I just realized that the speed of light, c, is not only the speed of light but also the speed of everything in the universe. In fact, it is the only speed in the universe: all matter and energy is always moving through spacetime at this exact speed, without exception.
This may seem preposterous since we obviously move at different speeds just by sitting, walking, or running. But those are all changes of our velocity through space, and the catch is that they are always counterbalanced by changes of our velocity through time. The net result of which is that our velocity through spacetime — our universe’s three spatial dimensions plus one time dimension — always remains the same at c.
This is a direct consequence of special relativity. Everyone is probably familiar with the fact that the rate at which time passes for a mass slows down as it approaches the speed of light. The exact relation is given by the Lorentz factor, where v is the speed of the matter and c is the speed of light:
I was taught to derive this from the second postulate of special relativity using a contrived experiment of measuring the speed of light on a moving platform, such as a train. But if you rather postulate that “all matter moves through spacetime at speed c,” then the Lorentz factor falls out as a simple application of the Pythagorean Theorem:
Here something with no speed in space (x=0) has time speed c, whereas something moving with non-zero space speed has time speed t. How elongated this time is compared to c is just the ratio c/t, which gives us back the Lorentz factor:
This conveys to me three important points about the universe. Firstly (and a little flippantly), this feels like pretty convincing evidence that the universe is, in fact, a simulation. I mean, it’s such an obvious hack that the programmers made to dumb things down. It’s like they were writing Flying Toasters and one of them wanted to give the toasters some real physics—make them bounce and accelerate and stuff. But the tech lead said, “Jeez, stop overengineering everything — all we’re doing is making a screensaver here. Just have all the toasters fly at a fixed speed and leave it at that.”
Now, this isn’t to diminish how complex our universe, as there is still a lot of physics going on in it. In fact, relativity made our universe much more complicated than it was originally thought. But the key thing is that this complexity arose out of simplifying assumptions, because special relativity’s two postulates are “physics is the same for everyone” and “the speed of light is the same for everyone.” These two statements would definitely make the universe much easier to program even if they ultimately gave rise to more complex emergent behavior. For an analogy, consider the Atari game Asteroids, which is played in a wraparound universe. Wraparound is actually a simple programming trick used to deal with limited memory, but it changes the universe from an infinite flat one into a curved Euclidean 2-torus. It’s a concrete case where writing simpler code actually makes the universe more complex.
But, speaking of screensavers, cosmology does provide other interesting hints that, if our universe is a simulation, then it probably is on the level of a screensaver. Let’s say for a moment that the universe didn’t spring out of inherently unstable nothingness but that it was rather created by something for the mundane purpose of watching what would happen. In that case, the Big Bang was probably the whole show. In fact only the first second was in any way exciting because that’s when the fundamental forces were differentiating and space was expanding by handful of 10¹⁰s. And then maybe whoever was watching hung around to watch nucleosynthesis for the next twenty minutes and enjoy it like an afterglow. But after that the universe didn’t undergo another phase change for 300,000 years, and arguably nothing else has ever happened since. So if these beings were interested in the universe when it was a quadrillion-Kelvin quark–gluon plasma, but lost interest once it cooled to just a billion-Kelvin gas plasma, then they probably wouldn’t even notice it as the 3-Kelvin mostly empty space that it is today.
Also consider that 90–95% of all stars that will ever exist have already been created. Consider that one day our universe will be dominated by dark energy driving an ever-accelerating expansion, shrinking what is observable until the last stars each become their own isolated orrery–universes. Consider that all the information in our 3D universe can actually be encoded on its 2D boundary, meaning the bigger the universe is technically the less information it contains. (… Actually that last one is making more and more sense every year.)
So yes, there is enticing evidence that we live in a screensaver universe. After all the real work has been done and the operator has stepped away from the keyboard, we are the flying toasters that keep the screen just active enough to prevent cosmological phosphor burn-in.
But the two other important points this conveys to me are a little more real. Second, consider that, no matter how fast or how slow you go, as far as the universe is concerned you’re always moving the exact same speed; the only difference is where you’re heading. So your perspective is important. Don’t beat yourself up if you think you’re not getting where you or what you want fast enough—the universe doesn’t even notice. All that matters is that you’re on the right path and have the right demeanor.
And third, this does tell us that the universe wants us to move. Light moves through space entirely at speed c, so it never experiences time. We are cursed that we actually do experience time, but in a way that the universe has given us a trade-off. The more active we are and the more we move in space, the more time the universe will give us to do it. Someone who sits still their entire life will burn through their time the fastest, whereas someone who moves around is given more time to do whatever it is they’re doing. Now, the actual scale of this difference for us on Earth is sadly negligible. You can sprint for your entire life and the Lorentz factor will only give you one extra microsecond versus the person who was lying on a couch the whole time. Even an astronaut who spends a lifetime up in orbit only nets themselves another second. But that moment is real and it is time. And that’s the one thing that we’re never given any more of. Use it wisely.