I didn't enjoy it, partly because I find it creepy that Dr Who did an abortion metaphor episode, and because I find it even more creepy that in the end it was pro life holy shit guys, and partly because the science was so goddamn bad.
Firstly, just because you scale up an animal does not mean you scale up the bacteria living on it. Elephant bacteria and mouse bacteria are still bacteria-sized, why would a giant space creature have giant bacteria?
Secondly, how could a single celled life form maintain structure at that kid of size, in earthlike gravity? It would just collapse.
Thirdly, how would the crumbling moon just 'dissipate', at best it would form a dust ring around the planet or slowly drift away into space, it wouldn't just disappear like a fart in a spacious room.
Fourthly, how can the creature have been sitting there and growing for millions of year, yet the moon only increased rapidly in mass in the last 50?
Fifthly, how the fuck does a newly hatched creature immediately lay an egg, and how the fuck does it lay an egg almost the size of itself? Holy shit again, do these people actually know the mechanics of egg-laying or childbirth? Your alien laid an egg so big that it has to have a moon sized vagina
Sixthly, how exactly was the creature taking in the energy to grow to that kind of size? Was the energy already stored up in the egg in some kind of yolk? Was the egg somehow absorbing energy from the sun, perhaps? Either one is problematic for reasons I can't be bothered to explain.
Finally, why were there so many extraneous characters in this episode? All you needed were Clara, the Doctor and an astronaut. In fact, you could even have gotten rid of the astronaut and still had the same moral dilemma, and the same trick with the lights, at the end. The kid was annoying, why do you keep doing kid episodes? Gah.