Physics in the Movies

nucal writes "Here's a site rating Insultingly Stupid Movie Physics. A really thorough site with a rating system which ranges from GP (Good Physics) to XP (Obviously physics from an unknown universe)." My vote goes to the helix of M&M's.

Comments

Explosions in space

[SVDave]

I am reminded of what J. Michael Straczynski, creator of Babylon 5, said about the sounds of explosions in space in B5. He said to think of it as music. In the real world, there's no music in the blackness of space, playing dramatically as ships go by, but even physicists don't get upset when they hear music in space in the movies. So think of the sounds of the explosions as music, added for effect.

BTW, I was mildly amused by the ego on display in their review of The Matrix:

The Matrix had real potential as a cerebral thriller. ... We would have preferred less oracle mumbo jumbo. ... The Matrix fails to meet its potential because it just can't leave the artificial science in the computer simulation along with the artificial intelligence.

Somehow, I don't think the creators were aiming to make it a "cerebral thriller". If the maintainers of intuitor.com didn't like The Matrix, that's fine, but they should review the difference between "fails to meet its potential" and "fails to meet your expectations."

Re:Outrunning the sun

[Spock the Baptist]

Arrrrrgh! No! no! no!

Mr. Ebert confused the speed of the shadow of an object on Earth with the speed of the Earths Terminator.

Here's my e-mail to Mr. Ebert...

Mr. Ebert recently wrote in his review of THE MUMMY RETURNS:

"4. I have written before of the ability of movie characters to outrun fireballs. In "The Mummy Returns," there is a more amazing feat. If the rising sun touches little Alex while he is wearing the magical bracelet, he will die (it is written). But Rick, carrying Alex in his arms, is able to outrace the sunrise; we see the line of sunlight moving on the ground right behind them. It is written by Eratosthenes that the Earth is about 25,000 miles around, and since there are 24 hours in a day, Rick was running approximately 1,041 miles an hour."

Mr. Ebert is in error.

Mr. Ebert has over-simplified the geometry, and physics of the velocity of shadows generated by the Sun.

While it is true that the Earth's rotates with an angular velocity of ~7.29e-5, and thus has a tangental rotational velocity of ~1041 mph, it is manifestly untrue that a shadow cast by mountains, canyon walls, etc. also travel at 1041 mph.

The velocity of the shadow is a function of not only the Earth's angular velocity, but also of the hight of the object, the time of day, as well as the time of year.

Consider the shadow cast by a flag pole. The length of the shadow is infinite at sunrise, but at local noon it will be at minimum at local noon. If the pole is located along the equator, and it's an equinox the the shadow will have a length of zero. Thus in six hours the shadow will have gone from infinitely long to infinitely short, thus having an average velocity that is infinite. (It is written by Zeno of Elea) A second example may serve to make my point a bit better. Consider the same day, and the same flag pole, but this time let us stipulate that the flag pole is 100 feet tall. As 09:00 local time the Sun will be 45 degrees above the horizon therefore the shadow will be 100 feet long as the oppsite, and adjacent sides of a 45 degree right triangle are equal. Thus, in the three hours between 09:00, and 12:00 local time the shadow of the flag pole will have moved 100 feet. Thus, the average speed at which the shadow will move in this period will be 100 feet / 3hours = 33.33... feet per hour, or ~0.0063131313... mph. Manifestly, this is very much less that 1041 mph.

How does they know these things are unphysical?

[rsidd]

I'm not at all impressed by their movie reviews. Take AI, which gets their worst rating: they're not impressed that the robots are self-sustaining, "what about energy, refuelling, rebuilding?" They claim it violates the laws of thermodynamics. Well, first law -- how do they know it's being violated? Maybe the things run on solar energy, or geothermal energy, or some such thing which is not inexhaustible but is "forever" on the timescales we're concerned with. Second law -- the earth is not a closed system, it constantly gets energy from the sun. Second law doesn't apply. Maybe they have automatic robot factories which run on solar power, it's not impossible.

That wasn't the only example. He can't conceive of a machine which can act as a helicopter and a submarine at the same time -- but a hundred years ago people couldn't have conceived of helicopters in the first place. Why should he evaluate everything by present-day technology?

The Phantom Menace review was even worse. There was no real "physics" being objected to, only stuff like "if the force field can stop water, why doesn't it stop humans who are 80% water?" If we don't know how it works, how can we pass judgements on such things? Perhaps it actively detects the presence of humans or biological objects. Perhaps it only stops liquids and not solids. Perhaps any number of other explanations.

Remember Clarke's third law: "Any sufficiently advanced technology is indistinguishable from magic." Conversely, in the movies, anything which looks like magic could be the product of sufficiently advanced technology.

Overall, I'm not impressed.