writes "Nature.com is reporting that there may be evidence of 6 dimensions. Galaxies seem to behave as there were more matter in them than is actually visible. 'One explanation, they say, is that three extra dimensions, in addition to the three spatial ones to which we are accustomed, are altering the effects of gravity over very short distances of about a nanometre.'" Update
: Like most of string theory, this is acknowledged by its authors to be "extremely speculative."