KentuckyFC writes: The origin of the heat generated inside the Earth is one of the great mysteries of geophysics. Researchers know that almost all this heat is generated by the decay of radioactive elements such as potassium-40, thorium-232 and uranium-238. But what they don't know is how these elements are distributed inside the planet and how much heat each contributes. In the next few years, they hope to get some answers thanks to the emerging science of antineutrino geophysics. Since radioactive decay produces antineutrinos, an experiment that measures these particles coming out of the Earth should provide a detailed picture of the distribution of the elements within it. But there's a problem. Nuclear reactors also produce copious numbers of antineutrinos and these can swamp the signal from inside the Earth. What's needed is a map showing the distribution of reactor antineutrinos so that geophysicists can choose the best places to put their experiments. Just such a map is exactly what a team of nuclear physicists has now produced. The map shows that planned experiments in Hawaii and Curacao, off the coast of Venezuela, are in excellent locations and that Japan has recently become a much better site thanks to the shut down of the country's nuclear industry following the 2011 Tohoku earthquake. But a European experiment currently being planned in south-east France doesn't come off so well.