Earth 20

''Home of the Society of Super-Heroes, a team of adventurers and space champions assembled by Doc Fate to include Green Lantern, The Mighty Atom, Immortal Man, Lady Blackhawk and the Blackhawks. Earth 20 occupies a binary universe, which tunes itself to occupy the same space as Earth 40 once every 100,000 years, with catastrophic consequences. See also Earth 40.''