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The coerstone of mode cosmology is the belief that the place that we occupy in theUniverse is in no way special. This is known as the cosmological principle, and it is anidea which is both powerful and simple. It is intriguing, then, that for the bulk of the historyof civilization it was believed that we occupy a very special location, usually the centre, inthe scheme of things.The ancient Greeks, in a model further developed by the Alexandrian Ptolemy, believedthat the Earth must lie at the centre of the cosmos. It would be circled by the Moon, the Sunand the planets, and then the ‘fixed’ stars would be yet further away. A complex combina-tion of circular motions, Ptolemy’s Epicycles, was d...

For most of history, astronomers have had to rely on light in the visible part of the spec-trum in order to study the Universe. One of the great astronomical achievements of the20th century was the exploitation of the full electromagnetic spectrum for astronomicalmeasurements. We now have instruments capable of making observations of radio waves,microwaves, infrared light, visible light, ultraviolet light, X-rays and gamma rays, whichall correspond to light waves of different (in this case increasing) frequency. We are evenentering an epoch where we can go beyond the electromagnetic spectrum and receive in-formation of other types. A remarkable feature of observations of a nearby supeova in1...