If you want a science fiction email with a galaxy, you’ll need faster than light travel. The alternative takes decades or centuries to reach a strange star system, which is not nearly as much fun. So you start with a wild scientific idea, add some technology and poof! Quam Celerrime ad Astra. Everything from wormholes to space is used in sci-fi, but perhaps the most famous is FTL tropical warp drive.
Warp drive has been used in sci-fi since the 1930s, but it was made popular by the 1960s television program Star Trek. Although based on the theory of general relativity, where space and time can be distorted by gravity, the TV series did not provide details. Warp coils, mumble mumble, dilithium crystals. Note the fact that relativity clearly states that objects cannot move faster than light. Without warp, Captain Kirk would never have been able to enchant beautiful strangers.
The idea was interesting enough that some scientists are trying to develop a theory on how it can work. Physicist and science fiction author Robert Forward, for example, suggested several ideas. But things really started when Miguel Alcubierre wrote an article in Classical and quantum gravity it can be called warp drive.
The paper demonstrated how the general relativity of space could be distorted in a way that made FTL travel possible. Theoretically, a ship could never travel by space faster than light, but you can form a skewed bubble space around the ship, which can reach distant stars in almost no time. The idea became known as the Alcubierre ride.
There was only one problem. Although the Alcubierre ride was possible within general relativity, it only worked if you could get an exotic material with a negative mass in the hands of a planet. All matters have a positive mass, so it’s a deal. Even Alcubierre said the idea is unlikely to work in real life.
New research solves some of these problems, but introduces others. Work by Alcubierre and Lobo mostly concentrates on the shear effect of the weak field. They find that small shear effects are similar to an unresponsive drive, as suggested with the EM Drive. They also found that although the propulsion still requires negative mass energy, this can be hypothetically done with a ship with a positive finite mass.
Another recent paper by Erik Lentz follows a different approach. He notes that there are certain warp configurations that look like solitons. Solitons are a wave effect that is self-reinforcing. Solitons can retain their shape while moving at a constant velocity and have been observed in water and other liquids. Lentz showed that while soliton warp bubbles require an incredible amount of dense material, they do not need the energy of the case to be negative.
Both of these ideas also have one other problem. By creating a relativistic bubble around the ship, they effectively isolate the ship from the outside world. This is known as the horizon problem and it means that the ship bubble cannot be controlled from within the ship. The voyage of the ship must be controlled from the outside. Jean Luc Picard may be ship captain, but he can not just ‘make it so’.
Of course, warp is still hypothetical. There are profound theoretical challenges, to say nothing of engineering. But maybe we’ll work it all out in the 23rd century, and we can finally turn to the stars quickly.
Reference: Alcubierre, Miguel. “The warp drive: moving fast within general relativity.” Classical and quantum gravity 11.5 (1994): L73.
Reference: Alcubierre, Miguel and Francisco SN Lobo. “Warp Drive Basics.” Wormholes, chain drives and energy conditions. Springer, Cham, 2017. 257-279.
Reference: Lentz, Erik. “Break the warp: hyper-fast solitons in Einstein-Maxwell plasma theory.” Classical and quantum gravity (2021).