Dark Energy
A critical research problem in cosmology is the need to understand the accelerating expansion of the Universe. This acceleration requires something new and strange---Dark Energy---which could arise from the energy of the vacuum (the cosmological constant) or a new ultra-light particle; alternatively it could indicate a flaw in Einstein's General Relativity, perhaps signaling that our three-dimensional world is embedded in a Universe of higher spatial dimensions. Any of these possibilities would represent a major shift in our current understanding of the nature of matter, energy, space, and time. In order to sort out the possibilities and pin down the nature of the dark energy, we need to make more precise measurements of its properties; the key property of dark energy that determines the expansion history of the Universe is its equation of state parameter, w, the ratio of its effective pressure to its energy density. In order to precisely measure w and its possible time evolution, we must build a powerful new instrument and a flexible and responsive data management system to accompany it, while continuing to develop improved methods of analysis.
Three experiments are currently searching for dark energy:
