전에 게시판에서 소개받은 www.scientificamerican.com에 들렀다가. 마이클 크라이튼의 타임라인에 영감을 주었다는 michio kaku라는 물리학자와의 대담이 실려있어, 그 중 흥미로운 부분을 발췌했습니다.
뒷북이 아닐까 걱정이 되지만요.^^  



SA: The idea in Timeline is that you can "fax" particles into the past. What is the kernel of truth there?

MK: In the last 10 years, there has been enormous progress in something called quantum teleportation. This is not science fiction anymore. Now, to be real, we're not talking about sending Captain Kirk across space and time. But we are talking about sending individual photons across space. In a few decades, maybe we will teleport the first virus, if the virus consists of a few thousand molecules. But at the present time, that's the limit of what we can do. And we can only teleport things in space, not time. But the concept of faxing matter is not totally out of the question. And that was also raised in my book. So there is a little bit of truth there.

SA: In Timeline the characters travel back to France in A.D. 1357 because the wormhole happens to let out there. They have six hours to return, but their six hours in the past are synchronized with the present. How plausible is all that?

MK: It depends. There are many designs for time machines. Wormholes from the vacuum would connect randomly with any point in space and time, so the other end would connect God knows where. Probability-wise the wormhole would be more likely to connect with the universe back in time, rather than the present. And if the mouths of the wormhole are stationary relative to each other, time will pass at the same rate at each mouth.

SA: Wouldn't time travel lead to paradoxes?

MK: There are about four or five main classes of paradox. The most famous is called the Grandfather Paradox, and that's when you go back in time and kill your parents before you were born. If you kill your parents before you were born, how could you be born and kill your parents before you were born? There are two schools of thought on this. First is the Russian school. Igor Novikov [of Copenhagen University] is a well-known cosmologist. He proposes that free will is somehow abridged by going backwards in time. Something happens to prevent you from killing your parents before you are born. Or let's say, for example, that you went backwards in time to when Queen Elizabeth's forces defeated the Spanish Armada. And let's say you give a submarine to the Spanish with machine guns; then of course you're altering human history and we are all speaking Spanish now. Novikov says that's not possible, because when you go backwards in time and give the submarine to the Spanish, something prevents you. Well, my attitude is, in the future, advanced civilizations might simply mail the submarine to the Spanish without any free will being abridged; inanimate matter will go through the time machine and change the past. That's why I tend to doubt the Novikov interpretation. It's simply too much to assume that the laws of the universe conspire to prevent paradoxes.


SA: Then what resolves the paradox?

MK: I prefer the "many worlds" interpretation. [Editor’s note: Quantum physics describes a particle by a probabilistic wave function, such that its position is indeterminate until the wave function "collapses" and the particle assumes a definite, though randomly determined, position.] The many worlds theory simply says that maybe the wave [function] never collapses. Maybe the wave just keeps on bifurcating every time it hits an obstacle. So the timeline is constantly bifurcating because the wave is bifurcating all the time. We just happen to be in one thread of this wave. And we have the illusion that we are the only ones. In this other thread, they think they are the only universe. The reality is, nobody's function has collapsed.

In time travel scenarios, you would simply go from one thread to the next, one timeline to the next timeline. And the two look awfully similar. If the many worlds theory is correct, it means that if you go backward in time and kill your parents before you were born, they are somebody else's parents. The timeline has diverged. Your parents gave birth to you, in your universe, in your timeline. So if you have the many worlds theory, there are no paradoxes, just different timelines.