Thursday July 24, 2003
Talk bad science
Â· It is possible to be too rational. So there I was, having a quiet hungover moment with a friend at the weekend, watching Honey I Shrunk The Kids with his daughter, when suddenly he could take it no more. “Surely if pressure is proportional to force divided by surface area, and the area of their feet is proportional to the square of their dimensions, then shrinking a human by a factor of 100 will increase the pressure per square inch exerted by their feet by a factor of 10,000.” Milly, having clearly dealt with similar issues on many previous occasions, didn’t even bother to look up from the screen. “From 2 psi (per sq inch) to 20,000 psi, sufficient to break concrete,” continued her father, triumphantly. “They get lighter too, dad,” she mumbled. “Well even if that’s true, their surface area to volume ratio has increased so much that they should be freezing to death. And their legs would snap, since the strength of a structure is also proportional to the cross sectional area.”
Â· Now, the international superweb being what it is, you are never alone, no matter how deviant you are. And so I am proud to be able to present you with our big find of the weekend, the Insultingly Stupid Movie Physics Pages (www. intuitor.com/moviephysics/). It’s their indignation that makes it such good fun. For example, from their review of Star Wars: “In the great battle scene, the bad guys drive up in giant tanks and attempt to blast the good guys who are protected by their force field. This force field is transparent to visible light but nevertheless repels blasts of visible laser beams.” And they reserve particular derision for spaceships exploding in space (where there is no air, and no one can hear you scream) and the fact that you cannot only see it, but also hear it, with the sound waves miraculously arriving not just through a vacuum but at the same time as the light.
Â· But it gets worse. Proper little Rottweilers, these physicists, and they follow through on the maths. People flying backwards when hit by bullets? Not when the velocity of the victim will be equal to the velocity of the bullet multiplied by the ratio of the mass of the bullet to the mass of the victim – 0.4 miles an hour, they reckon. Copper-plated bullets flashing off steel? They snort with laughter. And 1,000 rounds a minute from a gun, for three minutes, works out at 45kg of metal. So where are the henchmen with the wheelbarrows full of ammunition? And now ask yourself, will the world be a better place when we are in charge? Of course it will be.