I know that at the end of my eight episode series on string theory, that I said I would never talk about string theory ever again.

But listen, folks, we've got a problem. Gravity. No, not the usual problem

with gravity, which is that our theory of gravity is fundamentally incompatible with our theory

of literally everything else, hence string theory and loop quantum gravity and other solutions to that riddle.

And no, it's not the other problem with gravity, which is that it has solutions which contains

singularities like the centers of black holes in the beginning of the universe, which is a big

headache if you're trying to solve for situations like what happens at the center of a black

hole or at the beginning of the universe. No, it's neither of those. Today's problem with gravity

is that it's weak. Very weak. Super weak. Imagine the weakest possible thing. Imagine the force

of a gentle breeze that barely moves a single

hair on your head. It's weaker than that. Imagine a butterfly brushing its wing against your

skin. It's weaker than that. Imagine if someone says, hey, check out my new super spicy hot wings. And then you

find that it's just chicken drumsticks dipped in water. It's weaker than that. Imagine

meeting a new family. A couple of parents, four kids. Three of the kids are pretty much the same. Same eye and hair

color, maybe a little variation. Maybe kid number three is a bit taller. Maybe kid number two

talks a bit much. But you can definitely tell that they're related. There's something in common.

Even though they're a little bit different, it's just variations on a theme.

Three kids all from the same family.

You can just tell they are related.

Now, imagine that you meet kid number four.

And kid number four is a 300 foot tall purple giant.

Kid number four is gravity. Kid number four is weird. Kid number four is gravity kid number four is weird kid number four doesn't fit

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