Quantum Mechanics

"That’s right, it’s a quantum mechanics textbook. It’s not even as an undergraduate textbook, it’s a graduate, PhD-level textbook. But when I started my PhD, I was expected to buy some textbooks with part of my stipend, a few hundred pounds. I was given a list of books by my PhD supervisor and Messiah’s two-volume book on quantum mechanics was top of the list. It’s the book I needed to get me up to up to speed to work on the area of research I was doing for my PhD, which was nuclear physics. For me, it’s still the Bible of quantum mechanics that I go to when I want to look something up that I’ve forgotten. Get the weekly Five Books newsletter The book was originally written in French and it goes further than all that undergraduate stuff about atoms being in two places at once and it throws a lot of the laws of physics out of the window and says… Yes. You cannot say for sure where an atom is until you look at it. Looking at it makes it decide. Only when you look at it is it in one place. Well, yes. I mean, you don’t look. You send an atom through something with narrow slits in the top and bottom and you hear a blip when it hits the other side. You send loads of atoms and so would expect to see loads of hits at the top and the bottom adjacent to the two slits. But you don’t. What you get is an interference pattern like you would with waves washing through both slits at the same time. But you get this effect even when you send only one atom at a time. But if you spy on it then it only goes through either the top or the bottom and not both at once. It’s as though it knows you’re looking. If I knew that then the King of Sweden would be calling me up with the Nobel. It’s counterintuitive and weird but we’ve learned to accept it. Quantum mechanics is hugely accurate – most of modern scientific development is based on it and on what it tells us about the subatomic world, but at its heart it says that an atom can be in two places at once. We’ve learned to live with that. You mean why doesn’t your hand go through a table? Because electromagnetic forces hold the atoms together and give rigidity. Atoms themselves are mostly empty space – there’s a nucleus and then these electrons buzzing around. The nucleus has a positive charge and the electrons have a negative charge, so the negative charges repel each other and it is this electromagnetic force between the atoms in my hand and the atoms of the table that give rigidity and solidity."