Scientists detected the gravitational waves after a pair of unusual black holes collided.
Riverside, California and Sendai, Japan, the largest city in the area hardest hit by the earthquake and tsunami, have been sister cities since 1957 and have maintained close cultural ties since then exchanging students, baseball teams and museum exhibits.
We speak with the mayor of Riverside, Ron Loveridge about how Riverside is responding to the tragedy.
Robin Young and Jeremy Hobson are hitting the road. Our Tumblr brings you behind the scenes of our election coverage.