The Physics of Star Trek

Perennial

CHAPTER ONE

NEWTON
Antes

"No matter where you go, there you are."
--From a plaque on the starship Excelsior, in Star Trek VI: The Undiscovered Country, presumably borrowed from The Adventures of Buckaroo Banzai

You are at the helm of the starship Defiant (NCC-1764), currentlyin orbit around the planet Iconia, near the Neutral Zone. Yourmission: to rendezvous with a nearby supply vessel at the other end ofthis solar system in order to pick up components to repair faultytransporter primary energizing coils, There is no need to achieve warpspeeds; you direct the impulse drive to be set at full power for leisurelyhalf-light-speed travel, which should bring you to your destination ina few hours, giving you time to bring the captain's log up to date.However, as you begin to pull out of orbit, you feel an intense pressurein your chest. Your hands are leaden, and you are glued to yourseat. Your mouth is fixed in an evil-looking grimace, your eyes feellike they are about to burst out of their sockers, and the blood flowingthrough your body refuses to rise to your head. Slowly, you loseconsciousness . . . and within minutes you die.

What happened? It is not the first signs of spatial "interphase"drift, which will later overwhelm the ship, or an attack from a previouslycloaked Romulan vessel. Rather, you have fallen prey to somethingfar more powerful. The ingenious writers of Star Trek, on whomyou depend, have not yet invented inertial dampers, which they willintroduce sometime later in the series. You have been defeated bynothing more exotic than Isaac Newton's laws of motion--the veryfirst things one can forget about high school physics.

OK, I know some trekkers out there are saying to themselves,"How lame! Don't give me Newton. Tell me things I really want toknow, like `How does warp drive work?' or `What is the flash beforegoing to warp speed--is it like a sonic boom?' or `What is a dilithiumcrystal anyway?'" All I can say is that we will get there eventually.Travel in the Star Trek universe involves some of the most exotic conceptsin physics, But many different aspects come together before wecan really address everyone's most fundamental question about StarTrek; "Is any of this really possible, and if so, how?"

To go where no one has gone before--indeed, before we even getout of Starfleet Headquarters--we first have to confront the samepeculiarities that Galileo and Newton did over three hundred yearsago. The ultimate motivation will be the truly cosmic question whichwas at the heart of Gene Roddenberry's vision of Star Trek and which,to me, makes this whole subject worth thinking about: "What doesmodern science allow us to imagine about our possible future as acivilization?"

Anyone who has ever been in an airplane or a fast car knows thefeeling of being pushed back into the scat as the vehicle acceleratesfrom a standstill. This phenomenon works with a vengeance aboarda starship. The fusion reactions in the impulse drive produce hugepressures, which push gases and radiation backward away from theship at high velocity. It is the backreaction force on the engines--fromthe escaping gas and radiation--that causes the engines to "recoil"forward. The ship, being anchored to the engines, also recoils forward.At the helm, you are pushed forward too, by the force of thecaptain's seat on your body. In turn, your body pushes back on theseat.

Now, here's the catch. Just as a hammer driven at high velocitytoward your head will produce a force on your skull which can easilybe lethal, the captain's seat will kill you if the force it applies to youis too great. Jet pilots and NASA have a name for the force exerted onyour body while you undergo high accelerations (as in a plane or duringa space launch): G-forces. I can describe these by recourse to myaching back: As I am sitting at my computer terminal busily typing, Ifeel the ever-present pressure of my office chair on my buttocks--apressure that I have learned to live with (yet, I might add, that my buttocksare slowly reacting to in a very noncosmetic way). The force onmy buttocks results from the pull of gravity, which if given free reinwould accelerate me downward into the Earth. What stops me fromaccelerating--indeed, from moving beyond my seat--is the groundexerting an opposite upward force on my house's concrete and steelframe, which exerts an upward force on the wood floor of my second-floorstudy, which exerts a force on my chair, which in turn exerts aforce on the part of my body in contact with it. If the Earth were twiceas massive but had the same diameter, the pressure on my buttockswould be twice as great. The upward forces would have to compensatefor the force of gravity by being twice as strong.

The same factors must be taken into account in space travel. If youare in the captain's seat and you issue a command for the ship toaccelerate, you must take into account the force with which the seatwill push you forward. if you request an acceleration twice as great,the force on you from the seat will be twice as great. The greater theacceleration, the greater the push. The only problem is that nothingcan withstand the kind of force needed to accelerate to impulse speedquickly--certainly not your body.

