Time Travel Theories and a Whimsical Look at Physics

Time Travel:
Based on science, yes. Possible, probably not, at least not yet. Did I take some creative licence in Time Meddlers and Ice Tomb, for that matter? Absolutely. Or the stories wouldn't be exciting and ultimately the experiment would fail.

But I can tell you which theories I based the multiverse time machine on. The discussion may be long, complex, and dry if you're not a scientist, so I'll try to simplify and make it more interesting.

First we must discuss physics.

According to string theory, everything is composed of strings, both matter and energy. These strings can move and vibrate, giving the observed particles their flavour, charge, mass, and spin.

But what is string theory, you ask? Well, I imagine my characters in Ice Tomb, particularly Dmitri, the astrophysicist, can explain it better. So I've placed an excerpt from the book below.

“The music is rather disturbing, isn’t it?” she said.

“No, not entirely,” said Dmitri, frowning. “It repeats. A pattern of four. It’s telling us something in a language of mathematics and waves.”

“What sort of language is that?” asked Allan. “I’ve studied a lot of ancient languages, but nothing that has to do with waves.”

Erica stared at him for a minute, trying to dredge up a memory that was buried in her brain. “Yes, you did. You said in the chamber beneath the sphinx there were strange oscillating lines and four numbers repeated over and over.”

“Well, yes. As I told you before, four was a special number to the ancients. Native Americans had a widespread numerical theme consisting of the four directions of space, the four divisions of time – day, night, the moon and the year – the four parts of everything that grows – the root, the stem, the leaves and the fruit. I could go on. There were others as well. The Greeks believed that everything consisted of four elements – earth, air, fire, and water. But the physicists I consulted seemed to think the numbers had more to do with quantum mechanics.”

“That’s it,” said Dmitri. “The music of the spheres.”

“What are you talking about?” asked Cathy, looking as frustrated as a child tackling a Rubix cube.

Dmitri smiled. “It is really clever and not likely, unless Allan is more correct than we imagined.”

“You think this was created by an ancient race?” asked Erica, wrinkling her forehead into the tight-fitting headgear beneath her helmet.

“Anything is possible. The music makes it frighteningly so. You see, Pythagoras—the father of mathematics who lived in Greece around 550 BCE—developed the notion that each element of the universe played its own music. He and his followers were the first people to relate numbers with music. They supposed the elements of numbers were the elements of all things, and the whole heaven to be a musical scale and a number. In this way, music was number and the cosmos was music.”

“So we’re listening to the music of the universe,” said Cathy, her face contorted in disbelief. “It isn’t very good, is it?”

“Wait. Wait,” said the astrophysicist holding up his hand.“There’s a great deal more to it. First, we’ll finish with Pythagoras's theory. He defined music as consisting of three types. Of course, there was ordinary music made by plucking strings or blowing pipes. Then there was the continuous but unheard music made by each human being that reflected the harmonious and inharmonious resonance between the soul and the body. I won’t touch that one. The third type was the one I mentioned – the music of the cosmos itself or "the music of the spheres." He broke down this music into a scale counting outward from earth – to the moon was a whole step, from the moon to Mercury, a half step, from Mercury to Venus, another half step, from Venus to the Sun was a minor third, from the Sun to Mars, a whole step, from Jupiter to Saturn, a half step, and from Saturn to the sphere of the fixed stars, another minor third. If you played it on a scale it would be C, D, E-flat, E, G, A, B-flat, B, D – the Pythagorean scale. The distance between the planets was believed to be a gigantic musical scale.

“Are you all with me still?” asked Dmitri, studying their frowning faces.

Erica nodded vigorously, although she still couldn’t guess what this ancient belief had to do with the discordant music on the computer.

Cathy shook her head. “I never studied music.”

“That doesn’t really matter, dear. As long as you understand that sound, including music, travels through space in waves.”

“I know that much,” she replied.

He continued. “So what you’re looking at now are sound waves transcribed from something else, I believe. Produced to signify what, you ask? Surely not Pythagoras’s music of the spheres. I don’t think so. Not exactly, but in a way he might have been very close to the truth that we are just now starting to realize. You see, Allan was right. The number four is very significant in quantum mechanics.”

“Quantum mechanics? Are we getting into physics?” Cathy asked, now with a very distraught look on her face.

“Yes, Cathy,” said Dmitri sympathetically. “A branch of physics that links our whole universe together. But first, we will deal with the number four. In quantum mechanics, the infinitely small particles that make up our world, there are four forces that come into play. The strong force that holds neutrons and protons together in an atom.” He held up his hand. “Don’t worry about it, Cathy. You don’t have to understand everything.”

“I was going to say, I do know what atoms are.”

“Good,” said Dmitri. “But atoms are not the smallest particles. They have a nucleus of neutrons and protons, surrounded by electrons, correct?”

Cathy nodded with a gleam of understanding in her eyes. Erica crossed her arms. This was far too slow for her taste. “We all understand about atoms,” she said. “And most of us know that quarks hold the nucleus together. Can we get on with it? What has this got to do with the music on the computer?”

