Interesting tidbit I picked up from <a href="http://slashdot.org/article.pl?sid=00/05/14/1339252&mode=flat&threshold=3">slashdot.org</a> is this <a href="http://www.npl.washington.edu/AV/altvw100.html">report</a> by John G. Cramer about the <a href="http://monet.physik.unibas.ch/~schatzer/ytg.html">Yilmaz Theory of Gravity (There are no Black Holes)</a>. This is (yet another) extension to Einstein's General Relativity which has the interesting property that black holes don't exist. Its other advantageous attributes include:<i> <ul> <li>The new theory is compatible with all experimental data (what it [sic] is essential, of course). <li> The strong equivalence principle, which means the equivalence of inertial mass, active gravitational mass and passive gravitational mass, is a direct consequence of a multiplicative gauge invariance. The equivalence principle is not deducible in Einstein's theory, where it has to be included as an additional assumption. <li> There exist closed solutions for gravity waves for arbitrary field strengths. The wave equation (see below) is exactly satiesfied [sic], and not only in the weak field limit as in general relativity. <li> Remarkably, H. Yilmaz also claims to have found a way to quantize the theory. ... </ul> </i> Here is a list to John's <a href="http://www.npl.washington.edu/AV/">other writings</a> on Alternate Views.