by Tom Rogers
A madman has placed a bomb aboard a city bus filled with unsuspecting riders. The bomb will demolish the bus if it slows below 50 mph (80.5 km/hr). Just when disaster seems certain, a heroic cop perilously jumps aboard and bravely takes charge. After numerous near disasters on congested streets, his superiors—typical bosses who, of course, always know best—unwittingly direct him onto an uncongested route containing an unfinished overpass bridge with a 50-foot gap. Naturally, to keep from exploding, the heroic cop orders the bus’s driver to speed up and jump the gap— doing the impossible to compensate for his bosses’ directive.
I had written that the jump couldn’t have been made on the bridge as shown in the movie. My reader wrote that if I watched in slow motion I’d see that the jump was actually done. Sure enough, when viewed this way, there are images of a bus flying through the air—exactly what the moviemakers wanted viewers to see. But look closer: the incline or ramp required for jumping is nonexistent. At the gap, the bridge is flat. Even traveling at 70 mph (113 km/hr), when the bus reached the far side of the gap, the bus would have been about 3.8 ft (1.16 m) below the roadway, slammed into the edge, and been blown apart by the bomb. (See Chapter 8 for more detail on speed.) As for the missing section of bridge, look even more closely: it’s possible to see its shadow on the ground below. There was no gap. It was created on film with thousands of dollars worth of special effects.
Even thousands of dollars worth of special effects couldn’t gloss over flaws in The Core [XP] (2003). The entire movie was based on an absurd premise: a sinister earthquake weapon, developed by an unscrupulous scientist working for misguided military men, had stopped the rotation of the Earth’s core thereby disrupting Earth’s magnetic field. A group of stereotypical movie heroes, inside a magical ship, must bore down to the core and restart it. In the process, they risk their lives braving the horrifying dangers of various petty human conflicts, not to mention other inconveniences like pressures and temperatures exceeding those directly beneath the Hiroshima atomic bomb blast.
It seemed obvious The Core did not contain rigorous science. Yet, in response to my review, a self-proclaimed scriptwriter indignantly wrote that “the science in The Core was mostly accurate.” His key argument: the moviemakers had retained a PhD scientist as a consultant.
In reality, the moviemakers retained not one but three respected planetary scientists (all with PhDs). They were used for the momentous task of providing background information like: “. . . . the scale and size of things, how hot it gets in the core and what kind of material could conceivably withstand such a temperature.”1 (Hint: There isn’t one.) Who cares that the science consultants didn’t sit in the director’s chair and didn’t have real authority over the movie’s content. Just being there said . . . well, that they were there. The man who did sit in the director’s chair (Jon Amiel) and did have authority over movie content described it as: “…a little bit of science, a certain amount of fact and a lot of fiction.” Strangely, the movie’s science accuracy didn’t seem to top his list of concerns. He is, after all, a boss and may have bungled the description, but then the PhD science consultants were mysteriously silent about correcting him.
California Institute of Technology physicist Dr. David Stevenson was not so silent. At about the time the movie came out, he had actually published a paper in the prestigious scientific journal Nature–— to the glee of The Core’s producers who smelled publicity—outlining a way to send an unmanned probe into the core. Although some of his colleagues scoffed at it, the proposal had a serious purpose: to generate discussion. However, even Dr. Stevenson admits it was close to science fiction: The Earth’s crust would be split with a nuclear bomb and the crack filled with a million tons or so of molten steel topped with a small probe.The molten steel would sink towards the core, carrying the probe with it. In theory, the probe would last just long enough to send back some information before being destroyed by the extreme conditions.
The joyful producers contacted Dr. Stevenson, offering payment for public endorsements—a golden opportunity for both the movie’s backers and the good doctor. He declined. It wasn’t the “fantastic/ridiculous stuff about sending a manned probe to the core”; he felt this could never be mistaken for serious science because it was obvious fantasy. (Wow, if only he knew.) Instead, he primarily objected to the movie’s premise that the core had stopped rotating, thereby disrupting the Earth’s magnetic field— a notion he describes as “just silly.” Furthermore, he had issues with the movie’s simplistic explanation for how the magnetic field is generated.
