I have a ratty, gray T-shirt with an equation written on it. It’s my favorite t-shirt.
It’s partly my favorite t-shirt because it has hit the sweet spot of t-shirts: the point when it’s broken in to maximum softness and perfect fit, but has yet to develop holes and fall apart. It’s like wearing air.
But the other reason I love this t-shirt is because it has my favorite equation on it: Euler’s Identity—which I say is the most beautiful equation in the world!
But why is it the most beautiful equation in the world?
Because it relates two transcendental numbers (pi and e) by using i, the square root of negative one.
This equation is the perfect balance of simplicity and complexity. That’s what makes it beautiful.
But what gives me the right to make the aesthetic judgement of “beautiful”?
Well, that’s an earned right—one that can certainty be challenged. But it can only be meaningfully be challenged by those who have studied enough mathematics to come up with an alternative.