We start by reviewing the history of glory observations and their consequences, which is almost as remarkable as the phenomenon itself. We describe various proposed explanations of the effect: until recently, the best one available was based on a conjecture by van de Hulst, related with the geometrical theory of diffraction, which is also briefly discussed.

Observations

The earliest recorded observations of the glory were made between 1737 and 1739 (cf. Lynch & Futterman 1991), during a French geodetic expedition to Peru, undertaken to settle the dispute between Newton and Cassini on the figure of the Earth (occasioning Voltaire's famous quip: ‘Vous avez confirmé dans des lieux pleins d'ennui, Ce que Newton connut sans sortir de chez lui’). Early one morning, a few members of the expedition, including Bouguer and a Spanish captain, Antonio de Ulloa (who introduced platinum into Europe following this expedition), stood on top of Mount Pambamarca, in the Peruvian Andes.