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Scandals: Being True To Our Own Imaginations

Written by Gregory Benford

Illustrated by Laura Givens

Physics has been the forerunner of much of modern science, but perhaps we don't have enough verve, the true courage of our convictions.

Take just one example from our grandest province where we merge with astronomy— cosmology. Half a century ago, we should have seen the big bang coming; indeed, we did see it. And ignored it.

In the late 1940s George Gamow, Ralph Alpher and Robert Herman worked out element formation and the entire scenario that led to the famous 3 K (3 degrees Kelvin) background radiation. Yet the Steady State model held sway, and their work faded from view by the mid-1950s.

"We never quite thought through to the realization that the peak emission was observable in the microwave sky," Ralph Alpher said when I asked him about it after a colloquium at UC Irvine in the 1980s.

"Why didn't you go to the radio astronomers and ask if they could see the emission?" I prodded.

It turned out that they did. Radio astronomers at NRL and Johns Hopkins didn't think it could be done. Alpher took their word for it, he acknowledged ruefully

But in a way, Joe Weber did. I turned to Joe, standing at the wine-and-cheese reception after Alpher's talk. He couldn't recall if he had then even heard of the Gamow-Alpher-Herman work, but around 1950 he knew of Gamow's reputation. He asked Gamow for a thesis problem. Joe had capability in radar, learned in the Navy, extending up toward the microwave region. Was there some cosmological use for observations in such a range? "Gamow couldn't think of anything relevant," Joe said, shaking his head. "So I looked at stimulated emission instead." This work built on Einstein's ideas about photons of light (of any frequency) distributed into quantized levels, and how to release them, so they could all at once cascade down in a pulse. In that work he provided some of the theory that led to the maser. Indeed, when Charles Townes and others won their Nobel for inventing the maser, the only reason Weber wasn't on the list was the prize rules, which allow no more than three people per prize."

In the early 1960s, Steady State was in retreat and the group at Princeton including Dicke and Peebles began working on implications of an earlier, hot stage. They began building a radiometer, motivated by a desire to find a prior "big crunch" in a cyclic universe. They apparently did not recall the Gamow, Alpher and Herman work and replicated it. By startling coincidence, while they were still thinking through the details of how to detect the 3 K emission, it turned up nearby. The famous Bell Labs experiment, trying to see sources of noise in the sky, came upon the classic black-body signature, at just the right equivalent temperature, netting Penzias and Wilson a Nobel Prize.

But could the 3 K background have been seen earlier?

In 1976 I took a sabbatical from UCI to Cambridge's Institute for Astronomy. Martin Ryle and Tony Hewish had won the Nobel for pulsars, and I wanted to work on the plasma physics of rotating magnetized neutron stars. (A true, closed system solution to this problem remains elusive, decades later.) In discussing this with Ryle, I suddenly asked, "If someone had come to you suggesting that relic radiation around 3 K was detectable, say, around 1950, when could you have detected it?"

He thought and said, "It would have been a challenge, getting the signal to noise ratio down, but . . . perhaps a few years."

"Would you have put in that level of research investment?"

He shrugged ruefully. "Probably not, without a big authority behind the idea."

"An authority like Gamow?"

He laughed. "I'm really not sure. I think Hoyle would've frowned at the idea."

So I asked Fred Hoyle. Hoyle pointed out that there had been tantalizing detections much earlier, that nobody thought to relate to the Gamow-Alpher-Herman work. In 1941 Walter S. Adams found a puzzling excitation temperature of 2.3 K in interstellar CN absorption, and remarked on the lack of any obvious exciting source. This 2.64 mm measurement was near the blackbody peak, yet it escaped general notice for decades.

By 1956 Hoyle had seen Andrew McKellar's report on interstellar molecules, in which he proposed that the temperature of space is about 3 K. Gamow visited Hoyle in La Jolla in 1956 and told him he thought space was filled with microwaves at a temperature of about 10 or 20 K. Hoyle said the temperature could not be so high because of McKellar's work. He thought it should be zero K, the Steady State view.

Hoyle said that he would have encouraged such a test, but it had not occurred to him as plausible at the time. Ryle might have, but he was far from the particle-cosmological community in the USA, too. Hoyle was in a "scrimmage" with Ryle by then, and not likely to tell him of odd ideas from across the Atlantic. They were disputing the issue of radio source counts.

Ryle's collaborators found that the slope of the number of radio sources versus distance did not fit the Steady State prediction. There were too many at great distances, implying some evolution of the sources over time.

So instead of a direct test, we sat through the slow battles over source counts. Rather than testing the