Gravity.

Stupid, idiotic gravity.

We know there is gravity. The evidence supports it.

There are excellent theories to explain how it works. There’s even a “law” – a direct mathematical expression of its power, developed by Isaac Newton and perfected by Albert Einstein who took the “E” in “E=mc²” and accounted for its effect on “m” in a large body like a star. All the tiny errors in Newton’s theory disappeared.

It just can’t be reconciled with any of the other three “major forces” – electromagnetic, strong nuclear and weak nuclear. They’re all much much stronger than gravity. Take a 1. Put 42 zeroes after it. That’s how much stronger the electromagnetic force is compared to the gravitational force. Here’s a practical example

This bridge won’t collapse into the river below (at least not for a while, gravity is very persistent) because the electromagnetic forces holding it together are, in total, twice as strong as the gravitational forces trying to drag it into the river. That’s despite the fact that the planet exerting that force is much, much larger than the crest of the bridge.

Now, scientists have been putting forces together for donkey’s ages. Newton was the first one to realize “force pulling apple to earth is same force keeping moon in orbit”. One force. He proved it scientifically. Faraday was the first one to realize “light, electricity and magnetism are all the same force”. It took Maxwell to prove that because Faraday had poor math skills. Einstein said “mass and energy – same thing”. That’s been proven too.

At present, all the forces can be explained by one theory.

Except gravity. The equations that tie together electromagnetism, the strong nuclear force and the weak nuclear force are beautiful, if complicated, and have been supported experimentally. Gravity… just doesn’t fit.

Of all the candidates, only string theory easily ties together gravity with the other three. To paraphrase “if we didn’t know about gravity, these calculations would show it existed”. It’s not the first time that would have happened – Dirac’s equations predicted the existence of anti-matter, and that turned out to be real. Higgs’s calculations predicted a particle he modestly called the “Higgs Boson” that would explain why some particles have mass.

That turned out to be real too. There’s just one problem – string theorists haven’t worked out any experiment to confirm it. The equations are beautiful and they mesh. They just can’t give us anything to test.

So maybe the unthinkable is true. Maybe there are TWO forces in the universe that are utterly irreconcilable. Even at the moment of the “Big Bang”. <shudder>

Except there’s no evidence of that either. Even in supermassive black holes that we know exist. The forces – seem to be related. They just… can’t be.

So, please go study physics and enjoy your Nobel Prize when you figure this out.