"The Strangest Finding Since the Scientific Revolution" | Big Think

"The Strangest Finding Since the Scientific Revolution"

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The philosopher of physics explains the “unsettling” manner in which movement, at its most essential level, breaks down cognitive categories and exhausts the capacities of human logic.

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David Albert:

David Z Albert the is Frederick E. Woodbridge Professor of Philosophy and Director of the M.A. Program in The Philosophical Foundations of Physics at Columbia University. He is the author of "Time and Chance," "Quantum Mechanics and Experience," among others. He received his B.S. in physics from Columbia College (1976) and his doctorate in theoretical physics from The Rockefeller University. He lives in New York City.

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TRANSCRIPT:

Question: How does quantum mechanics contradict common sense?

David Albert: Here's the deal: quantum mechanics allows physical systems -- and the easiest systems in which to observe phenomena like this are very tiny systems like subatomic particles, electrons or neutrons or protons -- quantum mechanics apparently allows for the existence of physical conditions of material objects like electrons in which questions about where the electron is located in space seem to fail to make sense. Let me back up a little bit and explain this a little more slowly. There are experiments we can do where an electron passes through a certain apparatus, is fed into one end of an apparatus, comes out the other side of the apparatus. And the apparatus has several routes inside of it which the electron could potentially have taken from the input to the output. And there are experiments we can do with pieces of apparatus like this which, taken together, make a compelling case that although the electron went from here to there, it didn't go by route A, it also didn't go by route B, and it didn't go in any intelligible sense by both routes; that is, it didn't split in half, with one half taking one route and one half taking the other route; and it also didn't take neither route, okay?

And what's puzzling about that is that that would seem to be all the logical possibilities that there are. These experiments, you know, are now very routine experiments to do in physics laboratories. We've been good at doing experiments like this for something on the order of 70 years now. We're very good at doing them now. The results are very, very compelling. And after enormous soul-searching and puzzlement and confusion and so on and so forth, the sort of standard consensus understanding that evolved in physics of situations like this is that electrons could apparently be in situations where asking a question of the form "which route did the electron take?" was something like asking a question of the form "what is the marital status of the number five?" Or "what are the political affiliations of this tuna sandwich?" or something like that. These are questions that philosophers often refer to as category mistakes, okay? The very raising of a question about the political affiliations of a tuna sandwich or the marital status of the number five indicates that there's something basic that you're misunderstanding of what it is that you're asking a question about.

And the strikingly strange thing about quantum mechanics -- and indeed it seems to me a case could be made that this is the strangest and most unsettling result to come out of the natural sciences since the scientific revolution of the Renaissance -- is that even things like particles can be in conditions where it simply radically fails to make sense even to ask where the thing is located in space. What's particularly strange about this is that of course there are other circumstances where it does make sense to ask those questions about where it's located in space. The electron determinately goes into the box over here and comes out over there, okay? But we can give good arguments from these experiments that while it's inside, it's not merely that we don't know where it is, it's something much more radical and much more unsettling than that: that the very act of raising a question about where it is represents some kind of misunderstanding of what mode of being that electron is participating in while it's going through this device.

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