The View from the Centre of the Universe by Nancy Ellen Abrams and Joel R. Primack
After thousands of years of abstract theorizing, cosmology is finally coming close to a testable theory to explain the nature of the universe. In this essay based on their book The View from the Centre of the Universe, Abrams and Primack argue we need the modern equivalent of a creation myth to help fix the new cosmological ideas in our minds.
Those of us who are alive today have an extraordinary opportunity – the opportunity to see everything afresh through a new understanding of the universe itself. We are witnessing a full-blown scientific revolution in “cosmology,” the branch of astronomy and astrophysics that studies the origin and nature of the universe. The unrestricted, dataless fantasizing of theorists has been replaced by reliable theory tested against the entire visible universe. What is emerging is humanity’s first picture of the universe as a whole that might actually be true. We are the first humans privileged to see a face of the universe no earlier culture ever imagined. It is possible for the first time not only to understand the universe intellectually but to start developing imagery that we can all use to grasp this new reality more fully and to open our minds to what it may mean for our lives and the lives of our descendants. As we do this, we will discover our extraordinary place in the cosmos. We dare not undervalue this immense privilege, even though it is happening at the same time as some of the most barbaric and self-defeating behaviour our species has ever exhibited. This is all the more reason we need it.
The last time Western culture shared a coherent understanding of the universe was in the Middle Ages. For a thousand years, Christians, Jews, and Muslims believed that the earth was the immovable centre of the universe and all the planets and stars revolved on crystal spheres around it. The hierarchy continued on earth: God had created a place for every person, animal, and thing in a great chain of being. This picture of reality made sense of the rigid social hierarchy of that time. The medieval picture was destroyed by early scientists like Galileo. The cosmic hierarchy lost its credibility as the organizing principle of the universe and was replaced with the Newtonian picture: a universe of endless emptiness randomly scattered with stars, and our solar system in no special place. This picture was not based on evidence but was an extrapolation from Newtonian physics, which accurately explains the motions of the solar system but by no means the entire universe. The modern world has so deeply absorbed this bleak picture that it seems like reality itself.
Until the late twentieth century, there was virtually no reliable information about the universe as a whole. That has changed. Astronomers can now observe every bright galaxy in the visible universe and – because looking out into space is looking back in time – can even see back to the cosmic “Dark Ages” before galaxies formed and study in detail the heat radiation of the Big Bang. The great movie of the evolution of the universe is coming into clearer focus: we now know that throughout expanding space, as the universe evolved, vast clouds of invisible, mysterious non-atomic particles called “dark matter” collapsed under the force of their own gravity. In the process they pulled ordinary matter together to form galaxies. In these galaxies generations of stars arose, whose explosive deaths spread complex atoms from which planets would form around new stars, providing a home for life such as ours to evolve. Clusters, long filaments, and huge sheet-like superclusters whose building blocks are galaxies have formed along wrinkles in spacetime, which were apparently generated at the earliest moments of the Big Bang and etched into our universe forever. Every culture has had a story of the origin of the universe, but this is the first one that no storyteller made up – we are all witnesses on the edges of our seats.
The possession of this new picture is a gift so extraordinary that most of us don’t know what to do with it. We have been living for centuries in a black and white film. There were no obvious gaps in the scenes before us, so we didn’t notice that anything was missing. Becoming aware of the universe is like suddenly seeing in colour, and that changes not just what’s far away but what’s right here. The universe is here, and it’s more coherent and potentially meaningful for our lives than anyone imagined.
Most of us have grown up thinking that there is no basis for feeling central or even important to the physical cosmos. But with the new evidence it turns out that this perspective is nothing but a prejudice. There is no geographic centre to an expanding universe, but we intelligent creatures are central or special in multiple ways that derive directly from physics and cosmology, and this article discusses two of them: we are made of the rarest material – stardust – and we are at the centre of all possible sizes in the universe. In our new book, The View from the Centre of the Universe we also explain that we are at the centre of the habitable zone of both the solar system and the Milky Way and at the centre of our visible universe, and we are living at the midpoint of time for the universe, for Earth, and for the human species. Each form of centrality has been a scientific discovery, not an anthropocentric way of reading the data. Pre-scientific people always saw themselves at the centre of the world, however they imagined their world. They were wrong on the details, but they were right on a deep level: the human instinct to experience ourselves as central reflects something real about the universe, something independent of our viewpoint.
