Multiverse

The multiverse is a concept that refers to the existence of infinite universes that comprise everything that is. Each universe within the multiverse is referred to as a different "Earth," and each vibrates at a different frequency so that they cannot normally interact with or be seen by each other. If one is able to travel fast enough, it is possible to breach the laws of physics and travel between these Earths, although breaches can also be created by Vibers or by technological means.

History
In his early days as The Flash, Barry Allen traveled to Earth-8 where he met that Earth's Oliver Queen.

The earliest known contact between two separate Earths was when The Flash trapped Grodd on Earth-2. Grodd would later return to Earth-1, only to be sent back once again by the Flash.

The Black Flash came from his home world, New Earth, to feud with Earth-1's Flash.

Black Flash would later open up a number of breaches in Earth-1, linking to many different Earths from across the multiverse. Many metahumans came through the breaches, and some of them even fought the Flash, including Rainbow Raider and Dark Matter.

Known Parallel Universes

 * Earth-1
 * Earth-2
 * Earth-8
 * Earth-23
 * Earth-34
 * New Earth

Timelines
See also: Flashverse Timeline
 * Pre-Flashpoint Timeline
 * Flashpoint Paradox Timeline
 * Post-Flashpoint Timeline

Known Constants in the Multiverse

 * Barry Allen: Earth-1 / New Earth
 * Cisco Ramon: Earth-1 / New Earth
 * Rainbow Raider: Earth-1 / Earth-23