1. How did a physics professor get interested in crazy ideas?

Physicists are a very curious tribe. Physics, by its very nature, must be open to crazy ideas in order to explain the strange universe we live in. Many ideas in physics are extremely counterintuitive and run counter to our common sense, yet they have proven to be correct, or at least they have not yet been proven wrong. (In an important sense no theory can ever be proven correct, since there are always future tests we can dream up for it to pass.) In my research, I have looked into the idea—perhaps crazy--that some subatomic particles can move faster than the speed of light. Einstein said that such a thing was impossible and I'm a curious enough scientist to want to just test whether he was right.

2. Aren't all crazy ideas wrong and unscientific by nature? How can a crazy idea be true?

Crazy ideas are bizarre and often run against conventional wisdom. Most crazy ideas turn out to be wrong, when tested against what is found in nature, but a small fraction of them turn out to be right. Crazy ideas are neither scientific nor unscientific by virtue of being crazy. For an idea to be called "scientific" it needs to be testable, or what has been called "falsifiable." So the idea thatrocks have feelings, but they can never communicate their feelings to us is clearly untestable, and therefore unscientific. The idea that God created the world a bit over 5,000 years ago, but designed it in such a way as to make it look in all respects as if it were billions of years old is also untestable, and hence unscientific. However, the crazy idea that rocks could communicate with us is testable, provided it was spelled out how this might be done, and what we might expect to find.

3. You distinguish crazy ideas from nutty ideas--what's the difference?

By crazy ideas I refer to those which are bizarre, but are not in conflict with the basic laws of nature as we know them. Nor are they in conflict with existing experimental data about the world, even if they do conflict with both common sense and much conventional wisdom. In contrast, "nutty" ideas (also "flaky" or "loony") are much less deserving of our attention, because they are in conflict either with the basic laws of physics or with much existing experimental data. In some cases, the distinction between the two categories will be a bit blurry, but I'd probably want to move the idea of communicating rocks to the nutty category, but certainly not the idea of communicating plants -- which may even be true.

4. You discuss some pretty dangerous ideas--that HIV is not the cause of AIDS, for example. Should a scientist like yourself engage with such ideas?

Do you worry that you give dangerous ideas credibility that they don't deserve? The idea that HIV doesn't cause AIDS is a very dangerous one, because if people believed that HIV were a harmless "passenger virus" they might not be careful to avoid dangerous behaviors that led to transmission of HIV. Before I wrote the chapter on this idea I did agonize quite a bit about the very point you make that I might be giving this dangerous (and almost certainly wrong) idea a credibility it didn't deserve. In the end I decided that it was important to write the chapter precisely because the idea was so dangerous. It has already gotten a lot of publicity in recent years, both because of efforts of its promoters, and because the South African President has apparently indicated his belief in it. If I could show, by careful analysis, exactly why the idea was wrong, and how you can analyze similar wrong-headed ideas that are presented in a manner that seems to be very persuasive because of all the "facts" marshalled in their favor, I would be performing a useful service. In fact my book is only partly about the nine crazy ideas themselves. The more important lesson (shown through the nine examples) is how one can go about sorting the "wheat from the chaff" when looking at crazy ideas -- and how to do it without simply relying on the opinions of experts.

5. Just wondering, is time travel possible? Have you ever tried it?

With each of the crazy ideas in the book I give it a rating based on my highly subjective "cuckoo scale." Zero cuckoos means -- maybe it's true, why not? Three cuckoos means -- almost certainly it's impossible. On this scale I give time travel two cuckoos. It is not entirely in the realm of science fiction. Putting it differently, time travel science fiction, particularly such recent works as Michael Creighton's book Timeline, do have a basis in real science, and cannot be dismissed as being impossible. One interesting vehicle for time (and space) travel is the wormhole, which is a theoretical solution to the equations of general relativity. No one has yet observed a wormhole, so we don't yet know if they really exist in a stable form, but if they do, and if we could survive the trip through one we'd come out the other side in a different region of space and time, or possibly even in a different parallel universe. I have tried it, and can assure you that it works. From a recent visit to the year 2004 I learned that my book will become a best seller. Also, if you read the book carefully I'll also disclose at one point what the Dow Jones average will be for the year 2004 based on my recent trip.