by Marcus Chown
Holmdel, New Jersey, Spring 1965
It was depressing enough that the persistent, inexplicable microwave hiss was still there after Penzias and Wilson had cleaned the pigeon droppings from the twenty-foot horn. Even more depressing was the fact that the pigeons, having been sent away, returned to Crawford Hill – they were homing pigeons, after all – and had to be shot. Penzias and Wilson were not even able to console themselves with the thought that the birds had died for science; the two scientists were in the same position they had been in since teaming up the previous summer – unable to do any astronomy.
Just as they were succumbing to despair, Penzias happened to make a serendipitous phone call to a radio astronomer friend called Bernie Burke at the Department of Terrestrial Magnetism in Washington DC. It was about another matter entirely, but at the end of the conversation, Penzias could not stop himself moaning about the annoying hiss of static they were picking up at Crawford Hill. Burke sat up. He had recently been to a talk by a Princeton researcher called Jim Peebles and recalled that Peebles’ boss, Bob Dicke, was supervising the building of a small radio telescope on the rooftop of the geology building at Princeton to look for microwaves that had survived from a possible hot, dense phase of the early universe.12
Immediately, Penzias got off the phone to Burke and phoned Princeton. At the time, Dicke was having a ‘brown bag’ lunch with his team in his office. There followed a short, technical exchange, involving phrases like ‘microwave horn’ and ‘cold load’. The members of Dicke’s team exchanged glances, and when Dicke put down the phone, they already suspected what followed. ‘Well, boys,’ he said, shaking his head. ‘We’ve been scooped.’
The next day, Dicke’s group drove over to Holmdel, only thirty miles from Princeton. After examining the twenty-foot horn, the radio receiver and the cold load, and talking briefly with Penzias and Wilson about their experimental set-up, Dicke admitted that the game was up; the two astronomers had stumbled upon precisely what the Princeton team had been planning to look for.
Most of the light in the universe is tied up in the afterglow of the Big Bang. If you were to tune an old ‘analogue’ TV between the stations, 1 per cent of the ‘static’ on the screen would be from the Big Bang. Before being intercepted by your TV aerial, it has travelled across space for 13.82 billion years, and the last thing it touched was the fireball of the Big Bang. By discovering the cosmic background radiation, Penzias and Wilson had helped prove that the universe had not existed forever but had been born in a fireball: the Big Bang.13
The two teams – Penzias and Wilson, and Dicke’s group – decided to announce their discovery in back-to-back papers in The Astrophysical Journal Letters. Ironically, Penzias and Wilson were adherents of the idea proposed in 1948 by Fred Hoyle and two colleagues that the universe has existed forever and had no hot, dense beginning. As supporters of this ‘steadystate theory’, they were not happy about making a claim that what they had stumbled on was evidence of the rival Big Bang theory. In their paper, they mentioned only the annoying hiss of static, which they believed was an experimental result that would hold up whatever, while leaving the speculation about the precise identity of the hiss to the accompanying paper by Dicke’s team.
Two weeks before the papers were due to be published, the phone rang at Crawford Hill, and Penzias picked it up. It was Walter Sullivan, a science reporter at the New York Times. He had been on the trail of another story when he happened to call the offices of The Astrophysical Journal, and an editor had let slip that the journal was about to publish papers reporting a mysterious radio signal that was potentially from the beginning of time. Sullivan grilled Penzias about the work with the twenty-foot antenna.
Wilson’s father was visiting him from Texas at the time. An habitual early riser, the next day he got up well before his son and walked to the local drugstore. When he came back, he thrust a copy of the morning’s newspaper into the face of his bleary-eyed son. There, on the front page of the New York Times, was a picture of the twenty-foot horn, with an account of The Astrophysical Journal Letters papers.
*
Gamow, by now retired and living in Boulder, Colorado, read the story in the New York Times, but to his dismay could see no mention of his name, nor those of Alpher or Herman. It is fair to say that he awaited the publication of the papers in The Astrophysical Journal Letters with intense interest.