By the way, this same problem crops up in different contextsthroughout Star Trek--even on Earth. At the beginning of Star TrekV: The Final Frontier, James Kirk is free-climbing while on vacation inYosemite when he slips and falls. Spock, who has on his rocket boots,speeds to the rescue, aborting the captain's fall within a foot or twoof the ground. Unfortunately, this is a case where the solution can beas bad as the problem. It is the process of stopping over a distance ofa few inches which can kill you, whether or not it is the ground thatdoes the stopping or Spock's Vulcan grip.

Well before the reaction forces that will physically tear or breakyour body occur, other severe physiological problems set in. First andforemost, it becomes impossible for your heart to pump stronglyenough to force the blood up to your head. This is why fighter pilotssometimes black out when they perform maneuvers involving rapidacceleration. Special suits have been created to force the blood upfrom pilots' legs to keep them conscious during acceleration. Thisphysiological reaction remains one of the limiting factors in determininghow fist the acceleration of present-day spacecraft can be, andit is why NASA, unlike Jules Verne in his classic From the Earth to theMoon, has never launched three men into orbit from a giant cannon.

If I want to accelerate from rest to, say, 150,000 km/sec, or abouthalf the speed of light, I have to do it gradually, so that my body willnot be torn apart in the process. In order not to be pushed back intomy seat with a force greater than 3G, my acceleration must be nomore than three times the downward acceleration of falling objects onEarth. At this rate of acceleration, it would take some 5 million seconds,or about 2 1/2 months, to reach half light speed! This would notmake for an exciting episode.

To resolve this dilemma, sometime after the production of the firstConstitution Class starship--the Enterprise (NCC-1701)--the StarTrek writers had to develop a response to the criticism that the accelerationsaboard a starship would instantly turn the crew into "chunkysalsa," They came up with "inertial dampers," a kind of cosmic,shock absorber and an ingenious plot device designed to get aroundthis sticky tittle problem.

The inertial dampers are most notable in their absence. For example,the Enterprise was nearly destroyed after losing control of the inertialdampers when the microchip life-forms known as Nanites, as partof their evolutionary process, started munching on the ship's centralcomputer-core memory. Indeed, almost every time the Enterprise isdestroyed (usually in some renegade timeline), the destruction is precededby loss of the inertial dampers. The results of a similar loss ofcontrol in a Romulan Warbird provided us with an explicit demonstrationthat Romulans bleed green.

Alas, as with much of the technology in the Star Trek universe, it ismuch easier to describe the problem the inertial dampers address thanit is to explain exactly how they might do it, The First Law of StarTrek physics surely must state that the more basic the problem to becircumvented, the more challenging the required solution must be.For the reason we have come this far, and the reason we can even postulatea Star Trek future, is that physics is a field that builds on itself.A Star Trek fix must circumvent not merely some problem in physicsbut every bit of physical knowledge that has been built upon thisproblem. Physics progresses not by revolutions, which do away withall that went before, but rather by evolutions, which exploit the bestabout what is already understood, Newton's laws will continue to beas true a million years from now as they are today, no matter what wediscover at the frontiers of science. If we drop a ball on Earth, it willalways fall. If I sit at this desk and write from here to eternity, my buttockswill always suffer the same consequences.

Be that as it may, it would be unfair simply to leave the inertialdampers hanging without at least some concrete description of howthey would have to operate. From what I have argued, they must createan artificial world inside a starship in which the reaction force thatresponds to the accelerating force is canceled. The objects inside theship are "tricked" into acting as though they were not accelerating. Ihave described how accelerating gives you the same feeling as beingpulled at by gravity. This connection, which was the basis of Einstein'sgeneral theory of relativity, is much more intimate than it may at firstseem. Thus there is only one choice for the modus operandi of thesegadgets: they must set up an artificial gravitational field inside theship which "pulls" in the opposite direction to the reaction force,thereby canceling it out.

