And actually later in life he said that he regretted calling it the theory of relativity and wished that instead he had called it the theory of invariance . So once we knew all this, my father and I now had a concrete plan.
well, I assumed that all of the invariance people had already-- sorry-- had already tried all of their invariance stuff. So I wasn't going to try that.
So I wasn't going to try that. I'm not an expert in invariance . makes sense. it's been 50 years.
It might look something a little bit more like jazz as an analogy. And he got Einstein's idea of invariance , the idea of using symmetry to understand what remains invariant if I change perspective.
That's the idea of a horizon. And that's the thing about invariance .
So if there's one thing that you remember about physics, let it be that. It was Einstein who first recognized this link between invariance and reality. And I would actually argue that this was Einstein's single greatest contribution to physics, which I realize is a very bold statement.
So when I heard about this problem-- well, I assumed that all of the invariance people had already-- sorry-- had already tried all of their invariance stuff.
Because the thing he won the Nobel Prize for barely cracks the list of the best things he ever did. But the best thing he ever did was to illuminate this link between invariance and reality. Because it set the future trajectory of modern physics in motion.
That's the idea of a horizon. I needed my dad because that second reference frame gave my life a sense of invariance and created between us a shared reality.
That's what an invariant is. And when people want to study sliceness, they still use invariance , but they come up with some invariant. Maybe it's still integer valued, but it has this property that when you compute this integer for a slice knot, you're supposed to get zero.
to glimpse the reality behind appearances. And there's a good reason that no one before Einstein thought of this link between invariance and reality. And it's that before Einstein, everyone shared the same reference frame.
That's the idea of a horizon. So spacetime-- this unified, four-dimensional spacetime that was left invariant by Einstein's theory of invariance -- turns out not to be invariant after all.
There's one technique-- we have a lot of ways to power this technique, but there's just one technique people use to show something's not sliced in general, which is that we have these-- we have these things called invariance , which we assign to knots.
And they're different, so our knots are different. That's what an invariant is. And when people want to study sliceness, they still use invariance , but they come up with some invariant.