This theory was put forward by Albert Einstein. Simply put, a "wormhole" is a space-time tubule connecting distant regions of the universe. Dark matter keeps the wormhole exit open. Wormholes can connect parallel universes with baby universes and provide the possibility of time travel. Wormholes may also be time tunnels connecting black holes and white holes, so they are also called "grey tunnels".
Theoretically speaking, wormholes are multidimensional space tunnels connecting white holes and black holes, which are ubiquitous but fleeting.
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