Monday, May 13, 2013

Dancing on the Ceiling

While choreographed dances are bound by the laws of physics, certain tricks can make the seemingly impossible a reality. In the video below, you can see two dancers walking on walls, dancing on ceilings, and adapting to changes in the direction of gravity. Or so it seems.

Choreographer and dancer Derek Hough performed those feats about a week ago on the popular Dancing with the Stars TV show. Although Derek added modern flair to this trick, the method to his dance has been used in performances for over half a century. Surprisingly, this seemingly physics-denying method has even been used to simulate real physics principles in iconic movies.



So how does he do it? The room in the video actually rotates as a unit, and all of the furniture is nailed to the walls and ceiling. Also, the camera remains attached to the rotating room, making it appear as though the dancers are defying gravity.

Famed Broadway dancer Fred Astaire popularized this method in a dancing routine from the 1951 movie "Royal Wedding." In the video below, you can see how Astaire's performance appeared on screen and how it appeared to the crew filming the rotating room.



Space Odysseys and Artificial Gravity


Since Astaire's performance, several directors have reproduced this method in other films. 2001: A Space Odyssey, for example, had a variety of rotating sets that simulated the weightlessness of space on screen.

In the iconic film, astronauts live aboard a giant space station that generates artificial gravity. This idea extends beyond science fiction, however; in fact, NASA scientists have proposed building a spacecraft with a centrifuge to limit the negative effects of microgravity on crew members.

Such a spacecraft would have a large doghnut-shaped, rotating section. With enough rotational speed, astronauts will stay glued to the outer hull of the oval space station.

So why does rotation keep the astronauts stuck to the floor? The reason stems from the same physics behind the outward "force" you feel when riding a merry-go-round or spinning swing ride at an amusement park. Often called centrifugal force, the sensation you feel pulling outward is actually your body resisting the effects of the spinning ride. In short, your body's inertia causes the sensation.

Some rides take full advantage of this effect by spinning riders who are pinned to a wall before removing the floor from underneath the riders. Consequently, the riders seem to "float" above the floor while sticking to the wall.

The riders' bodies are constantly resisting the spinning motion of the ride; if the walls suddenly fell down, the riders would fling out tangentially. Instead, the walls push back on the riders, and the pseudo centrifugal force counteracts the centripetal force that points toward the center of the ride.

In 2001: A Space Odyssey, a rotating room mimics this effect when a stewardess walks into a centrifuge that seems to flip the direction of gravity. In the two following videos, you can see how the scene appeared on film and how it appeared to the film crew.

Original Scene


Rotating Camera


More Examples


Anyway, let's get back to some more rotating room examples. One of my favorite scenes that used the effect comes from Christopher Nolan's thriller about dream hijacking: Inception.



And no list would be complete without Lionel Richie's Dancing on the Ceiling. Here's a behind-the-scenes look:



Den of Geek has a more complete list of movies and music videos using the rotating room.

Hopefully with these behind-the-scenes explanations, you can keep these rotating scenes in perspective.

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