CHAPTER SEVEN

Holodecks and Holograms

“Oh, we are us, sir. They are also us. So, indeed, we are both us.” Data to Picard and Riker, in “We'll Always Have Paris”

When Humphrey Bogart said to Ingrid Bergman at the Casablanca airport, “We'll always have Paris,” he meant, of course, the memory of Paris. When Picard said something similar to Jenice Manheim at the holodeck re-creation of the CafŽ des Artistes, he may have intended it more literally. Thanks to the holodeck, memories can be relived, favorite places revisited, and lost loves rediscoveredalmost.

The holodeck is one of the most fascinating pieces of technology aboard the Enterprise. To anyone already familiar with the nascent world of virtual reality, either through video games or the more sophisticated modern high-speed computers, the possibilities offered by the holodeck are particularly enticing. Who wouldn't want to enter completely into his or her own fantasy world at a moment's notice?

It is so seductive, in fact, that I have little doubt that it would be far more addictive than it is made out to be in the series. We get some inkling of “holodeck addiction” (or “holodiction”) in the episodes “Hollow Pursuits” and “Galaxy's Child.” In the former, everyone's favorite neurotic officer, Lieutenant Reginald Barclay, becomes addicted to his fantasy vision of the senior officers aboard the Enterprise, and would rather interact with them on the holodeck than anywhere else on the ship. In the latter, when Geordi LaForge, who has begun a relationship with a holodeck representation of Dr. Leah Brahms, the designer of the ship's engines, meets the real Dr. Brahms, things become complicated-

Given the rather cerebral pastimes the crew generally engage in on the holodeck, one may imagine that the hormonal instincts driving twentieth-century humanity have evolved somewhat by the twenty-third century (although if this is the case, Will Riker is not representative of his peers). Based on what I know of the world of today, I would have expected that sex would almost completely drive the holodeck. (Indeed, the holodeck would give safe sex a whole new meaning.) I am not being facetious here. The holodeck represents what is so enticing about fantasy, particularly sexual fantasy: actions without consequences, pleasure without pain, and situations that can be repeated and refined at will.

The possible hidden pleasures of the holodeck are merely alluded to from time to time in the series. For example, after Geordi has barged in rather rudely on Reg's private holodeck fantasy, he admits, “I've spent a few hours on the holodeck myself. Now, as far as I'm concerned, what you do on the holodeck is your own business, as long as it doesn't interfere with your work.” If that doesn't sound like a twentieth-century admonition against letting the pleasures of the flesh get the better of one, I don't know what does.

I have little doubt that our century's tentative explorations of virtuai reality are leading us in the direction of something very much like the holodeck, at least in spirit. Perhaps my concerns will appear as quaint in the twenty- third century as the warning cries that accompanied the invention of television a half century ago. After all, though cries continue because of the surfeit of televised sex and violence, without television there would be no Star Trek.

The danger that we will become a nation of couch potatoes would not apply in a world full of personal holodecks, or perhaps holodecks down at the mall; engaging in holodeck play is far from passive. However, I still find the prospect of virtual reality worrisome, precisely because though it appears real, it is much less scary than real life. The attraction of a world of direct sensual experience without consequences could be overwhelming.

Nevertheless, every new technology has bad as well as good sides and will force adjustments in our behavior. It's probably clear from the tone of this book that I believe technology has on the whole made our lives better rather than worse. The challenge of adjusting to it is just one part of the challenge of being part of an evolving human society.

Be that as it may, the holodeck differs in one striking way from most of the virtual-reality technologies currently under development. At present, through the use of devices that you strap on and that influence your vision and sensory input, virtual reality is designed to put the “scene” inside you. The holodeck takes a more inventive tack: it puts you inside the scene. It does this in part by inventive use of holography and in part by replication.

The principles on which holography is based were first elucidated in 1947, well before the technology was available to fully exploit it, by the British physicist Dennis Gabor, who subsequently won the Nobel Prize for his work. By now, most people are familiar with the use of three-dimensional holographic images on credit cards, and even on the covers of books, like this one. The word “hologram” derives from the Greek words for “whole” and “to write.” Unlike normal photographs, which merely record two-dimensional representations of three-dimensional reality, holograms give you the whole picture. In fact, it is possible with holography to re-create a three- dimensional image that you can walk around and view from all sides, as if it were the original object. The only way to tell the difference is to try touching it. Only then will you find that there is nothing there to touch.

How can a two-dimensional piece of film, which is what stores the holographic image, record the full information of a three-dimensional image? To answer this we have to think a little about exactly what it is we see when we see something, and what a photograph actually records.

