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The Mystery of Empty Space |
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Get ready to re-think your ideas of reality. Join UCSD physicist Kim Griest as he takes you on a fascinating excursion, addressing some of the massive efforts and tantalizing bits of evidence which suggest that what goes on in empty space determines the properties of the three - dimensional existence we know and love, and discusses how that reality may be but the wiggling of strings from other dimensions. From the opening of a 43 minute lecture, 'The Mystery of Empty Space: Higgs Bosons, Vacuum Energy and Extra Dimensions', May 2001. Scientists currently believe that most of mass of the universe is not the stuff of stars, dust, planets and people. The atoms and ions which constitute all of the known matter seem to be rivaled by the presence of an unidentified and invisible form of mass. The Standard Model of particle physics may need to be expanded to include new families of particles which could explain the missing mass. These particles would have been created and annihilated along with other known particles in the early universe just after the Big Bang, with a certain abundance remaining in the universe today as dark matter. The CDMS group along with several other collaborations across the world are on a quest to solve this great cosmic mystery... Dark matter may sound very mysterious, but it is simply a name which astronomers give to any stuff in the universe which we can detect gravitationally but not "see". In other words, for many possible reasons, the material is not emitting light of any wavelength which we can detect, but we can measure its gravitational effect on other objects in the universe. The first evidence of dark matter was found in clusters of galaxies back in the 1930's. Astronomer Fritz Zwicky discovered that the mass of luminous material in a cluster of galaxies (i.e. the galaxies themselves and any gas which was detected) was much less than the total mass of the cluster implied by the velocities of the galaxies. Evidence of dark matter has since been found within galaxies, and it appears that more than 90% of the total mass of the universe may be dark matter. The search for dark matter continues. Some dark matter is in the form of 'brown dwarfs', 'black dwarfs', and planets, which we know exist but which are generally too faint to be detected other than by their gravitational effect. It seems unlikely, however, that these dim objects can account for all of the missing mass. There are many other candidates, ranging from as yet undetected exotic particles to black holes. Stay tuned to 'The Universe' for more on dark matter.
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".....Above us only sky...."
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