NASA's Juno spacecraft will swing by Earth today for a "gravitational slingshot" that will send it toward Jupiter at 165,000 mph. To celebrate this triumph of science, Bill Nye is hosting "Why with Nye," an eight-part YouTube series that will explain the Juno mission and the some of the many mysteries of Jupiter. In this episode, Nye describes what we know (and what we have yet to learn) about the planet's Great Red Spot, a massive storm that's barely changed in more than 300 years. The best part of this video? Bill Nye in a raincoat and bowtie! In pretend rain! And lightning!