Comments on early space controversies

Cummings and Lanzerotti reply: We thank Bruce McKellar , Filippo Frontera , and Howard Bond for their comments in response to our article on early debates in space science that appeared in the February 2025 issue of Physics Today.

As McKellar states, there was certainly a great controversy exercised by Sydney Chapman over the existence of Kristian Birkeland’s geomagnetic field–aligned currents. That important space science controversy was resolved by measurements taken by the 1963 38C satellite ¹ and analyzed by one of us (Cummings) with Alexander Dessler. ² The controversy was not related to the debate, described in our feature, on whether the magnetosphere is open or closed. Alv Egeland and William Burke cover the life and career of Birkeland in more detail in their 2005 book, Kristian Birkeland: The First Space Scientist.

We particularly thank Frontera and Bond for adding personal details to the story about the determination of the distance scale of gamma-ray bursts. They cite our failure to mention the role of the BeppoSAX satellite and its scientific team. Unfortunately, the word limit for our Physics Today article forced us to make difficult choices as to what to include. The contributions of BeppoSAX and its team and the observation of GRB 970508 and its afterglow in its host galaxy are described in chapter 9 of our 2023 book, Scientific Debates in Space Science: Discoveries in the Early Space Era.