Animators tend to be magicians on the
paper – making things disappear and reappear at will. In doing
this, we break a fundamental law of physics. The law of conservation
of mass tells us that mass is neither created nor destroyed. This is
a core principle across scientific fields form chemistry to physics.
It's quite intuitive as well – things can squash, stretch, break
and bend, but their mass cannot disappear or be created from nothing.
Animated films tend to break this law because animators can determine
where and how much mass a character might have frame to frame. In
fact, in hand-drawn traditional animation, maintaining consistent
volume and mass on a character from drawing to drawing is one of the
most essential and challenging parts of the job. Three good examples
of animators breaking this law can be found in the films Despicable
Me, Wreck-It Ralph, and the TV cartoon, Courage the
Cowardly Dog. Breaking the law of conservation of mass is a great
use of the freedom of the animation medium.
When two supervillians have an all-out
duel to steal the moon, you know some laws of physics will probably
be broken. Despicable Me is a fun film with physics that
appear to be inspired by the animation of classic Looney Tunes. The
film has cartoony physics throughout, but a pivotal moment at the
climax hinges on its unrealistic depiction of physics. In the scene,
the protagonist Gru uses a shrink ray to shrink the moon down to a
hand-held size. He then brings it back to Earth and is able to hold
it in his hand. Looking past the made-up science of a “shrink ray,”
the shrinking of the moon is a violation of the law of conservation
of mass. When Gru shrinks the moon, its mass goes from enormous to
minuscule – and when we see Gru holding it in his palm while on
Earth, we see that it weighs as much as a baseball. The mass just
disappeared. If the shrunken moon was incredibly dense, as though the
entire mass was squeezed into that small ball, it would have passed
the test. While this alternative could have led the story another
good direction, the filmmakers decided to ignore this law of physics
and let the story carry on, logical or not.
Another example of ignoring the law of
conservation of mass can be found in Disney's Wreck-it Ralph.
Depending how you see it, this film takes place in another universe
than ours. The video game world is wilder and more exaggerated
physically than ours. In the racing game, Sugar Rush, the animators
took our laws of physics and gave them an overdose of sugar. The
sequences in this game are full of bouncy characters, fast cars, and
interactive candy as part of the setting. In one scene, Felix and
Sgt. Calhoun are trapped in a pit of Nesquik sand underneath a tree
of Laffy Taffy vines. By making the vines laugh, the vines grow down
from where they are hanging just low enough for our heroes to grab
them and be rescued. This scene breaks the law of conservation of
mass with the spontaneous growth of the Laffy Taffy vines. Triggered
by laughter, the vines acquire mass out of thin air. The vines did
not stretch to reach down to reach our heroes – this would
have been acceptable under the law of conservation of mass. The
animators broke the law of conservation of mass because it is not an
issue with the audience. In this case, it was even staged to enhance
the gag and distract you from the physical law they were breaking.
As mentioned earlier, traditional
hand-drawn animation can be more prone to breaking this law of
physics. This is due to the fact that unlike 3D animation, hand-drawn
animation needs to be redrawn every frame, leading to varying forms
and volumes from frame to frame. Whether it's accidental or on
purpose, traditional animation is a great medium for breaking the law
of conservation of mass. One great example comes from the television
series, Courage the Cowardly Dog. The show is about a cowardly
dog whose family is constantly thrown into supernatural danger. The
animators had a lot of fun pushing the physics and shapes of the
characters. In the episode “Little Muriel,” Courage's mother
Muriel is turned into her younger self. We follow the tiny, bouncy
young girl throughout the episode, before Courage finally manages to
get her back to her normal size. He does this by throwing her into a
tornado – of course. In the end scene, we see Muriel and her
clothes grow to her normal self, at least five times the size of her
young self. Not only does she somehow lose her mass in shrinking down
to her younger self, but she acquires just that much mass later on.
Scenes like these can be found in just about any cartoon, and it will
never be an issue. Like earlier, the animators can choose to still
follow the law of conservation of mass in these shrinking/growing
scenes if they are going for a
certain gag. For example, if instead of being shrunk, the character
was squeezed down to
the size of a golf ball: same mass, different size. This goes to show
how understanding these rules of physics can drastically change the
effect of a story.
The law of conservation of mass is fun
to break. The idea of something disappearing or shrinking, appearing
or growing, is an instant gag great for animation. For traditional
animators, it's as simple as changing the volume of a character from
frame to frame, whether it's intentional or not. For 3D animators, it
involves changing the pre-defined masses of your characters. Either
way, it is a law of physics that is constantly broken. Being aware of
this law can benefit an animator in creating scenes like the ones
explained here.
