Theoretical physicist and string theorist Michio Kaku shares his thoughts on time travel, matter-fabricators and 2001: A Space Odyssey.
Also, be sure to check out Professor Kaku's latest book, Physics of the Impossible, available from Doubleday.
1. If time machines exist, can we ever hope to meet our older, or
younger, selves?
A. That is a big "if." But assuming they exist, then there is hope that we might meet our older or younger selves, but they won't be exactly "us." The river of time, I believe, may fork into two rivers if we travel in time.
Hence, if we jump from one time line to another time line, we may meet ourselves in the past, but these people won't really be "us." They will be genetically identical to us, but will be a younger or older version of ourself in a parallel universe. Hence, we won't have any time paradoxes. So if we change the past, we change someone else's past, who is genetically identical to us, but is not really "us." Of course, we won't know for sure until we finally build a time machine. (In fact, I give a blueprint for a time machine in my book, Physics of the Impossible, which is consistent with all known physics.)
2. Since we haven't ever met any time travelers from the future, does that mean they will never be invented?
A. No. Perhaps we are not interesting to them. We think we are so great that they will want to visit us, but maybe we are too primitive for them. After all, if we see an anthill, do we go down to the ants and say "I bring you beads. I bring you trinkets. Take me to your leader"? Some of us may even have the urge to step on them.
But the technological distance between an ant and us may be small compared to the technological chasm between us and a time-faring civilization. They may be thousands to millions of years ahead of us in technology, and hence have no interest in visiting us. But one day, if someone knocks on your door and says she is your great-great-great-granddaughter, do not slam the door. Perhaps in the far future our descendants will develop time machines, and want to visit their illustrious ancestors.
3. Are fears of robots taking over the world, Terminator-style, ever founded in reality?
A. Yes, robots may eventually take over the world. But we will have plenty of warning. Right now, robots have the intelligence of a cockroach. A retarded, stupid cockroach. Our most advanced robots take about six hours just to walk around a strange room. It may be years to decades before they are as smart as a mouse, then a rabbit, then a dog or cat, and finally a monkey. By the time they have the intelligence of a monkey, they can be dangerous, since they will have agendas of their own. But we will have plenty of warning. By the time they are as smart as a monkey, I think we should put a chip in their brains to turn them off when they have murderous thoughts. The key is that we will have plenty of time before these robot creations become truly sentient and conscious, with their own goals and desires.
