Tom Posted December 5, 2011 Share Posted December 5, 2011 http://www.physorg.com/news/2011-12-dark.html Currently, these galactic rotation curves represent key evidence for the existence of dark matter ? since the outer stars of spinning galaxies often move around a galactic disk so fast that they should fly off into intergalactic space ? unless there is an additional ?invisible? mass present in the galaxy to gravitationally hold them in their orbits. The issue can be appreciated by considering the Keplerian motion of the planets in our Solar System. Mercury orbits the Sun at an orbital velocity of 48 kilometers a second ? while Neptune orbits the Sun at an orbital velocity of 5 kilometers a second. In the Solar System, a planet?s proximity to the substantial mass of the Sun is a function of its orbital velocity. So, hypothetically, if the Sun?s mass was reduced somehow, Neptune?s existing orbital velocity would move it outwards from its current orbit ? potentially flinging it off into interstellar space if the change was significant enough. The physics of the Milky Way Galaxy is different from the Solar System, since its mass is distributed more evenly across the galactic disk, rather than 99% of its mass being concentrated centrally ? the way it is in the Solar System. Snippet. TL;DR: Italian mathematician creates formula that can mimic the rotation curves of spiral galaxies without the need for dark matter Link to comment Share on other sites More sharing options...
DocM Posted December 5, 2011 Share Posted December 5, 2011 True, simple modifications to the gravity formula get rid of the galactic rotation issue - but there are still questions about gravitational lensing effects. Perhaps so, perhaps not. Time will tell, but this paper from Sept. 2011 is interesting - http://arxiv.org/PS_cache/arxiv/pdf/1109/1109.3189v2.pdf Link to comment Share on other sites More sharing options...
neoadorable Posted December 6, 2011 Share Posted December 6, 2011 so what does it all mean? there's no dark matter? i was hoping it'd be the key to FTL flight... Link to comment Share on other sites More sharing options...
DocM Posted December 6, 2011 Share Posted December 6, 2011 T's a possible way to account for the fadt rotational speed of outer parts of galaxies without dark matter, which would mean modifying Newton's gravity equations. No FTL implications. Link to comment Share on other sites More sharing options...
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