The Physics of Star Trek (21 page)

A famous experiment in high school physics involves putting an electric buzzer in a bell
jar, a glass container from which the air can be removed by a pump. When the air is
removed, the sound of the buzzer disappears. As early as the seventeenth century, it was
recognized that sound needed some medium to travel in. In a vacuum, such as exists inside
the bell jar, there is nothing to carry the sound waves, so you don't hear the buzzer
inside. To be more specific, sound is a pressure wave, or disturbance, which moves as
regions where the pressure is higher or lower than the average pressure propagate through
a medium. Take away the medium, and there is no pressure to have a disturbance in.
Incidentally, the bell jar example was at the origin of a mystery I discussed earlier,
which was very important in the history of physics. For while you cannot hear the buzzer,
you
can still see
it! Hence, if light is supposed to be some sort of wave, what medium does it travel in
which isn't removed when you remove the air? This was one of the prime justifications for
the postulation of the aether.

I had never taken much notice of the sound or lack of it in space in the series. However,
after Steven Weinberg and several others mentioned that they remembered sound associated
with Star Trek explosions, I checked the episode I had just watched“A Matter of
Perspective,” the one in which the Tanuga IV space station explodes.

Sure enough,
kaboom!
The same thing happened in the next episode I watched (when a shuttle which was carrying
stolen trilithium crystals away from the
Enterprise
blew up with a loud bang near the planet Arkaria). I next went to the most recent Star
Trek movie,
Generations.
There, even a bottle of champagne makes noise when it explodes in space.

In fact, a physics colleague, Mark Srednicki of U.C. Santa Barbara, brought to my
attention a much greater gaffe in one episode, in which sound waves are used as a weapon
against an orbiting ship. As if that weren't bad enough, the sound waves are said to reach
“18 to the 12th power decibels.” What makes this particularly grate on the ear of a
physicist is that the decibel scale is a logarithmic scale, like the Richter scale. This
means that the number of decibels already represents a power of 10, and they are
normalized so that 20 decibels is 10 times louder than 10 decibels, and 30 decibels is 10
times louder again. Thus, 18 to the 12th power decibels would be 10
(18)^12
, or 1 followed by 11,568,313,814,300 zeroes times louder than a jet plane!

FASTER THAN A SPEEDING PHASER: While faster-than-light warp travel is something we must
live with in Star Trek, such a possibility relies on all the subtleties of general
relativity and exotic new forms of matter, as I have described. But for normal objects
doing everyday kinds of things, light speed is and always will be the ultimate barrier.
Sometimes this simple fact is forgotten. In a wild episode called “Wink of an Eye,” Kirk
is tricked by the Scalosians into drinking a potion that speeds up his actions by a huge
factor to the Scalosian level, so that he can become a mate for their queen, Deela. The
Scalosians live a hyperaccelerated existence and cannot be sensed by the
Enterprise's
crew. Before bedding the queen, Kirk first tries to shoot her with his phaser. However,
since she can move in the wink of an eye by normal human standards, she moves out of the
way before the beam can hit her. Now, what is wrong with this picture? The answer is,
Everything!

What has been noticed by some trekkers is that the accelerated existence required for
Deela to move significantly in the time it would take a phaser beam to move at the speed
of light across the room would make the rest of the episode impossible. Light speed is 300
million meters per second. Deela is about a meter or so away from Kirk when he fires,
implying a light travel time of about 1/300 millionth of a second. For this time to appear
to take a second or so for her, the Scalosian clock must be faster by a factor of 300
million. However, if this is so, 300 million Scalosian seconds take 1 second in normal
Enterprise
time. Unfortunately, 300 million seconds is about 10

years.

