A young phsyicist at Cornell says that while gravity tests out on Solar System scales, when it comes to the distances of the farthest galaxies, which are billions of light years from our own Milky Way galaxy, Einstein's Theory of General Relativity needs to be modified on cosmic scales to account for the mysterious effect of dark energy.
"Einstein's theory of General Relativity tells us how gravity determines the relationship between the matter in the Universe and the Universe's size," says Cornell’s Rachael Bean. "If matter in the Universe is attracted by gravity, then the Universe's size should be expanding at an ever slowing rate (decelerating). What observations show, though, is that in the last 6 billion years (out of the Universe's 13.7 billion year existence), the expansion has been speeding up. So we need new physics, labeled 'dark energy', to explain this apparent disparity."
"There are two broad possibilities for what dark energy is. Either it is a strange, new type of matter that is not attracted by gravity, or Einstein's Theory of General Relativity needs to be modified on cosmic scales. Part of my research is to try and understand the origins of dark energy and how we can use current and future astrophysical surveys to measure its properties."
Bean studied and compared the data collected from the recent Cosmic Evolution Survey, or COSMOS, which involved a number of telescopes both on the ground and in Earth orbit, including the Hubble Space Telescope (HST) that examined over two million galaxies, along with distant exploding supernovae and the relic csomic background radiation created just 400,000 years after the formation of our Universe in the Big Bang.
"My paper uses a combination of large scale structure and distance measurements to test gravity on cosmic scales to see whether it is consistent with GR or not," declares Bean. "What I find is that there is a better fit to one time slice in the weak lensing data from the COSMOS survey using the HST, between 3 and 7 billion years after the Big Bang, if gravity is allowed to deviate from GR." She suggests that the results could "indicate that dark energy is related to a modification to gravity rather than a new type of matter."
Casey Kazan
Sources:
Rachael Bean: A weak lensing detection of a deviation from General Relativity on cosmic scales
http://www.centauri-dreams.org/
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