An exclusive interview with Star Trek science advisor Erin MacDonald

Season 2 of Star Trek: Strange New Worlds goes boldly in many new directions for the series. But its most audacious moment isn't when Illyrian civil rights attorney Neera Ketoul calls out Starfleet's hypocrisy for discriminating against genetically modified people, or even when two lower deckers from the USS Cerritos stumble into the live-action universe of Strange New Worlds. It's when Uhura broadcasts a song into a fold of subspace, accidentally generating an "improbability field" that traps the ship in an alternative reality where everyone is forced to express themselves through music.

That is the surprisingly thought-out explanation for Subspace Rhapsody, Star Trek's very first musical episode, in which the crew of the USS Enterprise must figure out how to close the improbability field before disaster ensues. As Spock and Uhura attempt to analyze the phenomenon, they and other members of the crew begin spontaneously breaking into song, leading to embarrassing and character-revealing moments as the rules of the musical universe force them to divulge their innermost feelings. It could have gone off the rails quickly. But the episode manages to tell an entertaining, and very Trek-y, story about a crew trying to regain control of their ship after encountering an unexplained space anomaly. And the musical performances are pretty damn impressive, too.

The fact that this episode didn't feel like a gimmick is largely thanks to the input of Erin MacDonald, Star Trek's resident science advisor, who consults on every series currently in the works. MacDonald, who earned her Ph.D. in astrophysics before pivoting to a career in science communication and eventually getting hired to consult for Trek, worried that the musical episode would be impossible to explain with science. But when the writers insisted they needed a scientific reason for Spock to spontaneously start crooning about the intermix chamber, MacDonald rose to the challenge.

I recently spoke with MacDonald for a National Geographic article on science in science fiction. That article contains some highlights of our conversation on the science of Star Trek, but the entire interview was too damn interesting not to publish in full. It can be found below, lightly condensed and edited for clarity.