The International Geophysical Year was an 18-month scientific exploration of the Earth's physical aspects. The observance was organized by the International Council of Scientific Union and coincided with a period of maximum solar activity. Scientists from 67 nations worked together to perform experiments and observations, the results of which were shared. Many new features of the Earth and its space environment were discovered, including the Van Allen radiation belt. It was during this period that the first artificial satellites were launched: Sputnik and Explorer.