The Universe Within: Discovering the Common History of Rocks, Planets, and People

by Neil Shubin

  The good news was that, now free of anyone else’s priorities, Penzias and Wilson were able to turn the dish to their real goal—observing the radio waves that hit Earth from space. But their wonderful contraption was not up to the new job. The sensitivity, so essential for their gig with NASA, made the dish a nightmare to work with. It picked up all kinds of faint signals and noise, almost like persistent static on a TV.

  Their efforts to remove the noise read today like an attempt to find and remove a fine needle from a shag rug. First they tried to filter out the signals produced by radios. No luck; interference remained. Then they cooled the detector to -270 degrees centigrade, a temperature at which molecules come close to stopping their movement. Still interference. They climbed inside the detector and found that birds had sullied the interior via their digestive processes. Wiping away the evidence of those encounters helped a bit, but the interference remained. This background noise was constant through day and night and was about one hundred times more than they would have expected.

  Unknown to Penzias and Wilson, a set of Princeton scientists used computer models to make a conjecture. If there was a big bang, some of the energy should be remaining in the heavens, drifting like smoke from an explosion. With 13.7 billion years of cooling and expansion since the event, this radiation should be found everywhere and be of a particular wavelength. This was quite a specific quantitative prediction, and it offered no room for waffling. A friend showed Penzias and Wilson these papers, and immediately they saw the real meaning of their static interference. The background interference was not noise; it was a signal. And it was of the exact type predicted by theory. Penzias and Wilson had discovered the remnants of the big bang, a discovery that won them the Nobel Prize in 1978.

  Being a fossil hunter, I dig in the ground to uncover relics. But every astronomer is a paleontologist of sorts. As Carl Sagan famously said, the light of the stars we see was formed in chemical reactions from a long time ago. The vastness of space means that starlight hitting our eyes is no artifact; it is the real deal—a visitor from a time before the birth of our species, even in some cases our planet itself. With such time travelers coming down to us each night, the trick to reconstructing our past comes from learning to see the light and radiation of stars in new ways.

  For thousands of years, mankind considered itself the pinnacle of life’s creation on a planet sitting in the center of the universe. Science changed that perception. Leavitt, Hubble, and others helped us see that we live near the margin of a vast galaxy, in a universe of galaxies, with our planet one of many worlds. Darwin and the biologists had their say too. Our entire species is but one little twig on an enormous tree of life filled with all life on Earth. But each discovery that moves us from the center of creation to some obscure corner brings an entirely new relation between us, other species, and the entire universe. All the galaxies in the cosmos, like every creature on the planet, and every atom, molecule, and body on Earth are deeply connected. That connection begins at a single point 13.7 billion years ago.

  STARS ARE BORN

  As a species whose history has been in oceans, streams, and savanna plains, we humans have had our senses tuned to the chemical and physical world of land and water—to predators, prey, and mates we can see or hear. Nowhere in our history has there been a premium on the ability to perceive extra dimensions, times on the order of billions of years, or distances in a virtual infinity of light-years. To achieve these insights, we repurpose tools that served us so well in our terrestrial existence to new ends. Logic, creativity, and invention project our senses and ideas to the far reaches of time and space.

  The physics of the point that existed 13.7 billion years ago is mostly beyond our imaginations, not to mention our conceptual tools. Gravity, electromagnetism—all the forces at work around us did not have an independent existence. Matter as we know it didn’t exist either. With everything that would become the universe packed so tightly in one spot, there was an enormous amount of energy. In such a universe, the physics of small particles, quantum mechanics, and that of large bodies, general relativity, were somehow part of a single, overarching, and still unknown theory. Just what that theory is awaits the next Einstein.

  By about .000000000000000000000000000000000000000001 second the universe was roughly 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 degrees Fahrenheit, and the state of things starts to come more clearly into focus. This time begins the period of very rapid expansion of the universe. The big bang is not like an explosion where objects are projected from each other; space itself expands. With this expansion comes cooling over time. As the universe cooled and expanded, the forces and particles that make our world today emerged.

