The solar neutrino problem was a major discrepancy between measurements of the neutrinos flowing through the Earth and theoretical models of the solar interior, lasting from the mid-1960s to about 2002. The discrepancy has since been resolved by new understanding of neutrino physics, requiring a modification of the Standard Model of particle physics. Essentially, if neutrinos do have mass, then they can change from the type that had been expected to be produced in the sun's interior into a type that would not be caught by the detectors in use at the time. Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon, or tau) can later be measured to have a different flavor. ... The neutrino is an elementary particle. ... Earth is the current Good Article Collaboration of the week! Please help to improve this article to the highest of standards. ... The Sun is the star at the center of Earths solar system. ... The neutrino is an elementary particle. ... The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... Particles erupt from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ...

The sun is a natural nuclear fusion reactor, fusing hydrogen to helium. Our current understanding of physics is quite clear about what happens: four hydrogen nuclei (protons), with and without the help of catalysts, are transformed into helium, neutrinos, and energy. The energy is released as gamma rays and as kinetic energy of the particles, including the neutrinos — which travel from the sun's core to Earth without any appreciable absorption by the sun's outer layers. The Sun is the star at the center of Earths solar system. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... A semi-accurate depiction of the helium atom. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... A catalyst (Greek: καταλύτης, catalytÄ“s) is a substance that accelerates the rate (speed) or ease of a chemical reaction (see also catalysis) without itself being changed at the end of the chemical reaction . ... The neutrino is an elementary particle. ... This article is about electromagnetic radiation. ... Kinetic energy (SI unit: the joule) is energy that a body possesses as a result of its motion. ...

History of the problem

As neutrino detectors became accurate enough to measure the flow of neutrinos from the sun, it became clear that researchers weren't getting as many of them as the models of nuclear burning in the Sun predicted. In various experiments, the number of detected neutrinos was between 1/3 and 1/2 of the predicted number. Therefore either the current models of the sun were wrong, or the models of neutrino behavior were wrong. This came to be known as the solar neutrino problem. As one researcher put it, "we must trust the measurements, because even if they are wrong by three standard deviations, theory is incorrect." In probability and statistics, the standard deviation is the most common measure of statistical dispersion. ...

The solar neutrino problem was troubling because it meant that either general relativity was incorrect, models of stellar evolution were incorrect, or the Standard Model was incorrect. Since each of these models had proven remarkably accurate in other respects, the choice was an unpalatable one. For a non-technical introduction to the topic, please see Introduction to General relativity. ...

Early attempts to explain the discrepancy proposed that the models of the sun were wrong, i.e. the temperature and pressure in the interior of the sun were substantially different from what was believed. For example, since neutrinos measure the amount of current nuclear fusion, it was suggested that the nuclear processes in the core of the sun might have temporarily shut down. Since it takes thousands of years for heat energy to move from the core to the surface of the sun, this would not immediately be apparent. However, these solutions were rendered untenable by advances in helioseismology, the study of how waves propagate through the sun. Based on such observations, it became possible to measure the interior temperatures of the sun and these agreed with the standard solar models. There are unresolved problems of the structure of what was found with helioseismology. Instead of the old "pot-on-the-stove" model of vertical convection, horizontal jet streams were found in the top layer of the convective zone. Small ones were found around each pole and larger ones extended to the equator. As might be expected, these had different velocities. Temperature is also the name of a song by Sean Paul. ... Pressure (symbol: p) is the force per unit area acting on a surface in a direction perpendicular to that surface. ... A computer generated image showing the pattern of a p-mode solar acoustic oscillation both in the interior and on the surface of the sun. ... Convection is the transfer of heat by currents within a fluid. ...

Currently, the solar neutrino problem is believed to have resulted from an inadequate understanding of the properties of neutrinos. According to the Standard Model of particle physics, there are three different kinds of neutrinos: electron-neutrinos (which are the ones produced in the sun and the ones detected by the above-mentioned experiments), muon-neutrinos, and tau-neutrinos. In the 1970s, it was widely believed that neutrinos were massless and their types were invariant. However, theoreticians in the 1980s realized that if neutrinos had mass, then they could change from one type to another. Thus, the "missing" solar neutrinos could be electron-neutrinos which changed into other types along the way to Earth and therefore escaped detection. The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ...

