By the 1930s more careful calculations of tidal effects had thrown Darwin's fission theory into doubt.

Two more theories arose: the 'capture theory', and the 'co-accretion theory'. According to the Capture Theory, the Moon was formed independently of Earth and subsequently captured by its gravity; while the Co-accretion Theory argued that the Moon and Earth had formed in tandem, from essentially the same raw materials.

By the 1950s, with the era of actual space travel nearing, there were so many theories emerging that there was little consensus amongst scientists about the Moon's origin.