Skip to comments.First measurements of Earth's core radioactivity
Posted on 07/27/2005 11:13:59 AM PDT by LibWhacker
EARTH'S natural radioactivity has been measured for the first time. The measurement will help geologists find out to what extent nuclear decay is responsible for the immense quantity of heat generated by Earth.
Our planet's heat output drives the convection currents that churn liquid iron in the outer core, giving rise to Earth's magnetic field. Just where this heat comes from is a big question. Measurements of the temperature gradients across rocks in mines and boreholes have led geologists to estimate that the planet is internally generating between 30 and 44 terawatts of heat.
Some of this heat comes from the decay of radioactive elements. Based on studies of primitive meteorites known as carbonaceous chondrites, geologists have estimated Earth's uranium and thorium content and calculated that about 19 terawatts can be attributed to radioactivity. But until now there has been nothing definitive about exactly how much uranium there is in the planet, says geologist Bill McDonough of the University of Maryland in College Park. "There are fundamental uncertainties."
There is one way to lessen this uncertainty, and that is to look for antineutrinos. These particles are the antimatter equivalent of the uncharged, almost massless particles called neutrinos and are released when uranium and thorium decay to form lead. If antineutrinos are being created deep within the planet they should be detectable, because they can pass through almost all matter.
Now, the KamLAND antineutrino detector in Kamioka, Japan, has counted such antineutrinos. An international team of scientists analysed the data and found about 16.2 million antineutrinos per square centimetre per second streaming out from Earth's core. They calculate that the nuclear reactions creating these particles could be generating as much as 60 terawatts, but are most likely putting out about 24 terawatts (Nature, vol 436, p 499). "We have made the first measurements of the radioactivity of the whole of Earth," says John Learned, who heads the KamLAND group at the University of Hawaii in Manoa. The KamLAND group's finding is like unwrapping a birthday present, says McDonough.
With time, as more antineutrinos are detected, KamLAND may be able to determine once and for all whether radioactivity is entirely responsible for heating Earth or whether other sources, such as the crystallisation of liquid iron and nickel in the outer core, also play a significant role. "[Detecting anti-neutrinos] is the way of the future in terms of hard numbers about the system," says McDonough.
Antineutrinos could also reveal the radioactive composition of the crust and mantle, which will give geologists clues as to when and how they formed. But to do that, they will have to be able to pin down exactly where the antineutrinos are coming from, and this will require a whole network of detectors. "We are heading towards doing neutrino tomography of the whole Earth," says Learned. "This is just the first step."
How did they do that? The deepest well we ever drilled in the history of the world does not even gd deep enough to get 10% close to the center.
Now the anti-nuke extremists will be forced to boycott the entire planet.
Not such a bad idea, after all...
The article makes it clear that there is no need to dig down near the core. The antineutrinos pass through everything.
Neutrinos aren't much interested in 10% or 90% or 100% solid lead. If physics, especially particle physics were easy to do it then everyone would and you could be a pundit.
That is only a surmise. Maybe a hypothesis. Not at all certain. Probably not at all close to reality.
Well, I was ready to believe it!
Somebody asked a famous physicist maybe 100 years ago what caused the earth's mag field, and he said the iron core could be doing it, and that was that. Nobody has questioned it since, except right here.
WE'RE ALL GONNA DIE!!!
The neutrino and its friends
Neutrinos are one of the fundamental particles which make up the universe. They are also one of the least understood.
Neutrinos are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons.
Neutrinos are affected only by a "weak" sub-atomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it. If neutrinos have mass, they also interact gravitationally with other massive particles, but gravity is by far the weakest of the four known forces.
Three types of neutrinos are known; there is strong evidence that no additional neutrinos exist, unless their properties are unexpectedly very different from the known types. Each type or "flavor" of neutrino is related to a charged particle (which gives the corresponding neutrino its name).
Hence, the "electron neutrino" is associated with the electron, and two other neutrinos are associated with heavier versions of the electron called the muon and the tau (elementary particles are frequently labelled with Greek letters, to confuse the layman).
"No waste, no fuel, just free heat."
What do you mean by free heat? Nothing is Free. We get our water from "free rain" do you get water at your house for free.
There are also questions of heat production. Heat would be drawn off and the natural processes of replacing that heat would be slow, possibly too slow for economic operation.
Geothermal's been around for awhile now. The heat's free, but converting it to electricity turns out not to be. It's the old "the more efficient the system, the higher the cost" thing that only new technology can really address. When the conversion and transmission technologies improve there's no real reason geothermal can't be quite competitive with surface sources - at the moment it's only competitive in areas where you don't have to go too deep for the heat.
Your ability to cut and paste or forward e-mail is no indication of much of any thing. Yawn. See my tagline.
Watch your ego, it makes you appear the idiot.
So, miners actually help in cooling the Earth? Why are the environmentalists against miners and oil drilling? Aren't they supposed to be against global warming? ;)