Right. There's been a long running tradition of commentary on "the science content of science fiction" on this here blog. As there has been on Doug's blog - Doug, you might want to get in on this...
So Doctor Who. Assuming we're all comfortable with the fact that, having been obliterated by an over-sized thimble wielding a plunger, the Doctor was able to regenerate himself, let's deal with the real scientific misdemeanours of the season finale.
1) Whilst regenerating, the Doctor realises he is able to "siphon off" the excess energy from the regeneration process and channel it into his severed hand (which happens to be floating like a limp fish in a nearby glass case), thereby relieving himself of the inconvenience of changing bodies - and me of several months bemoaning the loss of David Tennant.
Wait. So is this because it's his hand? If so, why hasn't he been pulling off toenails and bits of hair and dotting them around the tardis (Tardis with a capital T?) in case of emergency? Being a timelord, you'd have thought it would have occurred to him before. And, according to Wired, he can only regenerate 12 times. Er, a) why has no one mentioned this before and b) is anyone keeping track? Oh and c) does this latest regeneration only count as half?
2) Now, I'm quite happy with the 27-planets-in-the-right-configuration-will-channel-enough-energy-to-destroy-all-matter theory. Yes, we'll let that one slip through. But did anyone understand how they towed the Earth back to the Solar System? Some sort of virtual lasso generated by a computer called "Mr Smith"... And let's not forget the dog. I'm sure he helped somehow.
3) If a human-timelord metacrisis is a problem, how long is it going to be before Billie's new beaux - Doctor Two (part Tate, part limp fishy hand) - gets into trouble? Or did it only cause a problem for Catharine Tate because her brain was too small to deal with it - yeah, probably. And do we care? Um, no. Despite certain similarities, e.g. actually being the same person, Doctor Two is nowhere near as attractive as our lord David Tennant. The Tate-isms are a real turn off.
Anyway, forget metacrises and fishy hands for a moment. Let's take a minute to remember Tate. Or not. As I've learned, the only way to enjoy her is to incorporate her into the now legendary Doctor Who drinking game*. According to The Rules, you must drink: every time there's a new monster (at least once an episode), every time the Doctor says "I am the Doctor" (at least a couple of times an episode), every time there's running (substantial proportion of most episodes) and every time Catherine Tate gets up your nose (=constant drinking). Dangerous.
*I'm not into drinking games. I'm very responsible actually. I was only enticed this once because it involved wearing silly hats.