Technically speaking nothing is faster than light. That’s it, the story’s over, time to go home. Except that is the very simple, very basic answer to the question “is anything faster than light?” A more complicated answer is that nothing is faster than light except for when we can come up with circumstances in which something technically is faster than light.
Science is a funny thing. It works best when you keep picking at it like a scab. And good science is always open to the possibility that it’s dead wrong, or that there are things we don’t understand, or that maybe there’s a loophole here and there that gets you around something that seems otherwise settled. Science shouldn’t hold grudges nor should it stick to anything as though it were written in stone.
So, to answer the question, maybe or maybe not. Let’s get a little deeper.
The Speed of Light
Light travels at 186,282 miles per second. That’s fast. A human once reached 24,816.1 miles per hour. That was in the Apollo 10 module in orbit. You can’t really hit that speed so well on Earth, nor should you want to.
You can thank Albert Einstein for putting a speed limit on the whole universe when he calculated that light was as fast as anything could or would ever go. If you haven’t read up on the science, the basic idea here is that only massless particles, like photons of light, can reach that speed in a vacuum. Nothing else could ever hope to reach that speed because of the energy it would take to do such a thing.
More mass requires more energy to achieve more speed. Accelerating a spaceship, for instance, to the speed of light would require an infinite amount of energy and infinite energy is not something that you can do. Not with science as we understand it right now, anyway. We’ll look into this a bit deeper in a moment.
Light can travel as fast as it does because it is a massless particle. The moment something has mass it necessarily must go slower because it has inertia working against it.
Why Can’t Things Be Faster Than Light?
So we briefly touched on why you can’t hop in a SpaceX rocket and travel across the galaxy at the speed of light. You need infinite energy to do such a thing. But also, you need to remember that the mass of matter increases the closer it gets to the speed of light. That means, at the speed of light, you would also have infinite mass. That’s why you need infinite energy to move it.
In physics, mass measures an object’s inertia. Inertia is the tendency of objects to resist changes in their state of motion. Or, as you may have heard, an object in motion tends to stay in motion, an object at rest tends to stay at rest. Force of some kind needs to act on them to change that state.
The mass that an object has as you increase its speed is inertial mass. That’s the energy that exists in any object that resists its change in motion. As you increase the speed of an object, that inertial mass increases to resist it. By the time you hit the speed of light, if you could theoretically do such a thing, you would have infinite inertial mass resisting you which would require infinite energy to keep pushing it forward.
Additionally, as an object increases in speed, general relativity also predicts that time slows down. The closer you get to the speed of light, the slower time goes. You’d never be able to reach the actual speed of light as a result.
Things That Seem Faster Than Light
Part of Einstein’s theory of general relativity that is significant to understanding whether something can travel faster than light is how he defined the limits of faster-than-light movement. When Einstein says nothing can travel faster than light, he uses the qualifier “in a vacuum.” That’s a condition that can be changed.
A simple example of this is something most of us have seen before – light traveling through water. Light isn’t just a particle, it’s a wave. Water and prisms can break up the wave function of light, you see that any time a rainbow appears. White light is broken into the color spectrum. Light itself ranges from infrared to ultraviolet and these frequencies travel at different speeds.
In effect, outside of a vacuum, this means that light travels faster than light. None of them go faster than light speed, however.
Another more cosmic example of something seemingly traveling faster than light is gamma-ray jet bursts. These are the brightest explosions in the galaxy and they happen when stars collapse or collide. Jets of particles are released and travel faster than light itself but still not in defiance of Einstein’s rules. That’s because the jets exist in these interstellar dust clouds, not a vacuum. In this medium, the gamma jets look like they’re traveling back in time because of their speed.
The fact that the size of the observable universe is 94 billion light years and the furthest object we can see is 47 billion light years away seems problematic if the universe is 13.8 billion years old. How did anything get that far away if nothing goes faster than light? This is where the “relativity” part of general and special relativity comes from.
Anything faster than light needs to have speed, that’s sort of the point. But the expansion of the universe did not happen at speed. This concept is a doozy so bear with us.
The universe, relative to you and a telescope, looks like it’s expanding rapidly outwards. You can pick a distant star and calculate the speed of its movement. But, again, relative to you. Space as a whole never expanded relative to anything so you can’t measure its speed. What happened, after the Big Bang, was that space between particles expanded.
So the fact that things are further away than we could ever reach even at light speed doesn’t mean they’re traveling at light speed. Technically, they don’t need to be moving at all. It’s space itself that is expanding, and continues to expand, giving the impression that things have moved faster than light speed across the universe.
