Two papers that appeared in 1974 changed the face of the universe. Independently authored by separate collaborations, one in the US and the other in Estonia, they argued that galaxies are 10 times as massive and extensive than had previously been thought. Both groups combined various astronomical observations to show that most of the universe’s mass is hidden in invisible clouds around galaxies. The universe itself, too, they illustrated, is heavier by a factor of 10 than had previously been believed, potentially changing human understanding of the fate of the cosmos. Their arguments marked “a watershed in our understanding of galactic structure, galaxy formation, and cosmology,” read a review in the 1999 centennial issue of the Astrophysical Journal.1 Five decades ago those papers proposed the existence of what we now know as dark matter.
Today dark matter is not only one of the pillars of modern cosmology but...
