by Adam Frank
Anyone who has heard the shift in pitch of a passing ambulance siren knows that motion and frequency are related. A stationary ambulance siren emits sound waves with a definite frequency (and a definite wavelength, which is directly related to frequency). When an ambulance moves towards you the sound waves get crowded together. The crowding forces the wavelength to get shorter and the frequency to rise (so that the pitch you hear is higher). When the ambulance passes and is moving away from you the siren’s sound waves are stretched out. The wavelength increases and the frequency drops (so that the pitch you hear is lower). This is the famous Doppler effect and it holds just as true for the light waves transmitted by galaxies as for the sound waves emitted by ambulances on Earth.
In the early 1900s astronomers began searching spectra from spiral nebulae for Doppler shifts. The goal was to find the motions of the nebulae (not yet recognized as galaxies) through space. Doppler shifts towards shorter wavelengths—or the blue end of the spectrum—would mean a galaxy was moving towards us. And Doppler shifts towards the longer wavelengths—or the red end of the spectrum—would mean a galaxy was moving away from us.
In 1912 astronomer Vesto Slipher, working at the Lowell Observatory in Arizona, had painstakingly accumulated enough light from a few distant galaxies to record a decent spectra.35 Most of Slipher’s galaxies showed redshifts. Only a few galaxies like Andromeda, the Milky Way’s neighbour, appeared to be moving towards us. With so many redshifts, Slipher’s data were intriguing, but they gave astronomers no purchase on an underlying pattern. Once spiral nebulae were recognized as galaxies, new questions emerged. Were all galaxies redshifted? Did they all have the same velocity? If not, which galaxies had the highest speeds? Was a galaxy’s redshift determined by its position in the sky or distance from Earth?
To unravel the enigma of the galaxy redshifts Edwin Hubble returned to the 2.5-metre Hooker telescope in 1928 with Milton Humason acting as assistant. Humason’s extraordinary patience and steady hands at the controls on long, cold nights made him the ideal partner. Through the exacting work of recording spectra from galaxies across the night sky, the pair hoped to find the relationship between velocity and distance for galaxies and pick up on a pattern that would make sense of Slipher’s initial discovery. Doppler shifts in the spectra would give them the galaxy’s velocity, while Cepheid variables would have to be identified in each galaxy to determine its distance from Earth. It was painstaking work but slowly a pattern did emerge.
FIGURE 6.4. The Hubble Law. Hubble discovered that all galaxies were receding from one another. In particular, the recession followed a simple law with galaxy velocities increasing with their distance from us. This is what would be expected for an expanding space-time.
In an epochal paper published in 1930, Hubble and Humason demonstrated that nearly all galaxies were redshifted, receding at tremendous velocities and, as the great English astrophysicist Arthur Eddington put it, were shunning us like the plague.36 More important, however, was the relation between recession velocity and distance. Hubble and Humason found that galaxy recession velocities increased as their distance increased. In a beautifully simple linear relationship, distant galaxies were moving away from us faster than those nearby. Hubble refused to interpret his own results, allowing theorists the prerogative of explanation. But he and most everyone else knew the message in the data. Einstein had been wrong. The universe was not static. It was moving.
Einstein’s equations had proven more prescient than their creator. By adding the cosmological constant, Einstein had prevented the mathematics from leading him to a conclusion that was now clear to scientists around the world: the universe as a whole was expanding. “It was my greatest blunder”, the chastened Einstein would later say about the cosmological constant.37 In our own era, Einstein’s blunder has returned in a different guise, reshaping modern cosmological debates away from the Big Bang. But in 1930 the cosmological constant was seen as nothing more than a mistake.
Einstein may have been wrong about the universe’s motion but so too was de Sitter. Hubble had found redshifts, but they were not the ones predicted by de Sitter’s expanding universe. The simple linear relationship between expansion and distance, so clear in Hubble’s data, did not match what de Sitter’s model predicted. If relativistic cosmology was to yield a theoretical complement to Hubble’s astonishing discovery of an expanding universe, it would have to come from someone other than Einstein or de Sitter. Remarkably, by 1930 the linear pattern of velocity and distance expansion had already been predicted by scientists not once but twice.38 More remarkable still, both solutions had been forgotten.
