Alternative versions of Superman establish a new continuity for DC, affecting not only Superman, but all of the DC Comics characters. The versions of Superman from this time period are traditionally divided into three main periods. The first version of Superman began being published by DC Comics in 1938 appearing in "Action Comics" #1. To explain discrepancies in the aging of Superman across several decades, his earliest stories were retroactively portrayed as having taken place on an alternative world called Earth-Two. These stories take place from 1938 until the late 1950s, although the exact dividing line is unclear and some stories happened identically to
Superman as tough as he is. In "Action Comics" #1, Superman could not fly. He traveled by running and leaping, which he could do to a prodigious degree thanks to his strength. Superman gained the ability to fly in the second episode of the radio serial in 1940. Superman can fly at great speeds. He can break the sound barrier, and in some stories he can even fly faster than light to travel to distant galaxies. Superman can project and perceive X-rays via his eyes, which allows him to see through objects. He first uses this power in "Action Comics" #11