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The radioactive decay of uranium was first discovered by Antoine Henri Becquerel in 1896. The Paris physician accidentally discovered that photographic plates wrapped in dark paper were blackened by invisible radiation was capable of discharging an electroscope. In 1898, a France couple, Marie and Pierre Curie, discovered the radioactive elements radium and polonium. Marie Curie also discovered the radioactive element thorium..

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In the span of history, a lot of people, religions and scientists have predicted the Apocalypse, the end of the world. There are thousands of different theories, but most of them are very, very unlikely to ever occur. But, a few of those theories do actually make some sense. Here are the three most realistic theories.