Lord Kelvin considered that the earth's core should have cooled some five hundred million years after creation. However today, almost five thousand million years after creation, the temperature at the centre of the earth is estimated to be between six and seven thousand degrees centigrade, close to the temperature on the surface of the Sun.

One can only estimate the temperature gradient from the centre of the earth to the crust on which our fragile world exists. When there is volcanic activity in one of the twenty two hotspots around the world, then molten rock from the earth's interior bursts through the crust. This molten rock or lava has a temperature that varies from seven to seventeen hundred degrees centigrade, depending on its chemical composition.

The earth weighs six thousand billion, billion tons which is an unimaginably large number. However the amount of heat energy that sustains both the core temperature and that of the magma existing from the core to the crust has a much larger value. The explanation that this incredible amount of energy results from radio-active disintegrations within the core and residual 'creation heat' has always seemed somewhat flimsy.

The only process that can create energy of such immense proportions is nuclear fusion not fission. In both reactions there is a mass loss, for the combined weight of the product particles is less than the weight of the reacting particles. For it was Einstein who realised that if the mass lost in a nuclear reaction was multiplied by the velocity of light squared, which is nine thousand million, then an incredibly large amount of energy would be produced. However a fusion reaction proportionately creates even more energy as the mass loss is greater than that occurring in a fission reaction. Hydrogen bomb blasts are measured in megatons of tnt whilst Atomic bomb blasts are measured in kilotons.

At the centre of the Sun core temperatures are estimated to be 17 million centigrade. This immense temperature is created by an extremely powerful fusion reaction. It can be shown that more energy is released when lighter rather than heavier nuclei undergo fusion. In the core of the Sun 2/1Hydrogen atoms are fusing together to produce 4/2Helium atoms. As the weight of each Helium atom is a lot less than the weight of the two hydrogen atoms then Einsteins' Law applies. There was amazement, back in the 1920's, when just one atom of 235Uranium split after a neutron collision. The research scientist marvelled at the movement of grains of sand that supported the uranium as the single nucleus splintered.

The only fusion reaction that man has created has been by surrounding an atomic bomb with heavy hydrogen atoms. When the fission reaction of the atomic bomb occurs then an immense temperature and pressure is created. These are the very conditions that enable the heavy hydrogen atoms to form a helium atom, and the subsequent mass loss, being far greater than that involved in the fission reaction of the atomic bomb, creates a blast of megatons of tnt that can literally shift mountains. This instantaneous fusion reaction produces a Hydrogen bomb but we have not yet been able to create the conditions necessary to harness a continuous fusion reaction.