A graduate of mathematics of Yale University, Charles Seife is a researcher and journalist. His writing has appeared in the New Scientist, The Economist and Scientific American. His first book, Zero: The Biography of a Dangerous Idea, won the PEN Award for Non-Fiction.
Since A BRIEF HISTORY OF TIME scientists have been in the midst of a revolution in cosmology. Gradually, astronomers and physicists are answering questions that have plagued mankind since prehistory: how was the universe born, how will it end? They are even now peering into the cradle of the universe – and into its grave. By the beginning of next year, scientists will have a clue to some of the answers. These will be among the greatest triumphs of science.
This book tells that story and will reveal results of the most advanced experiments in cosmology ever conducted. It’s a tale of men solving the insoluble, of the controversy and anger of rivals after the same goal. Even more thrillingly – it is a lucid explanation of new scientific ideas that stretch man’s powers of understanding to their highest levels.
A LOT OF people helped me write this book; it’s not possible for me to name them all. Over the past few years I have interviewed dozens of physicists, cosmologists, and astronomers who took the time to explain the nuances of their work to a journalist. I thank them for their enthusiasm and their patience. They are the reason that I wrote Alpha and Omega in the first place. (Of course, they bear no responsibility for any errors in this work—any mistakes are mine alone.)
I would also like to thank my editor, Wendy Wolf; my copyeditor, Don Homolka; and my agents, John Brockman and Katinka Matson. Last but not least, my parents, once again, have been an unwavering source of support (and constructive criticism) even through the most difficult times of their lives. Thank you for everything.
THERE IS LITTLE way to deny the big bang theory if you accept the fact that the reddening of galaxies is caused by the Doppler effect. Galaxies are speeding away, the more distant the faster, so the universe is expanding. But a small band of contrarians argue that the reddening is not caused by the Doppler effect. They argue that galaxies’ light reddens because it loses energy as it passes through space: light gets “tired.” This tired-light hypothesis was invented by astrophysicist Fritz Zwicky within a few months of the publication of Hubble’s paper on the expansion of the universe. Zwicky wanted to explain the reddening of distant galaxies without resorting to an ever expanding universe. In his tired-light scenario, distant galaxies are red not because they are moving, but because their light has traveled farther and gotten pooped out along the way.
When experimenters first measured the cosmic microwave background in the 1960s, they found that the radiation was too dim to be explained by Zwicky’s hypothesis. That realization relegated tired light firmly to the fringe of physics, but scientists still sought more direct proofs of the expansion of the cosmos. Two papers released in 2001 provide the best direct evidence yet.
The first measures the brightening and dimming of supernovae. Thanks to Einstein’s theory of relativity, we know that if distant supernovae are moving away at great speeds, their “clocks” tick more slowly than one on Earth, because of the phenomenon of time dilation. As a result, distant supernovae seem to explode and evolve in slow motion—they will appear to flare and fade at a more leisurely pace than nearby ones. A team of scientists led by Gerson Goldhaber of the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, has shown that this is, indeed, the case with forty-two recently analyzed supernovae. “It’s very unambiguous,” says LBNL supernova hunter Saul Perlmutter.
In the second study, Allan Sandage of the Carnegie Observatories in Pasadena and Lori Lubin, currently at the University of California at Davis, analyzed space-based measurements of the surface brightness of galaxies. Both the standard expanding-universe theory and the tired-light theory, they realized, predict that redshifted light should make distant galaxies look dimmer than they really are; since redder light is less energetic, galaxies will look dimmer no matter whether the reddening comes from tired light or from the motion of the galaxies. However, a galaxy will appear much dimmer at great distances if it is moving, for two reasons that do not apply to stationary galaxies.
The first reason, as in the supernova paper, is relativistic time dilation. Imagine that a galaxy spits out a photon toward Earth every second. Because the clock of a distant, moving galaxy is slow compared with one on Earth, the photons are more than a second apart from Earth’s point of view; fewer photons arrive in any given span of time, so the galaxy appears dimmer. The second reason is a phenomenon known as relativistic aberration, which distorts the apparent shape of the galaxy, making it appear much dimmer than it would be if it were stationary. These two effects, time dilation and aberration, only apply to moving, Doppler-shifted galaxies, not to stationary, tired-light ones.
Sure enough, when Sandage and Lubin measured the surface brightness of a number of galaxies, they found that the galaxies were much dimmer than the tired-light theory would suggest, and taking into account the fact that distant galaxies are a bit brighter than those nearby (because the ancient galaxies were populated by bright, young stars), the observation matched the moving-galaxy brightness prediction quite nicely.
“The expansion is real. It’s not due to an unknown physical process. That is the conclusion,” says Sandage. Tired-light theory has been thoroughly retired. Hubble was right: the universe is expanding.
SYMMETRY AND ASYMMETRY are powerful tools in the hands of the particle physicist. Indeed, the whole structure of the subatomic world seems to be built upon symmetries, and perhaps even supersymmetry, as discussed in chapter 10. The discovery of a new symmetry in the universe, or of the breakdown of a seemingly established symmetry, is usually the signal of a new fundamental truth about the way the cosmos works. Three of the key symmetries of particle physics are known by their initials: C, P, and T. These three symmetries seem to hold the secret of the difference between matter and antimatter.
