Theory:Doctor Who television discontinuity and plot holes/Wild Blue Yonder

You are exploring the Discontinuity Index, a place where any details or rumours about unreleased stories are forbidden.
Please discuss only those whole stories which have already been released, and obey our spoiler policy.

This page is for discussing the ways in which Wild Blue Yonder doesn't fit well with other DWU narratives. You can also talk about the plot holes that render its own, internal narrative confusing.

Remember, this is a forum, so civil discussion is encouraged. However, please do not sign your posts. Also, keep all posts about the same continuity error under the same bullet point. You can add a new point by typing:

* This is point one.
::This is a counter-argument to point one.
:::This is a counter-argument to the counter-argument above
* This is point two.
::Explanation of point two.
::Further discussion and query of point two.

... and so on. 

Newton merely added a new definition to the existing word gravity, which already meant tending towards the centre of the Earth, so why does the episode treat it as if he made it up for the "Mavity" gag?

the doctor can tell when time changes as we’ve seen before, but he seems surprised to hear Donna use the word mavity for the first time.