sep 1, 1961 - The Flash of Two Worlds

Description:

Barry Allen, the Silver Age Flash of Earth-1, accidentally travels to a parallel universe and meets Jay Garrick, the Golden Age Flash of Earth-2, in the first recorded instance of Multiversal travel; the Multiverse is discovered on Earth for the first time. With this discovery finally comes the revelation that the Golden Age and the Silver Age were not actually separate by reboots, but rather took place on different parallel universes in the DC Multiverse, with the Golden Age occurring on Earth-2, and then about 20 years later, the Silver Age beginning on Earth-1.

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