Welcome to the fourth dimension. And the fifth, and the sixth. A team of astrophysicists claims to have identified evidence that space is six-dimensional.

Joseph Silk of the University of Oxford, UK, and his co-workers say that these extra spatial dimensions can be inferred from the perplexing behaviour of dark matter. This mysterious stuff cannot be seen, but its presence in galaxies is betrayed by the gravitational tug that it exerts on visible stars.



Silk and his colleagues looked at how dark matter behaves differently in small galaxies and large clusters of galaxies. In the smaller ones, dark matter seems to be attracted to itself quite strongly. But in the large galactic clusters this doesn’t seem to be the case: strongly interacting dark matter should produce cores of dark material bigger than those that are actually there, as deduced from the way the cluster spins.



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 nanometre1.



The team argues that such astronomical observations of dark matter provide the first potential evidence for extra dimensions. Others are supportive, but unconvinced. Lisa Randall, a Harvard physicist who has explored the possibility of extra spatial dimensions, says “Even if their idea works, which it probably does, it may be an overstatement to use these observations as evidence of extra dimensions.”



Silk himself acknowledges that the proposal is “extremely speculative”.



More here.