We see objects either because they emit or reflect light, which then arrives at our eyes. When a three-dimensional object is illuminated, it scatters light in many different directions because of this three-dimensionality. If we could somehow reproduce the exact pattern of divergent light created when light is scattered by the actual object, then our eyes would not be able to distinguish the difference between the actual object and the divergent-light pattern sans object. By moving our head, for example, we would be able to see features that were previously obscured, because the entire pattern of scattered light from all parts of the object would have been re-created.

How can we first store and then later re-create all this information? We can gain some insight into this question by thinking about what a normal photographwhich stores and later re-creates a two-dimensional imageactually records. When we take a picture, we expose a light-sensitive material to the incoming light, which arrives through

the lens of the camera. This light-sensitive material, when exposed to various chemicals, will darken in proportion to the intensity of the light that impinged upon it. (I am discussing black-and-white film here, but the extension to color film is simpleone just coats the film with three different substances, each of which is sensitive to a different primary color of light.)

So, the total information content recorded on a photographic film is the intensity of light arriving at each point on the film. When we develop the film, those points on it that were exposed to a greater intensity of light will react with the development chemicals to become darker, while those not so exposed will remain lighter. The resulting image on the film is a “negative” two-dimensional projection of the original light field. We can project light through this negative onto a light-sensitive sheet of paper to create the final photograph. When we look at it, light hitting the lighter areas of the photograph will be predominantly reflected, while light hitting the darker areas will be absorbed. Thus, looking at the light reflected from the photograph produces a two-dimensional intensity pattern on our retinas, which then allows us to interpret this pattern.

The question then becomes, what more is there to record than just the intensity of light at each point? Once again, we rely on the fact that light is a wave. Because of this fact, more than just intensity is needed to characterize its configuration. Consider the light wave shown below:

At position A, the wave, which in this case represents the strength of the electric field, has its maximum value, corresponding to an electric field with strength E A pointing upward. At point B, the field is exactly the same

strength but is pointing downward. Now, if you are sensitive only to the intensity of the light wave, you will find that the field has the same intensity at A as it does at B. However, as you can see, position B represents a different part of the wave from position A. This “position” along the wave is called the phase. It turns out that you can specify all the information associated with a wave at a given point by giving its intensity and its phase. So, to record all the information about the light waves scattered by a three-dimensional object, you have to find a way of recording on a piece of film both the intensity and the phase of the scattered light.

This is simple to do. If you split a light beam into two parts and shine one part directly onto the film and let the other part scatter off the object before illuminating the film, then either one of two things can happen. If the two light waves are “in phase”that is, both have crests coinciding at some point Athen the amplitude of the resulting wave at A will be twice the amplitude of either individual wave, as shown in the figure below:

On the other hand, if the two waves are out of phase at point A, then they will cancel each other out, and the resulting “wave” at A will have zero amplitude:

So now, if the film at point A is photographic film, which records intensity only, the pattern recorded will be the “interference pattern” of the two wavesthe reference beam and the beam of light scattered by the object. This pattern contains not only the information about the intensity of the scattered light from the object, but information about its phases as well. If one is clever, one can extract this information to re-create a three-dimensional image of the object that scattered the light.

In fact, it turns out that one doesn't have to be all that clever. If one merely illuminates this photographic film with a source of light of the same wavelength as the original light that produced the interference pattern, an image of the object will be created exactly where the object was in relation to the film, when you look through the film. If you move your head to one side, you will be able to “look around” the edges of the re-created object. If you cover up most of the piece of film, and hold it closer to your eyes and look through the uncovered part, you will still see the entire object! In this sense, the experience is just like looking through a window at a scene outdoors, except that the scene you are seeing isn't really there. The light coming to your eyes through the film is affected in just such a way as to make your eyes believe that it has been scattered off objects, which you then “see.” This is a hologram.

Normally, in order for the reference light and the light from the scattered object to be carefully controlled, holograms are made using laser light, which is coherent and well collimated. However, so-called “white light” holograms exist, which can be illuminated by ordinary light to produce the same effect.

One can be trickier and arrange, just as one can using various lenses, for the image of the objects you see to appear to be between you and the film, and you will see before you the three-dimensional image of an object,

which you can walk around and view from all sides. Or you can arrange for the light source to be in front of the film instead of behind itas in the holograms on credit cards.

Presumably the former sort of hologram is used on the holodeck, and to re-create the image of a doctor in the sick bay, as in the Voyager series. What's more, in order to create such holograms, one would not need to use the original objects to make the holographic images. Digital computers are now sophisticated enough to do “ray tracing” that is, they can calculate the pattern of light scattered from any hypothetical object you want to draw on the screen, and illuminate it from any angle. In the same way, the computer could determine the configuration of the interference pattern that would be caused by merging the light from a direct beam with the scattered light from an object. This computer-generated interference pattern could be projected onto a transparent screen, and when this screen is illuminated from behind, a three-dimensional image is produced of an object that in fact never existed. If the computer is fast enough, it can project a continuously changing interference pattern on the screen, thereby producing a moving three-dimensional image. So the holographic aspect of the holodeck is not particularly far-fetched.

