An exotic theory, which attempts to unify the laws of physics by proposing the existence of an extra fourth spatial dimension, could be tested using a satellite to be launched in 2007. Such theories are notoriously difficult to test. But a new study suggests that such hidden dimensions could give rise to thousands of mini-black holes within our own solar system – and the theory could be tested within Pluto’s orbit in just a few years. Black holes of various masses are thought to have sprung into existence within 1 second of the big bang, as elementary particles clumped together...