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What is a wormhole? (Intermediate)

*Hey guys. I was wondering, what is a wormhole? I've seen many articles on them, but I can't really seem to understand. Are they even real?*

A wormhole is like a tunnel that connects two points in spacetime. If the wormhole is "traversable" it acts as a shortcut through spacetime. Imagine you are holding a piece of paper on which you have marked a point at each end. Now bend the piece of paper in half but don't let the ends touch. If you were to travel in normal space (ie along the sheet of paper) the trip from one of your marks to the other would be longer than if there were a tunnel or a "wormhole" connecting the two points on the paper through the empty space between them. Wormholes can connect different spots within a single universe or they can connect different universes.

Wormholes arise in solutions to Einstein's general relativity field equation, but are as of yet purely theoretical. Many of the solutions with wormholes require something called "exotic matter" or matter with negative energy density to hold the tunnel open and this exotic matter is purely theoretical as well.

Wormholes are a popular subject because if real they could allow the possibility of time travel since they are shortcuts in space AND time. If you've ever seen the movies Contact (based on the novel written by famous astronomer Carl Sagan) or Donnie Darko, their plots are based on the idea of wormholes.

*This page was last updated June 27, 2015.*

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