Hollywood Physics

Take a look at a few of cinema's most mind-boggling moments of scientific inaccuracy-plus a few rare films that manage to get things (mostly) right

As we reach the close of the summer blockbuster season, reports of a recent paper by two professors at the University of Central Florida recently caught our eye. In it, the physicists Costas Efthimiou and R.A. Llewellyn assert that movies are making their students dumber. ""Sure, people say everyone knows the movies are not real," says Efthimiou, "but my experience is many of the students believe what they see on the screen."

Whether you believe them or not, it's always fun to take a scientist's eye to the silver screen to see just how ridiculous things can get when directors and screenwriters set poetic license against physical reality. High-school physics teacher Adam Weiner does just that in his great new book Don't Try This at Home! The Physics of Hollywood Movies. Here, we take a look at a few of the worst offenders, and at the actual science behind them.

Deep Freeze from Above

In The Day after Tomorrow, the scariest antagonists (besides the alien zombie dogs on board the abandoned cargo ship) are the roving "hurricanes" of sub-zero air that put anything that falls below the "eye" of the storm into a deep freeze. In the film, these storms are said to derive their freeze-ray powers by rapidly sucking cold air (â€100Everett Collection

Enemy of the State: Right! Faraday Cage

Kudos to another unlikely laws-of-physics abider: the Will Smith vehicle Enemy of the State. In it, a kooky exâ€National Security Agency operative played by Gene Hackman lives and works in something he calls "the Jar," a structure surrounded by a copper mesh that he claims keeps the NSA's prying eyes off him because of its imperviousness to radio frequencies. As you've probably discovered yourself while in a building constructed with certain types of reinforced concrete, some materialsmetals have a knack forwill soaking up static electrical fields and sappping your cellphone reception--and copper is one of them. Whether built intentionally or not, this type of metallic shield is called a Faraday cage, after lifetime physics-hall-of-fame member Michael Faraday. Put simply, copper's conductivity effectively cancels out most electrical fields that come into contact with it, keeping the area inside a radio-free zone. Since the mesh surrounding Hackman's "Jar" is particularly fine, and because most radio and television waves have a wavelength of 500 fivecenti meters or more, they aren't able to penetrate. Come on in, Will, you're safe here!Everett Collection

Armageddon: Last by a Longshot

Oh Armageddon, where do we begin? Brought to us by master-of-realism Michael Bay, this 1998 film is among cinema's worst physics offenders. Let's try to tackle one of its most hilarious distortions of reality, the one at its core--that a nuclear warhead placed on an asteroid the size of Texas could successfully blow it apart, preventing a catastrophic collision with Earth. Let's ignore the fact that asteroids don't have fault lines, and if they did, they would not be easily detectable. Let's also put aside the fact that the prescribed 800-foot-deep hole in a Lone Starâ€size asteroid (Texas is 700 miles wide) would barely even scratch the surfaceonly get you 0.0004 percent of the way to the center. Or that Bruce Willis and friends miss their landing site by 26 miles, presumably putting keeping them away from the "fault line" anyway. Let's just focus on the amount of kinetic energy needed to blow an asteroid apart, and for its two massive halves (approximately 3 x 1025 kg each) to move far enough (one Earth-radius perpendicular to the impact trajectory) to miss the Earth in the three hour and 56 minute timeframe that marks this mission's absolute deadline. Granted, this calculation assumes a ton of ideal conditions, which almost certainly wouldn't exist. But even in a perfect scenario, a total kinetic energy of 3 x 1025 J would be necessary to separate the asteroid halves and propel them at the required 460 m/s. The biggest warhead built to date has a yield of 100 megatons, or 4.1 x 10^17 J. That's one one-hundred-millionth of the energy Bruce would need to save Earth--making this flick a bomb in more ways than one.Everett Collection

2001: A Space Odyssey: Right! Rotational Gravity

(Very) occasionally, a movie comes along that not only avoids completely defrauding the realities of the physical world but actually manages to get things mostly right. Most famous among these stellar students, especially in the sci-fi genre, is Stanley Kubrick and Arthur C. Clarke's 2001: A Space Odyssey. One of the concepts the film manages to tackle with accuracy is artificial rotational gravity. In the famous opening segue from a prehistoric monkey battle to the space age, we see a giant circular space station slowly revolving. Inside, people can walk and sit in chairs just like on earth. The shot stays put long enough to note that the station appears to be spinning at around one revolution per minute. Now, to simulate gravity, the centripetal acceleration created by the rotation must be equal to the acceleration due to gravity on Earth, or 9.8 m/s2. The radius of rotation also needs to be large enough for there to be minimal difference between the relative rotational velocity of a person's head and feet (something that-again- Armageddon fails to take into account). A quick calculation based on the 1rpm speed requires that the station have a diameter of 980 meters, or about the size of 10 football fields-huge, yes, but shown as such in the film. So you can't fault them for that. Oh, and this film portrays the silence of space better than any other I´ve seen. Bravo.Everett Collection