Bad physics in the movies may be worse than none at all.
AT YOUR NEIGHBORHOOD BOOKSTORE, you can now pick upEverything I Really
Need to Know I Learned From Watching Star Trek. Within its pages, author
Dave Marinaccio offers such nuggets of wisdom as the following: "If you
mess up something, it's your responsibility to make things right again.
(Say you disrupt history and cause the Nazis to win World War II. To
correct matters, you have to let Joan Collins walk in front of a car even
though you're in love with her.)"
But when Mr. Marinaccio runs across Goliath (he is Dave, after all), he'll
pull out his slingshot, churn through his Star Trek physics to calculate
the trajectory to the ogre's eye... and promptly send the rock sailing
straight into the ground. Snap, crunch, bye, bye, Mr. Marinaccio.
Sir Isaac Newton, father of calculus and physics, has been doornail dead
since 1727. In the succeeding 268 years, physics moved on to curved space,
quantum mechanics, quarks, black holes. Still Newton-ignorance bedevils the
entertainment business -- and it could cost the lives of cavalier book
writers such as Mr. Marinaccio.
Last weekend, I was watching old Star Trek, the episode titled "Damned If I
Can Remember the Name, But It's the One Where Spock Cries, Sulu Runs Around
Bare-chested with a Fencing Foil and The Enterprise Goes Back in Time."
What makes Star Trek enjoyable is Star Trek moments. Every time McCoy
scowls at Kirk, saying, "Damnit, Jim, I'm a doctor, not a (insert some
other profession.)" qualifies as a Star Trek moment. This episode, with
Spock crying, Sulu dashing and Enterprise time-travelling, is chockful of
Star Trek moments.
The plot is pure Star Trek, too. A mysterious malady unhinges the crew's
inhibitions. Sulu fancies himself a swashbuckler. Spock despairs; his
Vulcan nature prevents him from ever showing love towards his mother. And a
generic Irish character named O'Reilly locks himself in the engine room
and, over the intercom, regales the ship with Irish drinking songs. All
this while -- and this is very important -- the starship Enterprise is
Just minutes before the end of the episode, Captain Kirk and Scotty the
Wonder Engineer finally break the door open and rush in. Scotty turns in
horror to Kirk and says, "He's turned the engines off. It'll take 20
minutes to get them back on."
Kirk swivels around, shouts, "But you have to. We're going to burn up in
the atmosphere in eight minutes!"
"That's impossible, captain!" Scotty protests.
"Youcan'tjustgoandchangethelawsofphysics." But it's Star Trek, and you know
the Enterprise isn't going to become a flying shish-kebab (at least not
until the third movie).
You might notice, too, that they have already gone and changed the laws of
physics. Real objects don't move the way they do in Star Trek.
I FIRST MET NEWTON'S LAWS in high school physics. During one class, Mr.
"Fizzix" Hicken rattled off the first half of Newton's Law. Objects at rest
tend to remain at rest. Stare at a rock. That concept settled happily in
some nook of neurons and rested.
By and large, a non-moving object doesn't start moving unless something
happens: someone picks it up, a large wind gust blows it, an earthquake
jostles it. Overcoming rest -- to thwart inertia, to a lug some piece of
something from Point A to Point B -- requires effort. It's a concept obvious
However, the Mr. Hicken's next sentence jarred me: "If the object is
moving, it'll keep moving." Through the rest of class, I sat there thinking
simply, He's wrong. It takes energy to keep moving. That's the lesson of
experience. Running in circles is exhausting. Unpushed swings stop
swinging. Rolling stones stop rolling, become resting stones, and gather
moss. Rest, I believed, possessed a privileged place in the universe, and
all things tend to rest.
Objects in motion tend to stay in motion.
