Russell T Davies, showrunner on Doctor Who, has said that the ongoing references to “mavity” instead of gravity won’t be explained, even though there is an explanation.

Davies says:

“It’s not resolved, it’s permanent. It’s absolutely permanent. That’s what gravity is. It’s funny. It’s very funny and it makes me laugh and it’s staying.

“It’s enormously funny. All the comic strip people are having to do it, all the novel people are having to do it. How funny is that? I think people are kind of looking for a plot in it. I can’t imagine what that would be. What on earth would that be? If anyone came up with a good plot based on the fact that a word has changed two of its consonants then good luck. He said, having built entire plots out of puns!

“In the end, it’s immensely creative. That’s what’s brilliant.”

… Is it, though?

Okay, we get what RTD was going for: this was supposed to signify that time can easily change; we might infer that it foreshadows the Toymaker and the worlds of fantasy colliding with Doctor Who — i.e. the universe has suddenly changed because of the gods’ interference — but now he’s said that there was no plot in it, that possible reason has been wiped off the map.

So it’s because it’s “funny” and “creative” apparently. And I respect RTD a lot, but I don’t think it’s either of these things. It’s just sort of there.

And in future, it’ll wind its way back to “gravity” because it’s such a weird thing to uphold long-term — every mention of “antigrav” tech will have to be adjusted and similar, future audiences are going to be confused without a regular explanation, and other writers will move on. It’s not really permanent either then. So, uh, that’s mavity, the curio of the Fourteenth and Fifteenth Doctors’ eras.