Planet smallest known planet is PSR B1257+12A, one of the first extrasolar planets discovered, which was found in 1992 in orbit around a pulsar. Its mass is roughly half that of the planet Mercury. The smallest known planet orbiting a main-sequence star other than the Sun is Kepler-37b, with a mass (and radius) slightly higher than that of the Moon. Every planet began its existence in an entirely fluid state; in early formation, the denser, heavier materials sank to the centre, leaving the lighter materials near the surface. Each therefore has a differentiated interior consisting of a dense planetary core surrounded
The empire on which the sun never sets as "Christopher North" in "Blackwood's Magazine" in 1829, is sometimes credited as originating the usage. However, George Macartney wrote in 1773, in the wake of the territorial expansion that followed Britain's victory in the Seven Years' War, of "this vast empire on which the sun never sets, and whose bounds nature has not yet ascertained." In a speech on 31 July 1827, Rev. R. P. Buddicom said, "It had been said that the sun never set on the British flag; it was certainly an old saying, about the time of Richard the Second, and was not so applicable then as