Mathematics – Logic
Scientific paper
May 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aps..nws..a103h&link_type=abstract
American Physical Society, First Meeting of the Northwest Section May 21-22, 1999 The University of British Columbia Vancouver,
Mathematics
Logic
Scientific paper
Deep surveys of many kinds show that space and the matter within it, averaged over large volumes, are nearly uniform and uniformly expanding with time. Within this simple framework however there are still many possible universes with various spatial geometries and expansion histories. The geometrical shape of the universe is a relic of whatever process shaped the Big Bang at the beginning, inflation being one possibility. The history of the expansion, controlled by gravity, depends both on the geometry and on the dominant forms of energy in the universe--- the sum of all matter, light and possibly other more subtle forms of energy filling space. Einstein's General Theory of Relativity knits together the curvature, the expansion and the energy content, and describes how all these affect the propagation of light, thereby making predictions for the things that astronomers can measure. Exploding stars called Type Ia supernovae now give a brightness standard for measuring large distances with sufficient precision to begin to measure the history of the cosmic expansion and the large scale geometry of space. Two international teams have recently succeeded in obtaining high quality data on a few dozen supernovae at redshifts between 0.5 and 1 which indicate that the universe may be bigger and emptier than we expected, and likely to expand for much longer than it already has. The rate of expansion may even be accelerating, a sign that the universe may be driven apart by the repulsive gravity of an exotic new form of energy, such as Einstein's Cosmological Constant.
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