The Sciences

Expert Forum With Michio Kaku

A physicist and the end of the universe.


Sign up for our email newsletter for the latest science news

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


Age: 44

Gender: M

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


Age: 14

Gender: male

Location: Kentucky

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


Age: 17

Gender: M

Location: Texas

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


Age: 67

Gender: Male

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, ParallelWorlds (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

Age: 19

Gender: M

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.

Full name: Scott Jackson

Location: Irvine, California

Question: In "Seeing the Unseen" (December) E. L. Doctorow discusses the wall between science and the unfathomable. Later, in "How to Survive the End of the Universe" Michio Kaku discusses the theory of infinite parallel universes. The question is: Is the concept of infinity belong in the realm of science or in the realm of the unfathomable? That is to say, on which side of the wall does it lie?

Kaku responds: You raise some difficult theological and epistemological questions! In my personal point of view, everything is, in principle, knowable. We cannot know all the truths about the universe, but we can, with enough time, come arbitrarily close. For example, some infinities we see in physics are actually an illusion, created by our faulty mathematics and physics. The quantum theory of the relativistic electron, for example, was once thought to be hopelessly riddled with infinities, but Feynman, Schwinger, and Tomonaga won the Nobel Prize for showing how to banish the infinities of quantum-field theories. Similarly, the singularities we find in general relativity, such as black holes and big bangs, are actually due to the failure of Einstein's theory at these extreme points, signaling the necessity of a higher theory, such as string theory. Other infinities, such as the infinite number of universes in a multiverse, are perhaps real and physical and cannot be banished using clever mathematics. Of course, we can never know everything about the infinite number of these universes (it's hard enough knowing the truths about just our universe!), but personally I feel that if the theory is correct and we have enough time, we may come close to knowing about them as well. To sum up: I think, with enough time and patience, we will come arbitrarily close to knowing everything physical about the so-called unfathomable.

Full name: Robert J. Rorden

Location: Los Altos, California

Question: In your December 2004 issue Michio Kaku advocates sending a probe through a black hole. Here are some comments on this project. I believe that the nearest known black hole is near the center of our galaxy, about 50,000 light-years from here. If we build a probe that can accelerate to 70 percent of light speed (very expensive), it could make the trip in about 71,000 years. A signal could get back after another 50,000 to 121,000 years after launch. Can we build a machine that will work after 71,000 years in space, including millennia of intense ionizing radiation? Would anyone be listening? Will the human race even exist, considering its tendency to collective insanity (war)?

Kaku responds: Stellar black holes have been found in our vicinity, so we need not journey 25,000 light-years or so to the galactic center (where there is a monstrous black hole weighing about 3 million solar masses). But you correctly conclude that communicating with a probe sent to a black hole (by a Type 0 civilization like ours) would be impractical. My point is that a Type III civilization, perhaps 100,000 to a million years more advanced than ours, would have already mapped out most of the galaxy. Given these vast timescales, they would have enough time to send trillions of self-replicating robotic probes throughout the galaxy (exponentially growing like a swarm of viruses), to locate all the neighboring black holes, even traveling at sublight speed. Moreover, a Type III civilization may, by definition, have the ability to manipulate the Planck energy (10 to the 19 billion electron volts), so it is conceivable that they may be able to create wormholes to visit distant parts of the galaxy. In conclusion, what is impossible for a Type 0 civilization like ours may seem like child's play to a Type III civilization.

Full name:Jonathan Eziquiel-Shriro

Location: St. Augustine, Florida

Question: I read the December article on escaping an ending universe, and one small detail caught me for its omission. Actually it wasn't truly omitted, just possibly overlooked for importance. The seventh option for escaping the universe—using nanobots—talked about re-creating everything on another side, basically sending information through the wormhole via machine. Perhaps it is naive of me to assume, but isn't information all that our and any Type III civilization need to escape? The big concern, it seems, is the unknown of whether information can survive a wormhole trip. If somehow it can, perhaps one of those methods described would be enough; for example, just send raw data through and allow it to recombine at the other end. Perhaps a Type III would not need machines or devices to facilitate information dissemination. Perhaps the true power of the Type III civilization is to make all of history and time a singularity in itself that it could send where it wanted.

The other notion that occurred to me is that a Type III might not experience time as we do and could possibly experience all time as a moment. Wouldn't the ultimate harnessing of power allow a civilization to advance its understanding of dimensions and possibly transcend far beyond our current abilities? I tend to believe that the nature of a Type III civilization and its power-generating capabilities create possibilities way beyond the scope of our existence. Even a Type 1 civilization will have powers unimaginable to us today. This tends to lead me to the currently unimaginable conclusion that the members of a Type III civilization may become extracorporeal, no longer needing physical bodies to define them.

If that becomes the case, doesn't that radically change the need to escape our universe? Perhaps being as powerful as to exist on a higher plane beyond the constraints of our physical universe would mean such a civilization already regularly "jumps" from universe to universe at will—they are no longer bound by any sort of rules that we are. "Escape" might be a term that's only useful for us and our comparatively limited abilities of perception.

Nevertheless, we are only at the dawn of the first iteration of a Type I civilization. A lot of it seems to rest in the potential of chips, computing and entry-level quantum mechanics. Tasty stuff, but a meal so large we will be lucky to see the second course.

Kaku responds: You are correct that the important point is that information be sent through a wormhole to a neighboring parallel universe. However, information must come in a practical, sturdy, self-replicating form. For example, simply sending computer tape or digital code through the wormhole will not succeed. What is necessary is to send a probe that is self-replicating, which can create trillions of copies of itself, containing enough information to reclone their entire civilization. In other words, we need the hardware in addition to the software.

Full name: Keith Salvas

Location: Simi Valley, California

Question: I thoroughly enjoyed your article on "How to Survive the End of the Universe." However, I recently attended a lecture on supermassive black holes and I've found what appears to be a contradiction in one theory that makes traveling through such a place impossible. As the theory goes, if I could enter into the event horizon, then measure the circumference of space at a fixed point, by dividing by 2pi I should get the radius to the singularity. If I then move closer and make a similar measurement, I should get a radius that, when added to the distance I traveled from the first point, should equal the first radius. But the theory states that the sum of the two measurements would be greater than geometrically possible because the black hole stretches space. So here's the contradiction: If the singularity, which by definition is mass without volume, stretches space, then the closer I get to it the more space is stretched. So a geometric inch could be a mile, and the next inch inward could be 10 miles, and so on. This means that the closer I get to the black hole, the more space is stretched, to the effect that the closer I get to it the further away it becomes. The conclusion is that I could never reach the black hole itself because space becomes stretched infinitely at the singularity. This also makes the black hole a mini universe or a place where the universe is turned inside out. Do you have any comments on this apparent problem?

Kaku responds: Yes, as you approach a black hole, severe distortions of space and time take place, but they are visible mainly to someone far away observing you fall into the black hole. If you are unfortunate to fall into a stellar black hole, you will pass the event horizon and probably crash into the black hole itself in a blink of an eye. From your vantage point, death is mercifully swift. However, to an observer watching the event, he will see something quite different. Because light is stretched and redshifted as it reaches the observer, it appears as if you are slowing down in time. It appears as if you are moving in slow motion as you are being ripped apart. It seems to take thousands of years before you inevitably reach the vicinity of the event horizon.

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 70% off the cover price when you subscribe to Discover magazine.

Copyright © 2021 Kalmbach Media Co.