OK, let's forgive the Star Trek writers this lapse. Nevertheless, there is a much bigger
problem, which is impossible to solve and which several physicists I know have leapt upon.
Phasers are, we are told, directed energy weapons, so that the phaser beam travels at the
speed of light. Sorry, but there is no way out of this. If phasers are pure energy and not
particle beams, as the Star Trek technical manual states, the beams must move at the speed
of light. No matter how fast one moves, even if one is sped up by a factor of 300 million,
one can never move out of the way of an oncoming phaser beam. Why? Because in order to
know it is coming, you have to first see the gun being fired. But the light that allows
you to see this travels at the same speed as the beam. Put simply, it is impossible to
know it is going to hit you until it hits you! As long as phaser beams are energy beams,
there is no escape. A similar problem involving the attempt to beat a phaser beam is found
in the
Voyager
episode “The Phage.”

Sometimes, however, it is the Star Trek critics who make the mistakes. I was told that I
should take note of an error in
Generations
in which a star shining down on a planet is made to disappear and at the same instant the
planet darkens. This of course is impossible, because it takes light a finite time to
travel from the star to the planet. Thus, when I turn off the light from a star, the
planet will not know it for some time. However, in
Generations,
the whole process is seen from the surface of the planet. When viewed from the planet, the
minute the star is seen to implode, the planet's surface should indeed get dark. This is
because both the information that the star has imploded and the lack of light will arrive
at the planet at the same time. Both will be delayed, but they will be coincident!

Though the writers got this right, they blew it by collapsing the delay to an unreasonably
short time. We are told that the probe that will destroy the star will take only 11
seconds to reach it after launch from the planet's surface. The probe is traveling at
sublight speeds as we can ascertain because it takes much less than twice that time after
the probe is launched for those on the planet to see the star begin to implode, which
indicates that the light must have taken fewer than 11 seconds to make the return journey.
The Earth, by comparison, is 8 light-minutes from our Sun, as I have noted. If the Sun
exploded now, it would take 8 minutes for us to know about it. I find it hard to believe
that the Class M planet in
Generations
could exist at a distance of 10 light-seconds from a hydrogen-burning star like our Sun.
This distance is about 5 times the size of the Sunfar too close for comfort.

IF THE PLOT ISN'T CRACKED, MAYBE THE EVENT HORIZON IS: While I said I wouldn't dwell on
technobabble, I can't help mentioning that the
Voyager
series wins in that department hands down. Every piece of jargon known to modern physics
is thrown in as the
Voyager
tries to head home, traveling in time with the regularity of a commuter train. However,
physics terms usually
mean
something, so that when you use them as a plot device you are bound to screw up every now
and then. I mentioned in chapter 3 that the “crack” in the event horizon that saves the
day for the
Voyager
(in the feckless “Phage” episode) sounds particularly ludicrous to physicists. A “crack”
in an event horizon is like removing one end of a circle, or like being a little bit
pregnant. It doesn't mean anything. The event horizon around a black hole is not a
physical entity, but rather a location inside of which all trajectories remain inside the
hole. It is a property of curved space that the trajectory of anything, including light,
will bend back toward the hole once you are inside a certain radius. Either the event
horizon exists, in which case a black hole exists, or it doesn't. There is no middle
ground big enough to slip a needle through, much less the
Voyager.

HOW SOLID A GUY IS THE DOCTOR?: I must admit that the technological twist I like the most
in the
Voyager
series is the holographic doctor. There is a wonderful scene in which a patient asks the
doctor how he can be solid if he is only a hologram. This is a good question. The doctor
answers by turning off a “magnetic confinement beam” to show that without it he is as
noncorporeal as a mirage. He then orders the beam turned back on, so that he can slap the
poor patient around. It's a great moment, but unfortunately it's also an impossible one.
As I described in chapter 6, magnetic confinement works wonders for charged particles,
which experience a force in a constant magnetic field that causes them to move in circular
orbits. However, light is not charged. It experiences no force in a magnetic field. Since
a hologram is no more than a light image, neither is the doctor.

