What exactly is dark matter?

Thu, 02/02/2017
Picture Credit: 
UCI Physics
BBC World Service

Kevork Abazajian, a cosmologist at the University of California, Irvine, during an interview with BBC World Service on Newshour [said]: Dark matter has been a puzzle for almost 90 years as to what it is, and it basically is something that is contributing to the gravitational pull within galaxies and groups and clusters of galaxies ...

You can listen to the full podcast here. His segment begins at 18:46.