Vorsted-Gatt is as good a name as any for a comet! Comets are usually named after the scientists who discovered them, for example Hale-Bopp, Schwassmann-Wachmann, Shoemaker-Levy, and of course, Halley's Comet, the most famous of all. Vorsted-Gatt were a pair of names created by a random name generator with an obscurity factor of about eighty. Who they are or were doesn’t matter too much.

Mass and density are important factors in studying comets. The Vorsted-Gatt comet has a higher mass and density even by the first set of statistics than most of the famous comets of the Earth solar system. When Christo’s TARDIS gets the true figures it is a real monster. Annoyingly nobody seems to have put a list of comets according to mass and density on the internet, or at least not within easy reach by Google search, but take it from me, it’s a big one – a Billy special.

Of course, Chrístõ could have taken his Chrysalids with him on this trip and talked to them about mass and density in a clever way. Instead he has 3c with him, a bunch of underrated and undervalued kids who aren’t as thick as they are assumed to be. Even so, he does have to find creative ways to get the information across. These are children who wouldn’t want to listen to statistics. Talking about a big snowball, especially the sort Billy the class bully would make helps them connect. Of course, this is pure Doctor Who logic. The Doctor has to have somebody with him on a slightly different intellectual level to whom he can explain things that the audience will understand. The important thing is to explain without dumbing down. Not an easy task. I think it is achieved here.

I might be slightly out in my time scale for the disaster. I’m not sure if three weeks is long enough for a chunk of broken planet to travel through a solar system and cause so much devastation. All the most intelligent films about meteors striking planet Earth, for example Armageddon and Deep Impact allow time scales of months or years from identifying the threat to the actual catastrophe. I am assuming that the comet ripping the planet apart would send the chunks flying towards the Beta Deltan sun with some considerably more speed than an asteroid simply going astray from the asteroid belt or some other travelling object in the system. I hope so, because I have always complained about the Sarah Jane Adventures episode (Whatever Happened to Sarah Jane) in which a meteor approaches Earth within less than a day, and I don’t want to be open to the same sort of criticism.

The crux of the story, of course, is that Chrístõ acts like a typical Time Lord at first, not interfering with the affairs of the Human population of Beta Delta other than passing on the information to the authorities. When he finds that the Humans fail to act, however, he knows he has to go back and act as an untypical Time Lord. It is a dilemma for him, because he also knows that going back and changing things is disapproved of.

How he would change things was a big problem. I have already had a Ten story in which The Doctor moves a comet through time to make it avoid a planet. I didn’t want to repeat that trick. The clue was there all along in all that talk about mass and density and snowballs. I decided to have the TARDIS melt part of the comet so that its mass and density were reduced back to the safe size. How it did that is probably best not dwelt upon. Just assume that the TARDIS can do much more than just fly through time and space.

And don’t forget that comment at the end by young Billy, when he notes that they, the below average students who everyone dismisses, saved their solar system from disaster but nobody will ever know. They won’t even get to be recognised as heroes. Chrístõ assures them that HE knows, and that satisfies them. Look for more stories to come in which 3c prove their worth!

http://en.wikipedia.org/wiki/Comet