We are told that a lot of scientist believe there are 10 multi dimensions, the reason for this, is that gravity should be 10 X greater than it is, why can this not be explained by dark matter / anti matter existing in the same place as matter, this would account for low gravity on earth and the expansion of the universe, if so could we not measure this, as the dark matter would have a force but less than that of gravity. Or do I just not understand things.