The southern half of the Royal Observatory is devoted to astronomy and includes the 120-seat state-of-the-art Peter Harrison Planetarium, the most advanced in Europe and the only planetarium in London, with a digital laser projector that can show entire heavens on the inside of its 45-ton bronze-clad truncated cone. Galleries here trace the history of astronomy and interactive displays focus on such subjects as meteorites, space missions and the effects of gravity.