WEBVTT 00:00.000 --> 00:21.000 With the coming into view of a quantum mechanical picture of matter and of all that exists, 00:21.000 --> 00:29.000 many of the traditional ways in which physicists were thinking about nature had to change. 00:29.000 --> 00:36.000 In the pre-quantum world, Newton thought of objects as being made of particles, 00:36.000 --> 00:42.000 and the particles had mass, they had size, they had motion, 00:42.000 --> 00:47.000 then they had other attributes that later were added on, like electric charge. 00:47.000 --> 00:55.000 So the object, and all of these could be measured, so that in a Newtonian picture of physics, 00:55.000 --> 01:00.000 everything was made out of particles and the particles could all be measured, 01:00.000 --> 01:08.000 every aspect of them could be measured, so that the object or the matter was identical to its observables. 01:08.000 --> 01:12.000 Everything you could think about, you could measure. 01:12.000 --> 01:15.000 Quantum mechanics changed that in a profound way. 01:15.000 --> 01:21.000 Quantum mechanics began to show us that whereas matter obviously exists, 01:21.000 --> 01:27.000 the things that are available for us to know about it are limited. 01:27.000 --> 01:34.000 For example, the position and velocity of an object are not simultaneously knowable 01:34.000 --> 01:38.000 with arbitrary precision in the same direction. 01:38.000 --> 01:44.000 So in these ways, quantum mechanics gave us a sense of humility about our level of knowledge. 01:44.000 --> 01:49.000 matter exists, but what it presents to us is limited. 01:49.000 --> 01:54.000 There is only so much we can know about it. 01:54.000 --> 02:03.000 But there has been a very long-standing, and in fact ongoing, question in the field of quantum foundations 02:03.000 --> 02:11.000 as to what is actually going on, what is really happening to matter, so that it behaves in the ways that we see. 02:11.000 --> 02:18.000 For example, there is this simple experiment that people often use to describe quantum mechanics. 02:18.000 --> 02:21.000 They talk about a double-slit experiment. 02:21.000 --> 02:26.000 So in a double-slit experiment, you consider a situation where you have a source of particles, 02:26.000 --> 02:29.000 you have a wall, and the wall are, let's say, two holes. 02:29.000 --> 02:34.000 You close one hole, you look back behind the wall, and you have a detector. 02:34.000 --> 02:38.000 And from this source, you shoot off, let's say, bullets. 02:38.000 --> 02:47.000 Eventually, on this back surface, you see a pileup of incidents, of hits, of events. 02:47.000 --> 02:50.000 When you look at that distribution, you see a hump. 02:50.000 --> 02:54.000 Now you do the experiment again. You open this hole, and you close the other hole. 02:54.000 --> 02:59.000 Now from this one, you do the same thing. You see the same thing. It's just another distribution. 02:59.000 --> 03:06.000 Now the strange thing is that when you open both holes, you expect to see just the sum of the two distributions. 03:06.000 --> 03:09.000 In other words, you know, they would add up together. 03:09.000 --> 03:15.000 But in fact, you see a pattern that looks like an interference, looks like as if a wave went through. 03:15.000 --> 03:22.000 And in some places, what you see is less with both holes open than with one hole open. 03:22.000 --> 03:26.000 How is it that I open the second hole and some go away here? 03:26.000 --> 03:30.000 And this was the first hint that something very mysterious or something very strange is happening. 03:30.000 --> 03:34.000 That there seems to be a wave nature involved as well. 03:34.000 --> 03:44.000 Now the question is, how do we then have a coherent, consistent ontology, which means a description of existence, 03:44.000 --> 03:50.000 that is consistent with both this particle nature and the wave nature? 03:50.000 --> 03:53.000 And that's been a subject of great debate in quantum mechanics. 03:53.000 --> 03:58.000 And I would say at this point, there is not a definite answer. 03:58.000 --> 04:02.000 And this is an area which is still needing a lot of work. 04:02.000 --> 04:10.000 Whereas we know enough about the quantum world to predict the results of experiments extremely well, 04:10.000 --> 04:16.000 we don't have a clear understanding of the underlying things that are going on. 04:16.000 --> 04:27.000 One philosopher and mathematician by the name of Wolfgang Schmidt is proposing a picture these days of quantum mechanics 04:27.000 --> 04:31.000 in which he's invoking essentially a classical ancient picture, 04:31.000 --> 04:38.000 in which it kind of goes back to, for example, what the Greeks would have called the hylomorphic conception of nature. 04:38.000 --> 04:47.000 Whereas the hyla, which is the substrate of matter, and then morph, which is the shape of the matter. 04:47.000 --> 04:54.000 So if you think of a piece of marble, the marble, a big chunk of marble, there is, you can think of a statue as in there. 04:54.000 --> 05:02.000 But until the sculptor actually puts that shape in, carves that shape out of the marble, there is none of that statue in there. 05:02.000 --> 05:05.000 The statue is in there, but it's not really in there. 05:05.000 --> 05:08.000 It's really in the form that the statue is. 05:08.000 --> 05:11.000 But the form without the marble is also not a statue. 05:11.000 --> 05:14.000 So the hyla and the morph need to come together. 05:14.000 --> 05:24.000 So Wolfgang Schmidt kind of uses this to say that in reality there seems to be, at one level, a corporeal world, 05:24.000 --> 05:28.000 in which it's the world of objects we see and sense and touch. 05:28.000 --> 05:33.000 But then in another level there is the world of the physics, of the physicist, 05:33.000 --> 05:41.000 which is something in between sort of this corporeal world and this sort of the highly kind of space, 05:41.000 --> 05:43.000 this Greek highly concept. 05:43.000 --> 05:50.000 And that there is the potentiality that quantum mechanics talks about is really in this in-between state, 05:50.000 --> 05:52.000 which Schmidt calls the physical world. 05:52.000 --> 05:55.000 It makes for a difficult ontology. 05:55.000 --> 05:58.000 It's one that I don't feel like I fully grasp. 05:58.000 --> 06:07.000 But also I can tell you that it tells us there is still a lot of exciting work ahead. 06:07.000 --> 06:15.000 That even understanding the very basic nature of matter is still something that's not fully grasped. 06:15.000 --> 06:16.000 It's a humbling thing. 06:16.000 --> 06:25.000 It says that God created the world with much more depth and detail than our simple approximations 06:25.000 --> 06:28.000 can just dispatch and make it look like, oh yeah, we know everything. 06:28.000 --> 06:31.000 No, there is a lot more to learn.