The Geophysical Consequences of Professor Lyttleton

Abstract

HAD Professor Lyttleton sent me his letter¹ before publication, I would have suggested that he replaced his homely parable with a straightforward account of how his controversy with me has—unhappily—arisen. To judge from his recent review², from which the quotations I will use are drawn, he has become seriously displeased that his attempts to revive Ramsey's theory³, that the Earth's core is not iron but a phase change undergone by ferromagnesian silicates of the mantle at high pressure, has not “for some curious reason … found much favour with geophysicists”. He extended Ramsey's theory by postulating that the pressure at which this hypothetical phase change occurs decreases with increasing temperature. Thus starting with a cold accreted Earth—wholly of silicate with no iron core—the disseminated radioactivity heated the Earth up to the temperature at which the phase change to a denser state began at the centre. Thus the core grew and the Earth's radius contracted.