Friday, May 15, 2009

Easy as α β γ ?

Sometimes there are two sides to a story. For a long time one of my favorite fun physics stories is about the famous "Alphabetical Paper" of 1948. The brilliant young PhD student Ralph Alpher working with his advisor George Gamow were about to publish a major work about the origins of the elements after the Big Bang. In a burst of inspiration, Gamow invited the physicist Hans Bethe to include his name on the paper, even though he had not contributed to it at all. That way the paper would have been authored by Alpher, Bethe, Gamow, a play on the first three letters of the Greek alphabet alpha, beta, and gamma. It was a delightful pun, and their one page paper serendipitously ran in the April 1st issue of Physical Review Letters.

The theory itself was groundbreaking, and helped establish the groundwork for proving the universe began in a proverbial "Big Bang." The paper argued that if the universe began as a thick soup composed of hydrogen atoms, they would start bonding with each other forming heavier and heavier elements (Helium, Lithium Beryllium etc.) at predicable rates. Most importantly it predicted that by this nucleosynthesis method, there should 10 times more hydrogen in the universe than helium. AND THEY WERE RIGHT! Mostly, but more on that later. Actual observations of the ratio of H to He agreed with the 10:1 prediction and the paper would later serve as an important piece of evidence to prove the Big Bang.


However there is, like many things in life, much more to the story. It turns out that Ralph was never completely comfortable with the impromptu inclusion of the famous physicist on the author list. Hans Bethe was already an established and well known physicist, known for his work on nuclear reactions. During World War II he worked on the Manhattan Project helping to solve major theoretical issues with the bomb, among which were calculating the critical mass of uranium-235 and determining the explosive yield of the bombs.
Likewise George Gamow was also a giant in the field. He was able to first explain the radiation of alpha particles from radioactive sources, a particularly thorny problem that had plagued physicists for years.

Alpher however was still only a doctoral student at the time and was never happy about Bethe's inclusion on the list. Though Alpher had done the majority of the calculations and work in the paper, it often seemed that the two physics leviathans listed as authors received the lion's share of the attention. This was compounded later when Hans Bethe continued to develop the theory. He found later that while the paper's major finding about hydrogen fusing into helium was correct, helium fusing into other heavier elements could only happen in the intense pressures at the cores of stars and supernovas. That meant that these elements couldn't have formed on their own in the dense soup after the Big Bang, and Alpher's predictions for the heavier elements were incorrect.

Unfortunately for Alpher this wasn't the only time credit for one of his major discoveries went to someone else. After writing the "Alphabetical Paper" Alpher and Gamow partnered with Robert Herman and calculated that the Big Bang should have left an echo in all directions of the sky detectable as a very slight amount of heat. Unfortunately they predicted this at a time before the Big Bang was generally accepted, and his calculations were mostly forgotten.

Years later in 1964 Arno Penzias and Robert Wilson accidentally discovered the very cosmic microwave background radiation that Alpher predicted. Ironically they weren't even looking for it, they thought at first the echo of the beginning of the universe was from bird droppings! During their acceptance of the 1978 Nobel Prize, Wilson and Penzias made a special effort to thank Alpher for his contribution, but sadly today the memory of his importance to modern cosmology has largely fallen by the wayside.

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