The Rarest Material
Except for hydrogen, which makes up about a tenth of your weight, the rest of your body is made of stardust. Hydrogen and helium, the two lightest kinds of atoms, came straight out of the Big Bang, while a little bit more helium and essentially all other atoms were created later by stars. The iron atoms in our blood carrying oxygen at this moment to our cells came largely from exploding white dwarf stars, while the oxygen itself came mainly from exploding supernovas that ended the lives of massive stars. Most of the carbon in the carbon dioxide we exhale on every breath came from planetary nebulas, the death clouds of middle-size stars a little bigger than the sun. We are made of material created and ejected into the Galaxy by the violence of earlier stars. To understand how this happened – to appreciate the millions or billions of years it takes a star to produce a comparatively tiny number of heavy atoms, and the tremendous space journeys of those particles of stardust that have now come together to incarnate us – is a first step toward finding our place in the cosmos.
All the stars, planets, gas, comets, dust, and galaxies that we see – all forms of visible matter – make up only about half a percent of what’s out there. Most of the matter in the universe is neither atomic nor visible. It is not even made of the protons, neutrons, and electrons that compose atoms. It’s an utterly strange substance called “cold dark matter,” and its existence was only established late in the 20th century. But it accounts for about 25% of the universe. Dark matter neither emits, reflects nor absorbs light or any other kind of radiation, but its immense gravity holds the spinning galaxies together. But 70% of the density of the universe is not even matter – it’s “dark energy.” Dark energy causes space to repel space. The more space there is – and increasing amounts of space are inevitable in an expanding universe – the more repulsion. The more repulsion, the faster space expands, and this can lead to an exponentially increasing expansion possibly forever. The Double Dark theory explains how dark matter and dark energy interact over time to create the universe we observe.
Dark energy is in the nature of space itself. The Double Dark theory’s history of the universe is basically this: in the early universe there was relatively little dark energy because there was relatively little space – the universe hadn’t had time to expand very much, but there was the same amount of dark matter then as now. For about nine billion years, the gravitational attraction of the dark matter slowed the rate of expansion. The dark matter thinned out as the universe expanded, but since dark energy is a characteristic of space, it never thins out; instead its relative importance has tremendously increased with the amount of space. Now the repulsive effect of the dark energy has surpassed the gravitational attraction of dark matter as the dominant effect on large scales in the universe, and expansion is no longer slowing down but accelerating. The turning point was about four and a half billion years ago – coincidentally just when our solar system was forming.
All earlier cosmologies have been shared through symbolic images and stories. We too need to visualize our universe – not just random fragments of it, which is all that even the most stunning NASA astronomical photos give us, but the whole – so that we can see where we fit. Since 99% of the universe is invisible, the only way to visualize the whole is symbolically.
The Pyramid of All Visible Matter borrows an image everyone in the United States possesses: the pyramid topped by the all-seeing eye, which appears on the back of the dollar bill. The pyramid’s capstone is separated and floating above it, blazing with light, and dominated by an eye. This symbol can represent all the visible matter in the
universe – all the matter that people until the late twentieth century thought existed. The volume of each section of the pyramid is proportional to the density of that particular ingredient in the universe. The large bottom part of the pyramid represents the lightest atoms: hydrogen and helium, which are so plentiful that they far outweigh all the heavy atoms – the stardust – that makes up not only living things but Earth and all rocky planets in the universe. Within the capstone, the fraction of stardust associated just with living things or the remains of living things is very tiny. Within that very tiny fraction, the matter associated specifically with intelligent life is vanishingly small – yet it is only that which looks at and grasps this pyramid. The very human-looking eye at the centre of the capstone represents the trace bit of stardust associated with intelligent life. The eye is the only part not drawn to scale. Think of it as being like an enlarged detail of a city centre, inset on the corner of a large-scale map. The inset is way out of proportion to the size of things surrounding it, but everyone knows that an inset on a map is a zoom-in visualizing something important on a different size scale. Here, in the same way, the eye on the capstone is a zoom-in to the presence of intelligent life. Without a zoom-in we could not even see the matter associated with intelligence on the pyramid, since it is so rare. Intelligence bursts out only from tiny bits of stardust.
The Pyramid of all Visible Matter stands on the solid ground of Earth with a few plants for emphasis. But now we know that there is a hidden base extending deep underground. This is shown in the second figure, which we call the Cosmic Density Pyramid.