Sir Isaac Newton devised the first theory of relativity. To illustrate
this old style relativity, let's say we have a watermelon and a pane of
glass. To avoid the complications of gravity(which has the annoying
tendency to pull things down) and air resistance (which slows stuff down),
let's say this pair of objects is hanging out in the middle of interstellar
space. As far as physics is concerned -- even the classical Newtonian sort -- a
watermelon zooming in on a resting pane of glass at 100 miles per hour is
exactly the same as if the watermelon were sitting motionless and along
comes this 100 mph piece of glass. It's just a different way of looking at
the same problem, different "frames of reference" in the words of
physicists. Where the watermelon and pane of glass end up depends only
their relative speed and direction. (Einstein, for his theory of
relativity, the one called special relativity, added the condition that the
speed of light is the same no matter what. That one condition leads, for
instance, to the paradox of twins aging at different rates if one goes
cavorting about the universe on a spaceship while the other stays on
Once you move the watermelon and glass pane from outer space to our
everyday gravity-bound existence, the preceding example is no longer true.
Gravity is an extra force that complicates the equations. But what really
changes everything is friction, that stickiness when two things rub.
Friction is the reason why the part Newton's First Law, having to do with
moving objects, is so contrary to common sense.
On Earth, there is a special frame of reference: the one with all the
resting rocks. The Earth is, obviously, much larger than the watermelon and
the glass pane. Objects are constantly rubbing against the Earth and the
layer of air it pulls along. When a baseball springs off a hitter's bat
heading for the deep right field bleachers, molecules of oxygen, nitrogen
and hydrogen BOIING off it and slow it down. The collisions between
ball, air and Earth scatter the ball's motion until its direction and speed
match that of the surrounding planet.
This is rest.
FORCE EQUALS mass times acceleration.
F = ma
That's the central lesson of high school physics: Newton's Second Law. The
force on an object is equal to its mass multiplied by its acceleration.
Winches and pulleys, blocks slipping down a slope, pendulums rocking back
and forth. Almost every problem is a variation of Newton's Second Law.
A quiz: Dave Giantkiller is swinging his slingshot around in a circular
motion. At the point indicated in the diagram below, he lets the rock fly.
In what direction does the rock go?
I WISH TELEVISION and movie writers wouldn't mess up three-century-old
physics. It's a hopeless wish. For instance, in the climactic scene of the
movie Batman, Vickie Vale tumbles off a very tall steeple in the Gotham
Cathedral. Batman jumps after her and catches her. Actually, I don't
remember quite how they end up falling together, but anyway, there they are
falling, destined to become sidewalk indentations, when the caped hero
throws out his bat-hook which snags a convenient hook-snagging portion of
the cathedral and brings them to swift stop in mid-air, well above the hard
You don't have to hit the ground to die. The force of breaking their fall
would likely snap a couple of necks and rupture a host of internal organs.
For the numbers-averse, skip to the next paragraph. For people who like
numbers, here's a back-of-an-envelope calculation. Mass: about 300 pounds
of Michael Keaton, Bat suit, and Kim Basinger. Acceleration: Assume the Bat
rope stretches about 10 feet. Terminal velocity -- the speed at which the
downward tug of gravity on a falling person is balanced out by the slowing
effects of air resistance -- is about 150 miles per hour. Those assumptions
lead to an deceleration of 1200 feet per second squared as the Bat rope
snaps taut. Convert those numbers into metric (physicists always use
metric, because it's simpler), insert them into F=ma, and here's the
answer: some 50,000 Newtons. Most people will think it odd that falling out
of cathedral will produce boxes and boxes of Fig Newton cookies, so here's
a picture (albeit a rather contrived one) of what 50,000 Newtons would do to
you: You're suspended horizontally above the ground. Three Toyota Corollas
are snugly attached to your belt. The cars are dropped.
Here's a one-number description of an equivalent situation. Take a long
rope. Tie one end securely to a building. Tie the other end around your
waist. Jump onto a motorcycle. Speed away from the building at 150 miles
per hour. Ride until rope runs out.