Alexander Friedmann, a young Russian theorist, was the first to discover the correct version of an expanding relativistic universe. The son of a ballet dancer (his father) and a piano teacher (his mother), Friedmann had survived the horrors of World War I and the communist revolution with his scientific ambitions intact.39 A mathematical physicist, he was deeply interested in the mathematical properties of general relativity’s cosmological models. In a 1922 paper published in the famous German journal Zeitschrift für Physik, Friedmann found a new cosmological solution to the equations of general relativity that included both matter (unlike de Sitter’s) and expansion (unlike Einstein’s).40
Exploring the field equations of general relativity, Friedmann found a broad solution with three possible versions of cosmic history, each of which predicted the form of expansion Hubble had discovered. Two of Friedmann’s solutions had a space that was infinite and unbounded. In these universes any two randomly chosen points would move farther away from each other as cosmic time marched forward. The third solution began with expansion but eventually turned around and started to contract. Space was finite and bounded in this version of the universe and two randomly chosen points would first move away from each other before eventually being swept back together. The trajectory the universe took in reality depended on the balance between cosmic expansion and the force of gravity pulling everything back together—a balance that could be described in a single number.
If the average amount of mass-energy in the universe (its mass-energy density) was above a critical value, then gravity would eventually beat expansion and the universe would slow down, change direction and collapse on itself. But if the mass-energy density in the universe was below this critical density, the universe would expand forever, thinning out until it was all but empty. If the mass-energy density was exactly equal to the critical density, the universe’s expansion would be slowed by the force of gravity but only enough to halt its stretching infinitely far into the future.
The critical density parameter could be cast in a form called omega (Ω): the ratio of the actual density in the universe to Friedmann’s critical value. It was omega that set both cosmic fate and cosmic geometry in his models. An omega larger than 1 meant a closed and finite universe, a moving version of Einstein’s 3-D hyperspheres; an omega equal to or less than 1 meant a space that was infinite and unbounded. The search for omega’s real value would come to dominate observational cosmology for decades to come.
FIGURE 6.5. Cosmic geometry and the omega parameter. In the expanding cosmological models of Friedmann (and Lemaître), the global geometry of space-time depends on omega, a number describing the mass-energy content of the universe.
Reading over Friedmann’s paper, Einstein at first rejected the work, warning that the results appeared “suspicious”. After a series of exchanges with Friedmann, the young Russian proved his case, and Einstein withdrew his objections. But, as sometimes happens, Friedmann’s work failed to reach the small band of cosmological cognoscenti and within a few years it was forgotten.
Eight years later, in 1930, Hubble’s discovery of the expanding universe was sinking into the minds of theoretical astrophysicists around the globe. So completely had Friedmann’s work disappeared, however, that even Arthur Eddington, one of the first astrophysicists to embrace Einstein’s relativity, could wonder out loud at a conference why
no cosmological solutions could match the observed expansion. Ironically, Eddington’s mistake lay buried not just in the journals but, in a way, right under his own nose.
Georges Lemaître, a professor of astronomy in Belgium, was a former student of Eddington’s. Lemaître was not just a scientist working at the frontiers of theoretical cosmology; he was also a Catholic priest. Like Friedmann, he too had seen the horrors of World War I through close-range fighting and the use of poison gas.41 The experience propelled the quiet young man to a life of both science and spirituality. After first studying general relativity with Eddington and then getting his PhD at MIT, Lemaître began exploring new cosmological solutions. In 1927 he derived the same expanding-universe model that Friedmann had found a few years earlier. Lemaître published his work in a little-known Belgian journal, where it languished, but he did manage to show Einstein his paper at a conference. Once again, however, the great scientist missed the chance to see the truth in his own equations. Einstein told Lemaître: “Your calculations are correct but your physics is abominable.”42
Once Hubble’s results made news, Lemaître immediately contacted Eddington. The quiet priest informed Eddington of his own solution and its nearly perfect prediction of the observed form of cosmic expansion. With Eddington’s help, Lemaître’s results quickly gained attention from the scientific community. Hubble’s data now had their stunning interpretation. Galaxies were not flying through space away from one another; space, or rather space-time itself, was expanding. The linear pattern of galaxy recession velocities increasing with distance was to be expected if all of space were being uniformly stretched, carrying the galaxies along with it like pennies glued to an expanding rubber sheet. Without a doubt, the universe itself was expanding.
