A fundamental part of science fiction is the ability to traverse worlds in the blink of an eye. From Star Wars to Star Trek, in order to tell sweeping sagas of the cosmos, some form of faster-than-light travel (or FTL) is employed. This literary device is often used because the reality of space is that it’s pretty huge. With current technologies available to us, the nearest star would take almost 81,000 years to get to! Not a very compelling story, if you ask me. One of the ways to circumnavigate this inconvenient path was popularized in the hit TV show Star Trek with their use of what they called the warp drive. By filtering antimatter through dilithium crystals (not real, unfortunately), Star Trek ships could generate a “warp bubble” around a ship. This warp bubble would allow a ship to to travel vast distances at FTL speeds. While this is fine science fiction mumbo-jumbo, how does this help me set foot on another world for real?
Luckily, most physicists are just about or even nerdier than the writers of science fiction. In a paper published in 1994 by theoretical physicist Miguel Alcubierre, he outlines a mathematical model that could bring warp drives into the realm of reality. So let’s dive into some math, shall we?
What is space?
Before we get into the nitty gritty, we need to talk about space. What is it exactly? Besides being literally everything, how do you quantify space in a meaningful way? A simple 2D graph can help with that.
Imagine you are a creature that lives in a world of only up and down, forwards and backwards. A simple way to explain to a friend where to meet for coffee would be to use an x,y coordinate system. Placing yourself at the center of the coordinate system you could say “I’ll meet you at (-4,-2) from my house”. Unfortunately we don’t live in a Flat Stanley world so let’s complicate things a bit more and add in side-to-side motion and an extra dimension to this graph.
Now your friend has to navigate a world of 3 dimensions x,y,z (forward/backwards,up/down,left/right). So when you ask to meet for coffee, you could say “Meet me at (3,2,4) from my house.” This is the world we live in and this system works pretty well to describe space.
A more complicated version of space: Spacetime
But then along comes Einstein and he decides that even this description of space was too boring and simple and thus General Relativity was born. He folded time as an added dimension into the model and created the concept of spacetime. Instead of you moving around in just 3D space, you are moving in space while also traveling in a forward direction through time. Complicated? Yes, but the annoying part of his description of spacetime was his cosmic speed limit: the speed of light. Under Relativity, nothing can travel faster than the speed of light. While the speed of light is pretty fast (186,000 mi/sec), this number is staggeringly slow compared to the size of even our galaxy. At the speed of light it would take over 100,000 years to cross! So that’s it, right? Einstein doomed us to stay within our solar system? Well, that’s where the math comes in.
Now Einstein figured out that space is not static, rather a dynamic fabric that can stretch and bend. This warping of space is actually what we call gravity. If we visit back to our 2D graph we can represent this warping like the top of the trampoline.
Using this model, we can redefine what gravity actually is. Under conventional physics, gravity is something big, like the Earth, pulling other objects towards it. However under Relativity, gravity is actually the curving of space towards the object in question, creating a sort of “well” that other things can fall into. This curvature is important because it’s going to allow us to circumnavigate that pesky cosmic speed limit.
The warp drive in real life
Miguel Alcubierre realised this warping of space could be useful in transporting a spacecraft at superluminal speeds. While no thing can travel faster than the speed of light, no such constraint exists for the warping of space, hence space can be crunched and stretched at any speed you wish. Let’s revisit the trampoline analogy again. If we took a section of spacetime and kept it flat, that is unaffected by gravity, and represent this with a plate. Here is where our starship will reside. Using the malleability of space, you would contract the trampoline in front of you while expanding the trampoline behind you, moving the space around you while your bubble of space remains stationary. So instead of you moving through the universe, you move the universe around you. Another way to look at this is to imagine traveling across a compressing spring.
Your spaceship resides within the center uncompressed space while the compression and expansion travels around you. So, while the expansion and compression is traveling around you at light speed, your spacecraft remains stationary thus avoiding the speed of light constraint.
Unfortunately, there are some huge caveats. While space can be bent like a trampoline, it is a pretty stubborn fabric to bend. While large things like the Earth can bend space, Alcubierre proposed exotic matter is needed to create this expansion and compression effect. Exotic matter is the umbrella term for all not understood or undiscovered states or forms of matter. In this case, the exotic matter needed is negative energy. Even if you could manage to find some, under Alcubierre’s model you would need a negative energy mass equivalent to the size of Jupiter. This was slightly mitigated in 2011 by advanced propulsion physicist, Harold “Sonny” White by slightly modifying the geometry of the warp bubble to oscillate. This would lower the energy requirements to something more reasonable like the mass of an American buffalo. Still a tremendous amount, considering no form of the matter has been discovered yet, but an amount that is within the realm of possibility.
Even with the reduced energy requirements there’s a slight issue of dirt. If you’ve ever driven during a snowstorm, snow can cause quite a problem for your windshield. Now imagine the snow hitting your car at several times the speed of light. While space may seem empty, it is actually full of microscopic grains of dust that float between the planets. A warp ship traveling through the cloud could potentially obliterate itself on a rock the size of a pinhead. And dust it doesn’t directly run into could be picked up by the warp field and brought along for the ride like the wake behind a boat. This is fine while you’re traveling, but where does this wake go when you stop? Well, the current fear is that the dust you have collected will be hurled in front of you, obliterating the planet you have arrived at.
This all sounds discouraging, but NASA is nevertheless undeterred. Dr. White, at NASA’s Eaglehead laboratories is currently working on advanced deep space propulsion tech, one of those being testing the viability of Alcubierre’s warp drive. In the meantime, I’ll have to be content with my model rockets.
What is more possible
While we may have to wait awhile to hear the phrase “warp factor 5”, there are still cool spacecraft ideas being developed today. For the more nerdier inclined, I have linked several cool concepts that we may live to see come to fruition.