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According to the folks who know a lot about such things, the Earth is over four and a half billion years old. So, it does make you wonder why it is still so hot. There are still many places where volcanoes shoot up molten rock and geysers of boiling water erupt. Some countries like Iceland even use this heat for heating and power.
If you go down into a deep mine, you will find that the temperature increases about one degree Fahrenheit for every 60 feet you descend. If you do the arithmetic that would make the core of the Earth one hundred thousand degrees F., which it is not, your thermometer will read only around eleven thousand degrees. So, the degree of heating must slow down at a level much deeper than we can dig. But, that is still hotter than the surface of the sun which comes in around ten thousand degrees F. Where does that heat come from?
The major source of heat is from the decay of the radioactive isotopes of Thorium, Uranium and Phosphorus occurring naturally in the Earth’s mantle, an 1800 mile thick layer lying under the Earth’s crust—the part we live on.
An isotope is another form of the same element differing only in the number of neutrons. Chemically they behave the same, but the additional neutrons can make the nucleus of some elements unstable. This instability results in the emitting of rays or particles in an attempt to become more stable. Nature doesn’t like instability.
When the radioactive isotopes of Uranium, Thorium and Phosphorus decay they release heat in the same way as the Uranium isotopes do in a nuclear reactor.
This heating will not go on forever. In a few billion years the isotopes heating the mantle will all have decayed and the planet will cool and become as cold as the moon, but by that time the sun will have become a red giant, its surface extending well beyond Earth’s orbit.
That will heat things up again and if we’re still around we had better have moved out of the neighborhood.
If you go down into a deep mine, you will find that the temperature increases about one degree Fahrenheit for every 60 feet you descend. If you do the arithmetic that would make the core of the Earth one hundred thousand degrees F., which it is not, your thermometer will read only around eleven thousand degrees. So, the degree of heating must slow down at a level much deeper than we can dig. But, that is still hotter than the surface of the sun which comes in around ten thousand degrees F. Where does that heat come from?
The major source of heat is from the decay of the radioactive isotopes of Thorium, Uranium and Phosphorus occurring naturally in the Earth’s mantle, an 1800 mile thick layer lying under the Earth’s crust—the part we live on.
An isotope is another form of the same element differing only in the number of neutrons. Chemically they behave the same, but the additional neutrons can make the nucleus of some elements unstable. This instability results in the emitting of rays or particles in an attempt to become more stable. Nature doesn’t like instability.
When the radioactive isotopes of Uranium, Thorium and Phosphorus decay they release heat in the same way as the Uranium isotopes do in a nuclear reactor.
This heating will not go on forever. In a few billion years the isotopes heating the mantle will all have decayed and the planet will cool and become as cold as the moon, but by that time the sun will have become a red giant, its surface extending well beyond Earth’s orbit.
That will heat things up again and if we’re still around we had better have moved out of the neighborhood.
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