Editor's Pick

ON 1 APRIL 1948, the journal Physical Review published a letter to the editor titled “The Origin of Chemical Elements” by Ralph Alpher, Hans Bethe and George Gamow. (Alpher and Gamow, second and third from left, respectively, can be seen here being interviewed for television the following year.) The article laid the foundations for the Big Bang theory by postulating how different elements and isotopes originated as a consequence of the rapid expansion and cooling of matter in the early universe.

Alpher was a 27-year-old employee at Johns Hopkins University’s Applied Physics Laboratory, helping develop ballistic missiles and associated systems. He was also pursuing a doctorate at George Washington University, where Gamow was his thesis advisor. Bethe, a nuclear physicist at Cornell University, was not involved in the research. Gamow included him as the second author, with his permission, because he wanted to make a pun about how their surnames sounded like the first three letters of the Greek alphabet.

Alpher’s calculations helped explain the creation of the various isotopes of hydrogen and helium but failed to accurately predict how larger elements were created. This was done by the British astrophysicist Fred Hoyle, who had derisively coined the term “Big Bang”—he preferred the competing Steady State theory—and postulated that all other elements were produced inside stars. He was, however, unable to explain the prevalence of helium in the universe, and the Big Bang hypothesis was vindicated by the discovery of cosmic background radiation. The consensus at the end of the 1960s was that the isotopes created in the first few minutes after the primordial explosion combined with each other inside the stars. By then, Gamow had died, and Alpher had left cosmology to go work at General Electric. Bethe was awarded the 1967 Nobel Prize in Physics for his foundational work on the nuclear reactions taking place inside stars.