Can We Tell Whether the Universe Is Rotating? - Comments

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    Rotating Universe
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Discussion Overview

The discussion revolves around the question of whether the universe is rotating, exploring theoretical implications and experimental evidence related to this concept. It touches on aspects of general relativity, cosmology, and the interpretation of cosmic background radiation data.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question whether the rotation of four-dimensional space could lead to hyperbolic expansion of three-dimensional sub-space over time.
  • One participant argues that there cannot be an invariant answer to the question of rotation due to the lack of a preferred method to distinguish between "space" and "time," which complicates the definition of three-dimensional sub-space.
  • Another participant references the Cosmic Background Radiation experiment (COBE 2006), which suggested that the overall rotation of the universe is zero, although this is within the limits of the instrument's accuracy.
  • A historical perspective is provided regarding Kurt Gödel's 1949 solutions to Einstein's field equations, which involve a rotating universe and the implications for time travel, raising doubts about the nature of the universe's rotation.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the universe's potential rotation, with some highlighting theoretical models and others referencing experimental data. The discussion remains unresolved, with multiple competing perspectives present.

Contextual Notes

The discussion includes limitations related to the definitions of space and time, as well as the accuracy of experimental measurements, which may affect interpretations of the universe's rotation.

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Can We Tell Whether the Universe Is Rotating?

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Does rotation of four dimensional space result in hyperbolic expansion of three dimensional sub-space with increasing time?
 
bahamagreen said:
Does rotation of four dimensional space result in hyperbolic expansion of three dimensional sub-space with increasing time?

There can't be any invariant answer to this, because there is no preferred way to split up spacetime into "space" and "time", so there is no invariant definition of "three-dimensional sub-space".
 
The Cosmic Background Radiation experiment (COBE 2006) data indicated that overall rotation of the universe was zero, which was within the limits of accuracy of the instrument.

In 1949, Kurt Gödel proved the existence of solutions involving closed time-like curves, to Albert Einstein's field equations within the Theory of General Relativity. His solution required a rotating universe, which would allow time travel to the past and caused Einstein to have doubts about his own theory. His solutions are known as the Gödel metric. Hollywood time travel stories are very popular 'Star Trek IV' etc. However, time traveller's from the future are either very discrete or choose to come to our period (I don't blame them!). Or the universe does not rotate significantly, as indicated by COBE.
 

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