Einstein’s theories certainly changed the world but he may not have got all of them right, according to University of Salford scientists.
For more than 80 years, astronomers have been searching for a mysterious substance known as ‘dark matter’. It was believed for decades that dark matter had to exist, to explain observations of abnormal speeds of galaxies.
However, the new version of Einstein’s general relativity developed at the university explains the observed speeds without needing to assume that dark matter exists at all.
One of the scientists, Tim Hodgkinson, said: “It was a true revelation to us when we realised that this could explain the anomalous observations that have puzzled the astrophysics community for over 80 years.”
The scientific research was conducted by Edmund Chadwick, Tim Hodgkinson and Graham McDonald of the University’s Materials & Physics Research Centre.
The team restructured a version of Einstein’s equations, which are due to appear in the online edition of the research journal Physical Review in July. Their innovative research is expected to cause major implications regarding the awareness of galaxies and the universe.
There may also be ramifications in key areas of theoretical physics, due to their dependency on Einstein’s concept of general relativity.
Mr Hodgkinson explained: “Some people might argue that Einstein’s theory, in which there is curvature of space and time due to mass, already includes a form of space-time expansion.
“We introduced an explicit expansion factor in general relativity to see what would result. Initially, we had only the slightest suspicion that this would lead us to consideration of whether dark matter existed.”
An earlier theory called MOND (MOdified Newtonian Dynamics) had attempted to explain the observed speed anomaly through an amendment in Newton’s Law of Gravity.
The amendments of the MOND law have been successful in fitting astronomical observations, without needing to assume the existence of dark matter. But, the Newtonian modification was ad-hoc, as it was designed to only fit the anomalous observational data.
Edmund Chadwick said: “Since MOND is not really based on a physical or dynamical principle, it has been a central goal of recent theoretical physics research to reproduce a MOND-scaling effect through a satisfactory update of Einstein’s general relativity.
“After working through some rather complex mathematics, a remarkably simple result finally emerged.
“We found a simple way to link gravitational theory with the characteristics of MOND, and there is also a hint at a possible physical origin of this linkage.”
Graham McDonald recollects how the team released their discovery. Mr McDonald said: “During the calculations an odd, but beautifully simple, expression emerged for how this new expansion could vary in space.
“If the theory was correct, then this mathematical expression had to have some kind of physical interpretation. We eventually found that the speed of spherical shock waves (just like those in acoustic explosions) has exactly this type of dependence.
“This seems like a pretty bizarre connection, until one notes the prevalence of shock waves in current theories of galaxies and the universe. In particular, many scientists believe that the Big Bang itself was just like an acoustic explosion.
“Ideally, the application of this updated general relativity theory to galactic-scale problems was going to have some connection to the dynamical character of an underlying physical phenomenon.
“This new work has thus taken steps towards both a gravitational theory that supports MOND-type scaling and providing possible physical reasons for this scaling. These developments now pose many further questions regarding the origin and evolution of galaxies and the universe.”
The full paper can now be downloaded here: http://arxiv.org/abs/1307.3937
Picture courtesy of Harvard-Smithsonian Center for Astrophysics, with thanks.
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