re Henry Baker's large fantasy collection... 1. yes, gravitational lenses work for gravity as well as photons... a fact which nobody has ever had any interest in before (and I don't see why they should now either) 2. dark matter is an example of stuff which never "coalesces" particularly. Or at least that was the usual picture: DM consists of some kind of massive fundamental particles which have little or no interaction with normal matter particles or each other, besides gravitatonal. They got generated in the big bang at some temperature, and have gradually cooled off ever since. There is a blob of dark matter forming a rough spherical blob centered at each galaxy. The galaxies are however not sphere shaped usually. The rotation curves of galaxies are way different from what they should have been which is the main way they deduced the DM is there. Normal matter hits itself and emits heat hence slows down and coalesces. Dark matter never hits, never emits heat, never slows down, never coalesces particularly. 3. there were some crazy non-Einstein theories of gravity, some of which were claimed to explain the gravitational effects of dark matter without needing to assume the existence of the dark matter. And perhaps they indeed will need to be dusted off to explain this discrepancy. You've inspired me to send a note to John Moffat, inventor of one non-Einstein gravity theory, to bring this to his attention. -- Warren D. Smith http://RangeVoting.org