throwing higher and higher velocity particles at matter, three people in germany, lisa meitner, otto hahn, otto-- strassman, i think, anyway, what they did was they threw slow moving neutrons at uranium isotopes and they found a reaction that changed the world. and the reaction that changed the world is that what you see before you here. it's in your textbooks. the first page in the chapter, fission and fusion. and all we're saying is that it turns out if a slow moving neutron taps into uranium 235 isotope-- [makes sounds] --it will lay it right in half, and the isotopes, instead of a little particle coming off like maybe a proton or an alpha particle, the whole things falls on half. wild. and-- [makes sounds] here's a typical reaction. there are many reactions. this is just the typical one. the uranium busts in half into krypton and barium. these are about halfway down the periodic table from where the uranium is. and the neat thing was, is there were also an ejection in the average of about three more neutrons. now, if you can slow these neutrons down-- they're going kinda fast-- if you