The discovery of the expanding universe was big news. From Europe to Japan to America, Hubble’s discovery made for breathless headlines in newspapers and thrilling announcements in the radical new medium of the age: radio. It would be no small irony that at the moment Hubble discovered the expanding universe of space-time, radio was rebuilding the human universe by contracting space and constructing an entirely new form of experienced time.
EVERY HOME SHOULD HAVE A RADIO!
The twentieth century’s most intimate and enduring experiment in experienced time was born at an invitation-only white-tie party at New York’s Waldorf-Astoria Hotel.43 The invitations had gone out to the city’s elite: celebrities, politicians and pundits. But the most honoured guests that night were an entire nation of radio listeners. It was November 15, 1926, the night the National Broadcasting Company, a true radio broadcasting network, was born. From 8:00 to 10:00 p.m. the same music accompanying the elegant dancers at the Waldorf was also emanating from radio sets across the continental United States. The music was carried on waves of electromagnetic radiation broadcast by a network of antennas spanning the country from New York to Los Angeles.44 A different station owned each antenna tower, and each station had just been brought under the programming supervision of NBC.45 Though the BBC had managed to make its first near-national broadcast four months earlier, via the long-wave antenna of station 5XX, the Daventry-based station had far less ground to cover and remained an experiment. NBC’s Waldorf broadcast announced the beginning of true synchronous programming, and the impact of that night on Americans’ experience of time would echo through the decades. The first true culturally shared sense of simultaneity—the first American experience of a nationwide “now”—was born.
As a commercial venture, broadcast radio began inauspiciously. In 1889 physicist Heinrich Hertz discovered how to generate and receive long-wavelength electromagnetic (radio) waves by driving oscillating electric currents though metal wires.46 The business and political worlds took notice but were unsure what to do with the new invention. With telegraph and telephone wires becoming ubiquitous across the world, the first uses for the new wireless technology were imagined to be point-to-point communication. In other words, the killer application for radio was expected to be radiotelegraphy.
The Marconi Wireless Telegraph Company of America, founded by the brilliant Italian pioneer Guglielmo Marconi, started with a simple business plan.47 American Telephone and Telegraph dominated the American telecommunications business of the day. Marconi wanted to upend AT&T’s dominance of telegraphy by replacing wires with waves. By the end of the twentieth century’s first decade, radiotelegraphy had made inroads in at least one domain: ship-to-shore communications. The potential for this form of radiotelegraphy was made concrete in 1912 when Morse-coded radio bursts broke news of the Titanic’s sad fate. The story of the Titanic’s sinking spread by radio from the Carpathia, the first ship to reach survivors, over to Newfoundland and down the East Coast, relayed from one Marconi wireless station to the next.48
In spite of its importance for naval messaging, point-to-point radio telecommunication had obvious limitations. Any hack with a radio set could pick up what were intended to be confidential messages. Its inability to offer privacy made radio a poor replacement for the telephone. Taking radio beyond radiotelegraphy would require entrepreneurs who could imagine it as something more than a wireless telephone.
