In recent years we have come to grips with how little we really understand about the universe at a fundamental level. A vast amount of data about the universe at large distance scales is now available. By studying the patterns of hot and cold regions in the Cosmic Microwave Background, a lot is known about how matter and energy are distributed in the universe. The fact that supernovae in distant galaxies are dimmer than had been expected implies that some mysterious dark energy is driving an accelerated expansion of the universe. The fact that stars rotate so quickly about the centers of galaxies implies that most of the mass in those galaxies is in the form of dark matter made of particles that haven't yet been discovered. Putting together lots of pieces of data like these, a description of the universe has emerged in which less than 5% of the density of the universe is made of stuff that we can identify. The rest is a big, confusing mystery.
The amazing thing about this story is how it connects the structure of the universe at the largest distance scales with its fundamental building blocks. Physicists like Alan Guth in the 1980's began the program of using theories about elementary particles to explain some big mysteries of the universe, like why it looks so similar in regions of space between which light should not have had a chance to communicate. We expect that future atrophysical and cosmological observations will continue to guide us in the hunt for new particles, and vice versa. One thing we have studied here at William & Mary is how the distribution of galaxy clusters in the sky may help to constrain some possibilities for new particle physics. We have also been investigating models of dark matter which would explain some unusual astrophysical phenomena, such as a recently discovered excess in cosmic ray positrons. There's a lot of data out there. It's exciting to ponder the secrets yet to be uncovered.
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