  Einstein’s relation E = mc2 holds a key to the early events of the universe. The equation reveals the relationship between energy (E) and mass (m). Since the speed of light (c) is a huge number, it takes an enormous amount of energy to make an ounce of mass. The converse is also true: an infinitesimal amount of mass can be converted into a vast amount of energy.

  One-trillionth of a second after the big bang, the universe was the size of a baseball. The energy contained in the universe at these early moments was the raw material for the production of a gargantuan amount of mass. As space expanded, energy, following Einstein’s equation, converted into mass, in this case ephemeral particles. In such a hot and small universe, everything was unstable: particles formed, collided, and disintegrated only to repeat the process trillions upon trillions of times.

  The particles at this moment of history were of two opposing kinds, matter and antimatter. Matter and antimatter are opposites and annihilate each other on contact. As energy converted to mass, no sooner were matter and antimatter particles produced than they collided. Most of these collisions led to the particles being completely extinguished. If this were the complete state of affairs, we—people, Earth, even the Milky Way—would never be. Particles would have been destroyed almost as soon as they formed. A slight—and by that we mean about one-billionth of 1 percent—excess of matter over antimatter was enough for matter to take hold in the universe. Because of that tiny imbalance, we are, as the physicist Lawrence Krauss once described, every bit the direct descendants of that one-billionth of 1 percent surplus of matter over antimatter as we are of our own grandparents.

  At one second, our universe started to form entities we would recognize, if only very briefly. These are the collection of subatomic particles that make momentary appearances in some of the largest atom smashers today—leptons, bosons, quarks, and their kin.

  A little over three minutes after the birth of the universe began the stirrings of one of the deepest patterns in the world, captured by the chart that is the source of either awe or angst for young science students—the periodic table. The periodic table catalogs all known elements by the weight of their nuclei. The chart drawn for this moment of time would be a huge relief to our students. There would be only three boxes on it: hydrogen, helium, and lithium.

  Hydrogen and helium today remain the most common elements in the universe. Hydrogen makes up about 90 percent of all matter, helium about 5 percent. All of the others that compose us and run through the lives of people and stars are but a rounding error.

  After 300,000 years the universe had cooled and expanded enough so that true atoms could exist. Nuclei were able to pull electrons into their orbits. This new combination of electrons with atomic nuclei set the stage for reactions that underpin every moment of our lives today.

  We live in a daily marketplace of electrons, with trades measured in millionths of seconds. I write this book and you read it based on the energy released from these exchanges. The molecules in our bodies exchange these tiny charged particles as part of the daily business of their interactions. Some electron movements release energy; reactions involving oxygen tend toward this outcome. Other reactions serve to bind atoms into molecules or molecules with one another. These daily trades define the reactions between t
he planet’s atmosphere, its climate, and the metabolisms of every creature on Earth. When you eat an apple, electrons from that material course through your cells to drive the metabolism to power your body. The electrons inside the apple to begin with were derived from the minerals in the ground and the water that fell from the sky. The electrons in both have cycled through our world for eons. And all of these came about well before the formation of the planet, the solar system, or even the stars.

  With expansion and cooling, the stage was set: particles came together to make nuclei, nuclei came together with electrons to make atoms, and different atoms could now make the trades that are so essential for assembling ever-larger entities. One important thing had yet to take hold: gravity.

  About 1 million years after the big bang, the universe cooled and expanded to the point where matter could get big enough for the force of gravity to have a meaningful impact on the shape of things. Order and pattern in the heavens emerge via a balance of forces: gravity serves to attract objects, while other forces, such as heat, and more mysterious ones, such as dark energy, serve to repel them. These relationships define the origin of the patterns we see in the universe, from the shape of gas clouds and stars to galaxies and planets. More fundamentally, they explain how chemistry itself evolved from a periodic table with only three elements to the one with over one hundred we live with today.

