Brian Cox. Stephen Fry. Those people who correct plot-holes in any film or show on TV. To some we are the lifeblood of the internet, providing endless reserves of irritation and high horses to climb upon, but we see our devotion to facts as carrying out a valuable service: battling against the all too casual vandalism of science. Doctor Who has always been a show full of engaging storylines but it's also one which often summons forth the inner-pedant in some science geeks: much as we love the programme, there are some gratuitous abuses of physics we simply can't allow to pass without comment. And by comment we mean the shaking of fists and litres of beverages wasted thanks to indignant snorting. So, which scientific ideas in Doctor Who are possible and which ones are the sign of a script gone mad?
Impossible Concept #5: The Gelth
Shrieking ghosts with a love for possession, murder and universal domination - what's not to like? Unfortunately thanks to gases seeking equilibrium there simply can't be anything there to like in the first place. Like any other dead animal, humans go through the unpleasant process of producing gases as they decay, so the gaseous forms of the Gelth would simply have no way of entering an area which is already under high pressure. While these creatures lack any scientific plausibility compared to the fate of real-life corpses, they more than make up for that by saving us from the alternative of the only TV show possibly more gruesome than Gillian McKeith's latest poo-sifting outing. When we consider that, their huge entertainment value is simply an added bonus.
Possible Concept#5: Weeping Angels
Prepare yourself for a quick bit of quantum physics here. You might want to join me in grabbing a coffee if it's getting late. We have billions and billions of atoms in our bodies and, by extension, an even higher number of electrons. These electrons are one of a few fundamental particles have a really bizarre property known as wave-particle duality, meaning that they display both wave and particle behaviors in certain circumstances. One particular wave behaviour they can display is interference which can make the electron appear as if it is in two places at once, but this can only occur when nobody is observing it. Think about it: we can force a subatomic particle to behave as a particle just by looking at it. That's pretty amazing, right? What does all of this have to do with the Weeping Angels? When nobody is observing them their quantum state is changed and their electrons could potentially be free to move as waves, so some of the particles in a normally innocent-looking statue could theoretically move silently through the room as a wave until someone halts this process by looking at it again. Who ever said science couldn't be completely terrifying to someone remembering the observer effect in a dark hallway at 2am?