University of Minnesota
School of Physics & Astronomy


Viewing the Beginning of the Universe from the Bottom of the World

Clem Pryke at the South Pole with the Keck Array team
Clem Pryke at the South Pole with the Keck Array Team

Clem Pryke is a cosmologist who uses telescopes at the South Pole in Antarctica to learn about the origins of the Universe. Over the last couple of decades cosmology has moved from being the domain of mystics and philosophers to being a hard observational science. One of the pillars of this progress has been measurements of the radio "after-glow" of the Big Bang - known as the Cosmic Microwave Background (CMB).

Pryke and his collaborators have used a series of highly specialized radio telescopes at the South Pole to make increasingly precise measurements of the CMB. The South Pole is amongst the best places on Earth to make such observations - the extreme cold and high altitude combine to make the atmosphere there almost free of water vapor - and thus allows an incredibly clear view of the microwave sky.
While contemporary cosmology is well developed, many questions remain. For example, why is the Universe almost perfectly isotropic (the same in all directions)? The theory known as "Inflation" explains this and other mysteries through a tremendous hyper expansion of the fabric of space taking place in the first tiny fraction of a second after the Big Bang. Pryke and his colleagues recently discovered the first direct evidence confirming this theory in the form of B-mode polarization. This special polarization could only have been created by gravitational waves during the period of inflation. Gravitational waves are a ripple in space-time predicted by Einstein.

The researchers were surprised to detect a B-mode polarization signal considerably stronger than many cosmologists expected. The team analyzed their data for more than three years in an effort to rule out any errors. They also considered whether dust in our galaxy could produce the observed pattern, but the data suggest this is highly unlikely. “This has been like looking for a needle in a haystack, but instead we found a crowbar,” Pryke said.

Pryke and his collaborators are working to improve the performance of the instrument and have received a $1.25M NSF grant which will allow the Keck Array to run until at least 2016.

Clem Pryke is co-leader of the Keck-Array project (with John Kovac of Harvard). The collaboration has members at UMN, Harvard, Caltech, Standford and other institutions. The Keck Array is supported by the National Science Foundation and the Keck Foundation.

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