Recent estimates of the composition and geometry of the universe have been drastically revised over the past two years. Observations of tremendous stellar explosions known as supernovae have now been seen at cosmological distances, and have caused many cosmologists to now believe the universe is not only expanding, but that this expansion is accelerating. The unusual geometry that this implies is discussed. Even more powerful explosions known as gamma-ray bursts can be seen even further into the universe, and the limits that these impose not only on the geometry but on the composition of dark matter in the universe is discussed.

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