The Astral Mirror (22 page)

All around this country, grass roots organizations are forming to support a stronger, more effective space program. These groups include the National Space Institute, the L-5 Society, the Planetary Society, the AIAA, the A AS, and many others.

I urge you to join these groups, to use your energy and intelligence—and your experience in organization—to help these grass-roots groups to build a powerful voice in favor of a truly vigorous space program.

And more.

Twenty years ago, the environmental movement was as small and scattered as the space movement is today. Now the environmentalists are a powerful political force. Unfortunately, most environmentalists tend to look at the space program with suspicion, if not outright hostility. This is a tragedy for both sides, because the long-range goal of both sides is exactly the same: we both want a clean, green, safe planet Earth, a home world for humankind that is a good place to live on.

We must bridge these gaps of mistrust and misunderstanding between the environmentalists and the space enthusiasts. We must prove to our political and business leaders that either we reach into space or we collapse here on Earth and sink into decay.

You can help.

It is time you lifted your faces from those fantasies of the future and got to work here in the present. We build our future by what we do—or fail to do—today. Now. Here.

The future begins today. Let us build together the kind of future that we all want to live in. And let us start
now.

I do a good deal of lecturing around the country, on a number of topics. I like to spring this one on astronomy groups. It’s an old conundrum among astronomers and cosmologists: “If the universe truly holds many intelligent life forms, why have we not found any evidence of their existence?” This essay shows that we have. It takes a fairly detailed understanding of modern astronomy to find the weak points in my argument. Sometimes, I almost convince myself!

All right, so we believe that there could be older, smarter races out among the stars. Maybe they’ve even visited here. Perhaps they’re watching us with some gentle amusement as we sweat over our dinky little shuttle missions and Voyager probes.

When are we going to get some evidence about these alien races—some cold, hard facts that show they really exist?

Many astronomers and cosmologists will give you statistics. They’ll state that out of the billions and billions of stars in the universe, even if intelligent races arose on only one out of every hundred billion, there would still be a huge number of intelligent aliens out there. But we’re not interested in statistics and speculation now. We’re after
evidence—
something we see, hear, taste, touch, or smell.

And we want the evidence now, for us, not our descendants.

For years, astronomers have searched the stars for intelligent signals with radio telescopes. There are a hundred billion stars in the Milky Way galaxy. Unless intelligence is
very
commonplace, the chances of getting to chat with alien creatures on the radio during our own lifetimes are very slim at best.

All right. Somebody’s out there—we hope. But probably not close enough to reach by interstellar phone. So we run smack into the starflight problem again. If we have any hope of seeing or hearing them, either they have to get close enough to make at least a radio contact or we have to go out and find them.

Maybe they are out there, flitting around among the stars, but we just don’t know it. Maybe we’ve actually seen their starships without realizing it. What would a starship look like, from Earth?

Let’s try to construct a starship mentally and see if we can find anything in the heavens that fits the description. After all, we have some fairly decent telescopes and radio receivers. Maybe, if we know what to look for, we can come up with a hunk of evidence that shows they’re really out there.

We must assume that interstellar ships will be propelled by some form of rockets. We’re forced into this. No other propulsion system that we know of today can move a vehicle through space. Except solar sailing, in which you allow the minuscule pressure of starlight to push you along. But solar sailing is incredibly slow. It would take a ship hundreds of years to get from here to Pluto. Count it out as an interstellar propulsion system.

Perhaps a starship would have some form of propulsion that we don’t know about—antigravity, or something equally far out. But if we don’t know how it works, we don’t know what to look for. There could be a sky full of such ships and we’d never realize it.

So we’ll have to live with rockets.

Dr. Edward Purcell, a Nobel laureate in physics from Harvard University, tackled the very same problem some years ago. He worked out the mathematical foundations for interstellar flight; it is published in a book called
Interstellar Communications
(1963). But Dr. Purcell did the job in order to show that interstellar flight is not only impossible, it’s hogwash—pure and unadulterated!

