Hans Christian von Baeyer spoke to the William and Mary News about his recent book, Information, as well as about what non-physicists need to know about our world. The following partial transcript reflects that conversation. —Ed.
Q: What would you, as a physicist, tell freshmen English majors to help them understand their world?
von Baeyer: You don’t need to know specific facts. Perhaps you should consider that you live in a universe and the more you know about the universe, the better off you are. You become more comfortable and at ease. Some things in the universe are threatening, but as you learn about them, you become more comfortable. It’s like walking into a hotel room. At first, everything is strange, but you orient yourself. You figure out where this is and where that is; you make your surroundings compatible with your lifestyle and your imagination. The same thing happens with human relationships. You need to be comfortable, and perhaps more than comfortable; you need to be curious about your surroundings. Life is more interesting if you are curious about a person, or about the place where you live or about your world. If you know a little about the stars, then they become more fascinating to you. If you know a little about trees and birds, they can enrich your life.
Q: What would you tell a physics major?
von Baeyer: One article I wrote was about the lotus flower (The Sciences, January 2000). If I can relate physics to a lotus flower, that certainly enriches a physics major who has been dealing with little electronic machines all of his life.
von Baeyer: The reason is that on one level is the world of atoms and things like that, and on another, is [the world of] us. How do we know about this world? For example, we touch a chair. We don’t see the chair directly. What we do is get sense experiences. The sense experiences are what is in our brains. For our brains to go back to the atomic world and ask about what is really, really at the bottom of things is foolish, because we’re going to get it wrong every time. What we should do is be aware of the in-between piece, the information we receive in our brains about the thing. That is what the book Information is about. We need to be aware that the world is not only determined by what is at the bottom but also by the way it comes to us and by the way our brains arrange it. Now, you could talk about a chair, describe all that you see about it, its frame, its fabric, say what the chair is about; then I could come along and say the chair is 99.9 percent vacuum and there are these tiny, little electrons going round and round. Then comes the legitimate question: Is the chair really vacuum and electrons, or is it really the other thing that you perceive?
That’s why I say it is a foolish dichotomy. We should become more sophisticated. We should be aware that we will never get to the actual bottom. What we can do is to know quite a bit about the real world as modified by our own brain. You know you are sitting on a chair and it is holding you up. I know that if I took it apart into little pieces, I would find that it is vacuum and little electrons that are sort of hitting you and holding you up. Now, which view of the chair is correct? They both are correct. They both are part of this more sophisticated thing. When I say you shouldn’t ask, I mean that you shouldn’t tie yourself down to one fundamental picture of what the world is really, really like. I think you’re always going to get it wrong. The Greeks got it wrong, the alchemists got it wrong and the 20th-century physicists got it wrong. A few hundred years from now, people may be sitting around laughing about all these strings and quarks that we think right now are down there at the bottom of things. I am not going to hold my hand in the fire and say that strings and quarks are what the world is really, really like. The world is just as much determined by what goes on in my brain.
Q: In Information, you call the qubit the ultimate source of wonder. Why?
von Baeyer: The qubit? One thing that makes life simple when you look at information—at least mathematical information—is that it can be encoded in zeros and ones. [It can be reduced to bits.] Not everything can. Love is probably difficult to quantify in zeros and ones, but if everything you write, everything in the Encyclopaedia Britannica and the Bible and all of Swem Library is nothing but one long stream of zeros and ones, then perhaps you would think you can describe everything that way. But in 1925 and 1926, we started finding out that you cannot describe atoms in terms of zeros and ones because zeros and ones are fundamentally a question of either/or—the outcome is either zero or one. The either/or is fundamental; the thing is either this or it is that. There is nothing in between. But, by golly, with atoms, it is “and”—it is both zero and one. An atom is not here or there; it is here and there. Our minds cannot fathom that. You cannot think of your magazine in terms of little things that are floating between zeros and ones; you cannot write an English sentence in terms of things that are floating between zeros and ones.
Zeilinger’s principle, which becomes the last chapter of Information, says what is at the bottom is these qubits, these little balls of zero and one. Zeilinger doesn’t say that there is a world of atoms and there is our world and that we can’t communicate between them. That would be too depressing. What he says is that the world is really, truly made out of qubits and that our brains, our understanding, are such that out of every qubit we can pluck only one bit. That’s very interesting. It allows that the world is more complicated, and it acknowledges that we can talk only in bits. Each qubit can have an infinite amount of information, if you like, and all we can get out of it is one lousy bit. A great waste.
Q:To help explain a qubit, you use the example of a
cat in a box, suggesting that the cat is both dead and alive until we
extract our bit and it becomes either dead or alive. Are we culpable
for the outcome by looking?
von Baeyer: Ah, the ethics of it. The way you get out of that one is that a cat is so complex that it really is dead or alive, not dead and alive. The only examples of how you can get into trouble with the “and-ness” in individual qubits is to describe an electron, a photon or something similar. The more you get up the ladder of complexity, the less you get of this “and-ness.” One of the big questions of quantum mechanics has been, If an atom can be both here and there, why can’t I be here and there? Why do we never see the moon both here and there? By now, we know the answer to those questions. It has to do with complexity, with your interaction with the rest of the world, with your breathing and the way light is streaming. If I could put you in a perfect vacuum—of course, you would die—I could put you in a state where you are both here and there. But, of course, that’s unrealistic. No object as complex as you is ever completely separated from its environment.
Q: How does an understanding of qubits shape how you, as a physicist, see the world?
von Baeyer: After I published Information, I stopped for awhile, and I said, I’m not going to write another book. Then I got seduced and I started writing. I have a few chapters but I put them aside. It’s just too hard. What was that book about? It asks the question, In what way does a physicist see the world differently than do other people? An artist sees colors. A musician will be attuned to sounds. A psychologist sees facial expressions and such. The last chapter of my book will have to answer how I see the world differently now that I understand information. I don’t know the answer. I don’t know that I will write it.
This knowledge must creep in. The things that you know influence the way you appreciate the world. The fact that I think of the world as being made of qubits influences my appreciation, but it is a very difficult question. I’m not ready for that. Maybe after I retire, I’ll sit down … .