Who first determined that the universe is expanding? Traditionally, the credit goes to the American astronomer Edwin P. Hubble, who in 1929 reported that other galaxies appeared to be speeding away from us. He also described a correlation between their distances from Earth and the velocities at which they were moving, which is determined by a cosmic expansion rate now known as the Hubble constant (H). Hubble, who died in 1953, never received a Nobel Prize for one of history’s most significant astronomical discoveries, but he remains a legend in his field and in 1983 was honored with a namesake telescope.

But Hubble wasn’t the first person to show that faraway galaxies recede faster than close ones. Two years earlier, the Belgian priest, astronomer and physicist Georges Lemaître published similar findings in an obscure French-language journal. He even proposed an expansion rate nearly identical to Hubble’s original constant. In fact, many experts agree that Hubble simply confirmed the laws tentatively proposed by Lemaître and presented them to a wider audience. So why do we use H rather than L to express how quickly the universe is growing? In short, when an English publication finally reprinted Lemaître’s paper in March 1931, key sections were lost in translation....