I spent an entire semester several years ago, watching science fiction movies for their bad physics and reading science fiction books for thier good physics. Gotta love it. I don't think I'll ever be able to look at Indiana Jones in quite the same way again. In fact, it's hard to watch any SF movie these days with the same ability to suspend reality as I used to have.
This text is copyright Christine Bell. Reproduction is prohibited without the express permission of the author. And yes, the instructor used this paper for later semesters as an example paper, so if you're thinking of copying it and using it to fill some assignment of your own, you'll get exactly what you deserve if the instructor recognizes it and boots you out on your ... tail.
While Raiders of the Lost Ark and Indiana Jones and the Temple of Doom may be considered good movies from a purely entertainment-oriented point of view, they are sadly lacking in physical and historical accuracy in many sections. Since a paper covering all of the inconsistencies and improbabilities in them would be impractical, I have arbitrarily decided to focus on some of the numerous problems observed in the movies' traps.
It should be noted for reference throughout the paper that the setting of these movies is the 1930s. Also of note is the fact that the traps being discussed were presumably set up by some ancient civilization in the very distant past. Additionally, it can be assumed by the accumulation of dust, debris, and assorted denizens lurking in and around the traps, that these traps are not maintained on a regular basis, if they are maintaned at all. These three factors are very important when deciding what was and what was not feasible in this setting.
The Light-Triggered Trap
The first trap to be discussed is one that appears to be light-triggered. That is, the trap is sprung when light from a hole in the ceiling is cut off from a sensor, presumably when someone walks in front of it. This triggers a very powerful and fast-moving set of horizontally-placed stakes, with the intent of impaling its victim.
The first flaw with this trap is that it would presumably also be sprung every time night falls, a storm darkens the sky enough to cut off the light to that cave, or a stray animal wanders through. This would be very impractical, considering the energy output needed to spring and re-load the trap at least once per day for several hundred years.
Another problem is that in order to have a light-sensitive trap, it would be assumed that one would need a photodiode or its equivalent. Since the photodiode had not been invented in 1936, much less in the ancient times when the traps were created, we are left wondering what device they used to sense light.
This trap gets sprung in the beginning of the movie, and later apparently re-loads itself and re-springs itself. Even the most well-made device has some loss of energy, as per the laws of thermodynamics . Therefore, there should come a time when the device no longer has the energy to continue loading and springing, especially with the amount of force and speed it appeared to have.
Since it has already been pointed out that this trap should have been sprung at least once per day since the day it was created, it should have run out of energy long before Indy and his hapless henchmen wandered through. (We are, of course, discarding altogether the thought of a perpetual motion machine, which, to date, has yet to be invented.)
The Pressure-Sensitive Traps
The next two traps consisted of pressure-triggered traps. The first one was triggered by stepping on certain parts of the floor, leading to the firing of projectiles. The second consisted of a heavy object on a pressure plate, and the release of a very large, well-rounded boulder. While it is possible to build a trap that is triggered by a pressure-sensitive plate, there are obvious flaws to both traps.
The projectile trap, while appearing ingenious and devastatingly deadly, leaves a few questions unanswered. When the pressure plate in the floor is stepped on, it triggers the release of arrow-like darts. Unfortunately for anyone stepping on one, they are released with an amazing amount of force. It would almost appear that compressed air, or something else exerting a great deal of pressure was impelling these objects. If so, where was such pressure coming from? One possible answer could be some tightly pre-wound mechanism that was released when the plate had weight put upon it. This, unfortunately would, in this writer's opinion, make it a one-shot trap, as there would not be enough energy being put into the system to load more projectiles into the mechanism, much less to create the pressure needed to eject them the next time the trap was stepped on.
The next trap, which involved the removing of pressure from a pressure plate (as opposed to the preceding trap, which was putting pressure on the plate), appears to considerably bend and break the laws of physics.
The scene involves a gold idol resting upon a pressure plate. Our "hero," Indiana Jones, looks at the statue, mentally weighs a small bag of sand, and then removes a handful of the sand before quickly replacing the idol with the bag of sand. The pressure plate that the bag rests upon, pauses for a few moments and then lowers before triggering the "rolling boulder of death."
The first point to note is that the bag of sand is smaller in volume than the volume of the idol (even if the idol was hollow, which is unlikely). Since sand is only 3-4 times as dense as water, while gold is 9-11 times denser than water, it would take roughly 3 times as much sand to replace an equal volume of gold. Obviously, Indy's courses in science either didn't include much study of physics, or he had a very poor memory.
If, as was assumed, the idol was solid gold, the trap wouldn't have been triggered as easily as it was, because of yet another detail to which Indy seems oblivious. The idol should have weighed roughly 250-350 pounds , which is far too heavy for a single-hand grab, and, unless one is a weight lifter, to heavy for even a two-handed grab.
