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

by Neil Shubin

  The hills in Greenland form large staircases of rock that not only break boots but also tell the story of the stones’ origins. Hard layers of sandstones, almost as resistant as concrete, poke out from softer ones that weather away more quickly. Virtually identical staircases lie farther south; matching sandstones, siltstones, and shales extend from North Carolina to Connecticut all the way to Greenland. These layers have a distinctive signature of faults and sediment. They speak of places where lakes sat inside steep valleys that formed as the earth fractured apart. The pattern of ancient faults, volcanoes, and lake beds in these rocks is almost identical to the great rift lakes in Africa today—Lake Victoria and Lake Malawi—where movements inside Earth cause the surface to split and separate, leaving a gaping basin filled by the water of lakes and streams. In the past, rifts like these extended all the way up the coast of North America.

  From the beginning, our whole plan was to follow the trail of the rifts. Knowing that the rocks in eastern North America contained dinosaurs and small mammal-like creatures gave us the aha moment with Chuck’s geological reprint. That, in turn, led us north to Greenland. Then, once in Greenland, we pursued the discoveries on the ground like pigeons following a trail of bread crumbs. It took three years, but clues in the red beds ultimately led us to that frozen ridge I trekked with Farish.

  Follow matching rocks (black) to find fossils. Success working rocks in Connecticut and Nova Scotia led us to Greenland.

  From the top of the ridge, the tents of camp looked like tiny white dots just below the horizon. The crest was windswept, but the bluff of pink limestone on which we were seated formed a quiet shield for Farish and me to assess the discovery. Farish’s jubilation confirmed my hunch that the white spot in the rock was indeed a mammal tooth. With the characteristic pattern of three cusps and two roots, it was a dead ringer for one of these beasts.

  Armed with confidence that came from this first discovery, the team looked widely across east Greenland, eventually finding better mammal fossils in subsequent years. The fossils came from a small shrewlike animal about half the size of a house mouse. Although it lacks the sort of awe-inspiring skeleton that would grace a museum rotunda, its beauty lies elsewhere.

  This is one of the first creatures in the fossil record with our kind of teeth: those with cutting surfaces defined by cusps that occlude on upper and lower teeth with a tooth row subdivided into incisors, canines, and molars. It has an ear that is like ours also, containing little bones that connect the eardrum to the inner ear. Its skull pattern, shoulder, and limb are also decidedly mammalian. We don’t know for sure, but it likely had hair and other mammalian features such as milk-producing glands. Every time we chew, hear high pitches, or rotate our hands, we use parts of our anatomy that can be traced through primates and other mammals to the structures in these little creatures from 200 million years ago.

  The rocks also tie us to the past; rifts in Earth, like those that led us to find fossil mammals in Greenland, have left their traces in our bodies as much as they have in the crust of the planet. The Greenlandic rocks are like one page in a vast library of volumes that contain the story of our world. Billions of years of history preceded that little tooth, and 200 million years have followed it. Through eons on Earth, seas have opened and closed, mountains have risen and eroded, and asteroids have come crashing down as the planet has coursed its way through the solar system. The layers of rock record era after era of changes to the climate, atmosphere, and crust of the planet itself. Transformation is the order of the day for the world: bodies grow and die, species emerge and go extinct, while every feature of our planetary and celestial home undergoes gradual change or episodes of catastrophic revolution.

  Rocks and bodies are kinds of time capsules that carry the signature of great events that shaped them. The molecules that compose our bodies arose in stellar events in the distant origin of the solar system. Changes to Earth’s atmosphere sculpted our cells and entire metabolic machinery. Pulses of mountain building, changes in orbits of the planet, and revolutions within Earth itself have had an impact on our bodies, minds, and the way we perceive the world around us.

  Just like human bodies, this book is organized as a time line. We begin our story about 13.7 billion years ago, when the universe emerged in the big bang. Then we follow the history of our small corner of it to look at the consequences of the formation of the solar system, the moon, and the globe of Earth on the organs, cells, and genes inside each of us.

  CHAPTER TWO

  BLASTS FROM THE PAST

  H375,000,000 O132,000,000 C85,700,000 N6,430,000 Ca1,500,000 P1,020,000 S206,000 Na183,000 K177,000 Cl127,000 Mg40,000 Si38,600 Fe2,680 Zn2,110 Cu76 I14 Mn13 F13 Cr7 Se4 Mo3 Co1

  is a formula of elements that make up the human body. We are a very select mix of atoms. Bodies are mostly hydrogen: for every atom of cobalt, for example, there are almost 400 million of hydrogen. By weight, we contain such a large amount of oxygen and carbon that we are virtually unique in the known universe.

  One particular element missing from bodies tells a big story. Helium, the second-most abundant atom in the entire universe, has an internal structure that leaves it no room to trade electrons with others. Unable to make these exchanges, it cannot participate in the chemical reactions that define life—metabolism, reproduction, and growth. On the other hand, oxygen and carbon are about twenty times rarer than helium. But unlike helium, these atoms can easily interact with different elements to form the variety of chemical bonds that are essential in living matter. Reactivity is the order of the day for the common atoms of bodies. Loners need not apply.

