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Thursday, October 13, 2005

Message from Linde

Andre Linde (Stanford) sends some interesting comments on our paper Message in the Sky. He points to an earlier paper of his, and a nice interview in Slate, where he discusses the idea of creating a universe in the lab. In the comments section of the previous post I mentioned that one of the reasons I had been thinking about this topic is the work of Farhi and Guth (MIT) on the behavior of a false vacuum bubble created in the lab. I hadn't known that Andrei had also worked out the solution (although I should have). A false vacuum bubble can expand in a non-Euclidean way, so that the observer in the lab sees the bubble shrink while an observer inside sees it expand (inflate).

Andrei also had the idea that the creator of the bubble universe might like to send a message to its future inhabitants. He discusses tuning the fundamental parameters so that physicists in the bubble universe would understand that their physical laws had been adjusted just-so. Our proposal allows a bit more information to be encoded (or rather, read out), but the idea is similar. The problem with having special values of the constants is that some nutty physicists might come up with anthropic reasons explaining those values, and not figure out it was done intentionally ;-)

But why bother making a universe if it's going to run away from you? Wouldn't you want to have some power over how your creation unfolded, some way of making sure the beings that evolved in it turned out well? Linde's picture was as unsatisfying as Voltaire's idea of a creator who established our universe but then took no further interest in it or its creatures.

"You've got a point," Linde said. "At first I imagined that the creator might be able to send information into the new universe—to teach its creatures how to behave, to help them discover what the laws of nature are, and so forth. Then I started thinking. The inflation theory says that a baby universe blows up very quickly, like a balloon, in the tiniest fraction of a second. Suppose the creator tried to write something on it surface, like 'Please remember I created you.' The inflationary expansion would make this message exponentially huge. The creatures in the new universe, living in a little corner of one letter, would never be able to read the whole thing."

But then Linde thought of another channel of communication between creator and creation—the only one possible, as far as he could tell. The creator, by manipulating the cosmic seed in the right way, has the power to ordain certain physical parameters of the universe he ushers into being. So says the theory. He can determine, for example, what the numerical ratio of the electron's mass to the proton's will be. Such ratios, called constants of nature, look like arbitrary numbers to us: There is no obvious reason they should take one value rather than another. (Why, for instance, is the strength of gravity in our universe determined by a number with the digits 6673?) But the creator, by fixing certain values for these dozens of constants, could write a subtle message into the very structure of the universe. And, as Linde hastened to point out, such a message would be legible only to physicists.

"You might take this all as a joke," he said, "but perhaps it is not entirely absurd. It may be the explanation for why the world we live in is so weird. On the evidence, our universe was created not by a divine being, but by a physicist hacker."

Linde's theory gives scientific muscle to the notion of a universe created by an intelligent being. It might be congenial to Gnostics, who believe that the material world was fashioned not by a benevolent supreme being but by an evil demiurge. More orthodox believers, on the other hand, will seek refuge in the question, "But who created the physicist hacker?" Let's hope it's not hackers all the way up.

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