Carlos I. Calle - The Universe: Order Without Design

To Benjamin, who may live to see the answers to many of our questions.

uring a scientific conference held shortly after the introduction of the inflationary theory describing the first moments of the universe, I asked Howard Georgi of Harvard University, whom I had just met, for a quick explanation of the negative pressure idea that was central to the new theory. Georgi promptly told me that he didn't understand that concept either and suggested that I should ask Alan Guth, the originator of the theory, who was also at this conference. I never had a chance to ask Guth directly and it was only after careful study of the papers and books that were eventually published that I was able to get a feel for the idea.

My goal with this book is to explain not just this idea of a universe that starts out with negative pressure but also all the revolutionary concepts behind the new scientific theories that are taking us beyond the moment of the big bang. These exciting theories and models are beginning to describe for us a universe that was never born and will never die, a universe that is fully explained by science.

In writing this book, I had the assistance of many people. My thanks go first to my wife, Luz Marina, for her understanding and unselfish support during the many hours that I spent at the keyboard. I would also like to thank my son Daniel for his enthusiasm about the central idea of this book. I wish to thank Professor Matt Young, of the Colorado School of Mines, who carefully and thoroughly read the entire book and made helpful suggestions and corrections. I would also like to thank Kristine Hunt, who provided meticulous editing and who made sure that the manuscript was consistent. I am grateful to my agent, Susan Ann Protter, for her kind support throughout the entire project. Finally, I would like to thank my editor, Linda Greenspan Regan, for her efficient editing.

he light reaching your eyes after it is reflected by the light areas of the page that you're reading now originated a million years ago, deep in the interior of the sun, where the temperature reached 10 million degrees. Some 600,000 km (375,000 miles) beneath the gaseous, hot, bright surface that we see from our planet, the cores of two hydrogen atoms coalesced into the nucleus of a heavy form of hydrogen called deuterium. A few moments later, the newly formed deuterium nucleus collided with a third hydrogen nucleus to form helium. The second collision produced something else: a photon, a tiny bundle of light that immediately started on a long and fortuitous journey toward the sun's surface. Life wasn't easy for that photon. Countless times, atoms and electrons in the sun absorbed the photon only to regurgitate it almost immediately, not without taking away some of its energy. More times than you'd care to count, the photon got ejected in the wrong direction, losing most of the ground that it had gained in previous attempts.

A million years after it started on its journey, the photon finally reaches the surface of the sun and sets out toward the Earth. Eight minutes later it is absorbed and reemitted by the molecules that make up the paper of this book. An instant later, the photon comes out and enters the cornea of your eye. As it did in the interior of the sun and while traveling through the Earth's atmosphere, the photon once again is absorbed and reemitted by the molecules in the cornea and the lens. The ciliary muscles that surround the lens relax, decreasing the radius of curvature, sending the photon through the vitreous, jelly-like body toward the paper-thin retina. There, the retinal, a compound derived from vitamin A, absorbs the photon, ending its million-year journey.

The energy of the photon absorbed in the back of your eye alters the geometry of the retinal, and this change causes a series of molecular transformations that triggers an electric signal that is carried by the optic nerve toward your brain. When the electric signals from a few other photons that originated a million years ago in the depths of the sun follow the first one, your brain integrates these signals and begins to form the image of the words on this page.

The actual processes both in the eye and in the core of the sun are much more complicated than described here. At first glance-a physicist's glance, but a glance nonetheless-the thermonuclear reactions that take place in the sun shouldn't happen. The hydrogen nuclei have positive electric charges (they are actually single protons) that repel each other with a force that becomes extremely large when they are brought close to each other. The two colliding hydrogen nuclei don't have enough energy to overcome this electrical repulsion, even when moving at extremely large speeds near the center of the sun. How do they do it? They actually tunnel through the electrical barrier. It is as if you were repeatedly bouncing a tennis ball against a wall with your racket, hitting the wall higher and higher, when suddenly, a few feet before the ball reaches the top, the ball goes through the solid wall and appears at the other side. According to quantum mechanics, that's exactly what happens to the colliding protons in the sun so that they can create the photons that eventually enable you to read this page.

Your eye is able to detect about five consecutive photons in a relatively dark room. In the brighter room you're sitting in now, you are actually receiving millions of photons. But they have to be the right photons; they have to have the right energies or you wouldn't be able to see them. The photons that are created in the sun have way too much energy for your eye to detect them. If fact, they have so much energy that they would damage your eye. They are actually gamma rays, a type of radioactivity. It is through their very frequent collisions that they lose the exact amount of energy so that your eye can detect them. And it takes a million years of continuous collisions to achieve that.

The sun sends out photons with energies other than visible light. However, most of them are in the visible range of energies. What's more, the sun's photon output peaks in the yellow-green part of the spectrum, which happens to be where our eyes are most sensitive (Fig. 1-1).

Figure 1-1. The sun's energy received on Earth peaks in the visible region. The maximum value is in the yellow-green region, where our eyes are most sensitive.