Everything around you is made of atoms. Atoms are incredibly tiny. Millions of them could fit on the head of a pin. But inside each atom is a nucleus, and that nucleus holds enormous energy. On October 3, 1952, the United Kingdom tested its first nuclear weapon near Australia. The explosion created a massive mushroom cloud and a wave that sank a ship placed nearby. Britain became the third country to test a nuclear weapon, after the United States and the Soviet Union. Nuclear energy works by splitting the nucleus of certain heavy atoms, like uranium. When the nucleus splits, it releases energy and also breaks apart other atoms nearby. This chain reaction happens in a fraction of a second. The energy released is millions of times stronger than burning the same amount of coal. Scientists who studied nuclear energy faced a difficult question. The same science that could power cities could also destroy them. After the test, many scientists advocated for using nuclear energy for electricity rather than weapons. Today, nuclear power plants provide about ten percent of the world's electricity. The science of the atom gave humanity both its greatest source of energy and its most dangerous weapon.