Radioactivity has the connotation of being extremely dangerous. In many situations it is. However, it can also be wonderfully useful. Radioactivity has been used for both good and bad causes. It remains one of the most fascinating phenomena that man has discovered and replicated: the splitting of the atom. My question was: what is radioactivity and what can it be used for? In 1896, a Frenchman named Henri Becquerel accidentally discovered radioactivity. He placed uranium crystals on paper-covered photographic plates. He found that the crystals had clouded the plates when they were developed. Becquerel was extremely moved by this discovery. He called the rays “uranic rays” and assumed that they came exclusively from the element uranium. Scientist Marie Curie became curious about "uranic rays" and began researching them. She worked with her husband to invent a machine that measured weak electric currents so she could test different rock samples for rays. Curie found the element thorium, which emitted the same rays as Becquerel's uranium samples. Curie also found that the rays were stronger the more uranium was in the sample, that the rays were not an effect of accumulated heat or light, and that temperature had no effect on the rays. After long and meticulous research, he decided that the rays were the effect of a new property of matter: radioactivity. The word radioactivity comes from the Latin word “radius”, which means ray. Marie Curie's curiosity led her to conduct further studies on this mysterious property known as radioactivity. He found that a sample of a rock called pitchblende was very radioactive and remained radioactive even after most of the uranium in the sample was removed. The strength of its radioa...... middle of paper ...... transmits a greater amount of energy. The first nuclear fission reactor was created by a team led by Enrico Fermi in Chicago in 1942. It used natural uranium (uranium-225) to create uranium-235. Fermi is also known for the Fermi paradox and his work on the Manhattan Project. Nuclear energy can be used as a source of electricity. The nuclear bomb project created a lot of fear of radioactivity, but that fear has begun to dissipate. Radioactivity has a great deal of uses that could improve the world, rather than cause fear. Nuclear reactors currently represent the source of a fifth of the world's energy and this figure could increase to a quarter by the end of the century. It is used daily in medical procedures and other projects. The small change in an atom we call radioactivity has changed the world dramatically since Henri Becquerel found his blurred film.