The title of Penzias and Wilson’s paper was a masterclass in caution and dullness: ‘A Measurement of Excess Antenna Temperature at 4,080 Megacycles per Second’.14 Basically, all the two astronomers said was that ‘Measurements of the effective zenith noise temperature of the twenty-foot horn-reflector antenna at the Crawford Hill Laboratory, Holmdel, New Jersey, at 4,080 megacycles per second have yielded a value of about 3.5 degrees higher than expected.’ Nowhere in their brief paper did they mention that the radiation they had picked up might have come straight from a hot Big Bang. They merely noted, ‘A possible explanation for the observed excess noise temperature is the one by Dicke, Peebles, Roll and Wilkinson in a companion letter in this issue.’
Tipped off by Gamow, Alpher and Herman had made a beeline for their respective libraries the moment the two scientific papers came out. They could hardly believe that the Big Bang radiation had finally been found – that the stuff they had predicted on a blackboard in Washington DC seventeen years earlier was truly out there. It actually filled the universe, just as they had imagined. Both men raced to the end of the papers, and when they got there, they stood in a state of shock. Nowhere was there a mention of Alpher and Gamow’s groundbreaking work on element-building in a hot Big Bang. And nowhere was there a mention of Alpher and Herman’s prediction of the heat afterglow of the Big Bang. They had shown themselves to be magicians, but it looked as if nobody would ever know.
It was scarcely credible that they had been overlooked. Not only had they published the results of their hot Big Bang calculations in a series of technical articles in Physical Review, they had also written numerous popular accounts of their work. In fact, in 1952, Gamow had published a book for lay readers called The Creation of the Universe, in which he talked about the cooking of helium in a hot Big Bang and how this was connected to the temperature of the universe. In 1956, he had even aired his ideas in an article in the popular magazine Scientific American.
Other scientists were now taking credit for work they had done almost two decades earlier. For Gamow, Alpher and Herman, it was almost too much to bear.15
Holmdel, New Jersey, Autumn 1978
Wilson got the first inkling about the prize in early 1978. ‘Some guy published a prediction of future Nobels – I think it was in Omni magazine – and he listed us,’ says Wilson. ‘But he’d been wrong on a bunch of things, so Arno and I didn’t take it seriously.’ In the summer of 1978, there was another hint, this time from an Irishman who had worked at Bell Labs. Jerry Rickson, while visiting Sweden, had been buttonholed by one of the country’s leading radio astronomers. ‘He got asked some very detailed questions about Arno and me and our relationship,’ says Wilson. ‘Who did what – that sort of thing.’
Later, a Swiss colleague of Wilson’s was more blatant. Martin Schneider was late handing Wilson a progress report on an experiment, and when the pair ran into each other at Bell Labs, Wilson asked whether he could have the report on his desk the next day. ‘You won’t want it tomorrow,’ Schneider said, gleefully. ‘They’re going to announce your Nobel Prize!’
The next morning, the phone jangling woke him at 7am. It was another of his colleagues at Bell Labs; he had heard a news item on WCBS radio and wanted to know whether it was true what people were saying, that he and Arno Penzias had won the Nobel Prize? Wilson could not say for sure, but all doubt was removed with the arrival of a telegram from the Royal Swedish Academy of Sciences. The 1978 Nobel Prize in Physics had been awarded to Penzias and Wilson for their discovery of the three-degree cosmic background radiation.
For Alpher and Herman, the
award of the Nobel Prize in Physics added yet more salt to the wound. Penzias and Wilson had stumbled on the radiation they had predicted seventeen years earlier entirely by accident. And if that was not bad enough, the Bell Labs researchers had not admitted for two years afterwards that the signal had anything whatsoever to do with the birth of the universe.
Dicke and his colleagues maintained they had been unaware of Alpher and Herman’s 1948 prediction of the Big Bang afterglow, but they failed to put the record straight. To be fair, they tried on several occasions, but in Alpher and Herman’s opinion they did not try hard enough.* So the wound remained. As for Gamow, he remained bitter about the treatment he and his team had suffered until his premature death from alcohol-induced liver disease in 1968. His only good fortune was not to be around to hear of the award of the 1978 Nobel Prize in Physics.
Wilson, of course, had no power over the Nobel Committee. ‘I consider myself so lucky,’ he says.
