Moonscape
When I was about 12, my family took a roadtrip that took us through Eastern Canada. One town in Southern Ontario made a particular impression. In the midst of green and growing lands was a moonscape city of blasted land where no leaf of tree or blade of grass could grow. A few dead trunks of trees still stood, victims of some infernal process - my parents explained that it was the mining and refining of nickel, copper, arsenic and other materials that made these dead lands. I can't really be sure, but I think that city was Sudbury.
Not completely coincidentally, one of those deep nickel mines was the site of quite likely the most important discovery in fundamental physics in the last quarter of a century. That was the discovery of neutrino oscillations, which in turn imply that neutrinos have mass. Neutrinos were formerly thought to be massless, and the discovery of their mass is the first real crack in the "Standard Model" which has ruled particle physics for decades.
As often happens in physics, that discovery cleared up one mystery but posed several more. The mystery solved was the mystery of what happened to the solar neutrinos. The theory of stellar interiors makes quite precise predictions about the production of one of the three types of known neutrinos in the center of the Sun. These ghostly particles aren't impeded by the mass of the Sun and propagate out to the Earth in about eight minutes, unlike photons, the particles of light, which take about a million years to propagate to the surface of the Sun, and then another eight minutes to make the trip to Earth.
As one might expect, particles unimpeded by a few hundred thousand miles of Sun (or indeed, a light year of lead) are not so easy to arrest. The central detector in the Sudbury mine is a thousand tons of ultra pure heavy water. Trillions of neutrinos pass through it every second, but only a thousand or so a year are stopped and detected. Sudbury is just the most recent (or at any rate, one of the most recent) neutrino detectors built. The others had shown that there did not seem to be enough of the neutrinos produced by the Sun being detected.
In addition to the types of neutrinos produced in the Sun, experiments have shown that there are (at least) two other types of neutrinos. Eventually some clever people thought that it might be possible that the Solar neutrinos might be transforming into the other types of neutrino, something that couldn't happen unless the neutrinos had mass. The Sudbury detector was able to detect another neutrino type, and showed that just that must have been happening.
So why do the neutrinos have mass? And so what? The answers aren't known, but this new paper suggests that massive neutrinos might even account for the mysterious "dark energy" that appears to pervade the universe:
astro-ph/0602467
This post started out being about human caused environmental degradation, and I intend to say more on that subject some other time. Recent photos of Sudbury show that the moonscape is green and growing again - an apparent success story for environmental reclamation.
Not completely coincidentally, one of those deep nickel mines was the site of quite likely the most important discovery in fundamental physics in the last quarter of a century. That was the discovery of neutrino oscillations, which in turn imply that neutrinos have mass. Neutrinos were formerly thought to be massless, and the discovery of their mass is the first real crack in the "Standard Model" which has ruled particle physics for decades.
As often happens in physics, that discovery cleared up one mystery but posed several more. The mystery solved was the mystery of what happened to the solar neutrinos. The theory of stellar interiors makes quite precise predictions about the production of one of the three types of known neutrinos in the center of the Sun. These ghostly particles aren't impeded by the mass of the Sun and propagate out to the Earth in about eight minutes, unlike photons, the particles of light, which take about a million years to propagate to the surface of the Sun, and then another eight minutes to make the trip to Earth.
As one might expect, particles unimpeded by a few hundred thousand miles of Sun (or indeed, a light year of lead) are not so easy to arrest. The central detector in the Sudbury mine is a thousand tons of ultra pure heavy water. Trillions of neutrinos pass through it every second, but only a thousand or so a year are stopped and detected. Sudbury is just the most recent (or at any rate, one of the most recent) neutrino detectors built. The others had shown that there did not seem to be enough of the neutrinos produced by the Sun being detected.
In addition to the types of neutrinos produced in the Sun, experiments have shown that there are (at least) two other types of neutrinos. Eventually some clever people thought that it might be possible that the Solar neutrinos might be transforming into the other types of neutrino, something that couldn't happen unless the neutrinos had mass. The Sudbury detector was able to detect another neutrino type, and showed that just that must have been happening.
So why do the neutrinos have mass? And so what? The answers aren't known, but this new paper suggests that massive neutrinos might even account for the mysterious "dark energy" that appears to pervade the universe:
astro-ph/0602467
This post started out being about human caused environmental degradation, and I intend to say more on that subject some other time. Recent photos of Sudbury show that the moonscape is green and growing again - an apparent success story for environmental reclamation.
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