Frequently in Doctor Who, both in the new series and the old, there's mention of something called "artron energy", a form of energy that saturates time-travelers, in particular the Doctor but also Amy Pond, Rose Tyler, River Song, and at one point Mickey. It seems to be something that can be harnessed for power, something that has harmless (or possibly benevolent) mutagenic effects, and something that (possibly) provides resistance to strange temporal effects. But what is it, and where does it come from? Usually, people just assume that it's a form of background radiation from the Time Vortex. But because I'm more pathetically geeky than that, I'm going to suggest a stranger alternative.
The key is in the phrase occasionally used to describe the Doctor, "Complex Space-Time Event". Presumably, this differentiates him from a simple space-time event, which gives us a hint as to the nature of a CSTE. Because a simple space-time event is one that has a beginning, a middle, and an end. If you were to be able to draw an outline of it in four-dimensional space, it would have a single continuous shape; even though it moves through three-dimensional space, it is always connected in four-dimensional space. (If I move ten feet to the left, and you could see through time, you would see me as sort of a weird John-shaped tunnel through time.)
Think of it like a stylus moving on a seismometer. The stylus moves up and down erratically, but the line is always contiguous, and always moving forward. That's a simple space-time event. Always contiguous, always in one direction.
But the Doctor doesn't. He can, for lack of a better analogy, lift his stylus up and move it back to an earlier point on the paper. The shape of the Doctor in space-time is not one long line winding its way through three dimensions, it's a series of apparently unconnected shapes in various parts of the graph. He cannot be described with the normal geometry of space-time. He is, in short, a Complex Space-Time Event.
It's my suggestion that the act of traveling in time, moving in ways that are discontiguous, builds up a "charge" almost like shuffling across a carpet builds up static. (At this point in the explanation, my lovely wife reminded me of the exchange from the series itself: "Is that really how it works?" "No! But if that makes sense to you...") Normally, it evens out because you're properly in synch with space time. But Complex Space-Time Events don't dissipate the charge normally, they build it up...and that's artron energy.
Make sense? No? Good. At least I got it off my chest.