Certainly, Dr. Stevenson qualified as an open minded and imaginative scientist and had a reputation as such, so his less-thancomplimentary public comments about The Core must have really hurt.The movie’s producer contacted Dr. Stevenson, yet again, and chewed him out as though he had actually taken their money. Dr. Stevenson doubts he will ever be asked to consult on another movie.
The Core’s trailers alone boosted it to classic status. I was inundated with requests to review it even before it hit theaters. Rarely have I seen such excitement. The Core became a major contender for the distinction of “worst physics movie ever.” (See Chapter 20: All-Time Stupid Movie Physics Classics) It’s so bad it’s good. However, asserting that The Core’s science is “mostly accurate” is like insisting the Earth is mostly flat. At first glance it does look that way but even a little research shows it isn’t.
While not so noteworthy as The Core, Pearl Harbor [PGP-13] (2001) achieved status with its make-believe history as well as its make-believe physics (see Chapter 8). It tells the story of a young band of WWII fighter pilots stationed in Pearl Harbor just in time to survive various romantic entanglements as well as distractions, such as being strafed and bombed by Japanese planes.
Of course, the devastating U.S. defeat at Pearl Harbor isn’t the stuff for a traditional Hollywood happy ending. No problem—the moviemakers merely modified history: Pearl Harbor recruits were trained to fly fighters by, no less than, the famous Jimmy Doolittle and later assigned to fly bombers in his famous raid on Japan. The actual raid did little damage in Japan but was a public relations triumph in America and a useful high note for the movie’s ending.
When WWII started, Doolittle was actually in Detroit helping the auto industry prepare for wartime production. He had nothing to do with training Pearl Harbor-based fighter pilots and not a single one of them participated in his famous raid. In my movie review, I briefly commented about the moviemakers’ manipulation of history. (I have had at least one veteran write me that the movie made him sick to his stomach but, as mentioned earlier, military guys tend to be cranky. Geez, I wonder why.) The physics of dropping bombs in level flight is totally different from the physics of dogfighting. So, of course, training fighter pilots for a critical bomber mission when experienced bomber crews were available made perfect sense—in dreamland. The real Doolittle raiders were all from experienced B-25 bomber crews as would be expected.
Several readers wrote, with great authority, that the movie was right. One even recommended a book on the Doolittle Raid from a reputable author who backed the movie’s account. This seemed incredible and when I contacted the book’s author it turned out it was. He told me his book said nothing about fighter pilots from Pearl Harbor flying in the Doolittle Raid and that the idea was preposterous.Yet, I know of at least one otherwise intelligent individual who could pass a lie detector test while describing nonexistent passages supporting the movie’s false account.
Why would so many believe the movie’s bogus account? It had a persuasive pseudo-explanation: Pearl Harbor pilots were the only ones with combat experience. Combine this with compelling images and dramatic dialogue overlaid with rousing music and it went straight to the subconscious as fact. Of course, such misconceptions can be jolly fun, but internalizing them doesn’t exactly lead to clear thinking—but then, maybe one shouldn’t set such high expectations.
Lets be honest—extensive knowledge squeezes the very
joy out of misconceptions and heartlessly ruins their chances of being internalized. I have friends who can’t watch a movie version of a coma patient without commenting. Their son was in a coma following a serious traffic accident and they know all too well what real comas are like. Why of course, the patient suddenly wakes up fully alert years later and within hours proceeds to use undiminished martial arts skill for revenge against bad guys just like in Kill Bill [NR] (2003). Yeah, right. Real comas are heartwrenching. Their victims almost always require lengthy physical therapy and rarely completely recover.
