No Dark Matter?

First they invented dark matter. However, so far there is no evidence that such a thing exists, although the Higgs particle does turn out to have precisely the right properties to be the missing dark matter. Then they invented dark energy. And as far as I know, there's not even a candidate for what this mysterious substance might actually be.

This is all very radical, although I suppose that Planck's quantum hypothesis and the Bohr hypothesis about electronic orbits were just a radical in their day. But now there's another radical theory, although perhaps somewhat less radical than dark matter and dark energy.

According to Discover, Mordehai Milgrom proposed an alternative to dark matter and dark energy named MOND (MOdified Newtonian Dynamics), which consists of the idea that when the accelerations become very small the well-known formula F=ma changes to F=ma^2/a_0. Of course, there is no more theoretical justification for this formula than for the introduction of dark matter. Turns out Milgrom wrote a Scientific American article back in 2002 titled Does Dark Matter Really Exist?

The story is back in the pages of the popular science media is because in 2004 Jacob Bekenstein published a relativistic extension of MOND called TeVeS (Tensor, Vector, Scalar) which can correctly explain gravitational lensing and should be applicable to the problem of galaxy formation.

Also, here's a link to a webpage with many resources on Modified Newtonian Dynamics: http://www.astro.umd.edu/~ssm/mond/litsub.html.