When Alice took a trip through the looking glass, she entered a world where everything was reversed, as if it were reflected in the mirror. When she saw the text of the poem “Jabberwocky,” the letters and words went from right to left instead of from left to right. She had gone through a mirror reflection. The essence of P symmetry (the P stands for “parity”) is that Alice wouldn’t notice a difference in the laws of physics of her home world and the looking-glass world; after reflecting the universe in a mirror, the laws of physics stay the same.1 Until the late 1950s, scientists thought that P symmetry was a fundamental rule that governed the universe; if you somehow magically reflected the universe in a supermirror, the two universes would always be indistinguishable. However, on the subatomic scale, mirror-reflected matter has subtle differences from ordinary matter. Chen Ning Yang and Tsung-Dao Lee, working at the Institute for Advanced Study in Princeton, New Jersey, proposed a way to test whether P symmetry was violated in certain nuclear decays. Their experiment (which Chien-Shung Wu of Columbia University carried out) set up a situation where decaying cobalt nuclei spit out electrons both upward and downward. The result: more electrons traveled downward than upward. They also showed that if they had done the experiment in the mirror world, there would have been more upward-traveling electrons than downward-traveling ones. So their experiment revealed a difference between our universe and a mirror-image one; in one universe, more electrons traveled up, and in another, they traveled down. P symmetry was violated, because the mirror universe was not identical to our own. For this, Yang and Lee received the 1957 Nobel Prize in Physics.
When P symmetry fails, the laws of physics are slightly different in the looking-glass world.
For a time, physicists thought they could reinstate P symmetry by adding another condition, called C symmetry. Just as P symmetry has to do with replacing matter with mirror matter, C symmetry (the C stands for “charge”) replaces matter with antimatter. The combination of the two symmetries, CP symmetry, asserts that the laws of physics would remain the same if you replaced matter with antimatter and reflected the universe in a mirror. (The third type of symmetry, T, which stands for “time,” involves hypothetically doing an experiment in reverse.)
In Yang and Lee’s experiment, CP symmetry was true. If you replaced matter with antimatter and mirror-reflected the setup, the results would remain the same. Yang and Lee’s experiment showed a violation of P symmetry, but CP symmetry held fast—for another few years. In 1964, Val Fitch and James Cronin published a paper in Physical Review Letters that showed that the K0 meson (made of a down quark and a strange antiquark) decayed in a way that can only happen if CP symmetry is violated. The failure of CP symmetry holds the secret to understanding where matter comes from.2
A violation of CP symmetry can manifest itself in many different ways. Recent experiments at Fermilab in Batavia, Illinois, studied the decay of K mesons; in particular, the researchers paid careful attention to the angles at which the decay products flew away. Violations in CP symmetry show up as preferred angles, just as P-symmetry violations show up as electrons’ preference to fly down rather than up. But another manifestation, measured at CERN, is even more striking. In May 2001, after a decade of work, a collaboration at CERN presented measurements of twenty million K0 meson and anti-K0 meson decays. Anti-K0 particles decayed just a tiny bit faster than K0 particles. This means that if you could create a bunch of K mesons and anti-K mesons, you would see the antimatter versions wink out of existence before the matter versions do. In 1967, Russian physicist Andrei Sakharov proposed that this tiny asymmetry gives matter a slight, but crucial, edge over antimatter.
When the universe was born, presumably the energy of the big bang went into creating matter and antimatter in roughly equal proportions. If the amount of matter had been truly equal to the amount of antimatter, then the matter and antimatter in the universe should have annihilated each other, leaving nothing behind but a soup of energy. But since matter seems to have a small edge—matter lasts a little bit longer than antimatter and is thus “preferred” by nature—a tad more matter than antimatter survived, perhaps one part in a billion. That extra little bit is our inheritance. As antimatter and matter annihilated each other, the extra little bit remained and became the matter that forms the universe.
Scientists don’t have a full handle on the process of CP violation yet. For a long time, the K meson was the only particle that showed CP-violating tendencies, and to get a full mathematical portrait of the CP-violation process, it must be observed in another type of particle that contains a more exotic quark, like a bottom quark.3 Since bottoms are massive quarks, they are rare, and the particles that contain bottom quarks (and bottom antiquarks), like the B meson, are hard to make.
However, it is not impossible. For the past few years, the Stanford Linear Accelerator Center in California has been generating swarms of Bs and watching them decay. Another B factory in Japan has been doing the same thing. In 2001, the first results began to pour out. Sure enough, the teams in both California and Japan saw hints of CP violation in B mesons, and pretty soon the Tevatron accelerator at Fermilab will be producing scads of Bs as well. It is still too early to make a definitive statement, but scientists are almost ready to announce that they have finally found the last piece in the CP-violation puzzle. With the observation of CP-violation in B mesons, scientists will be able to paint the full mathematical portrait of the CP-violation process in quarks—and how the universe came to be populated with matter instead of antimatter.
