of hydrogen together, fusing them to create one atom of helium. once again, you get lots of energy and this time, just a tiny bit of short—lived radiation. creating mini stars inside reactors like this is one of the greatest technological challenges humanity has ever faced. get it right, and it holds out the potential for producing almost unlimited supplies of energy pretty much forever. that's because the hydrogen fuel fusion uses is so readily available. the key part of this reaction only lasts for five seconds and only generated enough power for 60 kettles, but it is an important proof that scientists are on the right track. there is still lots of work to do, and athina kappatou is one of a new generation of physicists who plan to do it at a scaled—up version of the uk reactor being built here in the south of france.