The standard model of modern cosmology is known as the hot big bang, a name that refers to the initial state of the universe some fourteen billion years ago. The name Big Bang introduced by Fred Hoyle in 1949 is one of the most successful scientific neologisms ever. How did the name originate and how was it received by physicists and astronomers in the period leading up to the hot big bang consensus model in the late 1960s? How did it reflect the meanings of the origin of the universe, a concept that predates the name by nearly two decades? Contrary to what is often assumed, the name was not an instant success—it took more than twenty years before Big Bang became a household word in the scientific community. When it happened, it was used with different connotations, as is still the case. Moreover, it was used earlier and more frequently in popular than in scientific contexts, and not always relating to cosmology. It turns out that Hoyle’s celebrated name has a richer and more surprising history than commonly assumed and also that the literature on modern cosmology and its history includes many common mistakes and errors. An etymological approach centering on the name Big Bang provides supplementary insight to the historical understanding of the emergence of modern cosmology.

The composition of the aurora borealis became a subject of scientific interest with the introduction of spectroscopy, but for a long time the aurora refused to reveal its secrets. After fifty years of research, the origin of the dominant green line of wavelength 5577 ÅÅ was still a mystery. Only in 1912 did progress finally begin to occur in the understanding of the aurora, a field of research which appealed in particular to Norwegian scientists. Prominent among them was Lars Vegard (1880––1963), who in 1923 suggested a new picture of the upper atmosphere and an explanation of the green line in terms of excitations of frozen nitrogen dust particles. Although apparently confirmed by cryogenic experiments, Vegard's theory was challenged by the Canadian physicist John McLellan (1867––1935) who in 1925, together with his postdoctoral student Gordon Shrum (1896––1985), reproduced the line in experiments with helium-oxygen mixtures. This is the story of how the enigma of the green auroral line was finally resolved and explained by the quantum theory of atoms, namely as a transition between two metastable states of oxygen. It is also the story of two of the period's leading specialists in auroral spectroscopy, their rivalry, and different approaches to the study of the northern light.