1. Parity is a mathematical term that has to do with symmetries in space. Technically, P symmetry is a reflection in three mirrors, rather than just one. You switch left for right, up for down, and front for back.
2. Scientists now think that the symmetry that holds true is CPT symmetry, where the T symmetry indicates that if the flow of time is reversed in a doppelgänger universe in addition to matter being switched with antimatter and reflected in a mirror, the new universe will be indistinguishable from our own. Nobody has yet found any signs of a violation of CPT symmetry.
3. The mathematics of CP violation relies upon an object known as the Cabibbo-Kobayashi-Maskawa (CKM) matrix. This matrix encodes cerain types of interactions between the quarks, and the terms in that matrix aren’t fully known, particularly the ones that involve CP violation. K mesons reveal some of the terms in the matrix, but another term is needed to figure out the entire matrix. This is why scientists need another particle to get a complete picture of the CP-violation process.
THE NOBEL PRIZES referred to in the text are as follows:
1933: P. A. M. Dirac, for the prediction of the antielectron. (Also Erwin Schrödinger, for quantum mechanics.)
1936: Carl Anderson, for the discovery of the antielectron. (Also Victor Hess, for the discovery of cosmic rays.)
1957: Chen Ning Yang and Tsung-Dao Lee, for the discovery of P violation in cobalt decays.
1965: Sin-Itiro Tomonaga, Julian Schwinger, and Richard Feynman, for renormalization in quantum electrodynamics.
1969: Murray Gell-Mann, for quantum chromodynamics.
1974: Antony Hewish, for discovering the first pulsar. (Also Martin Ryle, for inventing synthetic apertures—a technique related to interferometry.)
1976: Burton Richter and Samuel Ting, for discovering the J/psi meson.
1978: Arno Penzias and Robert Wilson, for the discovery of the cosmic background radiation. (Also Pyotr Kapitza, for low-temperature experiments.)
1979: Sheldon Glashow, Abdus Salam, and Steven Weinberg, for electroweak unification.
1980: James Cronin and Val Fitch, for the discovery of CP violation in K mesons.
1984: Carlo Rubbia and Simon van der Meer, for the detection of W and Z bosons.
1988: Leon Lederman, Melvin Schwartz, and Jack Steinberger, for the detection of the muon neutrino.
1993: Joseph Taylor and Russell Hulse, for the discovery of a binary pulsar, which confirmed the existence of gravitational waves predicted by Einstein’s theory of relativity.
1999: Geradus ’t Hooft and Martinus Veltman, for renormalization of electroweak theory.
2002: Raymond Davis Jr. and Masatoshi Koshiba, for the detection of solar and cosmic neutrinos. (Also Ricardo Giacconi, for pioneering work in x-ray astronomy.)
It is always difficult to guess the intent of the Nobel committee, and harder still to figure out who, within a large field, is going to get a prize for a particular discovery. The committee often lets political or philosophical bias get in the way of giving the awards to deserving candidates. Edwin Hubble never won a Nobel Prize, and Einstein’s prize, for an explanation of the photoelectric effect, was given despite his theory of relativity. Only two things are certain: at most three people can share a prize, and nobody can be awarded one posthumously.
Nevertheless, the past few years have seen a great deal of cosmology-related work that is worthy of Nobel Prizes. Here are my predictions about completed research that will eventually be awarded a Nobel, and my best guesses as to who will take home the prize:
For the discovery of dark matter (Vera Rubin and others)
For inflationary theory (Alan Guth)
For the discovery of anisotropies in the cosmic background radiation (Members of the COBE team, and possibly others)
For the accurate prediction of the power spectrum of the cosmic background radiation (Edward Harrison, P. J. E. Peebles, J. T. Yu, or others—Yacov Zel’dovich died in 1987)
For precision measurements of the power spectrum of the cosmic background radiation (Members of the Boomerang and DASI teams)
For the discovery of neutrino mass (Members of the Super-Kamiokande team)
For prediction of the spectrum of solar neutrinos from the sun (John Bahcall and others)
For the solution of the solar neutrino paradox (Members of the Sudbury Neutrino Observatory and the Super-Kamiokande teams)
For the discovery of dark energy (Members of the High-Z Supernova Search Team and the Supernova Cosmology Project)
For measuring the curvature of the universe (Members of the High-Z Supernova Search Team, the Supernova Cosmology Project, and Boomerang)
More difficult still is predicting Nobel Prizes for work that is yet to be completed, although the third cosmological revolution is pregnant with possibilities, including the following:
For the prediction and discovery of supersymmetric particles
For the creation and analysis of a quark-gluon plasma
For the prediction and discovery of curl-type polarization in the cosmic background radiation
For the identification of dark matter objects in the halo of the Milky Way
For the discovery of a new weakly interacting massive particle that contributes significantly to dark matter
For the discovery of the Higgs boson
For the analysis of weak decays in B mesons and the completion of the CKM matrix
For the discovery of double-beta decay and the proof that the Majorana picture of the neutrino is correct (unlikely, but if found, a certain Nobel)
For the direct detection of gravitational waves
A NUMBER OF EXCITING experiments were ongoing in 2002 in the five fields listed below. This is merely a selection, and a taste of things to come.
