Gravity doughnut may solve time travel problem

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Discussion Overview

The discussion centers around a theoretical proposal by physicist Amos Ori regarding a "gravity doughnut" that may provide a solution to the challenges of time travel, particularly the issue of traveling backwards in time. The conversation touches on concepts from general relativity and the implications of self-interacting gravitational fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Amos Ori suggests that a doughnut-shaped gravitational field could allow for time travel by curving space and time back on themselves without requiring exotic matter.
  • Some participants express skepticism about the concept of self-interacting gravitational fields, with one participant comparing it to an unobserved 'ultraviolet catastrophe' indicative of an incomplete theory.
  • Another participant notes that Ori's proposal may circumvent Hawking's chronology protection conjecture, which traditionally argues against time travel.

Areas of Agreement / Disagreement

Participants exhibit differing levels of interest and skepticism regarding the validity and implications of Ori's proposal, indicating that multiple competing views remain in the discussion.

Contextual Notes

The discussion does not resolve the theoretical implications of the gravity doughnut or its acceptance within the broader physics community, leaving open questions about its feasibility and the nature of the proposed gravitational fields.

Ivan Seeking
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"Gravity doughnut" may solve time travel problem

One of the major difficulties of traveling backwards in time has just been solved, according to an Israeli theoretical physicist. And the solution, he says, is doughnut-shaped...

...This is where Amos Ori from Technion, the Israel Institute of Technology in Haifa, comes in. He says that according to Einstein's theories, space can be twisted enough to create a local gravity field that looks like a doughnut of some arbitrary size. The gravitational field lines circle around the outside of this doughnut, so that space and time are both tightly curved back on themselves. Crucially, this does away with the need for any hypothetical exotic matter. [continued]
http://www.nature.com/news/2005/050711/full/050711-4.html
 
Physics news on Phys.org
The arXiv version is here.

Regards,
George
 
Ori is captivated by the concept of self-interacting gravitational fields, which I do not find very interesting. It's the sort of unobserved 'ultraviolet catastrophe' that signals an incomplete theory.
 
This is still interesting, because according to the author it does get around Hawking's chronology protection result (Phys. Rev. D46 (1992) 603).
 

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