Despite centuries of research, there still is much to know about the nature of the Universe. In fact, current understanding comprises less than 5% of the cosmological energy budget. Dr. Bharat Ratra, of Kansas State University, is a physical cosmology theorist working to find out what makes up the unknown 95% of the Universe's energy budget. His 1988 discovery, with Dr. Jim Peebles, of Princeton University, of dynamical dark energy models set him on a quarter century odyssey of using observational data to judge dark energy models. Fantastic improvements over the last decade in the quality and quantity of observational data indicate that this process is culminating. In addition, he uses novel techniques to analyze large data sets to extract reliable measures of cosmological parameters such as the Hubble constant, and has also studied the generation, evolution and consequences of a large-scale cosmological magnetic field. His research holds promise for shifting the  ways in which cosmology is understood.

The implications of the dark energy research Dr. Ratra is involved in are revolutionary within physics. Understanding dark energy and dark matter will lead to a factor of 20 increase of our physical world, measured in terms of the energy budget, which would be unprecedented in the modern era. In addition, the late 1990's discovery of accelerated cosmological expansion, which strongly hints at the need to improve upon either quantum mechanics or general relativity or both, will likely prove to be the beginning of another paradigm-shifting revolution in physics.

Dr. Ratra has written over 90 scholarly publications, which have been cited more than 10,000 times in scientific literature. As a theorist that has more experience working with data than most theorists, Dr. Ratra has a niche that has allowed him to make some interesting discoveries. For example, he and his collaborators work using median statistics to determine the Hubble constant has resulted in perhaps the most robust estimate of the Hubble constant to date and that can be used in conjunction with other data to help pin down other parameter values, such as the dark energy density parameter or the number of light neutrino species.

Current research includes:

• Dark Energy Models: Dr. Ratra continues to work within his original area of expertise, dark energy models, by using observational data to judge them.

• Large Data Sets: Dr. Ratra devotes much of his time to somewhat unconventional data analysis techniques applied to large data sets. For example, he and his collaborators have thrice  estimated, using median statistics, what they believe is the most robust and reliable estimate of the Hubble constant -- which is the current cosmological expansion rate.

• Cosmological Magnetic Field: Dr. Ratra studies the generation, evolution, and consequences of a primordial, very large scale, weak cosmological field. Dr. Ratra's research focusses on a new model, an extension of the standard models of cosmology and particle physics. In the near future new observational data could conclusively establish that such a magnetic field exists and can help shed light on the path we need to follow to extend the standard models.