Even if you buy such a possibility, other practical issues must bedealt with. For one thing, it takes some time for the inertial dampersto kick in when unexpected impulses arise. For example, when theEnterprise was bumped into a causality loop by the Bozeman as thelatter vessel emerged from a temporal distortion, the crew was thrownall about the bridge (even before the breach in the warp core and thefailure of the dampers). I have read in the Enterprise's technical specificationsthat the response time for the inertial dampers is about60 milliseconds. Short as this may seem, it would be long enough tokill you if the same delay occurred during programmed periods ofacceleration. To convince yourself, think how long it takes for a hammerto smash your head open, or how long it takes for the ground tokill you if you hit it after falling off of a cliff in Yosemite. Just rememberthat a collision at 10 miles per hour is equivalent to running fullspeed into a brick wall! The inertial dampers had better be prettyquick to respond. More than one trekker I know has remarked thatwhenever the ship is buffeted, no one ever gets thrown more than afew feet.

Before leaving the familiar world of classical physics, I can't help mentioninganother technological marvel that must confront Newton'slaws in order to operate: the Enterprise's tractor beam--highlightedin the rescue of the Genome colony on Moab IV, when it deflected anapproaching stellar core fragment, and in a similar (but failed)attempt to save Bre'el IV by pushing an asteroidal moon back into itsorbit. On the face of it, the tractor beam seems simple enough--moreor less like an invisible rope or rod--even if the force exerted may beexotic. Indeed, just like a strong rope, the tractor beam often does afine job of pulling in a shuttle craft, towing another ship, or inhibitingthe escape of an enemy spacecraft. The only problem is that whenwe pull something with a rope, we must be anchored to the ground orto something else heavy. Anyone who has ever been skating knowswhat happens if you are on the ice and you try to push someone awayfrom you. You do manage to separate, but at your own expense.Without any firm grounding, you are a helpless victim of your owninertia.

It was this very principle that prompted Captain Jean-Luc Picard toorder Lieutenant Riker to turn off the tractor beam in the episode"The Battle"; Picard pointed out that the ship they were towingwould be carried along beside them by its own momentum--its inertia.By the same token, if the Enterprise were to attempt to use thetractor beam to ward off the Stargazer, the resulting force would pushthe Enterprise backward as effectively as it would push the Stargazerforward.

This phenomenon has already dramatically affected the way wework in space at present. Say, for example, that you are an astronautassigned to tighten a bolt on the Hubble Space Telescope. If you takean electric screwdriver with you to do the job, you are in for a rudeawakening after you drift over to the offending bolt. When you switchon the screwdriver as it is pressed against the bolt, you are as likely tostart spinning around as the bolt is to turn. This is because the HubbleTelescope is a lot heavier than you are. When the screwdriver appliesa force to the bolt, the reaction force you feel may more easily turnyou than the bolt, especially if the bolt is still fairly tightly secured tothe frame. Of course, if you are lucky enough, like the assassins ofChancellor Gorkon, to have gravity boots that secure you snugly towhatever you are standing on, then you can move about as efficientlyas we are used to on Earth.

Likewise, you can see what will happen if the Enterprise tries topull another spacecraft toward it. Unless the Enterprise is very muchheavier, it will move toward the other object when the tractor beamturns on, rather than vice versa. In the depths of space, this distinctionis a meaningless semantic one. With no reference system nearby,who is to say who is pulling whom? However, if you are on a haplessplanet like Moab IV in the path of a renegade star, it makes a greatdeal of difference whether the Enterprise pushes the star aside or thestar pushes the Enterprise aside!

One trekker I know claims that the way around this problem isalready stated indirectly in at least one episode: if the Enterprise wereto use its impulse engines at the same time that it turned its tractorbeam on, it could, by applying an opposing force with its ownengines, compensate for any recoil it might feel when it pushed orpulled on something. This trekker claims that somewhere it is statedthat the tractor beam requires the impulse drive to be operational inorder to work. I, however, have never noticed any instructions fromKirk or Picard to turn on the impulse engines at the same time thetractor beam is used. And in fact, for a society capable of designingand building inertial dampers, I don't think such a brute force solutionwould be necessary. Reminded of Geordi LaForge's need for awarp field to attempt to push back the moon at Bre'el IV, I think acareful, if presently unattainable, manipulation of space and timewould do the trick equally well. To understand why, we need toengage the inertial dampers and accelerate to the modern world ofcurved space and time.

Continues...
Excerpted from The Physics of Star Trekby Lawrence M. Krauss Copyright © 1996 by Lawrence M. Krauss. Excerpted by permission.
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