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Time Travel?
Wednesday, April 05, 2006 at 01:12 PM
Leader
Apparently, it is not possible to build a time machine by plugging in a string of Christmas lights and then spinning them over your head really, really, fast:
Thus it appears that the closed timelike curves appearing in [1] are the result of starting with a pathological spacetime instead of Minkowski space. There is no reason to believe on the basis of [1] that CTC's could be produced in the laboratory, even if we had sufficient technology to control a density of electromagnetic radiation so large as to have measurable gravitational effects.
I invite you to read the whole paper.
Setting ε = 0 and consequently λ = 0, we have the metric
It is straightforward to compute the connection and curvature from this metric...
Yup, pretty straightfoward.
Well, suffice it to say that these physicists are taking issue with another physicist's theory:
With a brilliant idea and equations based on Einstein's relativity theories, Ronald Mallett from the University of Connecticut has devised an experiment to observe a time traveling neutron in a circulating light beam. While his team still needs funding for the project, Mallett calculates that the possibility of time travel using this method could be verified within a decade.
To determine if time loops exist, Mallett is designing a desktop-sized device that will test his time-warping theory. By arranging mirrors, Mallett can make a circulating light beam which should warp surrounding space.
OK, using mirrors is probably a better idea than twirling a string of Christmas lights.
Putting the engineering details aside, I'm bringing this up because the PhysOrg article describing Mallett's ideas does not reference the criticisms from Ken D. Olum and Allen Everett of Tufts Univeristy in Maryland. The PhysOrg article was linked from Drudge.
It just seems to me that a quick reference to the fact that Mallett's ideas are hardly universally accepted, and indeed have been refuted (though Mallett insists there is a flaw in the reasoning of his critics), should have been included. Explaining science to laypersons is hard enough. But neglecting to show how ideas are debated and challenged (in a generally friendly way) makes things worse.
And I think showing how a community can engage in debate without resorting to threats and violence can be instructive in this environment.
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Angry in the Great White North by Steve Janke is licensed under a Creative Commons Attribution-Share Alike 2.5 Canada License.
Based on a work at stevejanke.com.