Will we ever get to rewind time, or fast forward through it? Sanden stops by to tell us all about how time works. He also has a couple ideas about how we might make time travel a reality! But one tricky thing about time travel is that it’s full of paradoxes — so we look into those, too. And science fiction expert Lisa Yaszek swings by to tell us just how long humans have been thinking about time travel (hint: a really long time).

Listen closely for the mystery sound, and the moment of um: how do clothes get dirty even though you can’t see it?