Boomerang: This Antarctic balloon-based observatory has already revolutionized the field of CMB astronomy. First deployed in early 1999, Boomerang (the name is derived from Balloon Observations of Millimetric Extragalactic Radiation and Geophysics) provided the first highly detailed measurements of the background radiation. It has undergone a refit to make it sensitive to polarization and will likely return results shortly.
DASI: Like Boomerang, DASI (the Degree Angular Scale Interferometer) is a sensitive Antarctic observatory. However, it is ground-based and uses interferometry rather than bolometers to do its measurements. DASI scientists first released high-quality data in April 2001, and in September 2002 DASI was the first instrument to detect the polarization of the cosmic microwave background.
CBI: The Cosmic Background Imager is similar to DASI, but it is based in Chile and is sensitive to smaller angular scales compared with DASI and Boomerang. While less celebrated than DASI and Boomerang, CBI has already provided significant support for inflationary theory and is likely to make important observations over the next few years that DASI and Boomerang are unable to provide.
MAP: Launched aboard a Delta II rocket in June 2001, the Microwave Anisotropy Probe has been taking high-resolution pictures of the cosmic background radiation over the entire sky, unlike Boomerang, DASI, or any other earthbound telescope, which can only take a picture of a section of the sky. Such a detailed and comprehensive map will pin down the spectrum of the CMB with unprecedented precision. The first results arrived in February 2003, as this book was going to press.
ACBAR: First deployed at the South Pole in November 2001, the Arcminute Cosmology Bolometer Array Receiver is intended to take advantage of the Sunyaev-Zel’dovich effect to map out the distribution of matter in galaxy clusters. In 2006, an as-yet-unnamed telescope at the South Pole will perform a much more comprehensive Suryaev-Zel’dovich survey of the skies.
Planck: Scheduled for launch in 2007, this European satellite, like MAP, will observe the cosmic background radiation across the whole sky. Not only will it be more precise than MAP, but it will also be able to detect polarization, which MAP cannot do with any real resolution.
2dF: The Two Degree Field collaboration is using an Australian telescope to map galaxies and other objects in the sky. The project’s astronomers expect to map 250,000 galaxies, and they have almost reached their goal. The 2dF’s data have already revealed the distribution of matter in galaxy clusters, and the data are expected to get even better.
SDSS: The Sloan Digital Sky Survey is very similar to 2dF in its goals and methods; however, it is a more extensive search. SDSS researchers have already released some valuable data and are expected to return a lot more over the next few years.
SNAP: The Supernova Acceleration Probe is a proposed satellite that would use a very high-tech camera to take snapshots of the heavens in hopes of spotting supernovae, particularly type Ia supernovae. If it is launched, it would immediately reward the supernova hunters with a rich bounty of standard candles and allow cosmologists to figure out the rate of the expansion of the universe over an enormous time period.
RHIC: The Relativistic Heavy Ion Collider at Brookhaven National Laboratory smashes heavy nuclei, like gold, into each other at enormous speeds. Since the machine began operations in June 2000, evidence has indicated that the machine has produced a quark-gluon plasma, though the data are not strong enough for RHIC scientists to make a definitive claim. Expect an announcement of the discovery of a quark-gluon plasma in 2004.
BaBar: Based at the Stanford Linear Accelerator Center in California, BaBar is an instrument that analyzes B mesons. The first data arrived in 1999 and results have been trickling out since then. These measurements will help scientists fill in details about weak interactions and CP violation and will help explain why our universe is made of matter rather than antimatter.
Tevatron: After a $260 million refit, the Tevatron accelerator at Fermilab is having some teething troubles. Since it was turned on in March 2001, the proton-antiproton smasher has not been performing well. Once the kinks are worked out, however, the Tevatron is likely to pin down some of the details of the W bosons and should produce numerous B mesons, adding to the knowledge provided by BaBar. Furthermore, there is a very good chance that Tevatron will spot the lightest supersymmetric particle, and a slim chance that it will see the Higgs boson.
LHC: The Large Hadron Collider, at CERN in Geneva, Switzerland, will exceed the capabilities of Tevatron and RHIC. If the lightest supersymmetric partner is not found by the Tevatron, then it will be found by the LHC, or supersymmetry will be all but ruled out. It should also find the Higgs boson. The LHC is scheduled to be operational in 2007 but will likely be delayed.
NLC: The Next Linear Collider is a proposed $6 billion facility meant to complement the LHC; if approved, it probably will be built on the West Coast of the United States or in Germany. Unlike the other accelerators described here, the NLC would smash positrons and electrons together, instead of composite particles like protons or nuclei. This makes the NLC a scalpel to the LHC’s chainsaw. Once the LHC spots a particle of interest, the NLC would be able to investigate its properties in great detail. Such an expensive project is likely to face a rocky road ahead, but if it is commissioned, it will be a spectacular instrument.
LIGO: The Laser Interferometer Gravitational-Wave Observatory is a set of two facilities designed to detect the distinctive stretch-and-squash signature of a passing gravitational wave. The observatory started taking scientific data at the beginning of 2002 and is expected to release its first scientific results in 2003.