Experimental evidence for neutrino mass

The supernova 1987A produced an indication that neutrinos might have mass, because of the difference in time of arrival of the neutrinos detected at Kamiokande, and the small number detected versus the convective overturn model of supernovae. However, the data was insufficient to draw any conclusions with certainty. Multiwavelength X-ray image of the remnant of Keplers Supernova, SN 1604. ... SN 1987A was a supernova in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... The convective overturn model of supernovae was proposed by Bethe and Wilson in 1985, and received a dramatic test with SN 1987A, and the detection of neutrinos from the explosion. ...

The first strong evidence for neutrino oscillation came in 1998 from the Super-Kamiokande collaboration in Japan. It produced observations consistent with muon-neutrinos (produced in the upper atmosphere by cosmic rays) changing into tau-neutrinos. Actually all that was proved was that fewer neutrinos were detected coming through the Earth than could be detected coming directly above the detector. Not only that, their observations only concerned muon neutrinos coming from the interaction of cosmic rays with the Earth's atmosphere. No tau neutrinos were observed at Super-Kamiokande. More direct evidence came in 2002 from the Sudbury Neutrino Observatory (SNO) in Canada. It detected all types of neutrinos coming from the sun, and was able to distinguish between electron-neutrinos and the other two flavors. After extensive statistical analysis, it was found that about 35% of the arriving solar neutrinos are electron-neutrinos, with the others being muon- or tau-neutrinos. The total number of detected neutrinos agrees quite well with the earlier predictions from nuclear physics, based on the fusion reactions inside the sun. Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon, or tau) can later be measured to have a different flavor. ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ... Artists concept of SNOs detector. ...

In 2002 Raymond Davis Jr. and Masatoshi Koshiba won part of the Nobel Prize in Physics for experimental work that found the number of solar neutrinos was around a third of the number predicted by the Standard Solar Model. Raymond Davis Jr. ... Masatoshi Koshiba (小柴 昌俊 Koshiba Masatoshi, born on September 19, 1926 in Toyohashi, Aichi Prefecture -) is a Japanese physicist who won the Nobel Prize in Physics in 2002. ... Hannes Alfvén (1908–1995) accepting the Nobel Prize for his work on magnetohydrodynamics [1]. List of Nobel Prize laureates in Physics from 1901 to the present day. ...

Trivia

• The television show Law & Order had an episode that used the solar detection problem and the physics involved as a plot device.
• In the science fiction novel Songs of Distant Earth by Arthur C. Clarke, the sun has gone nova because of the solar neutrino problem.
• In the science fiction novel Fallen Angels by Larry Niven, Jerry Pournelle and Michael Flynn, the low number of neutrinos detected in fact was the result of a reduction in fusion in the Sun. As a result, the Earth rapidly entered a new ice age.

Law & Order is an American televison police procedural and legal drama set in New York City. ... A plot device is a person or an object introduced to a story to affect or advance the plot. ... Songs of Distant Earth is the common title of several science fiction works by Arthur C. Clarke. ... Arthur C. Clarke Sir Arthur Charles Clarke (born December 16, 1917) is a British author and inventor, most famous for his science-fiction novel 2001: A Space Odyssey, and for collaborating with director Stanley Kubrick on the film of the same name. ... Fallen Angels (1991) (ISBN 0743435826) is a Prometheus Award-winning novel by science fiction authors Larry Niven, Jerry Pournelle, and Michael Flynn. ... Larry Niven Laurence van Cott Niven (born April 30, 1938) is a US science fiction author. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Michael Flynn, (born 1947), sometimes published as Michael F. Flynn, worked full time as a statistician and wrote science fiction as a sideline for several years. ...

See also

• John N. Bahcall
• neutrino oscillation

John N. Bahcall (December 30, 1934 – August 17, 2005) was an American astrophysicist. ... Neutrino oscillation is a quantum mechanical phenomenon whereby a neutrino created with a specific lepton flavor (electron, muon, or tau) can later be measured to have a different flavor. ...

External links

• Solar neutrino data
• Nobel Prize in 2002, "partly for the detection of cosmic neutrinos"
• Solving the Mystery of the Missing Neutrinos
• Raymond Davis Jr.'s logbook
• Nova - The Ghost Particle