For a while now, them star gazers have been banging heads over the nature o’ gravity.<\/p>\n
Here’s the problem: when you look at the way galaxies are a-spinnin and a-spiralin, there just ain’t enough gravity to hold em together. So either there is some hidden mass putting its gravitational shoulder to the wheel: the so-called dark matter. Or there’s something wrong with the 1\/r^2 rule at large distances and gravity is stronger than we think at these scales.<\/p>\n
In 1981, Mordehai “Mouse” Milgrom modified gravity to cope with this problem in a theory called MOdified Newtonian Dynamics or MOND. It says that gravity is a little stronger over galactic distances and this is what stops spinning galaxies from tearin’ themselves apart.<\/p>\n
But the theory makes some strange predictions too. For example, it says that some galaxies should look as if they are surrounded by a ring of dark matter.<\/p>\n
Earlier this year, the Hubble Space telescope found exactly that — a ring of dark matter around the galaxy cluster Cl 0024+17<\/a>, which lies 5 billion light years from Earth. What astrogawpers actually saw were distorted images of galaxies behind Cl 0024+17 caused by the mass of Cl 0024+17 bendin’ light as it passed by, a phenomenon called gravitational lensing<\/a>. The astrobods used these distortions to infer the distribution of mass around Cl 0024+17 and concluded it must have a ring of dark matter even though they ain’t actually seen a ring of any kind.<\/p>\n So Mouse Milgrom is a-shoutin and a-ravin from the roof tops: this is exactly what his theory predicts. Could it be enough to prove MOND once and for all?<\/p>\n Probably not. Gravitational lensing data is notoriously difficult to interpret so the work is by no means done and dusted. But even if it’s right, one swallow, don’t a summer make. He’s gonna need a lot more evidence before his ideas become mainstream.<\/p>\n