Many years back I watched a Hunger Games film. I don’t know which one, but there was a huge clock and every hour some calamity was unleashed on the mannequins who were running around in the woods. I don’t remember much from this film, except a few scenes that bothered me.
In one scene, one of the mannequins tied some magic wire from some sort of magic tree and ran it into some body of water or other. Lightning would regularly hit the tree, because the tree wasn’t a tree, it was a lightning conductor or something. The mannequin wanted to redirect the electricity from the lightning-struck tree down to the body of water to kill whatever was in the water. Except that’s not how electricity works at all. The magic tree, it was explained in the film, had very low resistance. So attaching a parallel route to the ground of the same or perhaps slightly higher resistance was not going to suddenly stop the charge conducting to Earth via the tree roots. Also, electrifying the water would not have killed anyone in the water, because the water was already touching the Earth. Actually that mistake can be seen in games such as Bioshock too, but I digress.
The climax of this Hunger Games film involved one of the mannequins shooting an arrow with this wire tied to it at the source of the lightning. Except that isn’t how electricity works either. The lightning would strike because of the potential difference between the origin of the lightning and the thing being struck. Shooting a wire from the tree, which was the lightning conductor, back to the point of origin of the lightning would not have sent the lightning back whence it came. If anything it would have just grounded the point from which the lightning originated, stopping the lightning altogether. Ah, but they fired the arrow after the lightning had struck. So the charge had already reached the tree, where the potential difference between the tree and the origin of the lightning would have been great but in a polarity such that the charge would have experienced an electrostatic force away from the origin of the lightning, so the charge would have just continued to be conducted to the Earth.
I walked out of the cinema annoyed. The author did not understand basic electrostatics, and clearly neither did the publishers or anyone else in the publishing chain.
There have been many films where I’ve got annoyed because of bad physics. In the X-Men: First Class there’s a scene where Magneto used his special abilities to turn a radio telescope around, but apparently Magneto can turn off Newton’s Third Law because he, despite exerting a force on the dish, experiences no force exerted on himself by the dish of the telescope. I’ve mentioned this scene in a blog post before about Newton’s Third Law.
In Elysium, the space station has artificial gravity because it is rotating. The angular speed of the space station could produce the necessary acceleration at the rim to simulate earth’s gravity, to be fair, but the rim isn’t enclosed. The air in the space station stays in place around the rim just because of centrifugal forces (which are measurable in an accelerating reference frame, such as the rim of the space station, so no, there’s nothing wrong with talking about fictitious forces such as the centrifugal force). Two problems. Firstly. The atmosphere on the space station was not deep enough, so the air would have escaped into space anyway. Secondly, simulating gravity by rotating the body can cause vertigo and sickness for people because of conservation of angular momentum. Every time someone turned their head they would have felt dizzy, and trajectories of projectiles would have appeared to be bizarre and hard to predict because of the Coriolis effect.
Sci-fi very often gets physics wrong, but it’s not the only film genre to do so. In Pirates of the Carribbean: The Curse of the Black Pearl, two characters sneak underwater whilst breathing by capturing a pocket of air under a rowing boat. The rowing boat was made from wood, which is less dense than water, and the vessel was filled with air, which is significantly less dense than water, being held under water by humans, who are also less dense than water. And yet they all sank to the bottom of the sea? No. That’s just nonsense.
Physicists see mistakes in films others sometimes miss. What can be frustrating is that those mistakes are effectively being taught to people who watch those films. The films are teaching incorrect physics. When they are watched by children, who sometimes have no reference frame for the physics being mangled in the films, it provides them with such a reference frame. It’s second hand experiential evidence of how the world works, which does not match reality. Nevertheless, the young people now have this picture in their mind of how reality works because they’ve seen it work that way in a work of fiction designed to look as realistic as possible.
Then, physics teachers have to convince these young people to change their perception of reality and challenge misconceptions. They can do this by creating cognitive dissonance; making the young people see evidence that contradicts their construction of the nature of reality, which they gleaned through watching films or cartoons or reading books in which the physics is incorrect. Cognitive dissonance isn’t fun. It’s uncomfortable to discover that your view of the nature of material reality is wrong. Physics teachers can look like people whose whole raison d’etre is to catch young people out and proclaim, “ah ha, you were wrong!” In a way, that is precisely what we do. So it’s no wonder we are seen as arrogant!
A short while ago I found a cartoon online and, try as I might, I cannot find the original creator. There are lots of versions of this and it has almost become a meme in itself. I have shared this with my pupils in school before. I’ll share it here, but if you are the creator of this works and want me to take it down because it is under copyright, please do contact me. The image is pretty accurate. It shows the every day experience of physicists when talking with the general public about aspects of physics most people get wrong.
It’s no wonder we are called arrogant and aloof is it?
Physics with Keith 