William Wootters, one of Wheeler's many students and now a professor of physics at Williams College in Williamstown, Massachusetts, sees Wheeler as an almost oracular figure. "I think asking this question— How come existence?— is a good thing," Wootters says. "Why not see how far you can stretch? See where that takes you. It's got to generate at least some good ideas, even if the question doesn't get answered. John is interested in the significance of quantum measurement, how it creates an actuality of what was a mere potentiality. He has come to think of that as the essential building block of reality."

In his concern for the nature of quantum measurements, Wheeler is addressing one of the most confounding aspects of modern physics: the relationship between the observations and the outcomes of experiments on quantum systems. The problem goes back to the earliest days of quantum mechanics and was formulated most famously by the Austrian physicist Erwin Schrödinger, who imagined a Rube Goldberg-type of quantum experiment with a cat.

Put a cat in a closed box, along with a vial of poison gas, a piece of uranium, and a Geiger counter hooked up to a hammer suspended above the gas vial. During the course of the experiment, the radioactive uranium may or may not emit a particle. If the particle is released, the Geiger counter will detect it and send a signal to a mechanism controlling the hammer, which will strike the vial and release the gas, killing the cat. If the particle is not released, the cat will live. Schrödinger asked, What could be known about the cat before opening the box?

If there were no such thing as quantum mechanics, the answer would be simple: The cat is either alive or dead, depending on whether a particle hit the Geiger counter. But in the quantum world, things are not so straightforward. The particle and the cat now form a quantum system consisting of all possible outcomes of the experiment. One outcome includes a dead cat; another, a live one. Neither becomes real until someone opens the box and looks inside. With that observation, an entire consistent sequence of events— the particle jettisoned from the uranium, the release of the poison gas, the cat's death— at once becomes real, giving the appearance of something that has taken weeks to transpire. Stanford University physicist Andrei Linde believes this quantum paradox gets to the heart of Wheeler's idea about the nature of the universe: The principles of quantum mechanics dictate severe limits on the certainty of our knowledge.

"You may ask whether the universe really existed before you start looking at it," he says. "That's the same Schrödinger cat question. And my answer would be that the universe looks as if it existed before I started looking at it. When you open the cat's box after a week, you're going to find either a live cat or a smelly piece of meat. You can say that the cat looks as if it were dead or as if it were alive during the whole week. Likewise, when we look at the universe, the best we can say is that it looks as if it were there 10 billion years ago."

Linde believes that Wheeler's intuition of the participatory nature of reality is probably right. But he differs with Wheeler on one crucial point. Linde believes that conscious observers are an essential component of the universe and cannot be replaced by inanimate objects.

"The universe and the observer exist as a pair," Linde says. "You can say that the universe is there only when there is an observer who can say, Yes, I see the universe there. These small words— it looks like it was here— for practical purposes it may not matter much, but for me as a human being, I do not know any sense in which I could claim that the universe is here in the absence of observers. We are together, the universe and us. The moment you say that the universe exists without any observers, I cannot make any sense out of that. I cannot imagine a consistent theory of everything that ignores consciousness. A recording device cannot play the role of an observer, because who will read what is written on this recording device? In order for us to see that something happens, and say to one another that something happens, you need to have a universe, you need to have a recording device, and you need to have us. It's not enough for the information to be stored somewhere, completely inaccessible to anybody. It's necessary for somebody to look at it. You need an observer who looks at the universe. In the absence of observers, our universe is dead."

universe_5.jpgSchrödinger's Cat
Erwin Schrödinger, a founding
father of quantum mechanics,
asked what would happen to a
cat locked in a box with a
radioactive element that may or
may not trigger the release of
poison gas during the experiment.
The short answer: The cat's fate
is undecided until the moment
someone observes the experiment.


Will Wheeler's question— How come existence?— ever be answered? Wootters is skeptical."I don't know if human intelligence is capable of answering that question," he says. "We don't expect dogs or ants to be able to figure out everything about the universe. And in the sweep of evolution, I doubt that we're the last word in intelligence. There might be higher levels later. So why should we think we're at the point where we can understand everything? At the same time I think it's great to ask the question and see how far you can go before you bump into a wall."

Linde is more optimistic.

"You know, if you say that we're smart enough to figure everything out, that is a very arrogant thought. If you say that we're not smart enough, that is a very humiliating thought. I come from Russia, where there is a fairy tale about two frogs in a can of sour cream. The frogs were drowning in the cream. There was nothing solid there; they could not jump from the can. One of the frogs understood there was no hope, and he stopped beating the sour cream with his legs. He just died. He drowned in sour cream. The other one did not want to give up. There was absolutely no way it could change anything, but it just kept kicking and kicking and kicking. And then all of a sudden, the sour cream was churned into butter. Then the frog stood on the butter and jumped out of the can. So you look at the sour cream and you think, 'There is no way I can do anything with that.' But sometimes, unexpected things happen.
"I'm happy that some people who previously thought this question— How come existence?— was meaningless did not stop us from asking it. We all learned from people like John Wheeler, who asks strange questions and gives strange answers. You may agree or disagree with his answers. But the very fact that he asks these questions, and suggests some plausible— and implausible— answers, it has shaken these boundaries of what is possible and what is impossible to ask."

And what does the oracle of High Island himself think? Will we ever understand why the universe came into being?

"Or at least how," he says. "Why is a trickier thing." Wheeler points to the example of Charles Darwin in the 19th century and how he provided a simple explanation— evolution through natural selection— for what seemed an utterly intractable problem: how to explain the origin and diversity of life on Earth. Does Wheeler think that physicists might one day have a similarly clear understanding of the origin of the universe?

"Absolutely," he says. "Absolutely."





Geons, Black Holes & Quantum Foam: A Life in Physics by John Archibald Wheeler with Kenneth Ford. New York: W. W. Norton & Company, 1998. Also check out Andrei Linde's Web site: http://physics.stanford.edu/linde.