Quantum Entanglement
Quantum entanglement directly contradicts Einstein’s theory of relativity and the idea that nothing can travel faster than light. According to quantum entanglement, two subatomic particles can be separated by light years but are still connected fundamentally. What happens to one particle will simultaneously happen to the other particle despite the great distance between them. That means something should be traveling faster than light to link them together, or so it would seem.
What does link entanglement particles, in this case photons, is a kind of randomness. The measurable states of these photons are unknown until one is measured but the moment that one is measured, it defines the state of its entangled partner as well. This is true no matter where the particles are in relation to each other. Only in measuring one can you determine the results of the other and it is always the same. Entanglement connects them, always, no matter the distance.
As it relates to light speed, entanglement is not actually breaking the rules. There is no communication between the particles and this has been proven in many experiments. Bizarre though it is, quantum entanglement is not faster than light communication or travel.
Wormholes as a Theoretical Shortcut
If we consider speed as a tool to help us cross a distance from A to B then a shortcut qualifies as a faster method of doing so. If you have to travel 100 miles away and you’re driving at 100 miles an hour, it’s going to take you one hour to get there. But if there’s a shortcut that takes 30 minutes off your time, did you travel 200 miles per hour to get there? Not necessarily. That’s kind of how a wormhole works. You could get somewhere technically faster than the speed of light without actually traveling faster than the speed of light.
Right now there’s some debate about whether a wormhole could ever be used for interstellar travel, and that’s fine. But is the concept sound? We have never seen a wormhole in space but the science behind them stands up. Even Einstein’s work allowed for wormholes so, at least theoretically, they could exist. They function as passages that burrow right through space-time itself.
Something with a large enough mass in space creates a curvature in space-time. A black hole is the most famous example of this. It can pull in light, and time itself dilates around it. Like a body resting in a hammock, with the hammock being space-time itself, the body pulls things down around it. They can’t escape.
Theoretically, something like a black hole could connect to another one somewhere else in space. That could be a wormhole, or an Einstein-Rosen Bridge as they’re also called. The distance between the two could be millions of light years.
There are different theories about how wormholes could form and their properties but it’s all just theory for now. In fact, we don’t even know how one could be created. It’s only the math that allows for their existence.
Could a wormhole allow for travel across the universe in a brief time? Maybe. Maybe not. It’s like asking if you’re going to like the dinner you have 1,000 days from now. You know dinner could exist, but you have no idea if you’ll like it or even what it is right now.
Alcubierre Drive
Science fiction loves faster-than-light travel and we suspend our disbelief to go with it. A starship has a warp drive or something and that’s fine, that’ll work. What do we have in reality? We have the Alcubierre Drive. Well, not in reality, but we’ve theorized it.
Physicist Miguel Alcubierre proposed his idea as a way of stretching space-time to allow faster-than-light travel. Treat space like a wave and stretch it to allow the space in front of an object to contract while the space behind expands. You, in your spaceship, ride a warp bubble across flat space. It circumvents the issue of all that inertial mass by keeping it locked in the bubble and, therefore, relative and local. Nothing in the bubble is moving faster than light.
The major downsides of this theory include the fact that no one knows how to make it happen in reality, nor do we have any idea how you would get out of the bubble once you got into it. You’d also need something called negative energy, again a theoretical concept, to make it work. You can see how that would be a problem.
Krasnikov Tubes
A Krasnikov tube is the solution to Alcubierre’s warp bubble issue. Krasnikov observed that, in Alcubierre’s bubble, you have no control. He proposed a new idea. Create a warp behind your spaceship that pushes you to your destination and then, when you’re ready to come back, use the “tube” it created to go back.
Thanks to time dilation, this sort of trip would usually result in the astronaut returning hundreds or thousands of years later. But in a Krasnikov tube, the tube created in your first flight unwinds time. You could return after a time relative to your own flight, not the time passed on Earth. So traveling to another galaxy, which might be a 3,000-year journey from Earth’s perspective, would only take you three years.
There is some obviously complex math involved, but the theory is that you open up a path through two spacetime dimensions, something like a wormhole, that exists in flat space but only on the path back to where you started from. It’s not a path through time and space, just time itself. You still need to travel across space.
The concept has its flaws also, especially when the idea of two of them being used comes into light and potentially one spaceship takes the wrong tube and goes three thousand years into the past. But there’s also the issue of even building such a thing, so maybe that’s not the biggest worry yet.
Is Anything Faster Than Light?
There are still several other theories about things that could potentially go faster than light, like quantum tunneling. Like what we’ve already covered, all of this can only exist on paper. Any practical application of this is potentially years off if it would ever be viable at all.
In the realm of theory, as we’ve seen, some things may be able to bend the rules. Other things don’t bend the rules, it’s just a matter of perception and understanding how general relativity works. Even a rainbow is going faster than light technically, at least in part, sometimes.