David Sarnoff was one of those visionaries.49 Born in 1891 in Uzlian, a Russian shtetl, Sarnoff immigrated with his family to the United States in 1900.50 A quick study, the young Sarnoff rapidly turned his fascination with the telegraph into a working knowledge of Morse code and a job as a telegraph operator. He was an ambitious man and rose quickly within the Marconi Company. When General Electric purchased the business in 1919 to create the Radio Corporation of America (RCA), Sarnoff was elevated once again. He would soon prove his worth to the new company. In a prescient memorandum on the future of radio, Sarnoff wrote,
I have in mind a plan of development which would make radio a “household utility.” . . . The receiver can be designed in the form of a simple “Radio Music Box” and arranged for several different wave lengths. . . . The box can be placed in the parlor or living room, the switch set accordingly and the transmitted music received.51
But this plan faced a classic technological chicken-and-egg dilemma. In 1919 RCA might imagine the public buying up a fortune’s worth of radio sets, but what would they listen to? There was no one broadcasting in 1919 and, therefore, no reason to buy a receiver.
By 1920, the broadcast problem began to resolve itself. In that year Frank Conrad, a Westinghouse employee in Pittsburgh, set up a transmitter in his home. Pulling a Victrola up to the microphone, Conrad occasionally played opera records for the smattering of radio enthusiasts who owned receivers.52 Conrad’s broadcasting exploits caught the attention of local newspapers and, soon enough, the attention of his bosses. On October 27, 1920, the first U.S. licenced radio station, KDKA, started transmitting from atop the Westinghouse building.53
Other stations appeared at a brisk pace. By the autumn of 1921 six to twelve new operations were setting up shop each month. As broadcasters appeared, so did their audience. By 1922 Americans were spending more than $60 million a year on home radio sets.54 The early growth of radio into the public consciousness was explosive. But early broadcasting bore little resemblance to what we experience today. In particular, the idea of programme time was yet to be invented.
At the start, American radio stations were entirely haphazard in their programming. They transmitted for at most a few hours each day, often appearing on the air only when their owners had time or opportunity. When a station in Schenectady, New York, began featuring regularly scheduled music, it was an important enough innovation to warrant a feature story in the Washington Post.55 One reason the Post ran the story was that Washington, D.C., listeners were picking up the Schenectady station. The ability of radio waves to bounce off electrically charged upper layers of the atmosphere meant that, in an era with few active transmitters, stations could travel hundreds of miles from their source. Radio was breaching distances for Americans in an entirely new way, introducing a single “now” to widely separ
ate populations hungry for programming they could count on. In a few years, radio would begin to set time by changing the behaviour of its listeners.
FIGURE 6.6. Family time around the radio circa 1940. Regularly scheduled programming by radio networks redefined the common experience of time for most Americans beginning in the 1920s. Television would deepen the experience of “programme time.”
The early days of radio had its share of cranks and innovators. Sometimes these were rolled into the same personality. The first form of regularly scheduled programming, destined to reshape the American experience of communal time, came not from RCA but from a medical quack in Milford, Kansas.
John R. Brinkley was a doctor of dubious credentials.56 He had made his fortune offering sexual restoration to men through, of all things, goat testicle implants. The wealth he gained in this pre-Viagra age allowed him to buy the radio station KFKB (which stands for “Kansas First, Kansas Best” or, alternatively “Kansas Folks Know Best”). With its powerful three-thousand-watt transmitter, KFKB reached across almost a thousand miles.57 While using the station for his own brand of hucksterism, Brinkley saw the power of the new medium. Only a few years after its inception in 1923, Brinkley’s KFKB provided radio with its first full day of scheduled programmes. A typical morning on KFKB treated listeners to a range of music and quackery. From 7:00 to 7:30 listeners heard hints to good health, followed by a half hour of Bob Larkin and His Music Makers. The half hour from 8:00 to 8:30 was lecture time with Professor Bert.58 And so the radio day unfolded as a mix of music, news and sales pitches from Dr Brinkley. Filling the day—that is, filling time—with continuous radio programming was a brilliant innovation that would outlive the good Dr Brinkley (by 1930 he had been exposed as a fraud and had his licence revoked).59