Key Vocabulary: spacetime, speed, kinetic energy, joules, mass, wormhole, parsec, lightyear, galaxy, star system, dimension, time dilation
This weekend, Solo: A Star Wars Story premieres in theaters across the world. The movie tells the origins of famous smuggler, Han Solo, how met his best friend Chewbacca, and of course got his hands on the fastest hunk of junk in the galaxy, the Millennium Falcon. It’s no secret I’m a Star Wars fan. As a kid, I idolized Han Solo, jumping into the driver seat of my parent’s minivan as it was parked in the driveway and pretending I was flying through a galaxy far, far away.
But how would traveling across the stars actually work? In Star Wars, ships cruise through hyperspace, traveling across an entire galaxy in seemingly a few hours. Is traveling faster than light even possible? Can humans one day hop from star system to star system? And if we could, how would this look like?
To be clear, this is not an attempt to assess the scientific accuracy of Star Wars is (hint: it’s not). Rather, think of this as a fun exercise in learning about the weird and too often unrevealed aspects of our Universe.
I’ve got a bad feeling about this: Constraints in hyperspace
Before we can figure out how we could one day zoom around the Universe like Han and Chewie, we need to define what we definitely cannot do within the boundaries of what is physically possible. Not to be a Luke Buzzkiller, but based on our current understanding of physics, traveling faster than the speed of light would be challenging to say the least.
Our first problem is the amount of energy it would take to get our ship to light speed. Light travels at about 3.0 x10^8 m/sec. To give you an idea of how fast that is, it takes about 8.3 minutes for a particle of light to travel the 150 million km from the Sun to the Earth. The amount of energy required to move anything with more mass than a subatomic particle at the speed of light would be astronomical.
Exactly how much energy are we talking about? We can calculate this pretty easily by using the kinetic energy equation (KE=1/2mv² ). Since we already know our velocity (speed of light), all we would need is the mass. According to Wookiepedia, the cargo capacity of the Millennium Falcon is 100 metric tons or 100,000 kg. However, there is no reference to the mass of the ship itself. Let’s estimate that the ship is at least the mass of the cargo. When we plug the mass (100,000 kg) with the speed of light (3.0×10^8 m/sec), we get 4.5×10²¹ Joules, about an order of magnitude greater than the entire world’s annual energy output. An entire planet of nearly 8 billion people uses a tenth of the energy in one year than it would take to get the Millennium Falcon to light speed. So while not technically impossible, it would take technology well beyond our current abilities.
There’s another problem with traveling at the speed of light, this one coming from Albert Einstein and his theory of special relativity. To explain this, imagine two sports cars competing in a 10 km race. They both have a top speed of 100 km/hr, so they should both finish the race in the same amount of time, 6 minutes. However, if the second car travels at a slight angle towards the finish line, it will take slightly longer to complete the race. The first car wins because it is taking a straight path from the start to finish. The second car moving at an angle must travel both forward towards the finish line and side to side. To put it another way, the second card is using part of the 100 km/hr to go to the side, leaving less to move directly towards the finish line.
Einstein theorized that moving through space and time works the same way, that they were just different dimensions of the same continuum. We can move through space in 3 different dimensions; back and forth, right to left, and up and down. But we are also moving through the 4th dimension of time. And just like our race cars, the more speed we dedicate to moving through one dimension, the less we can move through the others.
Instead of thinking that speed of light is 3.0×10^8 m/s, think of it as the top speed of going through all dimensions in the Universe. The faster we move through space, the slower move through time. This isn’t typically a problem in our everyday lives; any speed you have ever traveled at is minuscule compared to the speed of light. But as you approach lightspeed, you would start experiencing time at a different rate than someone who is motionless.
This would have some real consequences for those traveling across the galaxy. Those moving closer to the lightspeed would dedicate more of their speed to travel through space instead of time. As a result, they would experience time at a different rate than some who was relatively motionless, a phenomenon called time dilation. Say you were to travel at the speed of light to get to Alpha Centauri, the closest star system to Earth about 4.3 light-years or 4.07×10¹³ km away. In the time that it would take you to make a round trip, you would experience 8.6 years pass as if everything was normal, but nearly 200 years would have passed on Earth, turning most of your friends and family into force ghosts.
