The Physics of Star Trek (8 page)

First, however, the wonder of such “designer spacetimes” is that they allow us to return
to Newton's original challenge and to create iner-tial dampers and tractor beams. The idea
is identical to warp drive. If spacetime around the ship can be warped, then objects can
move apart or together without experiencing any sense of local acceleration, which you
will recall was Newton's bane. To avoid the incredible accelerations required to get to
impulse sublight speeds, one must resort to the same spacetime shenanigans as one does to
travel at warp speeds. The distinction between impulse drive and warp drive is thus
diminished. Similarly, to use a tractor beam to pull a heavy object like a planet, one
merely has to expand space on the other side of the planet and contract it on the near
side. Simple!

Warping space has other advantages as well. Clearly, if spacetime becomes strongly curved
in front of the
Enterprise,
then any light rayor phaser beam, for that matterwill be deflected away from the ship.
This is doubtless the principle behind deflector shields. Indeed, we are told that the
deflector shields operate by “coherent graviton emission.” Since gravitons are by
definition particles that transmit the force of gravity, then “coherent graviton emission”
is nothing other than the creation of a coherent gravitational field. A coherent
gravitational field is, in modern parlance, precisely what curves space! So once again the
Star Trek writers have at least settled upon the right language.

I would imagine that the Romulans' cloaking device might operate in a similar manner. In
fact, an
Enterprise
that has its deflector shield deployed should be very close to a cloaked
Enterprise.
After all, the reason we see something that doesn't shine of its own accord is that it
reflects light, which travels back to us. Cloaking must somehow warp space so that
incident light rays bend around a Warbird instead of being reflected from it. The
distinction between this and deflecting light rays away from the
Enterprise
is thus pretty subtle. In this connection, a question that puzzled many trekkers until the
Next Generation
episode “The Pegasus” aired was, Why didn't the Federation employ cloaking technology? It
would certainly seem, in light of the above, that any civilization that could develop
deflector shields could develop cloaking devices. And as we learned in “The Pegasus,” the
Federation was limited in its development of cloaking devices by treaty rather than by
technology. (Indeed, as became evident in “All Good Things ...,” the last episode of the
Next Generation,
the Federation eventually seems to have allowed cloaking on starships.)

Finally, given this general-relativistic picture of warp drive, warp speeds take on a
somewhat more concrete meaning. The warp speed would be correlated to the contraction and
expansion factor of the spatial volume in

front of and behind the ship. Warp-speed conventions have never been particularly stable:
between the first and second series, Gene Roddenberry apparently decided that warp speeds
should be recalibrated so that nothing could exceed warp 10. This meant that warp speed
could not be a simple logarithmic scale, with, say, warp 10 being 2
10
= 1024 x light speed. According to the
Next Generation Technical Manual,
warp 9.6, which is the highest normal rated speed for the
Enterprise-D,
is 1909 x the speed of light, and warp 10 is infinite. It is interesting to note that in
spite of this recalibration, objects (such as the Borg cube) are periodically sighted
which go faster than warp 10, so I suppose one shouldn't concern oneself unduly about
understanding the details.

Well, so much for the good news....

Having bought into warp drive as a nonimpossibility (at least in principle), we finally
have to face up to the consequences for the right-hand side of Einstein's equationsnamely,
for the distribution of matter and energy required to produce the requisite curvature of
space-time. And guess what? The situation is almost
worse
than it was for wormholes. Observers traveling at high speed through a wormhole can
measure a negative energy. For the kind of matter needed to produce a warp drive, even an
observer at rest with respect to the star-shipthat is, someone on boardwill measure a
negative energy.

This result is not too surprising. At some level, the exotic solutions of general
relativity required to keep wormholes open, allow time travel, and make warp drive
possible all imply that on some scales matter must gravitationally repel other matter.
There is a theorem in general relativity that this condition is generally equivalent to
requiring the energy of matter to be negative for some observers.