He first pointed out that the best you could hope for was a speed of about 99 percent of the speed of light. Fine, we can accept that. As we saw in “Starflight,” relativity theory shows that you can’t go faster than light, but at speeds close to light speed there’s a time-stretching effect that allows you to cover enormous distances while hardly aging a moment. Combine that with cryogenically suspended animation during the dull portions of the trip, and you’ve got the possibility of exploring practically the whole known universe within a human lifetime.

But how do you get to that speed? Purcell showed that if you use nuclear fusion engines—even fusion engines that are 100 percent efficient—the rocket ship needs about 1.6 billion tons of propellant for every ton of payload. Billion. A bit uneconomical.

So Purcell looked into the possibilities of using an antimatter drive for the rocket.

Antimatter was first predicted theoretically, and then discovered in experiments involving huge particle accelerators—“atom smashers” such as cyclotrons and synchrotrons. Whereas a normal electron has a negative electrical charge, an antielectron has a positive charge and is called a
positron.
A normal proton carries a positive charge, an antiproton is negative. For every normal type of subatomic particle there is an antiparticle.

Antimatter has the interesting property of reacting violently when it contacts normal matter. Both the normal matter and antimatter are completely annihilated and transformed into energy.

In contrast, our hydrogen fusion reaction turns only 0.7 percent of the original hydrogen’s matter into energy. A matter-antimatter collision turns 100 percent of the material into energy.

So Purcell examined the possibilities of using matter-antimatter reactions to drive a starship. He found that you need “only” 40,000 tons of propellant—half of it antimatter—for every ton of payload.

But two other problems arise. First: how do you hold antimatter? It can’t touch any normal matter, or
boom!
Perhaps a strong magnetic field—a “magnetic bottle”— could do it. Second, the rocket exhaust of an antimatter drive would pour out some 10
¹⁸
watts of gamma rays. That’s a billion billion watts of gamma radiation. This is more energy than the Sun lavishes on our Earth—and sunlight is far more gentle than gamma radiation. If you turned on that kind of engine, you’d bake Earth—or whatever planet you’re close to—to a fine dead ash.

Purcell concludes, “Well, this is preposterous.... And remember, our conclusions were forced on us by the elementary laws of mechanics.”

Preposterous? That’s his opinion. It would have been Leif Ericson’s opinion if one of his Viking cohorts had shown him the blueprints for a nuclear submarine. It would have been Orville Wright’s opinion if he had seen sketches of a swing-wing supersonic jet plane.

All that Purcell’s equations really show is that starships should be bulky—huge. And as for radiating 10
¹⁸
watts— marvelous! That kind of light bulb should be visible over long distances and help us to find starships, if they’re out there. It’s probably safe to assume that anyone smart enough to build a starship might also be smart enough to coast away from planetary neighborhoods before lighting up his main engines.

And, of course, the Bussard interstellar ramjet gets around the propellant problem almost entirely.

But there’s another consideration that leads to the conclusion that
anyone’s
starship is going to be huge—the time problem.

All starflights are going to be one-way trips, in a sense. Thanks to the time-dilation effect at near the speed of light, you can cover thousands of light-years in the subjective twinkling of an eye, but when you return to your home world, thousands of years will have elapsed there. Even in a very,
very
stable society, things would have changed so much that you’d be out of place. And even if your friends have tremendous life-spans, either they would be so different from you when you return as to be virtual strangers or they would be the biggest bores in the galaxy. People change, and cultures change, over the millennia.

So interstellar voyages are going to be one-way voyages, in effect—unless our concept of the universe is glaringly wrong.

This means that a starship will become all the home that its crew ever knows. Which, in turn, means that the crew’s family is going to be aboard. The ships will be little cities of their own—and maybe not so little, either. For just as the Old Testament patriarchs begat new generations, interstellar families are going to grow.

