如果(放射性衰变供应只有大约一半地球的热量)(http://physicsworld.com/cws/article/news/2011/jul/19/radioactive-decay-accounts-for-half-of-earths-heat),其余的热量来源是什么?![在这里输入图像描述][1][1]:http://i.stack.imgur.com/t13tq.gif