Sciencey Wiencey: Space Mopeds, Free Falls & Living Heads

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Guest contributor Caleb Howells investigates some questionable Doctor Who science.

Doctor Who is absolutely full of bizarre, ridiculous concepts. I’ve already covered some of the main ones, but now I’ll be looking at some specific things from individual episodes. I’ll start off with the ones that caused quite a bit of uproar from the fans, complaining that they were too unrealistic. But were they really? Well, we shall see about that.

Space Moped

The Rings of Akhaten promo pics13In The Rings of Akhaten, the Doctor and Clara have a ride on an unusual moped which rides through space, from one asteroid to another. Like a terrestrial moped, it has no covering. The people riding it are completely exposed, so how can the Doctor and Clara survive?

The show doesn’t elaborate at all, but we are left to assume there’s an air bubble around them. Now, is such a thing possible? Yes, as it turns out. It’s called a plasma window, which was developed for a particular type of welding which needs to be done in a vacuum. The plasma is produced by some means, and magnetism is used to form and control the plasma, keeping it in the desired shape. The plasma particles move about so rapidly (because plasma is very hot, and heat is simply the kinetic energy on a very minute scale) that the air particles can’t get past them.

In that use, the plasma window contains a vacuum, keeping out air. But we can just as easily do the opposite, which is what would be the case for the space moped. However, we see Clara reach her hand out to Merry and even make contact. To do this, one of them would have had to have been putting their hand through the plasma, which would have severely burnt them. That clearly wasn’t the case.

But note this. In the climax, when the Doctor goes to confront the monster, he can hear people from another asteroid singing. Yet there’s no air in space, so how could this be? Evidently, there was an air bubble around the entire asteroid system, meaning that there was still just as much air around the Doctor and Clara when they were flying between asteroids as when they were on them.

However, there’s a problem. I wasn’t able to find out the exact specifics of what a plasma window looks like, but apparently it’s very bright. Yet we can clearly see the background of space in the episode, with nothing blocking the view. Oh dear.

So, it’s almost possible.

The Tenth Doctor’s free fall

tennant-falls-end-of-timeTowards the end of his final story, the Tenth Doctor takes quite a fall, first crashing through a glass roof and then landing on what looks like a stone floor. This has been criticised a lot by fans, myself included, saying that it was completely over the top and way too unrealistic. Part of the reason is because the Fourth Doctor received a fatal injury from a much less impressive height.

For this section, I was going to time exactly how long it took the Tenth Doctor to fall, allowing me to then work out how high he fell from and then calculate the speed he was going when he hit the glass. I would then try to work out the injuries. I even found a professional research paper on free fall injuries while gathering information for this. However, I’m not going to do any of that. Why? Because I don’t need to.

During World War 2, an American pilot was flying over France, when a German plane shot him down. He ejected, but to make his day even worse, his parachute wasn’t working. He fell from about 22,000 feet – considerably higher than the height the Doctor fell from – and eventually landed in a train station. It had a glass roof, which is what broke his fall. He was injured, but alive.

This is basically a worse version of what happened to the Doctor, in some ways. The pilot was a human, not a Time Lord, and he fell from much higher than the Doctor did. However, I suspect the pilot was wearing a helmet (again, I wasn’t able to find out the specifics of this, so I’m surmising).

It seems, then, that the Doctor’s fall is actually rather probable. Well, not probable, but possible. There are an abundance of cases of people who have survived “definitely” fatal falls, and with the Doctor being a Time Lord, he has even more of a chance than most.

Surviving in space

doctor-smith-explosion-ship-christmasAt the beginning of The Doctor, the Widow and the Wardrobe, the Doctor is on a spaceship that’s about to attack Earth. He presses a button which causes the spaceship to explode. As it falls apart, the Doctor ends up hanging out of an exposed end of it, trying to reach a spacesuit. It gets torn from it’s attachments and is sent tumbling towards Earth. The Doctor decides to join it. He eventually catches up with it and climbs inside.

I remember a lot of people complaining about this scene in the comments of articles about the episode. I don’t know if most people actually said what they thought should have happened to the Doctor when in space, but I’m now going to tell you what would actually happen if you were in space without a spacesuit.

You wouldn’t explode. This is a relatively popular belief, annoyingly. In actual fact, the internal pressure of your body would be contained by your connective tissue, firmly keeping your body intact. That’s one point for the Doctor.

Secondly, your blood wouldn’t boil. This is also a popular belief, but again, it’s not true. Your blood is inside your body, therefore being in that enclosed, internal pressure I just mentioned. So far, so good.

Thirdly, you wouldn’t freeze. You would be in a vacuum, remember? So, just like how a flask keeps coffee hot, your body wouldn’t loose heat either. Well, you would, but only by radiation, rather than through conduction. So you would freeze to death eventually, but certainly not instantly.

However, this is where it starts going downhill for the Doctor. All the air in his body would be forced out from his lungs and intestines. Then the moisture on his tongue would start to boil and the blood vessels on the surface of his body – particularly the eyes, for obvious reasons – would break. And then the blood that’s directly exposed to the vacuum of space would boil.

What about the fact that, well, there’s no oxygen in space? Apparently a human can survive in a vacuum for about 15 seconds before they black out. But the Doctor’s a Time Lord, so he would reasonably be expected to last longer.

So, what happened in the episode was unfortunately not possible, but it wasn’t as ridiculous as most people claimed it was.

Living on a cloud

The-Snowmen-Doctor-Who-Christmas-Special-Trailer-(4)In The Snowmen, the Doctor parks his TARDIS on a cloud in the sky. He describes it as being made of “super dense water vapour.” I’ve never actually heard anyone complain about this, but it bothered me.

As a minor point, clouds aren’t made out of water vapour. They are made out of water droplets. Water vapour is invisible.

But anyway, that’s not really important.

Seemingly, the only thing special about the cloud was that it was incredibly dense. If the water droplets were dense enough to stand on, then the cloud would be, well, ice. Sure, you’d be able to stand on it. But it wouldn’t be able to stay in the air.

Living heads

Doctor-Who--Wedding-of-River-Song-trailer--(5)In The Wedding of River Song, the Doctor is taken to a cave system full of the heads of the people who the Headless Monks beheaded. “[They] behead you alive,” as Gantok puts it.

This is utter nonsense. Let’s presume the wound is cauterised, therefore stopping blood loss. Well that’s good, but your brain cells still need oxygen (4 or 5 minutes without oxygen results in permanent brain damage). So let’s say that at the wound, there are nanobots which take the oxygen from the air outside and put it into your blood. They would also have to pump it round the head, but let’s give them the benefit of the doubt and say they can do that.

There’s still a big problem. Your cells require nutrients (which is why you need to eat, in case that wasn’t clear). The nanobot system can’t provide this, so how are you supposed to get food? You can’t. Even if someone feeds you, the enzymes in your mouth can only break down certain types of food.

So far, I’ve been talking about Dorium’s condition. But it gets much worse when you consider the skulls. They are literally just skulls, with no skin or blood system, and look completely unaltered. If nothing else, how are they supposed to move?


In this article, I’ve discussed only a fraction of the ridiculousness of this wonderful show. However, I’ve tried to address some of the more commonly brought up issues with the science, as well as certain ones that I personally dislike. Hopefully this will help settle some debates about those particular things.