Hold on to your solar system, the Milky Way may be in store for a galactic collision sooner than anticipated. And speaking of collisions, evidence from craters on the Moon as well as an apparent dearth of craters on the Earth (I just wanted to say dearth and Earth in the same sentence) suggest that the current rate of asteroid and comet impacts on the Earth is 2-3 times higher now than it was a few hundred million years ago. Zoe Landsman joins us for a traveling Addie to discuss all this, new research on the likelihood of life in the ocean of Europa, and Top quark trivia.