Michio
Kaku (Andrea Brizzi)Michio
Kaku (Andrea Brizzi)
Not long ago in this space, I spoke with Michio Kaku, the author of “Physics of the Impossible” and a professor of theoretical physics at the Graduate Center of the City University of New York, about science-fiction-inspired technological breakthroughs that might actually occur within our own lifetimes. This week, Kaku talks about three long dreamt-of technologies that he categorizes as class I, class II and class III impossibilities — in other words, things you’ll simply never see during your time on earth. (Unless, like me, you plan to live forever.)
Teleportation
“The principle of teleportation is a class I
impossibility, in the sense that it is impossible today, but it doesn’t violate
the laws of physics, and it might be possible on a scale of one hundred years.
We can already teleport the information of a photon, cesium atoms and beryllium
atoms. If I have two atoms, A and B, they can be in different states, but I can
transfer the information of atom A into atom B, so that atom B becomes
indistinguishable from atom A. But you have to have A and B ready, so that the
information of A is transferred into B. We can already do this now with entire
atoms. I suspect that within a decade, we’ll be able to teleport the first
molecule, and maybe even a virus.
It’s not like in ‘Star Trek’ where you dissolve a person’s atoms and somehow radio this information to another source, and you recreate the person on the other side. You’d have to have, molecule for molecule, another object at the other end, whose information is different from yours. You know the movie ‘Invasion of the Body Snatchers’? A pod is created that has no life in it. But then the pod absorbs your identity, and wakes up, and it’s you inside the pod. That’s kind of spooky, right?”
Time Travel
“I call this a class II impossibility, that might be
realized centuries or millennia from now. Einstein’s equations, believe
it or not, do allow for time travel. But there are still problems with
time-travel devices. First of all, energy. Michael J. Fox put plutonium in a
DeLorean and rocketed back to the 1950s. You can calculate that plutonium is not
enough. You’re talking about the energy, basically, of a black hole or a star.
The next dispute is stability — how stable are these time machines? If you go
into it, will radiation kill you? Will it close up as you enter it? Now the
question of the paradoxes comes in. If you do send an object back in time, what
happens if you alter the past? What happens if you shoot your parents before
you’re born?
My favorite solution is the many-worlds theory: when you go backwards in time and you save Abraham Lincoln from being assassinated, you’ve actually saved someone else’s Abraham Lincoln. Your past cannot be changed, and you’ve gone to a parallel universe. If the river of time forks into two rivers, you hop across rivers after the fork. Another interpretation is if you go smoothly into the past, you fulfill the past. You didn’t alter the past — it was meant to be this way. And the third interpretation is, I think, the most implausible: you go backwards in time, you’re about to pull the trigger to kill your parents before you were born, but there’s something preventing you from doing it. For example, there’s a law of physics, called gravity, that says you cannot walk on the ceiling. You may want to walk on the ceiling but you can’t do it. Igor Novikov envisions a law of causality that works like this. I tend to disagree. How would you devise a law of physics to prevent causality change when anything can change causality? Just by the fact that you’ve entered the past, you’ve changed the weather pattern. You changed the objects around you. I don’t see that as a very strong possibility.”
Precognition
“I call this a class III impossibility, that cannot happen
with the laws of physics as we know them today. It turns out that
Maxwell’s equations, which are the equations for light, do in fact have
solutions that go backwards in time. So you could, in principle, send Morse code
to yourself in the past, and tell yourself about the stock market of the future.
This has been known for 100 years, that these marvelous equations which give us
television, radio, electronics, lasers, this phone call, do allow for this
bizarre set of advanced solutions. But — and here’s the big but — the solution
that goes to the past represents anti-matter. So when matter goes backwards in
time, it is indistinguishable from anti-matter going forwards in time. This blew
a lot of people’s minds. We know now that the laws of physics as presently
constituted do not allow for causality violations. The effect always comes after
the cause.
Let’s say you have a gateway from the future to the past, like a telephone conversation with your past self. If you believe in time travel the way I first presented it, this telephone call would not be to your real self — it would be to a self that is identical to yourself back then, but it is not yourself, because you never had memories of this phone call. You’re talking to another stream of time. It looks like you, it has the same memories of you, but it’s not really you. So causality is not being violated, unless you had new laws of physics. Even string theory — that’s my day job — has causality preservation. But there could be an infinite number of parallel universes. In other words, Elvis Presley could be alive in one of these parallel universes. Believe it or not, we physicists take this seriously. No matter how crazy it may sound.”