Oklo Constraint on the Time-Variability of the Fine-Structure Constant

The Oklo phenomenon, natural fission reactors which had taken place in Gabon about 2 billion years ago, provides one of the most stringent constraints on the possible time-variability of the fine-structure constant α. We first review briefly what it is and how reliable it is in constraining α. We then compare the result with a more recent result on the nonzero change of α obtained from the observation of the QSO absorption lines. We suggest a possible way to make these results consistent with each other in terms of the behavior of a scalar field which is expected to be responsible for the acceleration of the universe. 1 What is the Oklo phenomenon? Oklo is the name of the place of a uranium mine in Gabon, West Africa, near the equator. The mining company would supply the uranium ore to the French government. But in June of 1972, something unusual was noticed on the ore from Oklo; the abundance of U was somewhat below the world standard, 0.7202%, well beyond the limit of permissible range. This might have undermined the company’s reputation about the quality of their uranium. But finally after a few months of serious effort, French scientists came up with an unexpected, startling conclusion: The deficit of U was a real effect of that a self-sustained fission reaction took place naturally in Oklo about 1.8 Gys ago, during the period of Proterozoic, part of Precambrian. In other words, natural reactors did exist well before 1942 when Enrico Fermi invented the artificial reactor for the first time in Chicago. This has been called the “Oklo phenomenon,” since then [1]. The result of their work was published in many ways, including [2]. See the separate figure, gabon2.jpg. Figure 1: Oklo in Gabon, West Africa, near the equator There was a big press campaign, including the Le Monde article, for example, saying that Fermi was not an “innovator,” but was only an “imitator” of Nature. Even more surprising was that the occurrence of this “natural reactors” had been predicted much earlier, 17 years earlier by a nuclear geochemist, Paul K. Kuroda in 1955 [3]. He discussed Delivered at Astrophysics, Clocks and Fundamental Constants, 16-18 June 2003, Bad Honnef, Germany, to be published in Lecture Notes in Physics, Springer