TAMA, VIRGO: These are, respectively, Japanese and European versions of LIGO. Due to design drawbacks, they are unlikely to be as sensitive as LIGO.
ALLEGRO, AURIGA: Unlike LIGO, which uses interferometry to detect gravitational waves, these experiments, and several others, are based upon a tuning-fork-like detector that vibrates when a gravitational wave of a certain frequency happens by. The detectors are less sensitive than TAMA and VIRGO.
LISA: A NASA vision for the ultimate gravitational-wave detector, the Laser Interferometer Space Antenna will be a formation of three satellites that act as an enormous interferometer. Unfortunately, the technical hurdles are formidable, but if LISA becomes reality, it would be an enormous boon to cosmologists trying to study gravitational waves from the early universe.
Super-K: Though seriously damaged in late 2001, the Super-Kamiokande detector in Japan was the first to see convincing evidence that neutrinos have mass, and this announcement in 1998 was a watershed in neutrino physics. Basically an enormous cylinder of water studded with photodetectors, Super-K detects telltale flashes of light as neutrinos interact with the water. Though Super-K will continue taking data, it will not be fully repaired for several years.
K2K: Two hundred and fifty kilometers away from Super-K, the KEK laboratory in Tsukuba, Japan, has been creating a beam of neutrinos that shoot toward the Super-K detector. Since 1999, the detector has been registering how many neutrinos it sees, and compares this quantity to the expected number; the difference is already revealing limits on neutrino masses. Though the experiment has suffered because of the Super-K damage, it will continue once Super-K is up to the task.
SNO: The Sudbury Neutrino Observatory released its first results in July 2001 and produced quite a reaction, as its researchers provided strong evidence that electron neutrinos from the sun were turning into muon and tau neutrinos as they stream toward Earth. This solved the solar neutrino paradox. Unlike Super-K, SNO is filled with heavy water, which makes it more sensitive to certain types of weak reactions. The results from SNO are likely to pin down many of the properties of neutrinos with great precision.
KamLAND: Using an old neutrino detector in the Kamioka mine in Japan, where Super-K is based, the KamLAND experiment is designed to detect antineutrinos that come from fission in the nuclear reactors that dot the Japanese and Korean countrysides. In December 2002, the KamLAND collaboration revealed its first results, which showed that antineutrinos oscillate just as neutrinos do. As the experiment gathers more data, physicists expect that the KamLAND team will dramatically improve scientists’ knowledge about neutrino and antineutrino properties.
AMANDA, IceCube: An enormous neutrino detector made out of the Antarctic ice, the Antarctic Muon and Neutrino Detector Array has been measuring neutrinos and watching for WIMPs for the past few years. The equipment was upgraded in 1999 and 2000 and is still gathering and crunching data. AMANDA’s planned successor, IceCube, has just begun to receive funding from the National Science Foundation.
Then All-father took Night and her son, Day, and gave them two horses and two chariots and put them up in the sky, so that they should ride round the world every twenty-four hours. Night rides first on a horse called Hrimfaxi, and every morning he bedews the earth with the foam from his bit. Day’s horse is called Skinfaxi, and the whole earth and sky are illumined by his mane.
PERHAPS IT HAPPENED on a midwinter’s night thirty thousand years ago. A tribe of cavemen huddled close to the embers of a dying flame. A single hairy face gazed upward, bewildered. Against the innumerable, immutable pinpricks of light in the heavens, a star had moved. A human looked into the cosmos and saw the trail of a wandering god.
Even before the dawn of civilization, people gazed sky-ward and wondered. Who created the stars in the sky? How was the universe born? Will it end? If so, how? These are the most ancient questions of humanity. Yet, for millennia upon millennia, the only way to answer these mysteries was through mythology. Even today, the remnants of that mythology can be seen in the heavens. The tiny lights that meander slowly through the sky, better known as planets, bear the names of gods. Red Mars is gorged with the blood of conquest; bright Venus glitters in the morning with the allure of the goddess of love. Each civilization invoked its own gods to explain the creation of the universe, the existence of stars in the night sky, and occasionally the ultimate destruction of the cosmos.
Three revolutions separate modern cosmologists from the shamans and storytellers of the age of mythology. The first, which took place in the 1500s, was the most dangerous. Its enemies tried to stifle it with all the weapons in their arsenal: accusations of heresy and witchcraft. The second revolution, which began in the 1920s, was the most unsettling; the comforting concept of a clockwork universe was shattered, and humanity was suddenly alone in a vast, empty cosmos. For the first time, scientists saw evidence of the act of creation. These two revolutions take us to the present day, where we are in the midst of a third revolution, a revolution that is finally answering the eternal questions, revealing our origins and our ultimate fate.
If you look upward on a sunny day and squint your eyes just right, you can imagine the vault of the heavens as an immaculate blue dome, arching high above the wispy clouds that float slowly across the sky. To ancient peoples, the dome of the sky was a real object; the Earth was enclosed by a beautiful sphere that shone blue in the daytime as the sun slowly traveled from east to west. In the evening, tiny, flickering points of light mocked the humans far below, and a faint shimmering ribbon stretched across the giant ball surrounding the Earth.
