Case Western Reserve University Physicist Glenn Starkman, with his colleagues Tom Zlosnik and Pedro Ferreira from the University of Oxford, put their minds together during Starkman's John Simon Guggenheim Fellowship this past year to distil the essence of a ground-breaking but complex modification of Einstein's theory of gravity proposed by Jacob Bekenstein from Hebrew University.
While Starkman and his collaborators' four-page results, which have been submitted to Physical Review Letters for consideration, were not as straightforward as E=mc², they are helping to revive the centuries-old idea that the world and universe are permeated by an "aether" field. This new aether would pervade the entire universe, like a sea of arrows all pointing in nearly the same direction—forward in time.
According to Starkman, the effects of this aether could explain why galaxies don't fly apart even though they rotate too fast for the gravity of their observable stars and gas to keep them together.
The aether effectively "softens up" space, allowing masses to more easily bend it, and thus extending the effect of their gravity to greater distances. It could thus replace dark matter, the elusive weakly interactive particles whose presence in great abundance in a halo around each galaxy is the standard explanation for why galaxies hold together.
It would thus be an implementation of Modified Newtonian Dynamics (MOND), the 1983 proposal of physicist Moti Milgrom of the Weizmann Institute for Science, that the observed dynamics of astronomical systems from galaxies on up, was due not to the presence of dark matter but to the modification of Newton's laws of motion at the very low accelerations one finds in the distant reaches of these systems.
The aether could also be responsible for the accelerating expansion of the universe that scientists have measured. In this way it could function as a form of dark energy, driving the expansion of the universe at an ever increasing rate.
The possible marriage of dark matter and dark energy is one of the more attractive features of the new aether model, said Starkman.
What is particularly ironical for Starkman is that 109 years ago Case Institute's first physics professor—and this country's first Nobel Laureate in Physics—Albert Michelson teamed up with Western Reserve University chemistry professor Edward Morley just a short walk away from Starkman's Rockefeller Hall office to conduct experiments that disproved that light moves through an "aether" medium. Albert Einstein would incorporate those findings that light travels at the same speed in all directions into his special and general theories of relativity.
Starkman said his new work does not contradict Michelson and Morley's observations. The new aether field does not directly affect how light travels, except in so far as it changes the gravitational field in the distant regions around massive objects.
Such fields are often called "Einstein-aethers" because they accommodate Einstein's theory of relativity on the scales where it has been tested.
"General relativity is a beautiful, powerful theory that has many successes at the scale of our solar system and below," said Starkman. "But when you get to the scale of galaxies, it could be that its flaws are beginning to show."
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