Adapted from The Zoomable Universe: An Epic Tour Through Cosmic Scale, from Almost Everything to Nearly Nothing, by Caleb Scharf, with Illustrations by Ron Miller, by arrangement with Scientific American/Farrar, Straus and Giroux (US), Atlantic Books (UK), Cheers Publishing Company (China). Text Copyright © 2017 by Caleb Scharf, illustrations copyright © 2017 by Ron Miller. All rights reserved.
Do you want to hear the most epic story ever?
A long time ago the atoms in your body were spread across trillions of kilometers of otherwise empty space. Billions of years in the past there was no hint that they would eventually come to be configured as your eyes, your skin, your hair, your bones or the 86 billion neurons of your brain. Many of these atoms came from deep inside a star—perhaps several stars, themselves separated by many more trillions of kilometers. As these stars exploded, they hurled parts of themselves outward in a flood of scorching gas that filled a small part of one galaxy out of hundreds of billions of other galaxies, arrayed throughout a gaping span of space and time almost a trillion trillion kilometers across.
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Some of these atoms have been in the shell of a trilobite, perhaps thousands of trilobites. Since then, they've been in tentacles, roots, feet, wings, blood, and trillions, quadrillions of bacteria in between. Some have floated in the eyes of creatures that once looked out across the landscapes of 100 million years ago. Yet others have nestled in the yolks of dinosaur eggs or hung in the exhaled breath of a panting creature in the depths of an ice age. For others, this is their first time settling into a living organism, having drifted through eons in oceans and clouds, part of a trillion raindrops or a billion snowflakes. Now, at this instant, they are all here, making you.
Each atom is itself a composite that's one tenth of a billionth of a meter across—sitting on the precipitous edge of a universe between our perceived reality and the quantum world. Electrons hazily occupy much of the atom's empty space. Protons and neutrons cluster in a nucleus, 100,000 times smaller than its atom, and are themselves composed of other stupendously small things: quarks and gluons. An electron may have no meaningful property of size but could be thought of as 10 million times smaller than the nucleus.
Add up all the recognizable matter and there may be 10
80 particles such as protons, neutrons, electrons and other subatomic items in the known universe. That's a very big number, but it's also just peanuts, because there are probably a billion times more photons zinging around the cosmos. Yet this stuff is barely 5 percent of what we think is the total matter and energy content of space. Astronomical evidence suggests that there is a shadow realm of still mysterious subatomic particles and fundamental forces that constitute most of the cosmos—an underworld of dark matter and dark energy, dominating the entire universe but unseen by us.
Moreover, at some point 13.8 billion years ago all of this, seen and unseen alike, was squeezed into a far smaller, hugely energetic origin of space and time that we are still inside, along with any being that may exist a billion light-years from here. We're not truly disconnected, even now.
Quite a tall tale. Except this is not fiction, it is our current understanding of the universe and its history [see illustration above].
To examine and display what we truly know (and what we don't) about the entirety of nature, we turn to a tried-and-true approach—the simple premise of a 10-fold zooming view to tour the universe, from the edge of the observable cosmos to the innermost knots of reality. From fingers and toes to modern mathematics and measurements, we can all grasp the notion of powers of 10—sizes that shift by 10 times or by a tenth. Chain these sliding scales together across the three dimensions of space and that tricky thing we call time, and we have a language for expressing the continuities and relations of nature that extends far outside our common experience. The powers of 10 let us zoom from almost everything to nearly nothing.
Of course, a zoomable overview cannot recount every exact detail of the contents and history of the universe. Instead it takes us to specific waypoints throughout the physical scales of the cosmos across 62 orders of magnitude, from the quantum building blocks of the subatomic world to realms in which entire planets are mere droplets of frozen minerals and onward into the greatest expanse yet discovered, in which entire galaxies swarm like glinting motes of dust against the cosmic horizon.
This journey through all known scales of reality is, in essence, what “everything” really is. You might be tempted to ask what comes next. What is beyond the phenomenon we call the universe, beyond the everything? What might be “outside” the sunlit, mote-filled room of our observable reality? These are great questions, and in a very real sense anything “outside” our universe must be for now simply “not universe.” The threshold bridging these domains is a place hovering at our cosmic horizon, its scale set by the distance light travels during the age of the universe. Within the boundary is the observable universe. Just outside is a still-mysterious labyrinth.
We live our lives in a narrow slice of existence sandwiched between these extremes of the very small and the very large, looking, listening, smelling and feeling from inside the membranes of our mostly water multicellular bodies. Somehow, we construct meaning out of those senses, experience that slippery property known as consciousness and perhaps even possess that elusive quality we call intelligence. It may be that other complex life across the cosmos is built the same way, to act and feel and think just as we do. Or perhaps our biology is not the only way to construct living things; perhaps the notion that consciousness and intelligence arise from the electrochemical gunk of our brain does not apply to minds elsewhere in the universe.
Confronting these mysteries of self, and the many scales of the cosmos, all we can really do is cross our fingers and hope that our singular experience will not mislead us as we disentangle the big questions of existence.
Altogether our situation is a bit farcical. We're in a horrendously unsuitable place for gaining objective truths about the nature of reality. Adrift on one small rocky planet that orbits one ordinary star out of a trillion trillion stars in the observable universe, each one of us is locked inside a singular, self-aware speck of flesh, embedded in a web of biological evolution that sprawls across the eons. Even our bodies are not wholly our own, because they also serve as Darwinian battlefields for trillions of bacteria and viruses. And all of it, all of life as we know it, seems to emerge solely from interactions among mind-numbingly large numbers of duplicated molecular structures—the exquisite architectural interplay of DNA and RNA, which itself arises from the physics of protons, neutrons, electrons and electromagnetic forces. Such tiny components simply follow the fundamental “rules” of the universe that were frozen into place some 13.8 billion years ago. Yet, in concert, they build galaxies, planets, humans, birds and who knows what else across the cosmos [see illustrations above].
How does all this happen? How did this epic story really begin, and how—if ever—will it finally end? Such questions sit at the heart of our efforts to construct a rational picture of nature from our inconvenient vantage point. Any answer is a work in progress but must already exist in hazy outline among all the myriad intersections of the universe's dizzying scales. We invite you to explore them and delight in their beauty. After all, this is your universe as much as anyone else's.
