The Universe Within (3 page)

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.

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.

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.