Warning: Didactic astrophysicist ahead

Fifty years ago, when Doctor Who first hit the airwaves, it was designed to be an educational show, with some fun storytelling to make it more interesting. That’s why Ian and Barbara—science and history teachers, respectively—were slated to be the Doctor’s Companions.

Admittedly, those “teachable moments” were awfully heavy-handed at first (take, for example, the scene where the Doctor outsmarts the Daleks’ lock mechanism in The Daleks, or the emphasis on the date of Robespierre’s downfall in The Reign of Terror). One has to admit, though, that they tried hard to make the stories make some sort of sense, from a scientific standpoint.

Fast forward to the modern era, and scientific realism seems to have been largely thrown out the window. As long as you can utter some technical-sounding gobbledy-gook (or timey-wimey-ness, for that matter), you’re good to go. Yes, I know that to “reverse the polarity of the neutron flow” makes no sense, either, but somehow I feel like writers these days aren’t trying even as hard as that.

Take my favorite example: The Impossible Planet. For this story, the eponymous body is said to be “impossible” because it’s orbiting a black hole, and therefore “shouldn’t exist.” That’s utter rubbish. Maybe it’s improbable that a single planet would be left alone (that is, without its parent star) orbiting a black hole, but from a gravitational standpoint, a black hole is no different than any other object until you get really close (about three times the Schwarzschild radius, if memory serves)—nowhere near impossible.

For a black hole the mass of the sun, you’d have to be about 10 km (~6 mi) from its center (the “singularity”) to notice the relativistic effects. Clearly, the “impossible planet” was vastly further than that. Even if the black hole in question was a million times as massive as the sun, an orbit would have to be within 10 million km for any unusual gravitational consequences to kick in. That’s fifteen times closer than Earth is to the sun (or about five times closer than Mercury is).

One can even ignore the actual measurements and see plainly that the characters are observing the black hole from a much greater distance than three times the “blackness” in space (the diameter of the event horizon, or twice the Schwarzschild radius) that defines the black hole. At a distance three times the diameter of the black hole, an observer would see it covering approximately 19° of the sky. When you realize that the full moon only covers 0.5°, simple observation tells us that the “impossible” planet was well outside of the distance at which relativistic effects kick in.

We all know that Doctor Who takes enormous liberties all the time, so why have I got my knickers in a bunch about this particular instance? Aside from the fact that the error is particularly obvious to me as an astrophysicist, they named the whole damn episode after a conceptual error. That chaps my ass.

For the most part, I’ve learned to tune out the regrettable scientific inaccuracies in Who. Every once in a while, like the above example, a particularly egregious (to me) one slips past my willing suspension of disbelief and ruins the moment. There’s so much that a writer can do with the format, that it seems a shame to throw so much real, mind-boggling, awesome science out the window for an easy out or cheap thrill. But I suppose I can’t expect everyone to place as high a premium as I do on the science, especially if it makes the storytelling more difficult.

Image via Reddit (bloodster8)