Warp drives, commonly used in science fiction, are propulsion systems which allow spacecraft to travel faster than light.

The most notable usage of a warp drive is in the iconic science fiction show “Star Trek”. In the Star Trek universe, they’re used as a plot tool which allows the characters to explore galaxy.

Ships equipped with these ‘space engines’ can ferry people around the galaxy, deliver cargo between stars, or can even be used as devastating tools of war. Interest in the subject caused one reader to ask, “What is a warp drive and how do they work”?

Could a Star Trek warp drive ever cross the boundary from science fiction into science fact?

What Are Warp Drives?

Most versions of the warp drive use a loophole in general relativity to circumvent the universe’s ultimate speed limit – the speed of light.

As you (or anything else with mass) accelerate towards the speed of light, more and more energy is required to accelerate faster. Because of this exponential increase in the energy requirements, to accelerate just a single electron to the speed of light would require more energy/matter than exists in the entire universe. That’s why it’s called the ultimate speed limit.

A warp drive gets around the problem by not accelerating at all, and instead, manipulates the region of spacetime around the craft. You cannot accelerate anything with mass to the speed of light, but spacetime itself has no mass, and is not bound by this ultimate speed limit under general relativity. In fact, we believe that spacetime has already been ‘warped’ faster than light once before – during the resulting ‘cosmic inflation’ that took place just moments after the big bang.

How Does A Warp Drive Work?

The way a warp drive operates is relatively easy to visualize. It simply compresses the spacetime in front of the ship, and expands the spacetime behind it – like a surfer riding a wave of water.

This compression and expansion creates a ‘wave’ of spacetime that a ship could ride on. Since the ship isn’t moving at all, and is instead surfing this “spacetime wave” (which is now moving much faster than the speed of light), general relativity remains intact and time dilation is non-existent.





Problems With Warp Drives

How it manipulates spacetime to create the wave is where major problems arise. The first versions of the warp drive (Alcubierre’s warp drive) call for theoretical exotic matter and ‘negative energy’ which may or may not exist, and requires a spacecraft to harness the matter/energy equivalent of something the size of Jupiter.

Current Status Of Warp Drives

With the recent advances in theoretical physics and string theory, researchers (Dr. Gerald Cleaver & Dr. Richard Obousy) have calculated how a warp drive could work under M-theory – and it brings some good news. While still far beyond our level of technology, a FTL warp drive becomes a bit more plausible as the requirements become much more manageable by focusing on the physics of quantum field theory, instead of general relativity.

They worked out that under string theory, a warp drive would no longer require exotic matter, and the required energy would be roughly 100kg of antimatter (1019J) to warp the space around a ship the size of the space shuttle. Their version of the warp drive manipulates spacetime by shrinking and expanding the tiny, curled up, subatomic spacial dimensions that theoretically exist in string theory. Their version creates the exact same spacetime wave described above.

Warp Speed Limit

Interestingly enough, there is a limit to how much spacetime can be warped under M-theory. These physicists found that the ultimate warp speed limit (for an Alcubierre warp drive) is 1032C – or roughly 3.3 trillion trillion light years per second. Reaching this speed would require an incomprehensible 1031J of energy. However, if you could travel at that speed, you would be able to reach the edge of the visible universe (14 billion light years) in 4.4 femtoseconds flat.

Visualization of the Warp Drive

References:

Richard Obousy, Gerald Cleaver (2008). “Warp Drive: A New Approach”. arXiv:0712.1649

Alcubierre, Miguel (1994). “The warp drive: hyper-fast travel within general relativity”. L73–L77. arXiv:gr-qc/0009013

Broeck, Chris Van Den (1999). “A ‘warp drive’ with more reasonable total energy requirements”. arXiv:gr-qc/9905084

“Ideas Based On What We’d Like To Achieve“. NASA