  The relative proportion of atoms is only a part of what defines our bodily structure. Bodies are organized like a set of Russian nesting dolls: tiny particles make atoms, groups of atoms make molecules, and molecules assemble and interact in different ways to compose our cells, tissues, and organs. Each level of organization brings new properties that are greater than the sum of its parts. You could know everything about each of the atoms inside your own liver, but that will not tell you how a liver works. Hierarchical architecture, smaller things making larger entities with new defining properties, is the basic way our world is organized and ultimately reveals our deepest connections to the universe, solar system, and planet.

  The Russian nesting dolls of all matter: tiny particles make atoms, atoms make molecules, and molecules make ever-larger entities.

  Pick up a scientific journal in biology nowadays, and you stand a good chance of seeing a tree of relatedness. Every creature, from human to Thoroughbred to prize Hereford, has a pedigree—its family tree. These trees define how closely related living things are: first cousins are more closely related to one another than they are to second cousins. Knowing the pedigree becomes the basis for understanding how different creatures are connected to one another, how species came about, even why certain individuals may be more susceptible to disease than others. This is why doctors take family histories in medical exams.

  A critical insight of modern biology is that our family history extends to all other living things. Unlocking this relationship means comparing different species with one another in a very precise way. An order to life is revealed in the features creatures have: closely related ones share more features with each other than do those more distantly related. A cow shares more organs and genes with people than it does with a fly: hair, warm-bloodedness, and mammary glands are shared by mammals and absent in insects. Until somebody finds a hairy fly with breasts, we would consider flies distant relatives to cows and people. Add a fish to this comparison, and we discover that fish are more closely related to cows and people than they are to flies. The reason is that fish, like people, have backbones, skulls, and appendages, all of which are lacking in flies. We can follow this logic to add species after species and find the family tree that relates people, fish, and flies to the millions of other species on the planet.

  But why stop at living things?

  The sun burns
hydrogen. Other stars burn oxygen and carbon. The fundamental atoms that make our hands, feet, and brains serve as the fuel for stars. It isn’t merely the atoms in our bodies that extend across the far reaches of the universe: molecules that make our bodies are found in space. The building blocks for the proteins and larger molecules that make us—amino acids and nitrates—rain down to Earth in meteorites and lie on the rocky crust of Mars or on the moons of Jupiter. If our chemical cousins are in the stars, meteors, and other heavenly bodies, then clues to our deepest connections to the universe must lie in the sky above our heads.

  Detecting patterns in the sky—the shapes of galaxies, the features on planets, or the components of a binary star—is no easy task. Eyes take some time to adjust to the dark, but so too does perception. You need to train the eye to perceive faint patterns in the night sky. When it comes to deciphering fuzzy patches of stars through a telescope or binoculars, imagination and expectation have a way of conjuring mirages in the void. Removing these and actually seeing dim objects in space means emphasizing peripheral vision, the most sensitive light-gathering part of our eyes, to pick up faint light and discriminate fuzzy patches from one another. As we learn to see the sky, color, depth, and shape emerge in the world above our heads much like when a fossil bone pops into view on a dusty desert floor beneath our feet.

  Discriminating celestial objects is merely the first step in learning to see the sky. Like a painting that has graced a house for generations, the stellar landscape we encounter today is much the same as that witnessed by our parents, grandparents, even our apelike ancestors. Generations of humans have not only seen the sky but, over time, built new ways of perceiving our connection to it.

  Our relationship to the stars changed dramatically because of breakthroughs made by the Harvard Computers at the turn of the twentieth century. Edward Charles Pickering, then director of the Harvard College Observatory, had a problem that required serious computation and analysis. The observatory was collecting reams of pictures of constellations, stars, and nebulae—so many that just managing and plotting the images was a daunting task. Of course, digital computers as we know them didn’t exist at this time and the calculations had to be done by hand. Pickering was famously cheap and once declared in a fit of exasperation with his existing staff that he could hire his maid to do this work at half the cost. He fell in love with his new idea and ended up pressing his real maid, Williamina Fleming, into service at the observatory.

  At age twenty-one and with a young son, Williamina Fleming was abandoned by her husband, leaving her penniless and without a trade. Pickering first hired her to clean house. Then, after his boast, he brought her to the observatory to manage his celestial images. Upon receipt of a large donation, Pickering was able to add a number of other women to the group. What Pickering could never have planned was that from this team grew some of the greatest astronomers of the time, or any time for that matter. These women collectively became known as the Harvard Computers: they sat with the raw data of astronomy, pictures of the heavens, and made sense of them.

  Henrietta Leavitt, the daughter of a Congregational minister, came to the observatory in 1895, first volunteering and later earning a salary of thirty cents an hour. She developed a love for astronomy in school, a passion that served her well during the long years she had the mind-numbing task of cataloging photographic plate after plate of stars and nebulae.

