# Gödel's Universe

Gödel's Universe

In 1949, Kurt Gödel found a solution of Einstein's field equations and gave it to Einstein on his birthday [1]. This solution describes a homogeneous, anisotropic, and rotationally symmetric spacetime in which matter takes the form of a pressure-free perfect fluid with negative cosmological constant, where closed timelike world lines exist. Theoretically, traveling along such a world line allows an observer to travel into their own past. For an astounding and detailed visualization of how an observer would perceive such a travel, see [2, 3].

The manipulate graphic reproduces the famous illustration contained in the book by Hawking and Ellis [4], showing photons emitted by an observer on the axis of symmetry at the bottom; the photons spiral out, expand, and reconverge at the top. Light-like geodesics are shown as well as light cones that tip as you increase , producing the closed timelike curves. Further interpretations can be found in [5].

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