  How did the world of atoms that make our planet and our bodies come about from the three that existed 13.69 billion years ago?

  The march up the periodic table, from lighter elements like hydrogen and helium to heavier ones like oxygen and carbon, happens by the manufacture of ever-bigger nuclei. Under the right conditions two small nuclei can come together and make a larger one. The arithmetic of this combination depends on the physics of the nuclei themselves. In most cases, 1 + 1 does not equal 2: nuclei do not come together to make a new nucleus that is their simple sum. Often the new nucleus is lighter than that sum, and matter has been lost. But we know from Einstein’s E = mc2 that matter is not really lost; it is converted to energy. These fusion reactions, then, can release enormous amounts of energy.

  Humankind has tried to marshal the energies of fusion, but under normal circumstances atomic nuclei don’t fuse spontaneously. The reaction takes a lot of energy to jump-start. Using this principle, Edward Teller, the father of the hydrogen bomb, made the first fusion device by attaching an atom bomb to another machine that allowed for the combination of nuclei. Atom bombs release energy by fission, a reaction that doesn’t require much energy at the start. Teller, with his colleague Stanislaw Ulam, designed a system, code-named Ivy Mike, that was about the size of a small factory on the Pacific island of Enewetak. When it exploded in November 1952, the energy from the atom bomb forced the hydrogen atoms in the reactor to fuse, and a massive explosion ensued. Teller witnessed it from the seismograph in the basement of the geology building at the University of California at Berkeley. Enewetak was totally denuded, with a hole a mile wide in its center. Fragments from the island’s lush coral reefs were ejected fifteen miles away. In analyzing the detritus left from the conflagration, the scientific teams discovered that the energy caused a number of large nuclei in the neighborhood to fuse, thereby producing entirely new elements never before seen on the planet. They were given the names einsteinium and fermium, after the scientists whose breakthroughs told us of the energy inside the atom.

  Fusion reactions are the atomic engine that fuels the heat of stars. There is an essential difference between the Teller-Ulam device and celestial objects: Teller used an atom bomb to jump-start his fusion reactions, while the reactions inside stars depend on the force of gravity.

  We can see evidence of these kinds of reactions today. Stare long enough at the constellation Orion using your peripheral vision, concentrating on the three stars that make the dagger on its belt, and if weather permits, you will see the fuzzy patch known as the Orion Nebula. When seen through a telescope, the nebula gains texture and complexity, appearing as a broad cloud with a number of smaller stars inside. The nebula itself is a huge field of gas, which, not entirely unlike that of the primordial universe, is giving birth to stars—about seven hundred of them. Of course, given the distance of the nebula from us, we are looking at baby pictures of starry infants from thousands of years ago.

  During the formation of stars, fields of gas get so massive that the more particles they pull in, the stronger the force of gravitational attraction grows inside the cloud. At some point the mass of the gas cloud crosses a critical transition, and the gravitational attraction becomes a runaway process in which all the gas begins to collapse into a central point. Gravity pulls all the nuclei of the elements together, merging them. This union forces the nucleus to make a new combination; instead of one proton, it now forms a heavier nucleus with two. But this new nucleus is lighter than the sum of its parts. The lost mass, following E = mc2, is converted to an enormous amount of energy released into space.

  The size and life of any given star are defined by the push and pull that goes on inside the star: the force of gravity pulls elements in, and the heat of the fusion reactions works to separate things.

  Stars are like an engine that first consumes one fuel, then, as this fuel is depleted, begins consuming a new one. The most basic star is one that fuses the smallest atom, hydrogen, to make helium. The sun is one of these ordinary stars. Over time, as hydrogen is consumed and the conditions become right, the star shifts to fusing the helium it made. For a while, it chugs along consuming the nuclei of helium to make even heavier elements. Once the helium is depleted, fusion reactions consume those heavier elements. And so on. This process leads to the production of oxygen, carbon, and heavier atoms. Through the fusion reactions inside stars, the periodic table went from having only three elements to having scores of them.

