Watch Out For Black Holes!

Sometimes it's hard enough thinking about space-time in just four dimensions - x, y, z (the dimensions of space) plus time, as laid out by Einstein in his general theory of relativity. But scientists at Duke and Rutgers Universities in the US are working on a mathematical model of the universe that has five - x, y, z and time plus another spatial dimension. They call this model "braneworld", because it suggests that the visible universe is a membrane, like a "strand of filmy seaweed" floating in a larger universe. But how do we know which model is a more reliable representation of the universe? Such models make predictions about the nature of space, and in the case of braneworld theory, it predicts that our solar system should be peppered with several thousand small black holes left over from the early universe. In contrast, the general theory of relativity says that these black holes should no longer exist. Because black holes are essentially undetectable, we have to hunt for them by looking for their effects on radiation waves that go past them. Radiation from events such as gamma ray bursts http://en.wikipedia.org/wiki/Gamma_ray_burst can be bent by the gravitational pull of a black hole, and we can detect this so-called gravitational lensing. At the moment, we don't have enough evidence of gravitational lensing to say whether there are black holes in our solar system or not. But over the next few years, space scientists will be launching a satellite telescope that will be able to detect any changes in gamma ray radiation, so scientists will hopefully know which mathematical model is the most accurate representation of the universe.