What
is
surprising, perhaps, is the fact, mentioned earlier, that quantum mechanics, when combined
with special relativity, implies that at least on microscopic scales the local
distribution of energy can be negative. Indeed, as I noted in chapter 3, quantum
fluctuations often have this property. The key question, which remains unanswered to date,
is whether the laws of physics as we know them will allow matter to have this property on
a macroscopic scale. It is certainly true that currently we haven't the slightest idea of
how one could create such matter in any physically realistic way.

However, ignore for the moment the potential obstacles to creating such material, and
suppose that it will someday be possible to create exotic matter, by using some
sophisticated quantum mechanical engineering of matter or of empty space. Even so, the
energy requirements to do any of the remarkable playing around with spacetime described
here would likely make the power requirement for accelerating to impulse speed seem puny.
Consider the mass of the Sun, which is about a million times the mass of the Earth. The
gravitational field at the surface of the Sun is sufficient to bend light by less than
1/1000 of a degree. Imagine the extreme gravitational fields that would have to be
generated near a starship to deflect an oncoming phaser beam by 90¡! (This is one of the
many reasons why the famous “slingshot effect” first used in the classic episode “Tomorrow
Is Yesterday” to propel the
Enterprise
backward in time, again in
Star Trek IV: The Voyage Home,
and also mentioned in the
Next Generation
episode “Time Squared”is completely impossible. The gravitational field near the surface
of the Sun is minuscule in terms of the kind of gravitational effects required to perturb
spacetime in the ways we have discussed here.) One way to estimate how much energy would
have to be generated is to imagine producing a black hole the size of the
Enterprise
since certainly a black hole of this size would produce a gravitational field that could
significantly bend any light beam that traveled near it. The mass of such a black hole
would be about 10 percent of the mass of the Sun. Expressed in energy units, it would take
more than the total energy produced by the Sun during its entire lifetime to generate such
a black hole.

So where do we stand at the end of this game? We know enough about the nature of spacetime
to describe explicitly how one might, at least in principle, utilize curved space to
achieve many of the essentials of interstellar space travel ˆ la Star Trek. We know that
without such exotic possibilities we will probably never voyage throughout the galaxy. On
the other hand, we have no idea whether the
physical conditions
needed to achieve any of these things are realizable in practice or even allowed in
principle. Finally, even if they were, it is clear that any civilization putting these
principles into practice would have to harness energies vastly in excess of anything
imaginable today.

I suppose one might take the optimistic view that these truly remarkable wonders are at
least not
a priori
impossible. They merely hinge on one remote possibility: the ability to create and sustain
exotic matter and energy. There is reason for hope, but I must admit that I remain
skeptical. Like my colleague Stephen Hawking, I

believe that the paradoxes involved in round-trip time travel rule it out for any sensible
physical theory. Since virtually the same conditions of energy and matter are required for
warp travel and deflector shields, I'm not anticipating them eitherthough I have been
wrong before.

Nevertheless, I am still optimistic. What to me is really worth celebrating is the
remarkable body of knowledge that has brought us to this fascinating threshold. We live in
a remote corner of one of 100 billion galaxies in the observable universe. And like
insects on a rubber sheet, we live in a universe whose true form is hidden from direct
view. Yet in the course of less than twenty generationsfrom Newton to todaywe have
utilized the simple laws of physics to illuminate the depths of space and time. It is
likely that we may never be able to board ships headed for the stars, but even imprisoned
on this tiny blue planet we have been able to penetrate the night sky to reveal remarkable
wonders, and there is no doubt more to come. If physics cannot give us what we need to
roam the galaxy, it is giving us what we need to bring the galaxy to us.