It’s a complex problem to wrap one’s head around and almost seems too bizarre to be true. But amazingly enough, scientists have been able to verify Einstein’s predictions. Researchers at GSI Helmholtz Centre in Germany made a moving clock by accelerating lithium ions to one-third the speed of light. They measured the activity of electrons, which occur at a consistent rate and served as the “ticking” of the clock. They compared that to the “ticking” of lithium ions that were not moving and, just as Albert Einstein predicted more than 100 years earlier, the moving clock measured time at a slower rate.
Never tell me the odds! How we could, maybe, possibly, travel faster than light
Does this mean we are relegated to linger in our dim little corner of the Universe, only traveling to distant worlds in the movies and our imaginations? While physics certainly puts constraints on how fast we can go, there is potential for getting around on a galactic scale and a clue lies in one of the first lines we ever hear from Han Solo.
When Obi-Wan Kenobi and Luke Skywalker first meet Han and Chewie in the cantina on Tatooine, Han almost immediately brags about the speed of his ship, saying that the Millennium Falcon was able to make the Kessel Run in less than 12 parsecs. At first glance, this doesn’t make any sense; a parsec is a unit of distance roughly equal to 3.26 light-years or 3.08×10¹³ km, not a unit of time. Han was probably trying to pull a fast one on who he assumes to be a backwoods farm boy and a washed up old man by throwing out some impressive sounding jargon. But his braggadocio may shed give some insight on how faster than light travel would be possible.
To illustrate this point, take a piece of paper and write point A on the top. Then on the bottom, write point B, which should make both points around 15-20 cm away from each other. However, if you fold your paper in half, point A and point B become much closer to one another.
As we mentioned previously, Albert Einstein theorized that space and time were part of the same continuum, a fabric in which all objects in the Universe interact, with planets, light, and spaceships all moving through it. However, if you could create tunnel between two points on the space-time continuum, your trip across the galaxy could be much, much, shorter. These Einstein-Rosen bridges, or wormholes, are shortcuts that could at least theoretically allow us to cover great distances.
Take, for example, the Kessel Run, a hyperspace route used by scoundrels like as Captain Solo for smuggling contraband. If the Millennium Falcon were to make the trip in less than 12 parsecs, about 40 lightyears, it would cut hundreds if not thousands of lightyears off the journey between star systems. Indeed, researchers at the Autonomous University of Barcelona in Spain created a small wormhole in the lab, transmitting a magnetic field across two points in space. The ability to transport people through a wormhole is still a long way off, however, the idea is at least theoretically possible.
A bunch of mumbo-jumbo?
Speculating how the Millennium Falcon could trek through the stars is a fun exercise how faster than light travel could be possible. But even if Han were to take a wormhole through space-time, the journey would still be extremely long. The Milky Way is 100 million lightyears across; the light that reaches us from the other side of the galaxy was propagated when dinosaurs ruled the Earth. Even if you could take a shortcut, the trip would likely still be far beyond what humans could make in a single lifetime. The distances are just too vast and we have yet to make it past the Moon, a mere 400,000 km from Earth. Such technology, is centuries, if not millennia, away. Until that time, we are more or less stuck in our solar system
But as luck would have it, our solar system is an amazing place. There are at 6 least planets or moons that are at least potentially capable of supporting life. NASA is launching a mission to explore Jupiter’s moon Europa around 2025. Scientists believe there may be a water ocean underneath the surface, with a least a chance of supporting life. Suffice it to say that there’s plenty to explore right here in our own backyard
While we can’t take Star Wars literally in a scientific sense, the movies have inspired a host of innovations. From speeders to droids, even holograms and tractor beams, researchers are astonishingly close to developing technologies that mirror the films. Scientists have also speculated that space-time could be stretched, shrinking the immense distances to something more manageable to cross in a human lifetime.
Just remember that when you see a Star Wars movie, its purpose is not to be scientifically accurate. Its purpose is to be awesome. The familiar backdrop for learning about our mysterious and amazing Universe Stars Wars provides is simply an added bonus.
- What would it be like to fly in a real X-wing? We broke down the physics of piloting a starfighter in two parts. Read part 1 here and part 2 here.
- Researchers detecting gravitational waves, or ripples in the space-time continuum. Read our interview with Dr. Andy Bohn, an astrophysicist who worked on the project.