UC to host public talk on ‘dark energy’

Ratra was part of a group of researchers in the 1980s whose models contradicted conventional wisdom at the time that suggested the expansion of the universe was slowing down. Instead, Ratra and his colleague Nobel laureate Jim Peebles suggested that the expansion was actually accelerating because of something now called “dark energy.”

“We call it dark because it doesn’t seem to absorb or emit light. And we call it energy to distinguish it from matter,” Ratra said. “It’s not energy in the same sense as nuclear or chemical or electrical energy. All we can observe is its gravitational effects.”

But the theory is fundamental to a lot of other fields of astrophysics, he said.

Ratra is a guest of UC physics Professor Rohana Wijewardhana, who also studies dark energy and dark matter.

Wijewardhana likened the way we study the expansion of the universe to how we observe the Doppler effect.

“It’s like when a train is coming toward you, the frequency of the sound increases. When it moves away from you, the sound changes again,” he said. “If you look at galaxies, they’re moving away from us because the universe is expanding.

“The nature of dark matter and dark energy are unsolved questions in physics,” Wijewardhana said.

Ratra said now is an opportune time for physics students to pursue careers in cosmology, the study of the universe.

“Everyone has seen the new pics from the James Webb Space Telescope,” he said. “It’s a great time to get into cosmology as a career.”

Featured image at top: The James Webb Space Telescope captures an image of the colorful Carina nebula. UC's Physics Department will play host to Kansas State University physicist Bharat Ratra who will give a public talk about why the universe is expanding at an accelerated rate. Photo/NASA/