WHICH IS MORE SENSITIVE, YOUR HANDS OR YOUR BUTT? OR, TO INTERPHASE, OR NOT TO INTERPHASE:
Star Trek has on occasion committed what I call the infamous
Ghost
error. I refer to a recent movie by this name in which the main character, a ghost, walks
through walls and cannot lift objects because his hand passes through them. However,
miraculously, whenever he sits on a chair or a couch, his butt manages to stay put.
Similarly, the ground seems pretty firm beneath his feet. In the last chapter, I described
how Geordi

LaForge and Ro Laren were rendered “out of phase” with normal matter by a Romulan
“interphase generator.” They discovered to their surprise that they were invisible and
could walk through people and walls leading Ro, at least, to believe that she was dead
(perhaps she saw a replay of
Ghost
at some old movie house in her youth). Yet Geordi and Ro could stand on the floor and sit
on chairs with impunity. Matter is matter, and chairs and floors are no different from
walls, and as far as I know feet and butts are no more or less solid than hands.

Incidentally, there is another fatal flaw associated with this particular episode which
also destroys the consistency of a number of other Star Trek dramas. In physics, two
things that both interact with something else will always be able to interact with each
other. This leads us full circle back to Newton's First Law. If I exert a force on you,
you exert an equal and opposite force on me. Thus, if Geordi and Ro could observe the
Enterprise
from their new “phase,” they could interact with light, an electromagnetic wave. By
Newton's Law if nothing else, they in turn should have been visible. Glass is invisible
precisely because it does not absorb visible light. In order to seethat is, to sense
lightyou have to absorb it. By absorbing light, you must disturb it. If you disturb light,
you must be visible to someone else. The same goes for the invisible interphase insects
that invaded the
Enterprise
by clinging to the bodies of the crew, in the
Next Generation
episode “Phantasms.” The force that allows them to rest on normal matter without going
through it is nothing other than electro-magnetismthe electrostatic repulsion between the
charged particles making up the atoms in one body with the atoms in another body. Once you
interact electromagnetically, you are part of our world. There is no such thing as a free
lunch.

SWEEPING OUT THE BABY WITH THE BATHWATER: In the
Next Generation
episode “Starship Mine,” the
Enterprise
docks at the Remmler Array to have a “baryon sweep.” It seems that these particles build
up on starship superstructures as a result of long-term travel at warp speed, and must be
removed. During the sweep, the crew must evacuate, because the removal beam is lethal to
living tissue. Well, it certainly would be! The only stable baryons are (1) protons and
(2) neutrons in atomic nuclei. Since these particles make up everything we see, ridding
the
Enterprise
of them wouldn't leave much of it for future episodes.

HOW COLD IS COLD?: The favorite Star Trek gaffe of my colleague and fellow Star Trek
aficionado Chuck Rosenblatt involves an object's being frozen to a temperature of
-295¡Celsius. This is a very exciting discovery, because on the Celsius scale, absolute
zero is -273¡. Absolute zero, as its name implies, is the lowest temperature anything can
potentially attain, because it is defined as the temperature at which all molecular and
atomic motions, vibrations, and rotations cease. Though it is impossible to achieve this
theoretical zero temperature, atomic systems have been cooled to within a millionth of a
degree above it (and as of this writing have just been cooled to 2 billionths of a degree
above absolute zero). Since temperature is associated with molecular and atomic motion,
you can never get less than no motion at all; hence, even 400 years from now, absolute
zero will still be absolute.

1 HAVE SEEN THE LIGHT!: I am embarrassed to say that this obvious error, which I should
have caught myself, was in fact pointed out to me by a first-year physics student, Ryan
Smith, when I was lecturing to his class and mentioned that I was writing this book.
Whenever the
Enterprise
shoots a phaser beam, we see it. But of course this is impossible unless the phaser itself
emits light in all directions. Light is not visible unless it reflects off something. If
you have ever been to a lecture given with the help of a laser pointergenerally, these are
helium- neon red lasersyou may recall that you see only the spot where the beam hits the
screen, and not anything in between. The only way to make the whole beam visible is to
make the room dusty, by clapping chalkboard erasers together, or something like that. (You
should try this sometime; the light show is really quite spectacular.) Laser light shows
are created by bouncing the laser light off either smoke or water. Thus, unless empty
space is particularly dusty, we shouldn't see the phaser beam except where it hits.