The problem relates to the way that data are transmitted within the experiment. Neutrino speeds are estimated by dividing the baseline distance travelled (as calculated using GPS measurements) by the time-of-flight (as calculated using an atomic clock). The researchers have now realized that an optical fibre connecting the GPS signal to the atomic clock may not have been functioning correctly at the time when the measurements were made. This could have led to an underestimate of the time taken by neutrinos on their journey. ... more »
With each doubling of detector volume leading to a doubling in the neutrino detection rate, a contagious volume fever has spread among neutrino astronomers. In 25 years time the unit in which detector volumes are measured has evolved considerably. Gone are the days that these were measured in cubic meters. Following the delivery of the IceCube neutrino telescope, the cubic kilometer provides a more convenient unit. And plans for future neutrino telescopes promise to dwarf IceCube. The most ambitious are probably the plans for the Arianna neutrino observatory, that address the conversion of a hundred cubic kilometres of the Ross ice shelf into a colossal neutrino detector. ... more »
In 1967, one of the Vela satellites encountered a brilliant flash of gamma radiation. U.S. monitors went on the alert, keen to determine whether someone had broken the treaty. They discovered an eerie truth instead: Those high-energy flashes were happening on a regular basis, often once or twice a day. They were coming from all directions. And they were not coming from the Earth. ... more »
... in 1990, he came across articles written by David Hestenes, a physicist at Arizona State. Hestenes got the idea for the series when a colleague came to him with a problem. The students in his introductory physics courses were not doing well: Semester after semester, the class average never got above about 40 percent. "I noted that the reason for that was that his examination questions were mostly qualitative, requiring understanding of the concepts rather than just calculational, using formulas, which is what most of the instructors did," Hestenes says. Hestenes had a suspicion students were just memorizing the formulas and never really getting the concepts. So he and a colleague developed a test to look at students' conceptual understanding of physics. ... more »
Road Runner cartoons can easily and meaningfully be worked into the physics and physical science curriculum. Many vignettes involve fairly direct misrepresentations of specific physical principles. I developed the table below for my own use in deciding which clips to show and when. The two compilation videos are still in print as far as I know. I hope you find the information useful. (An asterisk denotes a particularly useful cartoon or vignette.) ... more »
The matter that matters is now called "Quasicrystal" in which the arrangement of atoms follows a definable mathematical pattern, but the pattern is not repeated. There are aspects of this patterning seen in the ancient concept of the "Golden Mean" as well as in medieval Islamic mosaics, which provide for a lot of analogies and pretty language in explaining what this stuff is. "There can be no such creature" is what Shechtman wrote in his lab notebook when he first observed the patterns that do not repeat themselves using electron diffraction. ... more »
Researchers from the Opera experiment at the Gran Sasso Laboratory in Italy, yesterday announced that they may have spotted their first oscillating neutrino... According to Opera spokesman Antonio Ereditato, confirming the muon-to-tau oscillation rules out the sterile neutrino hypothesis. But he pointed out that this is only Opera's first observed event, with a relatively low confidence level: there is still a 2% chance that their observation is an experimental artifact. “I would bet some money on it, but neither my life nor my scientific reputation” he told Nature. Ereditato will feel much more confident once Opera, which will run until the end of 2012, has spotted another three or four tau neutrinos, he says. The event is so unlikely that scientists do not expect it to happen more than ten times during the experiment's life. more »
In the 1970s, Hawking and Jacob Bekenstein showed that the information stored in a black hole is proportional to its surface area rather than its volume. This encoding of three-dimensional information on a two-dimensional surface came to be called the holographic principle. In 1997, Juan Maldacena of the IAS formalized the principle, showing that the string theory description of a black hole is mathematically equivalent to a quantum field theory without gravity that describes the surface of the black hole. more »
Verlinde uses the holographic principle to consider what is happening to a small mass at a certain distance from a bigger mass, say a star or a planet. Moving the small mass a little, he shows, means changing the information content, or entropy, of a hypothetical holographic surface between both masses. This change of information is linked to a change in the energy of the system. Then, using statistics to consider all possible movements of the small mass and the energy changes involved, Verlinde finds movements toward the bigger mass are thermodynamically more likely than others. This effect can be seen as a net force pulling both masses together. Physicists call this an entropic force, as it originates in the most likely changes in information content. more »
If it smells like entropy, and it behaves like entropy, it probably is entropy. more »
The problem is that galaxies rotate so fast that the matter they contain ought to fly off into space. Similarly, clusters of galaxies do not seem to contain enough mass to bind them together and so ought to fly apart. Since this manifestly doesn't happen, some force must be holding these masses in place. Astrophysicists have put forward two explanations. The first is that these galaxies are filled with unseen mass and this so-called dark matter provides the extra gravitational tug. The second is that gravity is stronger at these intergalactic scales and so does the job by itself, an idea called modified Newtonian dynamics or MOND. more »
There is a growing sense among physicists that all physical processes can be thought of in terms of the information they store and process; by some accounts information is the basic unit of existence in our cosmos. That kind of thinking has extraordinary implications: it means that reality is a kind of computation in which the basic processes at work simply chomp their way through a vast bedrock of information. And yet this is at odds with another of the great challenges facing modern science: understanding the nature of randomness. more »
Super-Kamiokande
Un Chien Andalou 1929
