Leonard Susskind - Why does mathematics work? - Differential Equations in Action

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So, more than half a century ago, Eugene Wigner wrote about, The Unreasonable Effectiveness of Mathematics in the Natural Sciences. >> Yeah. >> And, and, indeed one man can sit in one's living room and do Duncan experiments and, maybe you know what that word means? I don't. >> Duncan means thought. >> Okay, thought experiments. >> Thought experiments. >> You can do these thought experiments and come up with something like the gene-, General Theory of Relativity. You discover black holes and the curvature of space-time. And why is that so? Could it be that we only perceive what we can describe, without mathematics. And vice versa? Because mathematics is co-evolved with our brain. >> Look, Eugene Wigman made a big problem for every generation that came after him. To answer that question, why mathematics works. Why does mathematics? And sometimes I think to myself, what, how could it not work? The world has some coherence to it. Things don't just randomly happen. How do you describe things that don't randomly happen? If they don't randomly happen, you have to have some kind of quantitative framework for explaining what happens. So I can't imagine, on the one hand I can't imagine a world that didn't work according to some kind of laws and those laws being written mathematically. On the other hand, I also can't quite understand why mathematics works. So Eugene asked a very difficult question. And he didn't know the answer. And I think I, I, I don't know the answer, either. But here's what I would say. Here's what I would say. Not, why does mathematics work, but why do we need mathematics to explain physics, why is it so hard to explain physics in the English language? And the reason is, because, yeah, we may have evolved as a species on mathematical abilities, but we evolved them, in the context, of rather ordinary things. The ordinary things would be, how stones move when you throw them. When it comes to waves, we have some perspective about what a wave is because we see water making waves and so forth. We have a good concept of what a force is because if I give you a good shove, you'll say, oh, don't force me. We know what force means. But every time we enter into a new range of parameters We make things smaller than anything that we were, than we grew up with. Other words, we go to the quantum world. Or we go to the world of very, very heavy things and dense things. In other worlds, we go to the world of black holes. We suddenly find that the intuitions and the concepts that we evolved with are not sufficient to understand. An example, we use higher dimensional spaces all the time. We think we sometimes think for example, that the that space itself may be more than three dimensions. You evolve. You and I evolved in a world of three dimensions. We can't visualize more dimensions. And we can't because our it, it's not that we're not smart enough. It's that the neural architecture, the architecture of the brain itself. Was purposefully built, well it wasn't purposely built, but it evolved in the world of three dimensions. The architecture is appropriate for three dimensions and it's not appropriate for four, five, six, seven dimensions. If we think that we're interested in a space with seven dimensions or whatever, how would we describe it if we can't visualize it. We describe it by pure mathematics. We say a three dimensional world is described by a bunch of points that are labeled by X, Y, and Z that's an abstraction. I can visualize three-dimensions on my head, but I use x, y, an z to describe them mathematically. Now I go to four dimensions, or five dimensions. I can't visualize it anymore. I can't visualize it anymore. I can't close my eyes an see a, a five-dimensional world. But I can add two more letters to the alphabet. I can add the x, y, and z, w, and v. And now I have a five dimensional space. How do I work with it? I work with it using algebra. I work with it using using abstract mathematics. And I don't try to see it in my head. In trying to explain it to people who don't have the mathematical background, we get stuck. I can't say, now close your eyes and view in your head five dimensions, because I can't do it either. What I, all I can do is say, take x, y, and z and add v and w. Eventually if, eventually a person with this kind of mathematical background begins to develop mathematical intuitions for things. They don't need the same kind of visualization. So, we are stuck. We're stuck needing mathematics because evolution didn't equip us to be able to visualize quantum mechanics. It didn't visualize us to be able to, there sorry, it didn't equip us to be able to visualize 11 dimensional space-time. And tha, that's the reason. Evolution did it to us.
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Channel: Udacity
Views: 466,273
Rating: 4.9003615 out of 5
Keywords: differential equations, python, numerical methods, diffeq, numerical analysis, numerical approximation
Id: 2bgZmBAnhdg
Channel Id: undefined
Length: 5min 52sec (352 seconds)
Published: Mon Feb 23 2015
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