Any form of knowledge makes it harder to digest nonsense, and physics knowledge is no exception. Blatant disregard by moviemakers for well-established physics often gives people with physics knowledge mental indigestion. But, here’s a shock: physics knowledge isn’t the problem—ability to discern truth doesn’t lead to a life of boredom and suffering. It leads to a pleasant sensation: understanding. Internalizing cleverly packaged nonsense is the real problem; it leads to muddled thinking. Still, some may find this type of thinking, if not desirable, at least entertaining. For those who do then, please, read no further. It will spoil your fun.
Summary of Movie Physics Rating Rubrics
The following is a summary of the key points discussed in this chapter that affect a movie’s physics quality. These are ranked according to the seriousness of the problem. Minuses [-] rank from 1 to 3, 3 being the worst. However, when a movie gets something right that sets it apart, it gets the equivalent of a get-out-of-jail-free card. These are ranked with pluses [+] from 1 to 3, 3 being the best.
[-] [-] [-] A major plot pretext which defies the well established physics principles commonly taught in high school. In the best case, this brands a movie as a cinematic comic book or a fantasy.
[-] [-] Scenes which defy the well-established physics principles commonly taught in high school, and are not essential to the plot.
[-] Using an obvious stupid movie physics cliché.
[+] Avoiding lengthy mumbo-jumbo explanations when stretching physics in a gray area and using this technique only when it’s required for telling the story.
CHAPTER 2
MOVIEMAKER MATHEMATICS:
How Hollywood Shoots from the Hip
COUNTING SHOTS
The action hero kicks open the door and steps through with akimbo (one in each fist) .45 caliber Mac 10 submachine guns. At first the villains are dumbfounded, even though there’s a dozen of them and only one action hero. In predictable ignorance they reach for their weapons. The double Macs blaze out a high calorie response at a combined rate of 2,000 rounds per minute. Bottles and mirrors explode as bullets chew up everything in sight.The action hero sweeps the room with gunfire continuously for three minutes. Eventually, when the double Macs fall silent, the bad guys look like ground beef patties.
So, where are the sidekicks with wheelbarrows? Only 1.8 seconds of continuous fire empties the thirty-round magazine of a fully loaded Mac 10. Push a button, drop an empty magazine, snap in a fresh one, and it’s ready to zip off another thirty shots. Even if the action hero spends half his time reloading (of course, done off camera), in three minutes the two Mac 10s will blast out 3,000 chunks of lead weighing 15 grams each, for a total of 99 pounds (45 kg)—not including the weight of 3,000 empty cartridge cases and one hundred empty magazines now scattered on the floor. The action hero would need a sidekick with a wheelbarrow just to supply the ammo. Besides, how’s the hero going to reload when he has a weapon in each hand?
The hero could reduce weight problems by using a submachine gun with a slower firing rate and smaller bullets—at a cost of appearing less macho. But then the benefits would be mostly academic.When fired, gunpowder inside a cartridge burns, producing extremely hot, high-pressure gasses, which not only propel the bullet, but also momentarily torch gun barrel internals with a white hot flame. If not allowed to cool, the moving parts in any submachine gun, Mac 10 or otherwise, will seize, similar to the way a car’s engine eventually seizes when driven with an empty radiator. The short cooling time available during reloading would not prevent the disastrous temperature increase caused by three minutes of maximum rate firing. Submachine guns are lightweight devices designed for firing in a few, short, intermittent bursts.
Characters in The Matrix Revolutions [NR] (2003) actually did supply ammunition with wheelbarrows during the loading dock battle. Alas, the wheelbarrows weren’t for realism; they were a plot device used for placing a young hero in imminent danger.
The scene depicts a group of humans who have escaped from slime-filled bathtubs controlled by machines, who now live joyfully in a bleak, underground city. They are forced to make an Alamo-like stand when the machines decide to tunnel down and wipe them out. Their Alamo is a large concrete-domed room called the loading dock, which is defended, at least partly, by enormous, humanoid robotic devices called APUs, each of which is controlled by a person strapped to its front. Two gorilla arms extend from each APU torso, with heavy-duty, automatic 30-millimeter cannons attached in place of hands. These fire pretty much continuously at an invading horde of octopus-like machines called sentinels, which conveniently stream by the thousands directly toward the cannons.
