| 1905- Einstein's special theory of relativity published. |
1923-Hubble shows that the spiral nebulae are galaxies lying outside the Milky Way. |
1942-The colleagues detect radio waves from the Sun. |
1952-Baade announces a doubling of the distance-scale for the galaxies. |
1961-Gagarin makes first manned space flight. |
1971-2-First detailed closerange pictures of Mars( Mariner 9). |
1975-First images from the surface of Venus(Venera 9). |
1980-First images from the Saturn and its system(Voyager 1). |
1985-6-Halley;s comet returns, observed by the Giotto and Vega spacecraft. |
1990-Hubble Space Telescope launched and found to be defective. |