*
The afterglow of the Big Bang is the single most striking feature of our universe. If we had eyes that could see microwaves rather than visible light, we would see all of space glowing a dazzlingly brilliant white. It would be like being inside a giant light bulb. The question therefore arises: Why did it take until 1965 for the cosmic background radiation to be discovered by Penzias and Wilson – and then only by accident? The Nobel Prize-winning physicist Steven Weinberg has thought long and hard about this question and about why there was no earlier systematic search. In his popular account of the Big Bang, The First Three Minutes, he proposed three main reasons.
Firstly and most obviously, says Weinberg, Alpher and Herman were told by radio astronomers that the microwave afterglow of the Big Bang was undetectable. This was incorrect. Detecting it would admittedly have been hard, requiring a cold load with which to compare the temperature of the sky, but it could have been done.
The second reason why nobody looked for the fireball radiation, Weinberg says, is that its prediction emerged from a theory which was later discredited. By the 1950s, it was clear to everyone that most elements could not, as George Gamow had hoped, have been made in the Big Bang. Nature used two main furnaces to forge the elements: the fireball of the Big Bang, which made helium and the lightest elements in the first few minutes of the universe’s existence; and the stars, which subsequently created all the heavier elements. Unfortunately, when it became obvious that the Big Bang could not have made nature’s heavy elements, the idea was abandoned and Gamow’s baby was thrown out with the bathwater.
But the most important reason why the Big Bang theory did not lead to a search for the fireball radiation, Weinberg says, was that before 1965 it was extraordinarily difficult for physicists to truly take seriously a theory of the early universe. ‘The mistake of physicists is not in taking their theories too seriously but in not taking them seriously enough,’ says Weinberg.16 It was a simple failure of imagination. The temperature and density of matter in the first few minutes of creation were so far removed from everyday experience that it was hard for anyone to believe that they had ever actually occurred. Scientists could not imagine that anything as stark staring bonkers as the Big Bang could really be true. ‘The most important thing accomplished by the ultimate discovery of the three-kelvin radiation background was to force all of us to take seriously the idea that there was an early universe,’ says Weinberg.17
Vandenberg Air Force Base, California, 18 November 1989
The night before the launch of NASA’s Cosmic Background Explorer satellite, the COBE team flew out to Vandenberg Air Force Base, one hundred miles north of Los Angeles. They were put onto buses at around 3am, which put them down in a field about a mile from the launch pad. It was freezing and dawn was still some time away.
COBE, with its on-board microwave horns, was designed to observe the cosmic background radiation from above the Earth’s atmosphere, which made it difficult to observe from the ground. Impressed on the radiation is a ‘baby photo’ of the universe when it was just 380,000 years old and the matter of the cooling Big Bang was just beginning to clump together under gravity, to form what would eventually become galaxies. COBE was going to take that photo.
It was a large gathering and there was great excitement and anticipation. In the waiting crowd, stamping their feet to keep warm, were two elderly men who had been both surprised and pleased to be included. John Mather, project scientist and leader of the COBE team, had made a special point of inviting Ralph Alpher and Robert Herman. At long last, everyone recognised the prescience of the two magicians in predicting the afterglow of the Big Bang in 1948.
Notes
1 ‘Extra-Terrestrial Relays’ by Arthur C. Clarke (Wireless World, October 1945, p. 305).
2 The switching and the subtraction are done electronically.
3 Incredibly, it was possible to post a baby in the mail in the US until 1913 (‘A Brief History of Children Sent Through the Mail’ by Danny Lewis (Smithsonian.com, 14 June 2016: https://www.smithsonianmag.com/smart-news/brief-history-children-sent-through-mail-180959372/)).
4 An unlikely friend of George Gamow’s was the English quantum theorist Paul Dirac. Gamow liked to talk and Dirac was happy to listen, and the garrulous Gamow even taught his taciturn friend to ride a motorbike.
5 The term ‘Big Bang’ was coined in 1949 by Fred Hoyle, who, ironically, never believed in it.
6 Fred Hoyle would later discover that the route to building heavier elements involved three helium nuclei colliding to form a nucleus of carbon. This highly unlikely ‘triple-alpha’ process was significant inside stars because they maintained high densities and temperatures not simply for ten minutes but for millions and even billions of years.