However, holograms aren't all there is to the holodeck. As noted, they have no corporeal integrity. You can walk through oneor shoot through one, as was evidenced by the wonderful holographic representations created by Spock and Data to trick the Romulans in the episode “Unification.” This incorporeality simply will not do for the objects one would like to interact withthat is, touchon the holodeck. Here techniques that are more esoteric are required, and the Star Trek writers have turned to the transporter, or at least to the replicators, which are less sophisticated versions of the transporter. Presumably, using transporter technology, matter is replicated and moved around on the holodeck to resemble exactly the beings in question, in careful coordination with computer programs that control the voices and movements of the re-created beings. Similarly, the replicators reproduce the inanimate objects in the scenetables, chairs, and so forth. This “holodeck matter” owes its form to the pattern held in the replicator buffer. When the transporter is turned off or the object is removed from the holodeck, the matter can then disassemble as easily as it would if the pattern buffer were turned off during the beaming process. Thus, creatures created from holodeck matter can be trapped on the holodeck, as the fictional detectives Cyrus Redblock and Felix Leach found to their dismay in the Next Generation episode “The Big Goodbye,” and as Sherlock Holmes's nemesis Professor Moriarty surmised and then attempted to overcome in several other episodes.

So here is how I envisage the holodeck: holograms would be effective around the walls, to give one the impression of being in a three-dimensional environment that extended to the horizon, and the transporter-based replicators would then create the moving “solid” objects within the scene. Since holography is realistic, while (as I have explained earlier) transporters are not, one would have to find some other way of molding and moving matter around in order to make a workable holodeck. Still, one out of two technologies in hand isn't bad.

Where does all this leave the pure holograms, like the holographic doctor of the Voyager series? The answer is, Absolutely nowhere. With just the scattered light and no matter around, I'm afraid that these images would not be very effective at lifting, manipulating, or probing. However, a good bedside manner and compassionate words of advice, which are at the heart of good medical practice, can be dispensed by a hologram as easily as by the real thing.

SECTION

THREE The Invisible

Universe, or Things That Go

Bump in the Night

In which we speak of things that may exist but are not yet seen extraterrestrial life, multiple dimensions, and an exotic zoo of other physics possibilities and impossibilities

An aerial view of the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, housing the highest energy accelerator in the world, the Tevatron, and the world's largest production and storage facility of antiprotons. The ring housing the 4-mile in circumference accelerator is clearly

discernable. The circle in the foreground outlines an accelerator upgrade, the Main Injector, under construction. (Fermilab Photo)

John Peoples, director of Fermilab, shown with the antiproton source which he designed. The antiprotons produced by collisions of protons on a lithium target are stored in a circular beam using the array of magnets shown in the photograph. (Fermilab Photo)

A portion of the accelerator tunnel, 4 miles long, located 20 feet below the ground, housing the proton-antiproton beams, and the array of superconducting magnets (lower ring) used to steer and accelerate them to energies approaching 10 12 electron volts. {Fermilab Photo)

One of the two large detectors at Fermilab built to analyze the high-energy collisions of protons and antiprotons. The 5000-ton detector is moved in and out of the beam on large rollers. (Fermilab Photo)

The Harvard radio-telescope located at Harvard, Massachusetts, used to obtain the data for the Megachannel Extra Terrestrial Array (META) experiment designed to search for the signals of extraterrestrial life in our galaxy.

The META supercomputer array designed to scan millions of channels at a single time in the search for a signal of intelligent life elsewhere in the galaxy.

The new Billionchannel Extra Terrestrial Array (BETA)supercomputer which will be part of the next generation search for extraterrestrial intelligence.

The Andromeda Galaxy (M31). This is the nearest large spiral galaxy similar to our own, located about 6 million light years away. (Lick Observatory Photograph/Image)

A photograph of our own galaxy obtained using radio and microwave detectors aboard the Cosmic Background Explorer (COBE) satellite. This is the first true photograph of the Milky Way showing its spiral structure, as edge on from the vantage point of the earth. (NASA/COBE)

A high resolution photograph of the core of the galaxy M87, which is thought to house a black hole in excess of 2 billion solar masses. The small disk of ionized gas at the very center, almost perpendicular to the large radio jet seen to be emerging from the center is rotating at about 750 kilometers per second, which gives strong dynamical evidence for the existence of such a black hole. (Holland Ford and NASA)