An old car and its tire, photo by Will Langenberg via unsplash.com

The Wheelies Theory

A simple, unscientific theory about dark energy, the expansion of the universe, and accepting what we will never understand

I had a dream about dark energy the other night. I’m not sure why. I also had a dream about owning an ice cream shop. But that’s another story.

Anyway, dark energy is basically a mystery to us. We know that it helps explain why the universe is expanding instead of collapsing in on itself. That’s about it.

So I’d like to share a little metaphor that my dreaming mind cooked up that helped me accept the fact that we may never truly understand dark energy.

Imagine there is a civilization of tiny beings living inside of the front-right wheel of a car (which is exactly what my dream was about). Let’s call them Wheelies. The Wheelies have lived there for their entire existence, about 15,000 generations (twice as many generations as there have been of humans, allowing them to advance far beyond our relative stage).

Photo by Mason Jones via unsplash.com

Generation after generation, the Wheelies have discovered much about their universe. It revolves in a predictable way. It is round. It has an outer edge made of a rubber-like substance. It gets hot when it’s moving. The air pressure in their universe has been 28 pounds per square inch for thousands of generations, though science has proven that at one time it was only 14.7. And there is something outside of it that causes it to rotate.

But the Wheely scientists have a problem, and it has to do with that whole ‘something outside of it that causes it to rotate’ thing. They know it must be there, because nothing inside their universe can explain the energy needed to make it rotate. But they can’t really see it or experiment on it, as it’s (by definition) outside of their observable universe. All they can do is come up with theories about what it might be based on their experience.

Now we know, of course, that a wheel’s rotation in a car is caused by the axle connected to that wheel, which rotates because it is connected to the drivetrain, which is powered by the car’s engine, which starts to work because the driver turned the key in the ignition and pressed the gas, which she did because she needed to get to an important meeting across town.

Thinking about that chain of events which ultimately led to the Wheelies’ universe rotating, how could we ever expect them to use science to trace it back to the driver? They never could. Maybe they could figure out something about the axle. But no matter how smart they are or how much math they use, they’ll never be able to trace the source of the rotation back to the driver pressing her foot on the gas. It’s too far removed and they couldn’t possibly arrive at it using reasoning alone.

Maybe a Wheely who is a creative, science-fiction writer could dream up the engine and the driver behind it. Maybe all the Wheelies love that novel. Or maybe it’s their primary religious text, explaining where they came from and why their universe is the way it is, relying on faith instead of science because the science simply cannot reach those conclusions. Maybe that book is exactly correct. Maybe it’s way off.

Let’s give them some credit, though. Let’s say they advance to the point where they understand every facet of their universe (which is really just the inside of a car tire), including the fact that it rotates because it is connected to an axle. And let’s say they determine that the axle is rotating because of a theoretical engine-like thing (something has to make the axle rotate, right Aquinas?).

Engine and drivetrain via phoenixautoshop.com

Could you imagine a scenario in which even the most brilliant Wheely could theorize the four-stroke process in the engine? It seems like the furthest that the Wheelies could possibly hope to theorize would be that there is an engine-like thing, but as to how that engine works…there’s just no way they could figure that out.

Perhaps our “dark energy” is similar to the energy that the Wheelies discovered — the energy that comes from the rotating axle. We know what effect it has on our universe. We know when it started causing those effects, and we can predict what it will cause if it continues to do the same thing. But what if we are simply Wheelies, observing the effect of a process caused by something outside of our observable universe that we could never hope to fully understand?

After all, if the driver slammed the gas pedal for a long drive, that generation of Wheelies might definitively determine that their universe would be destroyed in a just a few thousand generations (tires do wear and tear and eventually pop, after all). However, as she takes her foot off the accelerator and the rotation of the wheel slows, they could also definitively disprove their earlier theory and prove that their universe will last for many millennia. Both theories were right, but they will never know why.

Our science and the Wheelies’ science have the same limitation: we can only figure out what is possible for us to figure out. Maybe dark energy comes from the axle that touches our universe, an axle that is but one moving piece in a larger system that exists outside of everything we’ll ever observe. No matter how much we learn about our universe, the stuff outside its boundaries may always elude all but our most imaginative minds.

But we shouldn’t be frustrated by the idea that we may never know the cause of dark energy. In that regard we can learn from the Wheelies: whenever they encounter a problem like this, they just roll with it.

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