When astronomers look into space, they see only the illuminated half a percent of what’s out there. It is as though great fleets of ghost ships made of dark matter sail through the cosmic ocean of dark energy, but in the blackness all we humans see are a few beacons lit at the tips of the tallest masts. Ordinary matter interacts with itself: particles interact to form atoms, atoms interact to form molecules, and under at least some circumstances molecules can form living cells and eventually evolve into higher life forms. But dark matter does none of this. When viewed in computer simulations that make dark matter visible, the stuff behaves like nothing anyone has ever seen before. Gravity swings clumps of it around in the presence of other clumps, but they can pass right through each other. Dark matter has some of the properties people imagine of ghosts: it goes through things, yet it has power over the ordinary world. Our kind of matter does not take up much space or contribute much to the total density of the universe, but it contributes out of all proportion to the richness of the universe.
The centre of all possible sizes
In mathematics numbers go on infinitely in both directions, but in physics there are a largest and a smallest size. The interplay of relativity and quantum mechanics sets the smallest size: general relativity tells us that there can’t be more than a certain amount of mass squeezed into a region of any given size. If more mass is packed in than the region can hold, gravity there becomes so intense that the region itself – the space – collapses to no size at all: a black hole. Any object compressed enough will hit this limit and suddenly become a black hole. Meanwhile, quantum mechanics also sets a minimum size limit but in a very peculiar way. The “size” of a particle is actually the size of the
region in which you can confidently locate it. The smaller the region in which the particle is confined, the more energy it takes, and more energy is equivalent to larger mass. There turns out to be a unique, very small size where the maximum mass that relativity allows to be crammed in without the region collapsing into a black hole is also
the minimum mass that quantum mechanics allows to be confined in so tiny a region. That size, about 10-33 cm, is called the Planck length. We have no way to talk or even think about anything smaller in our current understanding of physics. The largest size we can see is that of the visible universe; the distance to the cosmic horizon is about 1028 cm. From the Planck length to the cosmic horizon is a difference of about 60 orders of magnitude. The number 1060 is extremely big, but it’s not infinite. It’s comprehensible. With it, we have something to compare our size to. Adapting an idea of Sheldon Glashow, a 1979 Nobel laureate in physics, we borrow the ancient symbol of the uroboros – a serpent swallowing its tail – and reinterpret it as the “Cosmic Uroboros.”
The Cosmic Uroboros represents the universe as a continuity of vastly different size scales. The tip of the serpent’s tail corresponds to the Planck length, and its head to the visible universe. Travelling clockwise around the serpent from head to tail, the icons represent the size of the cosmic horizon (1028 cm), the size of a supercluster of galaxies (1025), a single galaxy, the distance from Earth to the Great Nebula in Orion, the solar system, the sun, the earth, a mountain, humans, an ant, a single-celled creature such as the E. coli bacterium, a strand of DNA, an atom, a nucleus, the scale of the weak interactions (carried by the W and Z particles), and approaching the tail the extremely small size scales on which physicists hope to find massive dark matter (DM) particles, and on even smaller scales a Grand Unified Theory (GUT) .
The size of a human being is near the centre of all possible sizes. And conscious beings like us couldn’t be anywhere else. Much smaller creatures would not have enough atoms to be sufficiently complex, while much larger ones would suffer from slow internal communication (limited by the speed of light) – which would mean that they would effectively be communities rather than individuals, like groups of communicating people, or supercomputers made up of many smaller processors.
On different size scales, different physical laws control events. For example, gravity is all-powerful on the scale of planets, stars, and galaxies, but on the sub-atomic scale, gravity is utterly irrelevant, and the weak and strong forces control. On neither of these size scales is electromagnetism important, yet on the human scale it’s what makes chemistry work and our bodies function. Size matters. The jurisdiction of physical laws is limited to a range of size scales, and this is the reason we can’t extrapolate from what is true on earth to what’s true in the universe – nor can we extrapolate safely in any context when the numbers or sizes we’re dealing with differ by many orders of magnitude. This was a fatal flaw of the Newtonian picture.
The island of size scales surrounding human beings is the “reality” in which common sense works and normal physical intuition is reliable. Most of us are rarely conscious of anything smaller than an insect or larger than the sun. These sizes define humanity’s native region of the universe, our true homeland. It’s not a geographical location: it’s a point of view – a setting of the intellectual zoom lens. We have named this central range of size scales “Midgard” because in the Old Norse mythological cosmos, Midgard was the human world. It was an island representing stability and civilized society in the middle of the world-sea, the Norse universe. The world-sea was large, and there was room not only for Midgard but for the land of the giants and the land of the gods. This is an excellent description – metaphorically, of course – of Midgard as the centre of the expanding universe. Our Midgard is the island of size scales that are familiar and comprehensible to human beings. But beyond the shores of Midgard in one direction – outward – into the expanding world-sea is the land of incomprehensibly giant beings, like black holes a million times the mass of the sun and galaxies made of hundreds of billions of stars. In the other direction from Midgard – inward, toward the small – lies a living cellular world, and beyond that the quantum world, and these microlands are the evolutionary and physical sources of everything we are. That may not make them gods, but compared to us they are more prolific, more ancient, universal, and omnipresent. Like the Norse Midgard, our Midgard is not isolated from these other lands in the world-sea. The bridge is the Cosmic Uroboros.