Who fashioned that sphere? Each culture had a different answer; every people had a story of creation, which told of how the gods came to be and how they created the universe. The Norse people, not surprisingly, thought that the universe was born from ice. As the frost encountered an enormous fire, it thawed and formed a giant named Ymir. Odin, chief of the gods, and his brothers slew Ymir and used his skull as the dome of heaven. They then fashioned the Earth from Ymir’s flesh, the oceans from his blood, and the clouds from his brains. They set the planets in the sky and made the glowing chariots of the sun and moon chase each other in the vault of the heavens—each eternally pursued by a wolf.1 The Pawnee Indians of central North America saw corn as the mother of all things; Mother Corn gave life to humanity, which emerged from the ground like the crops that the Pawnee depended on. Some cultures thought the universe began as a vast ocean; others, as a shapeless chaos. There are dozens and dozens of vastly different tales of the creation of the universe, but most of them focus on the same events: the birth of the gods; the creation of the heavens, Earth, and stars; and the fashioning of man and woman. These elements are the foundation of any religion, as they answer the fundamental questions that humans have been asking since the dawn of time. Before the scientific revolution gave humanity another tool with which to examine the universe, people could only explore its history and nature by listening to the stories of shamans and the musings of philosophers. Religion and philosophy formed the cosmologies of the ancients.
Two of these numerous cosmologies dominated the Western world, from before the ascent of Rome until the time of William Shakespeare. Even though these two traditions are mutually contradictory, they fused, and fashioned a story of the universe that was almost unassailable until the advent of the scientific method. The combination of an Eastern, Semitic cosmology, encoded by the Bible, and a Western, Greco-Roman one, became a solid structure that stood for more than a millennium. It took a cosmological revolution to tear the edifice down.
The word cosmos is the Greek word for “order,” and the cosmos—the universe as a whole—was the only order to be found in the chaos of Greek mythology. The sun traveled across the sky each day, guided by Helios, the solar charioteer.2 The moon waxed and waned each month, growing pregnant and barren in turn. And in the night sky, the stars remained fixed, except for five wanderers—the planets—that moved across the unchanging backdrop of the heavens.3 Even today, we know the planets by their Olympian names: Mercury, Venus, Mars, Jupiter, and Saturn are the Roman names of the Greek gods Hermes, Aphrodite, Ares, Zeus, and Cronus. The Greeks saw order in the clockwork motions of the heavenly bodies, and from early on in their civilization they began to work out the details of that clockwork. In 585 BC, the Greek mathematician Thales was the first to predict the coming of a solar eclipse. According to Herodotus, two warring peoples, the Medes and the Lydians, were astonished to see the day turn into night and decided that it would be a good time to put down their weapons.
By trying to understand how the heavens worked, Thales became the first starry-eyed cosmologist—to the amusement of his neighbors. “While he was studying the stars and looking upward, he fell into a pit, and a neat, witty Thracian servant girl jeered at him,” Socrates reportedly said, several centuries later. But Thales put all his concentration and observation to good use. He created an entire cosmos from the sheer power of his mind.
Perhaps because the Greek stories of creation were fragmentary and contradictory, Thales ignored them when building his cosmology. Though he believed that gods were everywhere in the universe, Thales took the act of creation out of the gods’ hands. In Thales’ universe, water was the source of all things; earth floated upon the water like a cork. Not everyone agreed with Thales that water was the primordial material from which the universe was made. Others, like Anaxagoras and Diogenes, argued that air came before water. (After all, water destroys fire, so water could hardly have given birth to fire.) Yet others argued that fire was prime. Empedocles, who lived at around 450 BC, refused to pick a single primal essence and instead argued that earth, air, fire, and water were the four elements. In different combinations, he declared, these four essences made up everything in the universe.
The philosophers also argued about the nature of the heavenly clockwork. They looked to the heavens and tried to figure out the order of the cosmos, and Earth’s place within that order. They began by describing the Earth itself. Pythagoras, an eccentric philosopher who is best known for his theorem about right triangles, argued that the planets, including Earth, revolved around a central fire. Others argued that the Earth was flat, and still others that it was spherical, but at the center of the universe. By the fourth century BC, Aristotle became the philosopher who mattered. Born in Macedonia, and tutored by Socrates’ student Plato, Aristotle, in turn, became the teacher of Alexander of Macedon—better known as Alexander the Great. And just as surely as Alexander conquered the West, so too did Aristotle’s philosophy.
Aristotle’s cosmos was exquisitely orderly. Everything had its place in the universe. Empedocles’ four elements had their natural positions; earth, the heaviest element, sank to the center of the universe, so the Earth, quite naturally, must be at the very center of the cosmos. Water was slightly lighter, so it floated above earth, but below air and fire, which were lighter still. Aristotle added a fifth element—literally, the quintessence—that was purest of all. Earthly things were made of earth, air, fire, and water; the quintessence was only found in the heavens. To Aristotle, the pure, unchanging heavens were made of stuff entirely different from the ever mutable, but motionless, Earth at the center of the universe. The moon, sun, and planets each revolved around the Earth in perfect, crystalline spheres, never ceasing in their motion, and filling the heavens with celestial harmony: the music of the spheres.
