The alternative title for this post was going to be "Yes, I know it's science fiction but I spend my time hitting my head on the sofa from sheer frustration when they try and do faux sciency bits and I don't see why you shouldn't suffer too" but I thought it was a bit long.
So, for those of you who don't watch Doctor Who, or have amnesia, the Daleks were plotting to destroy everything by aligning 27 planets in a certain way, including Earth. Presumably there was a feature in Evil Villains Monthly!1 about this, as it has featured in many a dastardly plot2 — although the Daleks were unusually pro-active in stealing and assembling the planets themselves rather than just waiting for the time to be right.
We learn that the planets 'fit together like an engine' and channel a stream of 'z-neutrinos' out into the universe at large. As far as I know, there is no such thing as a z-neutrino. However, if I had to be hit by a stream of subatomic particles, I would choose the neutrino — it was named 'the little neutral thing' for a reason. It barely interacts with anything, to the extent that billions of them have been passing through my head every second ever since I was born, with no apparent detrimental effects.
However, the z-neutrinos will apparently have the effect of cancelling out the electromagnetic field everywhere they touch. This explains the unusual choice of planets for doomsday device construction: if you want to make a large-scale field to focus destruct-o-beams with, you'd usually use something a bit stronger than gravitational fields (the electromagnetic field between two particles is 1,000,000,000,000,000,000,000,000,000,000,000,000 times stronger than the gravitational, which is why a fridge magnet sticks to the fridge despite an entire planet pulling down on it).
The Daleks' plan is to destroy everything by negating the electromagnetic force. It's true, this would tear atoms apart and nix all chemical reactions. But nuclear reactions would still be fine, so there would still be nuclear fusion to drive the stars — although without the repulsive force between positively charged particles, making it hard for protons to fuse together, fusion would happen faster. Neutron stars, which are held together by gravity and prevented from collapsing by the repulsion between the neutrons within them, would also be fine, as would black holes (if anyone could find the continuing existence of black holes a comforting thought).
I guess the main problem is that without EM fields, you can't emit or transfer energy as photons (the smallest possible packet of electromagnetic energy, made of an electric and a magnetic field crossed at right angles and oscillating alternately — AKA light, radio waves, etc). Since this is how heat travels through the vacuum, life would be a bit screwed without photons. So yes, it would be a cold, dark universe, with no planets, asteroids or other fun bits of rock, but it wouldn't be just dust or nothingness. Davros has not been keeping up with his theoretical physics.
It transpires that the planet-moving was accomplished with a Magnetron. This is very exciting — I'd been using mine to make the microwaves in my, um, microwave3, and all this time I never realised I could kidnap planets with it!
Finally, after the Daleks are foiled (sorry, was that a spoiler? come on, you know the Doctor always wins) the TARDIS and the Magnetron are used to pull the Earth back into position. Oddly enough, people on Earth are shaken around when this happens — despite the fact that the entire atmosphere is moving with them and there's nothing for them to buffet up against. Besides, we're hurtling through space all the time, and we don't fall around normally. And anyway, if as some result of culinary planet transportation (I'm still thrilled with my doomsday kitchen white goods) the Earth started to shake that much, Tokyo, New York, and all other cities with tall buildings would be rubble. I imagine this would dampen the celebrations somewhat.
But if you have to take away anything from this episode, take away the next big Olympic sport — Dalek curling.