Since 1904, Nobel Prize were awarded to twenty-six Soviets and Russians in physics, chemistry, medicine, economy, literature and peace. Mikhail Lomonosov proposed the law of conservation of matter preceding the energy conservation law. Since the time of Nikolay Lobachevsky (the "Copernicus of Geometry" who pioneered the non-Euclidean geometry) and a prominent tutor Pafnuty Chebyshev, Russian mathematicians became among the world's most influential. Dmitry Mendeleev invented the Periodic table, the main framework of modern chemistry. Nine Soviet/Russian mathematicians were awarded with the Fields Medal. Grigori Perelman was offered the first ever Clay Millennium Prize Problems Award for his final proof of the Poincaré conjecture in 2002. Alexander Popov was among the inventors of radio, while Nikolai Basov and Alexander Prokhorov were co-inventors of laser and maser. Many famous Russian scientists and inventors were émigrés, among them are Igor Sikorsky, and Vladimir Zworykin, while many foreign ones lived and worked in Russia for a long time, such as Leonard Euler, and Alfred Nobel. Russian discoveries and inventions include the transformer, electric filament lamp, the aircraft, the safety parachute, electrical microscope, colour photos, caterpillar tracks, track assembly, electrically powered railway wagons, videotape recorder, the helicopter, the solar cell, probiotics (found in some yogurts), the television, petrol cracking, synthetic rubber, and grain harvester.Mir, Soviet and Russian space station that operated in low Earth orbit from 1986 to 2001.