In this new episode of Short Talks from the Hill, a podcast from the University of Arkansas, Daniel Whitmire, an instructor in the mathematics department and a retired astrophysicist, discusses his theory for the existence of Planet X.

In 1985, Whitmire and collaborator John Matisse published an influential study suggesting that mass extinctions every 27 million years on Earth might be explained by the effects of an unproven planet orbiting the sun every 54 million years.

"We took our cue from the dinosaur extinction that was known to have been caused by impact of a comet or asteroid in the Yucatan Peninsula," Whitmire says.

Recent studies by paleontologists about mass extinctions have renewed scientific interest in Whitmire's theory.

To hear Whitmire talk about Planet X and mass extinctions, go to ResearchFrontiers.uark.edu, the home of research news at the University of Arkansas. Listeners can also find Short Talks From the Hill podcasts under the "Local & Podcast" link at KUAF.com.

Short Talks From the Hill highlights research and scholarly work at the University of Arkansas. Each segment features a university researcher discussing his or her work. For more information and additional podcasts, click on the Multimedia link at ResearchFrontiers.uark.edu.