This cosmology was based upon pure logic. Aristotle made certain basic assumptions—that the universe had to be finite, that everything had a natural place, that circles and spheres were the most perfect geometric shapes—and deduced what he thought was the natural order of the cosmos. Aristotle’s mentor, Plato, mocked the “light-minded men” who, “being students of the worlds above, suppose in their simplicity that the most solid proofs about such matters are obtained by the sense of sight,” and Aristotle agreed. Observation was for fools.
Aristotle’s cosmos was light on theology. It only required the existence of a “prime mover” to set the celestial spheres in motion—it did not specify the nature of that divine power. This, in part, is what gave Aristotle’s cosmos such longevity even after an entirely different culture became the foundation for Western religion.
“In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.” The beginning of Genesis is the basis for Jewish—and, later, Christian—cosmology. Its roots lie in the hazy past of the first civilization, in the Fertile Crescent. Thousands of years later after the Hebrew Bible was set down in writing, Christ took this ancient tradition and bent it into a new form.
Unlike the Greek cosmology, which could easily accomodate a pantheon of petty, squabbling gods, the Jewish cosmology tells of an omnipotent, omniscient God who creates the heaven and Earth out of nothing. He alone fashions the vault of heavens and the Earth below; he alone set the sun, moon, and stars in their places in the sky. His act of creation took six days, but the universe, complete with the heavenly bodies, was finished by the fourth. God created man on the sixth day—the culmination of his efforts.4 The hierarchy is clear. Genesis sets it out quite neatly. God is above all, and then comes man, which God created in his image. Then comes woman. Then the beasts of the field, the fowl of the air, the fish of the sea, herbs and plants, and then the Earth itself. Man has dominion over all; everything else in the universe is meant to serve him. The sun and moon were meant to divide the night from the day for man’s benefit; along with the innumerable stars, they were fashioned to provide him with light. Man is the center of the universe, both literally and figuratively.
When Rome conquered Greece, it absorbed Greek philosophy and culture—and its cosmology—and as the Roman Republic and Empire spread across the known world, so too did Aristotle’s picture of the universe. But Rome, in turn, would be conquered by Christianity, a religion that branched off of Judaism. At the end of the first century AD, Christianity was a small sect. Less than three centuries later, the emperor Constantine, ruler of the most powerful nation on earth, converted to Christianity. The Greco-Roman and Christian cultures began to merge. Aristotle’s ambiguous theology made it easy for the early Christians to absorb Aristotle, just as Rome had. (The New Testament was written in Greek, after all, so the early church had already absorbed a heavy dose of Greek culture.) Christianity, with Greek philosophical undertones, became the dominant cosmology in the Western world.
The Aristotelian component of Western cosmology had a very firm foundation—it was based upon observation of the natural world. In the second century AD, in Alexandria, the intellectual capital of the ancient world, the mathematician Ptolemy built an intricate, and incredibly complicated, model of the universe based upon Aristotle’s cosmology. The Earth was at the center of the universe, and the stars and planets whirled in circular orbits around it. To explain the complicated motions of the planets (such as the occasional backward, or retrograde, motion of Mars), Ptolemy proposed that the planets danced in tiny little circles called epicycles as they spun around the Earth.
Ptolemy’s clockwork universe worked beautifully. It explained the motions of the planets to fairly high precision, providing seemingly unshakeable support for Aristotle’s theory of the cosmos. By building upon Aristotle’s geocentric universe, Ptolemy had fashioned a powerful cosmology, one that had predictive power. Its ability to describe the motion of the planets, along with its “prime mover” that seemed to describe the Christian God admirably well, made the Aristotelian-Ptolemaic universe unassailable until Elizabethan times.
Aristotelian-Ptolemaic cosmology was embraced by the church, even though it sometimes contradicted the Bible. For instance, Psalm 148 exclaims, “Praise him, ye heavens of heavens, and ye waters that be above the heavens.” Though having a water above the heavens seemed to explain both the blueness of the sky and the source of rain, this was forbidden in the Aristotelian universe. Water is a heavy element, so it did not belong above the heavens; it was only allowed to exist in the earthly sphere.
Though the church struggled internally with the contradictions between Aristotle and the Bible, it eventually used Aristotelian cosmology as the basis for its own theology. To attack Aristotle became tantamount to attacking the truths handed down by the pope himself. And when a revolution toppled Aristotle, the church found itself on the losing side. It has never recovered.
1. Unfortunately for the sun and moon, the wolves catch up in the end.
2. One legend tells of a single, disastrous aberration in the sun’s daily course, when the son of Helios took the reins of the chariot. The son, Phaëthon, died due to his hubris and poor horsemanship.