The scene’s young hero—apparently underage for driving an APU—is relegated to the unglamorous task of wheelbarrowing ammunition. He waits nervously in a tunnel until the APU he is supplying runs out of ammunition.The situation is desperate. He scrambles to resupply the APU just as its driver is mortally wounded. The lad not only ends up driving the APU, but also using it to heroically save the day, at least temporarily.
It’s all very thrilling, except that using wheelbarrows to supply two cannons is as effective as powering a bus with a hamster wheel. Let’s assume a firing rate of six hundred rounds per minute for each APU cannon, and a cartridge similar to the 30 × 113-millimeter round used by the U.S. military in Apache helicopter gunships. Each cartridge has a mass of 447 grams. The total mass of ammunition required for one minute of sustained fire by an APU with both cannons blazing is a whopping 1,180 pounds (536.4 kg). A box containing one hundred rounds would weigh over 98 pounds (44.7 kg). With both cannons firing, this box would last a mere five seconds. Keeping the APUs supplied with ammunition would not have required wheelbarrows; it would have required a fleet of Mack trucks!
Hollywood moviemakers, traditionally, have never felt a need to count gunshots and keep them to a plausible level. In the heyday of cowboy movies during the 1950s, all handguns were six-shot revolvers, yet bursts of gunfire so regularly exceeded six shots that it became a hackneyed joke among moviegoers.
Counting shots was actually a plot gimmick in Clint Eastwood’s famous portrayal of a 44-magnum toting, rulebreaking detective in Dirty Harry [PGP] (1971). After shooting it out with bank robbers, Eastwood approaches one lying wounded in the street. As the robber is about to reach for a nearby shotgun, Eastwood levels his hefty revolver and goes into a lengthy dissertation about whether he has fired five or six shots. He had fired six but manages to bluff the bad guy into surrendering. In a later scene, Eastwood repeats the lines while leveling his revolver at a clever psychopath who is also about to reach for a gun. Unlike the bank robber the psychopath goes for the gun, but this time Eastwood isn’t bluffing. While bank robbers might be stupid, at least they’re not crazy.
Today, action movies are filled with semiautomatic handguns, which can blast from half a dozen up to twenty shots before reloading, not to mention the ubiquitous, rapid-firing submachine guns. Audiences simply can’t count shots like they used to. Nevertheless, filmmakers have actually begun responding to the jokes about firearms never running out of ammo. Movies now show guns being reloaded, at least occasionally. Eventually, Hollywood will also have to face the fact that submachine guns can’t be used in sustained fire for more than a few seconds. In the meantime, there are always wheelbarrows.
THE GEOMETRY OF SHOOTING FROM THE HIP
Hollywood is as creative about the geometry of aiming s
hots as it is about counting them. In movies, shooters—if they’re good guys—routinely hit tiny targets when firing handguns from the hip without using gun sights, while bad guys routinely miss, at least, when shooting at the hero. In reality even well-trained police officers can easily miss a human-sized target when shooting a handgun from the hip at distances over 10 feet (3 meters)—which just might explain why they’re trained to use a two-handed hold along with the gun sights. A little geometry combined with some physics illustrates why.
For simplicity let’s mathematically model hip-shooting as though the handgun has no recoil, the shooter’s elbow is fixed in space, and his wrist has no flexibility. Bullets tend to drop due to the downward force of gravity, but at close range the drop in a handgun bullet is so small that we’ll overlook it. The point of impact for the bullet, then, will be determined only by the alignment of the end of the handgun’s barrel, with a line drawn between the shooter’s elbow and the target. Let’s call this the aiming line.
This model of shooting from the hip focuses on horizontal misses, because the critical area—the torso and head—of humansized targets is roughly twice as tall as it is wide, so it’s easier to miss in the horizontal than vertical dimension. (These assumptions may seem too simplistic, but if a simple analysis indicates that a miss is likely, then a detailed one accounting for complexities like recoil, bullet drop, hand tremors, and misalignment of the body’s many joints will make missing even more likely.)
