and the three dimensions we are familiar with (length, width, and height) into a four-dimensional continuum, can bend or warp at any speed. Thus, the cosmic speed limit is not an obstacle in bringing the warp drive to the real world.
“If you wrap your ship in the fabric of spacetime and then that fabric goes faster than light, carrying you with it, that’s actually not breaking any laws of physics,” said Erin MacDonald, Star Trek science advisor and astrophysicist.
Physicist Miguel Alcubierre was the first to consider a serious scientific look at how these devices might work in a seminal 1994 paper on warp drive titled “The warp drive: hyper-fast travel within general relativity.” He devised a mathematical model that would contract spacetime in front of a ship and expand it behind the ship. While the “Alcubierre drive” could move a bubble of spacetime at any speed, he found that generating a bubble even as small as a few meters in diameter would require an amount of energy comparable to the mass of the sun, which is impractical with current technology. Furthermore, Alcubierre’s calculations required the existence of an exotic form of “negative energy” to make the drive compatible with Einstein’s theory of relativity. Unfortunately, negative energy appears to be a purely mathematical concept and “not something that seems to exist” in our universe, said Sabine Hossenfelder, physicist and science communicator.
In 2021, Alexey Bobrick, astrophysicist and pioneering warp drive researcher at Applied Physics, and Gianni Martire, co-founder of Applied Physics, published a paper in the journal Classical and Quantum Gravity titled “Introducing Physical Warp Drives.” In it, they describe the general geometry of a warp bubble with an inner passenger area where spacetime is flat, surrounded by a curved, outer wall that exerts a gravitational field. This stood in contrast to Alcubierre’s warp bubble, which does not gravitationally tug on objects outside of it — part of what Bobrick says makes it unphysical.
Their model does not require negative energy; however, it would still take several Jupiter-sized objects’ worth of energy to move a bubble several meters across, Bobrick said, “which is prohibitively too much.” Another problem is that their model’s warp bubble can only move slower than the speed of light. Nevertheless, physicists say it’s still an important step toward moving warp technology out of the realm of science fiction.
“Now we have a much better mathematical basis to study warp drives,” said Hossenfelder. “We know what the warped spacetime looks like.”
This leaves the window open to further research on warp drives. More theoretical work is needed to reduce warp drive’s energy needs. Practical challenges include generating and harnessing the immense energy requirements. Additionally, there should be a way to change the warp bubble’s speed to pick up and drop passengers riding the spaceship.
Though practical implementation remains far in the future, warp speed travel is now a lot more likely in a much shorter timespan than we previously thought.