  Fusion reactions in stars make most of the heavier elements in our bodies.

  Stars can consume ever-heavier atomic fuels until they hit a stopping point defined by the laws of physics and chemistry. That point—the element iron—holds a very special place in the periodic table. Elements smaller than iron can fuse and concomitantly release enormous amounts of energy. Elements larger than iron can also fuse but, because of the structure of their atomic nuclei, not as much energy is released. More energy needs to be put into fusing these larger nuclei than can be gained from the fusion reaction itself. If, for example, iron formed the basis for a power company’s nuclear reactor, less energy would be gained from the reactor than was put into it.

  This equation is losing math for a star, but a huge gain for us. As a star consumes all of the lighter elements, and marches ever higher in the periodic table in the fuels it consumes, iron accumulates in the center. As more and more iron accumulates, the fuel for fusion is consumed, nuclear fusion reactions cease, and the star begins to emit less heat. Iron nuclei, under the right conditions, can absorb energy, almost like a nuclear explosion in reverse. With so much energy released only to be absorbed, these conditions can set off a massive chain reaction that ends as a vast and catastrophic explosion. In seconds, these explosions release more energy than stars like our sun emit in their entire lifetime.

  We recycle. Hydrogen inside us comes from the big bang. Other elements come from stars and supernovae. And there they will return when the elements that compose us get spread around the universe by a future supernova.

  This blast is one kind of supernova (another kind can be triggered by collisions of stars). Supernovae work something like Teller and Ulam’s crude device. The energy of one explosion brings new kinds of fusion reactions. Recall those fusion reactions for elements heavier than iron? Supernovae release so much energy that these expensive reactions happen. All the elements heavier than iron, such as the cobalt and cesium in our bodies, derive from supernovae.

  Here comes the important part, at least for us. The blast of the supernova spreads atoms of the dead star across the galaxies. Supernovae are one engine that powers the m
ovement of atoms from one star system to another.

  The smallest parts of our bodies have a history as big as the universe itself. Beginning as energy that converted to matter, the hydrogen atoms originated soon after the big bang and later recombined to form ever-larger atoms in stars and supernovae.

  The sky, like a thriving forest, continually recycles matter. With the heavens so full of stars manufacturing elements, then occasionally exploding and releasing them, only to recombine them again as a new star forms, the atoms that reach our planet have been the denizens of innumerable other suns. Each galaxy, star, or person is the temporary owner of particles that have passed through the births and deaths of entities across vast reaches of time and space. The particles that make us have traveled billions of years across the universe; long after we and our planet are gone, they will be a part of other worlds.

  CHAPTER THREE

  LUCKY STARS

  Ever since the big bang, innumerable stars and galaxies have emerged and disappeared. We are relative newcomers to this party. By “we” I mean our entire solar system.

  It took big ideas and big science to see how our little patch of the universe came into being. The Swedish thinker Emanuel Swedenborg was occupied by important questions throughout his life. Born in 1688, he lived most of his eight decades believing he should have one great idea per day. In his early years, he worked as a natural philosopher seeking to intuit the structure of the natural world. He inferred, for example, the presence of nerves and a nervous system. Turning his thoughts to the cosmos, Swedenborg proposed a theory for the origin of the solar system. He envisioned that the sun developed from a cloud of gas and dust that collapsed on itself and condensed. As the sun took shape, the primordial dust remained as a disk of debris that swirled around the young star. Over time, portions of this cloud coalesced to form the planets of the solar system. The idea was to remain dormant until two decades later, in 1755, when the philosopher Immanuel Kant had his go at developing ideas on the origin of the solar system. The theory he ultimately developed was largely similar to Swedenborg’s.