7 ‘The Origin of the Chemical Elements’ by Ralph Alpher, Hans Bethe and George Gamow (Physical Review, vol. 73, 1948, p. 803).
8 Ralph Alpher’s son Victor writes that Herman had disappointed Gamow by refusing to change his name to ‘Delta’ (‘The History of Cosmology as I Have Lived Through It’ by Victor Alpher (Radiations, vol. 15, issue 1, spring 2009, p. 8)).
9 If the universe were shrunk by a factor of eight, the energy density of the matter particles would go up by a factor of eight. However, the photons would double their energy, so the energy density of radiation would go up by a factor of sixteen. So, even though today we live in a matter-dominated universe, in the past radiation would have been important. In fact, during the first few hundred thousand years of its existence, the universe was radiation-dominated.
10 The term ‘black body’ is unfortunate, since it refers to the spectrum off a bright fireball. However, there is method in physicists’ madness. A black body is an idealised body that absorbs all photons that fall on it and radiates nothing, hence its blackness. Inside the body, those photons bounce around, sharing their total energy and achieving a black body spectrum. Of course, to observe the spectrum a small hole would have to be made in the body to let out some of the light.
11 ‘Evolution of the Universe’ by R. A. Alpher and R. C. Herman (Nature, vol. 162, 13 November 1948, p. 774).
12 Dicke believed in the existence of relic heat radiation in the universe for the opposite reason to Gamow, Alpher and Herman. Rather than the universe beginning in a one-off Big Bang, he subscribed to the idea of a universe swelling and contracting throughout eternity like a giant beating heart. Such an ‘oscillating universe’ sidestepped the awkward ‘What happened before the Big Bang?’ question but had another problem. In 1957, Fred Hoyle and his co-workers had succeeded where Gamow had failed in finding a furnace in which elements heavier than helium could be forged: stars. But if the universe began as hydrogen, and stars then cooked some of it into heavy elements, what had happened to the heavy elements that had been made during the universe’s previous cycle of expansion and collapse? There must be a process that destroyed all the universe’s heavy elements between the big crunch at the end of a phase of contraction and the Big Bang at the start of the next expansion, and Dicke realised th
at extreme heat would do the job. During its compression, the universe must have been very hot – many billions of degrees. At such a temperature, the heavy elements would have been slammed together so violently that they would have disintegrated into hydrogen, erasing all traces of the previous era of cosmic history. An unavoidable consequence of such a primordial fireball phase was fireball radiation. Dicke, like Gamow, concluded that the early universe must be pervaded by leftover heat.
13 It took a little more evidence to prove the Big Bang theory beyond doubt. It was necessary, for instance, to measure the afterglow of creation at different frequencies to show that it did indeed conform to a black body spectrum. And it was necessary to observe the distant (and therefore early) universe. Such observations in the early 1960s revealed ‘quasars’, which no longer exist in today’s universe. They confirmed the Big Bang prediction that we live in a changing universe and not an unchanging one, as predicted by the rival ‘steady-state’ theory of Fred Hoyle, Tommy Gold and Hermann Bondi.
14 ‘A Measurement of Excess Antenna Temperature at 4,080 Megacycles per Second’ by Arno Penzias and Robert Wilson (Astrophysical Journal, vol. 142, July 1965, p. 419).
15 Actually, the cosmic background radiation had been both predicted and discovered before it was discovered. Not only had Alpher and Herman predicted it seventeen years earlier in 1948 but a decade earlier than that, in 1938, Walter Adams, using the biggest telescope in the world – the giant 100-inch reflector on Mount Wilson – had noticed something puzzling. Out in the cold of space, tiny dumbbell-shaped molecules of cyanogen were spinning faster than they should. Canadian astronomer Andrew McKellar suggested that they were being buffeted by something – radio waves at a few degrees above absolute zero. With the discovery of the cosmic background radiation, which permeates every pore of the universe, it suddenly became obvious what that ‘something’ was.