“Okay,” he said, looking long and hard at Erica. “We are not all scientists,” he remonstrated. “So,” he turned back to Cathy, “of the four forces, the strong force would be Number One. I’m going by their strength now. Every other force is weaker than the strong force, so the force of the quarks,” he looked pointedly at Erica, “that hold the nucleus together has to be exceedingly strong to overcome the natural repelling force of the particles. Remember how like charges repel each other. Now the next force would be the electromagnetic force that makes the magma circulate inside the mantle of the earth and powers our computers and televisions and the nervous system in our bodies, for that matter. The third force is the weak force, which has to do with particle decay. Please stop frowning, Cathy. There will not be an exam. Anyway, the only force that we should concern ourselves with is the final and fourth force - gravity.”

“Number Four,” said Erica with dawning comprehension.

“Exactly. The weakest force in our world, but of extreme importance. It keeps our feet on the ground, the planets circling the sun, and the universe from expanding too quickly and killing the heat that gives us life. It is possible that these ancients are trying to tell us something about the gravitational force, maybe a fluctuation.”

“Then why the music?” asked Erica, wincing again at the discordant notes coming from the tiny speakers beside the monitor.

“That’s where it gets a little bit strange. Could these ancients have known about string theory?”

Erica blinked. “The Theory of Everything.”

“This is really too much for me,” said Cathy. “It’s enough that you think the–(don't want to give away too much, wink, wink)—built this pyramid. But you’re suggesting they knew about physics – something that I can’t even grasp without a great deal of pain.”

Dmitri looked at her patiently. “It does not seem likely, does it? Yet it does not seem likely that they could have built a structure such as this beneath the ice, let alone a computer. The music speaks to me in particular. An astrophysicist. String theory states that all particles in the universe—such as quarks, electrons, and a very important one, the graviton—are themselves constructed of tinier units called strings. What makes it so wonderful is that it explains the universe in terms of music. Each particle’s properties are a reflection of the various ways a string can vibrate—the resonant patterns—which give rise to the four forces, just as the different resonant patterns on a string instrument give rise to different musical notes. What we might be seeing now is the computer picking up from some other source the actual vibrations of the universe, particularly the force of gravity—Number Four.”

“Then why is it discordant?” asked Erica.

Okay, I'll take over from here. You'll have to read Ice Tomb to find out why it's discordant.

In string theory, there are supposedly 11 dimensions, not just the three we are familiar with, plus time, but rather seven others, including a long one where gravity is leached from . . . another universe, explaining why gravity is such a weak force. In the other universe it's strong, but by the time it reaches us it's nothing but a faint signal. The theory suggests that there are multiple universes, an infinite number, floating in this very long, but slim (so we can't see it) eleventh dimension. Some of these universes are totally different from ours, but others may be almost identical, with potentially identical histories. These universes look like membranes sandwiched together—hence M-theory.

Physicists think that at very small distances—10 ̄ ³³centimeters—spacetime is foamy, called quantum foam, and the main structures at these quantum distances are probably wormholes—little bubbles—that pop in and out of existence. These wormholes could potentially be connected to the other universes in the eleventh dimension. If you could manipulate the quantum foam, you could go through one of these bubbles. Carl Sagan consulted Kip Thorne—American astrophysicist and one of the world’s leading experts on the astrophysical implications of Einstein’s general theory of relativity—to come up with an idea for a time machine to help him write his novel Contact. One of Kip Thorne's original ideas was that we could obtain a wormhole by grabbing one of these bubbles, expanding it, and stabilizing it with negative energy.

Negative energy is energy below the vacuum state—the state of motionless nothing.

The Casmir effect was first demonstrated in 1948, by Dutch physicists Hendrik B. G. Casimir and Dirk Polder, with two parallel plates, uncharged, in a state of zero energy. The pressure is greater outside the plates than between them, so they collapse, going to a lower energy state—negative energy. Theoretically what is produced from this experiment is exotic matter with negative energy density. This exotic matter is required to stabilize a wormhole. Morris, Thorne and Yurtsever pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time, and suggested that negative effect could be used to stabilize a wormhole to allow faster than light travel. It has also been proposed to expand and stabilize a wormhole to another universe—a traversable wormhole.

These theories are what I based the time machine on in Time Meddlers and the "other" thing in Ice Tomb. Granted, I'm not an astrophysicist, and some of these theories removed from the mathematics and broken down into simpler terms may not mesh entirely with their complex counterparts. I borrowed the experiment that produced the Casimir effect and negative energy to open a wormhole, but in practice, it would likely require a great deal more energy to do this than we can currently produce.

For a fascinating discussion on parallel universes with various physicists,see http://www.bbc.co.uk/science/horizon/2001/parallelunitrans.shtml.

For an interview with Michio Kaku about time travel, see http://www.sciam.com/article.cfm?id=borrowed-time-interview-w

For a youtube video explanation of quantum foam: http://www.youtube.com/watch?v=84_kXpsDJEk

For a youtube explanation of M-theory: http://www.youtube.com/watch?v=4BRhjntvGoE&NR=1 and a model of M-theory: http://www.youtube.com/watch?v=JXeDpO2MG6Q&NR=1

Also watch The "Bubble Universe" Theory on Youtube.