Abstract:

 Experiments and observations over the last two decades have provided strong

support for a "standard" model of cosmology that describes the evolution of the

universe from an early epoch of inflation to the complex hierarchy of structure

seen today. I review the basic physics, astronomy, and history of ideas on

which this model is based. I describe the data which persuade cosmologists that

(as yet undetected) dark energy and dark matter are by far the main components

of the energy budget of the universe. I conclude with a list of open

cosmological questions.

Short Bio of the Speaker:

Bharat Ratra, distinguished professor of physics in Kansas State

University, works in the areas of cosmology and astroparticle physics. He

researches the structure and evolution of the universe. Ratra joined Kansas

State University in 1996 as an assistant professor of physics. He was a

postdoctoral fellow at Princeton University, the California Institute of

Technology and the Massachusetts Institute of Technology. Ratra earned a

doctorate in physics from Stanford University and a master's degree from the

Indian Institute of Technology in New Delhi. Ratra's research has appeared in

100 scholarly publications, which have been cited more than 12,000 times in

scientific literature. In 1988, Ratra and Jim Peebles proposed the first

dynamical dark energy model. Dark energy is the leading candidate for the

mechanism that is responsible for causing cosmological expansion to accelerate.

The discovery that cosmological expansion is accelerating is one of the most

significant scientific discoveries of the last quarter of a century.