3. The Greek word planetos means “wanderer.”
4. The two Genesis stories of the origin of man and woman are somewhat contradictory. Genesis 1 has both man and woman being created on the sixth day; Genesis 2 starts with Adam and tells of Eve being fashioned from Adam’s rib. For this reason, some Jewish mystics believed that Adam had a wife before Eve, Lilith, who now wanders the Earth as a demon.
The indispensable catalyst is the word, the explanatory idea. More than petards or stilettos, therefore, words—uncontrolled words, circulating freely, underground, rebelliously, not gotten up in dress uniforms, uncertified—frighten tyrants.
HIGH UP ON a wall in the Vatican, there is a tiny yellow portrait, a relic of a four-hundred-year-old battle. Surrounded by flowers and laurels, and crested by the two keys to heaven, a bemused-looking bearded man gazes to his left. He would be unrecognizable but for a handy Latin inscription: “Galileus.” Galileo Galilei, the most famous scientist of his day, was condemned to perpetual imprisonment by the Roman Inquisition. Now that he’s back in favor with the church, his picture is adorned with the trappings and symbols of the pontiff. A few yards away, another bearded man on the wall stares to his right. His three-pointed hat reveals that he is a cardinal, a prince of the church. “Bellarminus,” Cardinal Robert Bellarmine, the chief of the Roman Inquisition, was the man who first tried to subdue Galileo. His portrait is also surrounded by laurels, and he too is adorned by the keys to heaven. Galileo and Bellarmine, adversaries in life, are both honored by the church, and their portraits adorn the same wall of the Vatican. Yet the two still look in opposite directions.
Four hundred years after the opening shots of the first cosmological revolution, the Roman Catholic Church is still struggling to come to terms with its past. When the discipline of science was born, the church tried to smash the scientists who trod carelessly across Christian theology. Unfortunately for some scientists, it was hard not to stray into forbidden territory, especially since the first major achievement of modern science was to shatter the ancient Aristotelian cosmos—to smash the cozy universe, as self-contained as a nutshell—into a thousand shards. For the first time, science provided genuine insight into the nature of the universe. A new breed of philosopher started telling a tale of how the cosmos was put together, contradicting the Aristotelian-Ptolemaic cosmology. The church, with its foundation perched upon that ancient nutshell, struck back.
The scientific cosmology eventually defeated the Aristotelian one, but this would not provide any consolation for Galileo, or for the other victims of that struggle. Centuries after the clash of theology with science, the church still suffers from losing the first cosmological revolution.
The church had a love-hate relationship with Aristotle and Ptolemy, the ancient Greek architects of Western cosmology. The Greek cosmos made a great deal of sense to the medieval mind; the stars and planets had their own natural places. So did the elements that made up all the matter in the cosmos. Heavy earth sinks to the center of the universe, forming the ground we walk on. Water, which is lighter, sits on top of the earth, forming the oceans and rivers. Air, lighter still, forms the atmosphere we breathe. Fire is the lightest element—after all, flames try to leap into the sky. The sun, moon, planets, and stars, made from some light, fiery substance, inhabit the heavens, revolving in crystal spheres about our planet. What made the cosmology even more attractive to the church was that Aristotle’s universe required a prime mover. The Greek cosmology was inherently a proof of a divine existence.
Few philosophers or theologians in the West questioned the idea that the prime mover, the being who set the crystal spheres in motion, was the Christian God. The church embraced Aristotle’s ideas, seeing the value of a proof of God’s existence. But before long, theologians realized that the Aristotelian cosmology, in fact, contradicted the Bible. The ancient Greek wisdom denied the existence of an omnipotent God—a heretical idea. Cracks in Aristotle’s nutshell universe began to appear very early in church history. Augustine of Hippo, the fifth-century scholar and saint, was one of the first to attack the ancient philosophy.
Augustine saw a problem with Aristotle’s ideas about the origin of motion, which comes from the prime mover. That idea in itself was not so troublesome to Augustine, but the devil was in the details. Aristotle’s prime mover twists the outermost crystal sphere, causing the motion of all things in the universe, be it the eternal spinning of the planets in the heavens or the motion of the flames on a burning piece of flax. Therefore, argued the ancient philosophers, if God decided to stop the motion of the heavens, then all motion on Earth and the very passage of time should cease. Water should abruptly stop flowing over a waterfall, and birds should freeze motionless in midflight. Since God doesn’t stop the motions of the heavens very often, this doesn’t seem like a theory that would get tested. But, in fact, it did, in a medieval sort of way. God did stop the motion of the heavens once, at least according to the Bible. And biblical history does not match up with Aristotle’s predictions.
Chapter 10 of the Book of Joshua tells of a battle between the Israelites and the inhabitants of the land of Canaan: “And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies.” The men of Israel were happily smiting and slaying, even though the heavenly bodies had stopped in their tracks. This biblical passage directly contradicts Aristotle, whose theory implies that the Israelites should have been as motionless as the sun and moon.
Realizing the contradiction between the Bible and Greek philosophy, Augustine argued that the passage of time was independent of the motion of the heavenly bodies; if the sun and moon stood still in the heavens, a potter’s wheel would still whirl around unabated. If Aristotelian philosophy and the Bible clashed, then Aristotle had to give way.