  As Leavitt knew, the different stars in the sky vary in color and magnitude of their light. Some stars are dim or small, others bright and big. Of course, there was no real way of knowing what magnitude meant for the real brilliance of a star, because an apparently dim star could be a big and bright one far away or a faint one relatively close.

  Edward Charles Pickering (upper row) and the “Harvard Computers.” Williamina Fleming is in the front row, third from left; Henrietta Leavitt is just to the right of Pickering. (Illustration Credit 2.1)

  Leavitt became fascinated by one type of star that changed regularly from bright to dim over the course of days or months. Mapping seventeen hundred stars, she charted every property she could measure: how bright they were, where they sat in the sky, and how rapidly these variable stars went from bright to dim. With all of these data, Leavitt uncovered an important regularity: there is a constant relationship between how fast some stars cycle from bright to dim and their real brightness.

  Leavitt’s idea seems awfully esoteric, but it is profound. Starting with the principle that light travels at a constant speed, and knowing how bright the star actually was and how bright it appeared, meant that the distance of the star from Earth could be estimated. With this insight, Henrietta Leavitt gave us a ruler with which to measure distances in deep space.

  We have to imagine astronomy in that era to appreciate the transformative power of Leavitt’s discovery. From the time of Galileo to Pickering, people observed the sky and saw the planets, nebulae, and fuzzy patches of light with ever-increasing clarity. But the central questions remained. How big is the universe? Is our own galaxy, the Milky Way, all there is?

  No sooner had Leavitt proposed her idea in 1912 than other astronomers began to calibrate and apply it to the heavens. One Dutch scientist used Leavitt’s ruler to measure the distances between individual stars. It gave him a big number. The galaxy is vast almost beyond imagination. Then Edwin Hubble, armed with Leavitt’s idea, used the biggest telescope of the time to change our view of the universe almost overnight.

  In 1918, Hubble, a Rhodes scholar and law student turned astronomer, deployed his enormous new Mount Wilson telescope to find one of the stars made famous by Leavitt. This star was special. It wasn’t alone in the sky; it sat inside a cloud of gas, known as the Andromeda Nebula. When Hubble applied Leavitt’s ruler to the star, he encountered a stunning fact: the star, in fact the whole nebula that contained it, was farther away from us than anything yet measured. The game changer came from the realization that this object was much more distant than any star in our own galaxy. This nebula was no cloud of gas; it was an entirely separate galaxy light-years from our own. With that observation, the Andromeda Nebula became the Andromeda Galaxy, and the world above our heads became vast and ancient almost beyond description.

  Hubble, using the largest telescope of the day, mapped everything he could see with Leavitt’s variable stars inside. The Andromeda and Milky Way Galaxies were only the tip of the iceberg. The heavens were filled with other galaxies composed of billions of stars. Many of the fuzzy patches of gas seen by observers for a century or more were really star clusters that lie far beyond our own galaxy. In a scientific age when people were grappling with the age of Earth, then thought to be on the order of 10 million to 100 million years old, the age and size of the universe revealed our planet to be just a minuscule speck in a vast universe composed of innumerable galaxies. These insights emerged as people learned to look at the sky in a new way.

  Hubble applied another technique to measure objects in the sky. This one relied on an essential property of light. Light radiating from a source that is traveling toward us looks more blue than light traveling away, which looks more red. This color shift happens because light shares some features with waves. Individual waves emanating from a source moving closer to you will look more compressed than ones moving away. In the world of color, more closely spaced waves are on the blue end of the spectrum, more separated ones on the red. If Leavitt’s technique was a ruler to measure distance in deep space, then the search for color shifts in light was a radar gun to measure speed.

  With this tool, Hubble found a regularity: stars emit red-shifted light. This could mean only one thing. The objects in the heavens are moving away from us, and the universe itself is expanding. This expansion is not a pell-mell scatter; the heavens are scattering from a common center. Wind things back in time, and all the matter in the sky was at some distant time occupying a central point.

  Not everybody liked this new idea; in fact, some experts hated it. Rival theories for the or
igin of the universe abounded. A proponent for one of them poked fun at Hubble’s by giving it the moniker “big bang.” Lacking in Hubble’s theory, or in any other for that matter, was direct evidence in the form of a smoking gun.

  The major breakthrough was an incidental by-product of people’s need to communicate with one another. With technological innovations in wireless technology and expanding international commerce and collaboration in the late 1950s came a demand for transmission of radio, TV, and other signals across the oceans. NASA devised a special satellite, code-named Echo 1, for this purpose. Looking like a large shiny metal balloon, it was meant to bounce signals transmitted from one part of Earth to another. The problem with this system was that the signals returning to Earth were often far too weak to interpret.

  Working for AT&T’s Bell Laboratories, at the time a utopia for scientists doing creative science, Arno Penzias and Robert Wilson were designing a radar dish to detect the extremely weak microwave signals reflected from NASA’s Echo 1 satellite. They spent a considerable amount of time, money, and expertise to develop a specialized radar dish for the task. Then, in 1962, NASA launched Telstar, a satellite that doesn’t passively bounce signals but relays them with a boost of its own. The bad news for Penzias and Wilson was that their dish was now useless for NASA.