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There is no indication that one day it is possible for a spacecraft to exceed the speed of light. But if it is not possible to travel faster than light in the cosmos, we can imagine that there are some kinds of shortcuts connecting two regions of space-time.
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wormhole
A wormhole is a concept that represents a solution of the Einstein field equations: a non-trivial structure linking separate points in spacetime. A wormhole can be visualized as a tunnel with two ends, each at separate points in spacetime (i.e. different locations or different points of time), or by a transcendental bijection of the spacetime continuum.
Wormholes are consistent with the general theory of relativity, but whether wormholes actually exist is not known.
A wormhole could connect extremely long distances such as a billion light years or more, short distances such as a few meters, different universes, or different points of time. This is proposed in Albert Einstein's special theory of relativity, where the combination of space and time into a single spacetime continuum could theoretically allow one to traverse both space and time using a wormhole, given the correct conditions.
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Different types of wormholes
Einstein's theory of general relativity contains solutions describing such shortcuts. They are comparable to tunnels dug by worms in an apple and allowing to pass more quickly from one region of the surface of this apple to another. For this reason, the physicist John Wheeler called them wormholes.
Unfortunately, crossing the tunnels of some of these solutions amounts to plunging into a black hole with a certain death halfway for travelers. Others are safe but their opening would require a much higher energy than that produced by the Sun. Moreover, such shortcuts in space would make it possible to travel in time, with all the paradoxes that this implies. Therefore, one considers that one can not travel between the stars with passable wormholes.
To date, there is no experimental evidence of the existence of wormholes.
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