Week 4 - the rate of rotation of galaxies. Another major piece of evidence is the fact the inner and outer parts of galaxies appear to rotate at the same rate. This does not make sense, on the basis of calculations of the gravitational force from the stars and dust clouds that are visible in galaxies. Use your understanding of circular motion to show how angular velocity of a star, around the centre of a galaxy, should depend on the distance from the centre of the galaxy. (Assume that the mass of the galaxy acts as if concentrated at the centre). Post your conclusions, together with comments on what distribution of matter would explain observations.
as we already know a neutrino, only with a rest mass greater than zero, is a candidate for dark matter. In the Gran Sasso laboratory Lucia Votano, the director of the laboratory, had announced "the OPERA experiment has reached its first goal: the detection of a tau neutrino obtained from the transformation of a muon neutrino, which occurred during the journey from Geneva to the Gran Sasso Laboratory." - meaning that there is deficiency in the standard model for particle physics because a neutrino must have a mass for this change to occur - said in 2010.
ReplyDeleteAn effort to determine the Dirac nature of the neutrino, called CUORE (Cryogenic Underground Observatory for Rare Events), is scheduled to begin in 2012. The detector will be shielded with lead recovered from an ancient Roman shipwreck, due to the ancient lead's lower radioactivity than recently minted leads. The artifacts are being given to CUORE from the National Archaeological Museum in Cagliari.