Several thinkers have mentioned in the past that a hollowed-out asteroid might make a good spaceship. Why not consider a larger body, something the size of the Moon or Mars? There would be plenty of room for families and cargo, and lots of hydrogen fuel locked away in the planet’s bulk. All the natural resources of a full-sized world would be right there. Sure, the planet-ship would be getting smaller all the time, but you could probably pick up other unpopulated chunks in your travels. In fact, the moons of ice-giant planets such as Jupiter might well be perfect fuel tanks for interstellar ships—little more than fat balls of hydrogen ice.

The starship crew would have to live underground when they’re in between stars, but they’d have to live indoors in a factory-built ship anyway. At least, on a reasonable-sized planet, when they got close enough to a warm star they could come outdoors just as soon as their atmosphere thawed out.

The propulsion system that pushes a moderate-sized planet through interstellar space at relativistic speeds (close to light speed) would have to be so powerful that it boggles the imagination. As we’ve already seen, it staggered at least one Nobel Prize winner. But it’s not beyond the known laws of physics! Certainly, we can’t build such a rocket engine now; but there’s no fundamental law of physics that says it’s impossible to build such an engine.

All right, now we know what to look for. At least, we think we know one of the things that we might want to look for. Is there anything resembling a planet-sized starship, using fusion or antimatter rockets, within sight of our telescopes?

Well, what would it look like through a telescope?

Most likely, what we’d see would not be the ship itself, but its exhaust plume, a huge, hot glob of ionized gas, which physicists call a
plasma.
The plasma would expand from the ship’s rocket nozzles to enormous dimensions in the hard vacuum of interstellar space. The plasma would be moving at speeds close to that of light, and so would show huge red shifts. And, unlike any natural heavenly body, the plasma exhaust might fluctuate unpredictably as the ship changed course or speed.

Over the past two dozen years, the entire astronomical community has gone out of its head trying to figure out what the “quasi-stellar objects,” or quasars, might be.

Quasars show enormous red shifts, amounting to speeds of close to 90 percent of the speed of light. Because of these red shifts, astronomers at first thought that the quasars were out at the farthest edges of the observable universe, and their red shifts are caused by the general expansion of the universe.

But quasars twinkle! Some of them brighten and dim over the course of a year or two, others in several weeks or days. A few have been seen to change brightness within a few minutes.

Partly because of this twinkling, many astronomers have leaned toward the idea that the quasars are relatively close by, perhaps not far from the Milky Way galaxy, perhaps actually within it. However, most of the evidence available points to the conclusion that the quasars are at least some distance outside the Milky Way, probably on the order of a hundred million light-years distant. This is still “local,” compared to the “cosmological” distances of billions of light-years that were originally assigned to them.

The quasars are apparently composed of very hot gases, plasmas, that are strongly ionized at temperatures of some 30,000 degrees Kelvin. The actual size of the quasars is not yet known. If they’re cosmologically distant, then they must be close to the sizes of galaxies. But if they’re close to the Milky Way or even inside it, they could be as small as star clusters or even smaller.

Neither cosmologists, astronomers, nor physicists have been able to explain what produces the titanic power output of the quasars. Their light and radiowave emissions are beyond anything that known natural physical processes can explain. Ordinary physical processes, such as the hydrogen fusion reactions that power the stars, just won’t fill the bill. Something else must be burning inside the quasars. A few scientists have suggested matter-antimatter reactions.

Could the quasars be powered by fusion reactors of the type that we would build someday to drive starships? They would run much hotter than the fusion reactions that power the stars. Or might the quasars truly be driven by antimatter reactions?

But if the quasars are starships, and what we’re seeing is part of the normal interstellar traffic of the Milky Way galaxy, how come all we see are
red-shifted
quasars? A red shift means the object is moving away from us. Why don’t we see any blue-shifted quasars, that is, starships heading toward us?