The theoretical account of gravity that currently appears to enjoy the greatest support from physicists and astronomers is Einstein's general relativity with allowances for dark matter (see here for background). Not all scientists agree, however, and they have tried to develop theories of gravity that don't need to invoke dark matter.
A new study has come along that comes down on the side of general relativity with dark matter (thanks to my wife for bringing it to my attention). As described in this article, the Princeton-based investigation:
...was one of the first rigorous tests of this theory of gravity beyond our solar system. The research found that even over vast scales of galaxies and clusters of galaxies, the equations of general relativity predict the way that mass pulls on other mass in the universe.
The new work also helps rule out a competing theory of gravity that seeks to do away with the need for bizarre concepts like dark matter and dark energy that have irked some scientists. This research indicates those pesky ideas may be here to stay.
Led by graduate student Reinabelle Reyes, the researchers obtained three types of measurements from roughly 70,000 galaxies. Statistical analyses then showed the data to be more consistent with general relativity than with two other, competing theories (one of the competing theories was described as yielding numerical values "somewhat different from those observed, but still ... within the margin of error").
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Yesterday was officially the fifth anniversary of this blog, the first posting of which occurred on March 12, 2005 (in that initial entry, I referred to myself as an associate professor of human development and family studies, but in 2007 I was promoted to full professor). I have enjoyed writing this blog and I will continue to do so. Only in the past year or so have I begun monitoring hit-counts for this site. As it turns out, the most recent complete month (February 2010) has been the best month for visits to the blog, with 196. That translates into 7 visits per day (February, of course, having 28 days). That may not seem like much, but I'm thrilled and thankful that anyone visits at all! If you've stumbled upon this site, I hope you'll continue to check back every so often.