Thursday, July 28, 2005

General Relativity Resolves Galactic Rotation Without Exotic Dark Matter

by F. I. Cooperstock, S. Tieu, Preprint in the physics archive.

The stars in galaxies are observed to have "flat rotation curves", the velocity of the stars is the same, independent of their distance from the center of their galaxy. However, when we look at the distribution of luminous matter in the galaxies, Newtonian gravity predicts that the velocity of stars should fall off. Hence all the buzz about "Dark Matter", that there must be non-luminous matter in galaxies which is causing the stars to rotate uniformly.
However, Newtonian gravity is not the final word. Einstein's 1915 theory of gravity, General Relativity, makes more accurate predications. It was thought though, that because gravity is very weak in galaxies (apart from black holes and the small supermassive region at the very center of the galaxies) that the differences between Newton's theory and Einstein's theory would be insignificant.
To the contrary, the authors point out that the differences are very significant. They claim to reproduce the observed rotation curves with a quite reasonable distribution of matter, consistent with the observed distribution of luminous matter using General Relativity instead of Newtonian gravity.
There's been a veritable industry of Dark Matter research with all kinds of exotic proposals for new, hereto unobserved forms of matter. This now appears superfluous.

No comments: