Science Fact or Cinematic Fiction: Gravity

Gravity may be the most ubiquitous of all physical laws among the layman. Its effects are witnessed constantly by everyone throughout their entire lives so this is not necessarily a surprising fact. What is surprising, however, is the amount of leeway the typical audience is willing to give entertainment media in its violation of this rule. The only loose consistency among film, games, and animation in regards to gravity is that it’s still generally in the downward direction. Aside from that, these three mediums will either stretch or entirely disregard the rules associated with this aspect of the physical universe for the sake of cinematic titillation. Typically, these violations are made to great success in arousing excitement in the viewer.

Breaching the rules of gravity is an easy way to appeal to the very primal emotions people associate with falling or flying. Exaggerating a fall from a ledge or building in film can incite a nervous uneasiness in the pit of the audiences’ stomach similar to what they might feel were they actually in the situation that’s happening on the screen. Likewise, giving the player-character in a video game the ability to fly may invoke an enlightening sense of freedom in the player as they’re suddenly able to explore a virtual world without borders or perform physical feats that in reality would be impossible for them. The explanation of the logic in either of these cases or the innumerable situations similar to them is minimal to non-existent, but the satisfaction they provide makes us willing to accept such impossibilities. When it comes to entertainment, regardless of the medium, gravity gets no respect.

Situations exhibiting nonsensical gravity occur often in film and games that involve interplanetary or interstellar travel. Among these titles, perhaps there is no more popular offender than the Star Wars films. When travelling about the vastness of deep space in starships, characters are always free to roam around the cabins unhindered by what should be zero gravity situations. There is no reasoning behind this in the films, though official Star Wars lore mentions a vaguely described device called an “artificial gravity generator”, which operates as a pseudonym for a magical force providing this gravity since current science is unaware of any means by which artificial gravity may be conjured by a single object onto another object and everything within it. Furthermore, there is a scene in second Star Wars film, The Empire Strikes Back, in which the characters land inside of a giant worm that dwells within a large asteroid. Uncertain of the situation, several characters exit the confines of the ship and walk around to explore the “cave” they’ve landed in. Here, the rationale of an “artificial gravity generator” is invalid since they presumably ventured beyond its influence when they left the ship and a body the size of an asteroid wouldn’t have enough gravity for the characters to move as if they were experiencing gravity similar to that on Earth. On the other hand, concerns about gravity are only one issue with this scene as the matters of air pressure and and temperature would also add complications.

So, is Star Wars guilty of ignoring the logic and laws of gravity for the sake of its fiction? Certainly. But is it alone in this violation? Well...

Your poorly explained "gravity generators" are unsatisfactory!

While live action may often utilize an elastic approach to gravity to simplify production or enhance action, in animation the laws of gravity may be broken for an even greater variety of reasons. A complication of the medium of animation is that every element in these films are fabricated from scratch. Gravity can just as easily be intentionally unbelievable as it may be unintentionally so. Also, in animation the rules of gravity may be subject to change constantly within the film, such as in Disney’s Tarzan. Leaping feats performed by the title character are far beyond what his less acrobatic and civilized counterparts can achieve not only due to his apparent superior physical strength but due to a seeming capability to suspend the effects of gravity when needed. For instance, during a chase scene that takes place approximately 35 minutes into the film, Tarzan performs some extreme vine swinging in an attempt to rescue Jane from angry apes. At the end of the chase, he makes one huge swing that launches him up from the trees he’s swinging on, out past the canopy, and onto one of the highest branches in the visible rainforest.

Tarzan, buddy, why not go to the moon while you’re at it?

While it’s tough to gauge the total distance traveled during that behemoth-of-a-swing due to inconsistent camera angles and motion in perspective, if we measure the slightly crouched Tarzan in that final frame as 5ft high, then Jane’s position at the peak trajectory stands about 20ft above that. Assuming that the total distance of the swing is only 40ft (the additional 20ft coming from the distance between the vine and the treetops in the first shot and the treetops to the bottom of the large branch in the second shot), then Tarzan managed to gain enough speed by swinging horizontally on vines to propel the combined weight of Jane and himself the equivalent height of a four story building. Furthermore, the effects of gravity operate on an object’s vertical motion at a parabolic rate. Regardless of whether an object is approaching its apex or descending from it, the acceleration or deceleration of motion should reflect this rate. If the rate of change in speed is identical for an object regardless of whether it’s traveling with gravity or against it, than the “Fourth Down at Half Time” rule should match up with Tarzan and Jane’s motion in this shot when played in reverse (“Fourth Down at Half Time” refers to the fact that an object will fall a quarter of the distance from its apex at half of the total time we are witnessing the fall). The entire upward motion of the swing takes 40 frames to complete and at the 20 frame mark Tarzan has just begun to enter the leaves of the canopy. If the large branch is our halfway mark and the canopy leaves stand approximately halfway between the branch and where Tarzan began his swing, than at half of the time of the entire motion he is closer to 2/3rds of the way down-- much further than he would if be the swing were realistic.

This is a movie with a constant investment in believable gravity as the prime visual appeal of Tarzan is his ability to swing effortlessly through the jungle like an ape. Yet, as previously illustrated, in certain moments of heightened action, the audience is willing to forgive certain embellishments if they can increase the excitement of the events. Having Tarzan zip like a torpedo to his destination on the branch a bit more quickly than is realistic may give the impression that he is in control of his motion when he’s in the jungle. Having a bit more air time at the apex of the swing may have been a bit “juicier” of an animated motion, but also could have made it look like Tarzan has a less-than-heightened ability to control his swings.

If film and animation are guilty of violating the rules of gravity as they see fit, games are guilty of entirely denying, freely amending, and publicly embarrassing them. A prime example of how games do this is the action title Ninja Gaiden.

In Ninja Gaiden, the player controls an angry master Ninja who must utilize all of his acrobatic and mystical skills to lay waste to an army of evil Ninjas and demons. Despite what many of the amazing feats Ninjas are capable of performing, the actions seen in the above video are entirely unrealistic. In the case of the multiple mid-air cross slashes (~30s), if one were to ignore the matters of teleportation and spontaneous acceleration, there is still a lack of downward acceleration as a result of gravity. An object in the air will always fall at a constant rate due to gravity regardless of its horizontal speed. Thus, the perfect horizontal slashes made by the hero ninja are--among other things--unrealistic.

Numerous other flairs of this performance also venture beyond simple exaggeration of realistic possibilities. At about 34 seconds into the video we witness a downward slice launch a decapitated head ten feet in the air, which would not happen regardless of the force of the sword strike. At 24 seconds into the video an enemy performs an air kick on the hero which launches him an additional five feet against the direction of gravity, yet the required force to achieve this action in addition to the pull of gravity would’ve launched the offending ninja directly into the ground. In fact, it’s safe to say that just about any action performed in this game that deals with gravity is, in one way or another, inaccurate.

Intentionally stretching the effects of gravity in film or games serves one primary purpose: to entertain. Violating this most commonplace of physical forces is a means by which entertainment media plays with viewers’ perception. Changing gravity can give added strength to a character we’re meant to believe is strong, it can give grace to characters we’re to believe are graceful, it can increase the impact of falling objects and make landings more painful. In the same sense that gravity gets no respect in film and games, it also gets tremendous respect because it is through the careful manipulation of it that an experience can be improved.