In December's "How to Survive the End of the Universe (In 7 Steps)," physicist Michio Kaku describes how a future civilization might beat a path to another universe when time's up in our own. His survival guide to the end of the cosmos generated quite a few insightful letters and questions from our readers. We presented some of those queries to Kaku. His answers appear below.
Full name: Richard Shelton
Location: New Orleans, Louisiana
Question: As the universe expands, will the constants change? For example will e, pi, c, and h all change due to the expansion? If so, at what degree of change will life become impossible due to the change in physical processes?
Kaku responds: At the present time, there is some speculation among physicists that these constants may change with time. Mathematical constants, such as e and pi, will not change, but G (Newton's constant), h (Planck's constant), and c (the speed of light) might. Years ago, the Nobel laureate Paul Dirac speculated that G might change over cosmological time periods. And more recently, there has been some data (hotly debated) that c might be changing with time, which in turn has created a small cottage industry of papers trying to modify Einstein's special theory of relativity. I personally remain cautious. So far, there is no solid experimental evidence that the fundamental constants are changing with time. And theoretically, string theory (the leading "theory of everything") predicts that these constants will not change at a fundamental level. Although I am skeptical of changing the fundamental constants, physicists should always remain open to "crazy" ideas, because one day one of them might be right.
If some basic constants were to change, however, life as we know it might be impossible. A slight change in G and the nuclear force, for example, might make stars burn out much too quickly for planets and life to form, or else nuclei might be unstable, and hence the atoms of our body may disintegrate. This is the anthropic principle, the fact that the fundamental constants seem to be finely tuned to allow for life. Changing them even slightly makes life impossible.
Full name: Grant Walker
Question: What exactly do scientists agree on what the physical form of a black hole is? I've seen many models, and they all show a flat plane, with the black hole sinking down into what looks like an odd-shaped hole in a flat plane. This confuses me because I know that space isn't a flat plane. Is a black hole more like a singular point in space that everything is sucked into, almost in the shape of a ball? Or do scientists perceive these models as portals into other dimensions?
Kaku responds: You are correct that the popular depiction of a black hole—a flat plane with a sinking hole in the center—is incorrect. Moviemakers forget that this funnel-like black hole is only a teaching device that we physicists use to describe curved space, which is difficult to illustrate.
For a nonrotating black hole, the most realistic description might be a black sphere. The sphere represents the event horizon, or the point of no return. Inside the sphere there is presumably a tiny dot, the black hole itself. For a rotating black hole, the black hole itself is probably a ring of spinning neutrons, which does not collapse because of centrifugal forces. The ring is then enclosed by the event horizon.
The debate occurs concerning what happens if you pass through the ring. Since gravity is finite inside the ring, mathematically you will fall outside our universe through a wormhole into a parallel universe. In fact, each time you pass through the ring, you enter a new parallel universe. However, there is a debate as to whether you can actually make it through the ring. Some physicists believe that the wormhole may close up as you enter it, or that you might be killed by radiation effects. This is still an open question.
Full name: Matthew Rhoda
Question: What is exactly hyperspace, and how exactly does one access it?
Can you overview the quantum "space foam" for me also?
Kaku responds: Hyperspace, simply put, is higher dimensional space-time beyond the familiar three dimensions of space and one of time. So far, there is absolutely no proof of the existence of hyperspace, although hyperspace gives us the most compelling method by which to unify the forces of nature. At present, several physics labs around the world are doing experiments to prove or disprove the existence of these higher dimensions.
Theoretically speaking, in something called M-theory, the universe can be considered to be a "membrane" floating in 11-dimensional hyperspace. This means there could be other membrane universes out there, also drifting in 11-dimensional hyperspace.
Space-time foam is simply the grainy structure of space-time at very small distances, the Planck distance, or 10 to the minus 33 centimeters. At these very tiny distances, we believe that space-time becomes foamy, with tiny little bubbles and holes emerging. These bubbles are "baby universes," and the holes are wormholes connecting our universe with another parallel universe. So far, our instruments are too primitive to probe these very tiny distances. Some believe that an advanced civilization might be able to grab one of these holes in the foam and stretch it, giving us a wormhole that may connect two points in space and time, although this is still speculative.
Full name: Jesse Franklin Wade
Location: Richmond, Virginia
Question: If I were to enter a parallel universe, would the atoms in my body then turn into energy since I would be out of phase?
Kaku responds: It is not clear if we can ever enter a parallel universe. However, if we could, the dynamics depend on precisely how we enter it. For example, if this parallel universe opened up via the "false vacuum" of inflationary theory, then the new universe would be based on a different vacuum, with potentially dangerous properties; that is, the protons and neutrons of our body might not be stable, and the atoms of our body would dissolve. Or, if we entered the parallel universe via a Kerr black hole, then it's not clear if we would be destroyed upon entering the wormhole. On the other hand, it might be possible to find false vacuums very similar to ours, or to build sufficient shielding to make possible a voyage through the Einstein-Rosen bridge. These, and many other fascinating properties of parallel universes, are discussed in my latest book, Parallel Worlds (Doubleday) which hit the bookstores in January. In that book, I speculate that any advanced civilization facing the ultimate Big Freeze that will destroy the universe will necessarily have to exploit the unified field theory and open up a gateway to a warmer, neighboring parallel universe.
Full name: Chris Soyars
Question: How can a nanobot be created that is smaller than an atom? Wouldn't the nanobot be made of atoms? Even if it were possible, how can you shrink DNA, which is molecular? I smell random speculation!
Kaku responds: Nanobots, of course, cannot be smaller than an atom. However, if a single sophisticated atomic nanobot could make it through a wormhole, then the rest of the information necessary to reconstruct our DNA need not be molecular at all. For example, a Type III civilization could send information (in the form of gamma-ray pulses or subatomic particles) across the wormhole, giving detailed instructions to the nanobot on the other side concerning how to reconstruct the DNA necessary to resurrect an entire civilization. Since information can be carried by subatomic particles and photons, then DNA molecules themselves need not be transmitted through the wormhole. All of this is sheer speculation, of course, but there is nothing in the laws of physics forbidding this, as far as we know.
Full name: Joseph J. Senderak
Location: Schaumburg, Illinois
Question: The article "How to Survive the End of the Universe" describing negative matter was interesting. This compound has been known since the 1960s. Anyone who watched Rocky and Bullwinkle cartoons will know it as upsidaisium.
Kaku responds: Negative matter has been featured in many science fiction stories (since it has antigravity properties) and even cartoons. Anything that "falls up" qualifies as negative matter. Unfortunately, in the realm of real physics, no one has yet found any negative matter (indeed, it would have been ejected by Earth billions of years ago), but the stakes are high. Anyone who finds negative matter will surely win the Nobel Prize. Also, remember that negative matter is the basic ingredient for time machines.