'We Don't Planet' Episode 4: What's the Evidence for Dark Matter? | Video

Astronomers can’t directly observe dark matter, but they know it’s there. In fact, the mysterious stuff is far more abundant than the “normal” matter we can see and touch. Learn about the evidence for dark matter in the fourth episode of "We Don't Planet."   

credit : Paul M. Sutter: Co-Host, Writer, Anna Voelker: Co-Host, Writer, Doug Dangler: Producer