TODAY MARKS five years since SciFriday debuted on SkyWatchTV! We celebrate by showing that first effort and discussing why Sharon is now literally half (but also twice) her former self.

Also: New research suggests that more than half of us are already resistant to SARS-CoV-2, which is very good news. In fact, it means we may have already reached “herd immunity” in many places.

See every new episode at www.SciFriday.tv!