crisscrossing Science Episode 094: Dark Matter

In this episode, Mike Crosser (professor of physics at Linfield College) and Chad Tillberg (professor of biology at Linfield College) discuss some of the theories as to why the Sun is orbiting within the Milky Way faster than it really should be. The Sun, in fact, isn't alone. Most stars, especially at the edges of most galaxies, are also moving too fast. Is there some dark material causing extra gravity, and is there another way to think about gravity?