Midgard spans about fourteen orders of magnitude, from 10-2 cm to 1012 cm, holding everything for which people have intuition. The figure also shows the approximate decade and technology by which scientists discovered the rest of the Cosmic Uroboros. The concept of Midgard has implications. People disagree on just about everything that has to do with spirituality, but the one thing they do tend to agree on is that whatever the spiritual may be, it’s not physical. Midgard, however, helps us understand why this “physical/spiritual” dichotomy is an illusion. Backing up a bit, in medieval cosmology heaven was understood to be physically enveloping the sphere of the fixed stars at a finite distance away from Earth (so close that in Dante’s Paradiso it was possible from the height of Paradise to see the shoreline from Asia to Cadiz). But after medieval cosmology was overthrown by the Newtonian picture, space was understood to go on forever, leaving no geographical location for heaven. God was said to be “outside the universe” or “in the heart.” Today most people still have the idea that the spiritual, if it exists at all, is mysteriously other than the physical or material world and “transcends” the physical universe. The concept of Midgard erases this, not by telling us what the spiritual is, but what the physical is.
Very large and very small structures on the Cosmic Uroboros are not physical in the usual sense of the term. Superclusters of galaxies are expanding apart and in billions of years will disperse; they’re not bound together by gravity but by our dot-connecting minds. In the opposite direction from Midgard toward the very small, there are elementary particles that are not really “physical” particles but rather quantum mechanical ones that are routinely in two or more places at once. The strange truth is that what we usually think of as “physical” is a property of Midgard, perhaps the defining property, and thus Midgard is what people generally think of as the “physical” universe. Beyond Midgard, however, lies most of the Cosmic Uroboros.
“Transcendence” should not be thought of as an imaginary leap to some place “outside” the universe. Transcendence is what happens many times within this universe, every few powers of ten. For example, on the atomic and subatomic scales, “human” means nothing. There is no humanness to our atoms. Whether atoms are inside us, inside a rock, or drifting through space, is all the same to them. On the atomic scale, therefore, even inside our own bodies we do not exist. “We” are something that transcends atoms. In the same way the universe as a whole transcends familiar Midgard. Amazingly, in this interpretation the difference between spiritual and physical becomes – in an approximate way – quantifiable with powers of ten. Things larger than about 1012 cm, or smaller than about 10-2 cm, can only be known through science and only experienced, if at all, spiritually. This includes most of the universe. The Cosmic Uroboros is a context for those exotic size scales of the universe that no one ever had a connection with before. Seeing and living on multiple levels at once is what “cosmic connection” is all about. It is not mystical; it is as practical – and essential – as the visualizations that athletes do before a competition, or concert pianists before they go out on stage. It situates us in reality at our best.
As a culture we now have the scientific ability to see so much more deeply into the universe than ancient people, yet most people experience the universe so much less and connect with it almost not at all. Widespread cultural indifference to the universe is a staggering reality of our time – and possibly our biggest mental handicap in solving global problems. We have libraries full of creation stories, and a culture of scepticism. Without a believable story that explains the world we actually live in, people have no idea how to think about the big picture. And without a big picture, we are very small people. A human without a cosmology is like a pebble lying near the top of a great mountain, in contact with its little indentation in the dirt and the pebbles immediately surrounding it, but oblivious to its stupendous view.
Religious stories can still arouse in many people a sense of contact with something greater than we are – but that “something” is nothing like what is really out there. We don’t have to pretend to live in some traditional picture of the universe just to reap the benefit of the mythic language popularly associated with that traditional picture. People around the world should be able to portray our universe with all the power and majesty that earlier peoples evoked in expressing their own cosmologies. Mythic language is not the possession of any specific religion but is a human tool, and we need it today to talk about the meaning of our universe. Big changes are happening on our planet, and shepherding ourselves through them successfully is going to require tremendous creativity. An essential ingredient may be a cosmic perspective, and such a perspective is just becoming available.