So, anyway, Batman should be dead, and a rather messy death at that. But
isn't "suspension of disbelief" synonymous with "movies"? If I can accept
for a couple of hours the idea of a millionaire running around in black
latex, why should a little wrong physics bother me? After all, science
fiction often revolves around fictional science. That isn't necessarily
bad. For the sake of story, it's often necessary to go invent some notion
like hyperspace to get the characters beyond the solar system and over to
the next star.
Sometimes I don't even mind wrong science. Star Trek is built on wrong
science. Despite all those time-travelling stories, the Star Trek universe
is, at its core, one that obeys the laws of Newton, not his successors.
Stardates flow at a steady rate, ignoring special relativity's expanding
and shrinking time conundrums. The Enterprise crew, zipping about the
galaxy at really, really fast speeds doesn't age any more slowly than the
folks back on Earth. Light travels at infinite speed. (Otherwise they can't
see what's behind them; the light would never catch up.)
It doesn't bother me that when Gene Roddenbery devised the Star Trek
universe he threw out Einstein's relativity. I don't expect television
writers to work through complex equations in order to write scripts.
Scientific preciseness would merely befuddle.
When starships fall out of the sky because their engines sputter and die,
however, that bothers me. Wrong science is no longer a storytelling
convenience designed to avoid obtuse technical jargon, but a cornerstone of
An orbit is a continuous state of falling. Air is again troublesome, so for
this explanation, let's go the moon (and ignore the slight atmosphere it
has). If you throw a watermelon horizontally, it'll go so far before
gravity tugs it back to the surface. Throw it faster and it'll go further
before it splats. But the surface of the moon is curved so that the farther
the ball travels, the farther it must drop before it hits the ground. Throw
the melon fast enough and the rate of falling is the same rate as the
surface curving away. The ball is in orbit.
Now remember Newton's First Law, the non-intuitive part of it. Objects in
motion tend to stay in motion.
The watermelon around the moon doesn't need any engines to stay up. Neither
did the Enterprise. Oh sure, some high-flying air molecules would bang into
them and might eventually knock them down. Such was the fate of NASA's
first space station, Skylab. But falling, the decaying inward spiral before
the final flameful plunge, took months, not minutes, and one would think
starships would hang out far outside the reach of the upper atmosphere
Answer to quiz: The rock is just like the watermelon around the moon,
except there's no moon, so there's no gravity, thus no force to drag the
rock down. So the moment it's let go, the rock zooms off in a straight
TO TEST THE PEOPLE'S KNOWLEDGE of physics, back in 1980, researchers at
Johns Hopkins University gave the above problem plus and three others to
undergraduate students there. A slim majority, 53 percent, answered the
slingshot question correctly. The most common wrong answer was to envision
the rock spirally outward (and into the ground). According to the
researchers, the explanations of those who drew the curving paths, were
"strikingly reminiscent of the medieval theory of impetus, which claimed
that an object set in motion acquires an impetus that serves to maintain
the motion." The students believed the rock somehow remembered that it was
moving in a circular path and sought to continue in that spiral.
In my physics class, Mr. Hicken gave us copies of the New York Times
article that reported the study's results. We were lucky. The previous
year, those four Johns Hopkins questions were the final exam in its
entirety. If I recall correctly, the class did so wonderfully, he had to
give them another final exam so as to not torpedo almost everyone's grades.
Encouragingly, though, in the Johns Hopkins study, students who had taken
physics did much better than those who had not. So it's a fixable
deficiency. But the converse is that those who have not taken high school
physics -- most people -- do not understand 300-year-old physics, to say nothing
of physics today.
Science has moved beyond Newton. Society must soon make important decisions
based on 20th century science: where to put nuclear waste, how to halt
global warming, whether to dabble in the genetic code. Yet if we cannot
figure out where a rock goes when it flies out of a slingshot, the
likelihood of correctly answering more difficult questions is not