It seems odd indeed that removing something heavy from the pressure plate, and replacing it with something lighter would cause the reaction it did. The pressure plate, perhaps using a spring or other balance mechanism, should have risen higher when a lighter object was put on it, not lowered. Yet, not only did this trap lower with the lighter object on it, but it paused for a while first, as if even the trap was unsure of the logic behind its own moves.
The trap further strains our belief by then causing a very interesting chain of events that have very shaky physical explanations, at best. A tremendous force causes walls to start falling, a door to start closing, and, later, a large, heavy boulder to start rolling.
Perhaps the falling walls could be explained by an explosive charge placed somewhere behind them. But where would they have acquired explosives from in that ancient time, especially ones that would still have some effect in 1936? Also, the walls continue to shake, as if some great mechanism is constantly agitating them. Not only do we see no evidence of such a powerful mechanism, but we also have no explanation for the tremendous output of energy.
The door, like others from Indiana Jones and the Temple of Doom, falls at an inconstant rate, and even appears to raise at times in between camera shots of it. For a large stone door to be sliding down, its momentum should definitely be much more constant than it is. If it were to be able to lift and fall at a number of different rates, it would take a very complex door mechanism indeed, something that was not evident in the movies.
The final action of this scene, is for a very large and very heavy boulder to roll along an ancient pathway in a mindless attempt to flatten our hapless hero. Like the doors mentioned in the paragraph above, it seems to suffer from a chronic non-conservation of time. One moment it was moving much more rapidly than one would think it could, and the next moment it was moving slowly enough for Indy to outrun.
The Moving Ceiling Trap
The first trap from Indiana Jones and the Temple of Doom suffers from the chronic non-conservation of time that is viewed in many other spots in these movies. It also has, as do many of the other traps, a very large energy output with each triggering and release.
The diminutive sidekick first steps upon a stone button in the floor that triggers the close of the two doors into a room. These doors close with a relatively constant speed, unlike their actions when they are triggered but a few minutes later.
The kid then leans gently against a large stone projection in the wall. Considering the weight of the child, we must assume that the trigger mechanism is very well-oiled, for it moves into the wall and springs the next phase of the trap.
The ceiling, which is on what looks to be a well-greased roller, starts lowering. This is all well and good, and one would assume that Indy and sidekick should be quickly squashed.
To make matters worse, though, large, sharp stakes start coming out of the ceiling and the floor, in an attempt to impale the hapless adventurers. At this point, time and reality appear to warp.
One of the first dilemmas is that of the moving stakes. Not only were there no holes originally visible in the floor and ceiling, but the stakes suddenly have skulls impaled upon them. Holes large enough to have large stakes and skulls on them should have been much more noticeable. This, though, is one of the least of our anochronisms.
Against all odds, our rough estimate for a 30-50 second life span (a very generous guess, all things considered) for the two is increased to several minutes, as the movement rate of the trap increases, decreases, and reverses while waiting for our dubious heroine to arrive on the scene. Willie has time to don a bathrobe, grab a lamp, scream at the sight of two skeletons, scream at Indy while he screams at her, scream at bugs, and, in general, have several minutes-worth of hysterics.
Once she has finally pulled the release mechanism, we have another apparent large expenditure of energy. The ceiling rises, and the stakes retract almost instantaneously, and definitely much faster than they lowered in the first place. Again, we are left to wonder where all of the energy is coming from that is being used to so efficiently retract and basically re-load these traps.
The Water Trap
The final trap to be discussed does not fall into the conventional mechanical trap mode as do the others, but since it too has many problems with time (and velocity and volume), it was deemed, in this author's mind, to be worthy of note.
This trap's trigger consisted of the evil cleric having his minions remove the supports to a very large cauldron of water. Nonetheless, as with all cauldrons of water, it can contain only a finite amount of liquid. This water then proceeds to race down tunnelway after tunnelway, while changing speeds frequently.
For most of the scene it races rapidly and furiously after our hapless trio. Even though it appear to slow down so that Indy and friends can outrun it, it still exits the caverns with enough force to force large stakes through solid stone walls. On top of gaining an unreasonable amount of velocity along the way, it also seems to have increased in volume by about 10,000 times , since being released from the cauldron. While it is true that it could have picked up debris along the way, all of the obstructions should have slowed it down much more, as well as some of it should have been diverted through other tunnelways.
Most of these traps suffer from various types of non-conservation, as well as other impracticalities. The most common being a non-conservation of time, while non-conservation of energy (or apparently limitless energy), momentum, and other problems with velocity and volume are also observed.
Some of these problems would not have occurred if they were constructed with modern-day techniques (i.e., electricity, the photodiode, and hydraulics), but considering the time period of the movies and of the traps, they are impractical, at best. Other problems, such as the non-conservation of time, are not so easily solved. All in all, the viewer can feel well and truly trapped by the bad traps in these two movies.