Matter Matter Everywhere

In which the reader explores transporter beams, warp drives, dilithium crystals,
matter-antimatter engines, and the holodeck

“Reg, transporting
really is
the safest way to travel.”
Geordi LaForge to Lieutenant Reginald Barclay,

in “Realm of Fear”

Life imitates art. Lately, I keep hearing the same question: “Atoms or bitswhere does the
future lie?” Thirty years ago, Gene Rod-denberry dealt with this same speculation, driven
by another imperative. He had a beautiful design for a starship, with one small problem:
like a penguin in the water, the
Enterprise
could glide smoothly through the depths of space, but like a penguin on the ground it
clearly would have trouble with its footing if it ever tried to land. More important
perhaps, the meager budget for a weekly television show precluded landing a huge starship
every week.

How then to solve this problem? Simple: make sure the ship would never need to land. Find
some other way to get the crew members from the ship to a planet's surface. No sooner
could you say, “Beam me up” than the transporter was born.

Perhaps no other piece of technology, save for the warp drive, so colors every mission of
every starship of the Federation. And even those who have never watched a Star Trek
episode recognize the magic phrase on the preceding page. It has permeated our popular
culture. I recently heard about a young man who, while inebriated, drove through a red
light and ran into a police cruiser that happened to be lawfully proceeding through the
intersection. At his hearing, he was asked if he had anything to say. In well-founded
desperation, he replied, “Yes, your honor,” stood up, took out his wallet, flipped it
open, and muttered into it, “Beam me up, Scotty!”

The story is probably apochryphal, but it is testimony to the impact that this
hypothetical technology has had on

our culturean impact all the more remarkable given that probably no single piece of
science fiction technology aboard the
Enterprise
is so utterly implausible. More problems of practicality and principle would have to be
overcome to create such a device than you might imagine. The challenges involve the whole
spectrum of physics and mathematics, including information theory, quantum mechanics,
Einstein's relation between mass and energy, elementary particle physics, and more.

Which brings me to the atoms versus bits debate. The key question the transporter forces
us to address is the following: Faced with the task of moving, from the ship to a planet's
surface, roughly 10
28
(1 followed by 28

zeroes) atoms of matter combined in a complex pattern to make up an individual human
being, what is the fastest and most efficient way to do it? This is a very timely
question, because we are facing exactly the same quandary as we consider how best to
disseminate the complex pattern of roughly 10
26
atoms in an average paperback book. A potentially revolutionary concept, at least so
claimed by various digital-media gurus, is that the atoms themselves are often secondary.
What matters more are the bits.

Consider, for example, a library book. A library buys one copyor, for some lucky authors,
several copiesof a book, which it stores and lends out for use by one individual at a
time. However, in a digital library the same information can be stored as bits. A bit is a
1 or a 0, which is combined in groups of eight, called bytes, to represent words or
numbers. This information is stored in the magnetic memory cores of computers, in which
each bit is represented as either a magnetized (1) or unmagnetized (0) region. Now an
arbitrarily large number of users can access the same memory location on a computer at
essentially the same time, so in a digital library every single person on Earth who might
otherwise have to buy a book can read it from a single source. Clearly, in this case,
having on hand the actual atoms that make up the book is less significant, and certainly
less efficient, than storing the bits (although it will play havoc with authors'
royalties).

So, what about people? If you are going to move people around, do you have to move their
atoms or just their information? At first you might think that moving the information is a
lot easier; for one thing, information can travel at the speed of light. However, in the
case of people, you have two problems you don't have with books: first, you have to
extract the information, which is not so easy, and then you have to recombine it with
matter. After all, people, unlike books, require the atoms.

The Star Trek writers seem never to have got it exactly clear what they want the
transporter to do. Does the transporter send the atoms
and
the bits, or just the bits? You might wonder why I make this point, since the
Next Generation Technical Manual
describes the process in detail: First the transporter locks on target. Then it scans the
image to be transported, “dematerializes” it, holds it in a “pattern buffer” for a while,
and then transmits the “matter stream,” in an “annular confinement beam,” to its
destination. The transporter thus apparently sends out the matter along with the
information.