Recently as reported on the BBC by Paul Rincon an experiment conducted on man made anti- matter to see if both matter and anti-matter are affected differently by gravity or not.
Both fell the same way.  Hydrogen is a proton orbited by an electron. Anti-Hydrogen is an electron orbited by the much heavier proton. Since both were not affected differently it suggests that mass is not an attraction for gravity at all.  Therefore New Gravity with a pull on space from every particle creates the flow which carries everything regardless of mass. Since it is now generally realised that the most fundamental basic element that exists anywhere is space it should be part of any physical law.
New Gravity is a simple answer to the problems that are created by belief in an attraction of mass for mass.