the C. Donald Shane Telescope 3.05-m (120-in.), completed in 1959 and named after a former director. Lick Observatory is still operated by the University of California Observatories, with headquarters in Santa Cruz.

life in the Universe The study of the possible existence of life in the Universe beyond the Earth is variously termed bioastronomy, astrobiology and exobiology. It covers questions on the existence of life on other planetary bodies in the Solar System, such as Mars and Europa; the study of organic molecules in giant molecular clouds and circumstellar material (see interstellar molecules) and in comets and meteorites; the study of planetary surfaces and atmospheres; questions of the origins of life, whether on the Earth or elsewhere (see also panspermia), and the range of conditions under which it can survive; and the search for life in space, by 'listening' for intelligent signals (see seti) and investigating extrasolar planets.

The first truly scientific ideas (as opposed to philosophical speculation on the 'plurality of worlds') on the possibility of extraterrestrial life followed the invention of the telescope. Early ideas were entirely anthropocentric and shaped largely by contemporary religious beliefs. In the late 18th century Immanuel Kant (1724-1804) formalized these ideas, proposing that all planets would have their own appropriate inhabitants matched to the conditions that prevailed upon them. There were suggestions that the Moon, with its 'terrae' and 'maria', and even the Sun, were inhabited. With improvements in telescope design during the 19th century, Mars became a focus of attention. The planet was soon being described as a world of reddish 'continents', dark 'seas' and white icy polar caps that grew and shrank with the passing of the Martian seasons. Some concluded that Mars might support life or even be inhabited. Schiapar-elli's identification of dark linear streaks - canali - on the Martian surface sparked a major debate on whether these features were natural or artificial (see canals, martian). By the mid-20th century new instruments and techniques had revealed Mars as a world incapable of supporting any form of reasonably advanced terrestrial

▲ libration Although the Moon is in synchronous rotation with respect to the Earth, ground-based observers can still, over the course of several lunations, see significantly more than just half of its surface. Libration in longitude (top) allows the observer to see slightly around the mean east or west limb, while the tilt of the lunar axis relative to the Moon's orbital plane allows regions beyond either pole to be seen on occasion.

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