Beyond Star Trek

by Lawrence M. Krauss

  1: Expanding space would require a kind of matter unlike anything we have observed directly—a kind of matter that is gravitationally repulsive rather than attractive. While the laws governing the behavior of matter on the subatomic scale make such a phenomenon realizable on that scale, we have no idea whether such material could be created even in principle on a macroscopic scale. Preliminary indications are not particularly encouraging.

  2: It would take more energy than the Sun will emit in its entire lifetime to make such material useful for moving any macroscopic object, even if the material could be produced.

  Now for the new results: In the past year, a number of researchers have subjected warp-drive theory to the same kind of scrutiny previously applied to the idea that wormholes might be used as shortcuts through space. Their findings have been no more encouraging. The theoretical physicist Larry Ford and his colleagues at Tufts University have shown that in order not to violate known laws associated with energy conservation, space must expand and contract (at any one time) only in the thin surface layer of a bubble surrounding the spacecraft. It turns out that to maintain a region of exotic matter within a thin shell encircling a macroscopic object like a spacecraft, you’d need an energy roughly equivalent to 10 billion times the entire mass of the visible universe! Perhaps we might imagine transporting single atoms at warp speed, but not spacecraft. The same kind of energetic arguments apply to wormholes and therefore to the time machines that might make use of them.

  There is a much more worrisome problem of principle, which makes warp drive look even less likely, if such a thing is possible. I did not explicitly mention it in my earlier book, because I believed that the other problems were bad enough. Perhaps I should have known better. It’s this: While warp drive allows you to travel globally from one point to a distant point faster than the speed of light, it still won’t get you there any sooner. How so? Well, say you want to travel 1,000 light-years in i second using warp drive. In order to arrange for the space in front of you to collapse, you must arrange for a proper configuration of matter to be distributed throughout it. To do this, you must, at the very least, send a signal all the way throughout this space. But it takes at least 1,000 years for this signal to spread across the region. Thus, while you could (in principle) travel arbitrarily fast once the warp front started to collapse, the “countdown” to takeoff would last 1,000 years. I suppose there is some comfort in being able to spend the 1,000 years waiting in comfortable surroundings instead of sitting inside a cramped spacecraft, but the end result is the same. However you slice it, you can never get from “here” to “there” in less than 1,000 years from the time you first start trying. As wonderful as the possibility seems, in the end warp drive is a cosmic letdown. Take that, Fox Mulder!

  Energy is energy, and even a million years from now, when we will know a lot more physics than we do today, the energy requirements to transport us throughout the galaxy will still be the same, and the energy required to manipulate gravity to bend it to our will seems to be greater than all the energy in the galaxy put together. This is why most physicists, myself included, find it so unlikely that Earth has been visited by aliens, especially aliens from a sufficiently advanced civilization willing to exhaust the necessary resources to travel all the way here just to insert metal objects up people’s noses or abduct the patients of a Harvard psychiatrist. Even if they did want to do kinky experiments, it hardly seems worth it.

  Fox Mulder, who has certainly replaced Star Trek’s Q as the most quotable person on television, once argued that “the easiest explanation is also the most implausible.” For many people, the easiest explanation for the vast number and variety of tales of alien sightings and abductions is that aliens have been here. But to physicists, this explanation is the most implausible—simply because the more mundane possibilities involve requirements far less daunting than those that face any interstellar travelers.

  Because we seem to be forbidden by energetics (if, perhaps, not by physics) from traveling at speeds greater than light, the plausibility of Area 51, Roswell, alien implants, and all of that becomes even more remote. Why should aliens devote the necessary resources to visit us if they are not aware that intelligent life exists on Earth? But in order to be aware of this, they would have to have received signals of our existence. We have only been emitting such detectable electromagnetic signals—via I Love Lucy, Star Trek, The Twilight Zone, NBC Nightly News, and so on, for little more than half a century. By 1947, the year of the first flying saucer sightings and of the Roswell incident, our broadcasts would just have begun to reach the closest star systems. It seems wildly unlikely that any civilizations living there would have had time, even had they possessed the necessary resources, to launch a mission to Earth that would arrive by 1947. The aliens in the movie Contact, who detected the TV signal showing Hitler opening the 1936 Olympics, sent back a reply which didn’t get here until 1996.

  There is a loophole I haven’t yet discussed, and it is one that is often brought up at my talks, either in the context of alien visitation or of our current view of the universe. What if the laws of physics aren’t the same out there as they are here! Indeed, if Q can transcend our laws of physics, why can’t the universe? One often finds in science fiction stories that in certain “weird places” the laws of physics don’t behave as they are supposed to. I still vividly remember the terror I felt as a child, watching a Twilight Zone episode in which the walls of a house suddenly became incorporeal gateways to another dimension and a small boy about my age fell through.

  It is impossible to guarantee—at least until one has turned over every last rock and explored every last nook and cranny—that there are no Twilight Zones in the real universe. So why are we physicists so conceited as to assume that our laws are universal? “What cosmic gall!” my wife often exclaims when confronted with like assumptions.

  Well, there are two answers, but they are both essentially the same. The first is that 400 years of success has indeed made physicists conceited. The second is that in those 400 years of success, every test we have performed to check for the universality of physical laws has come up positive.

  Rather than dwell on the details of the history of physics, I want to tell you about a modern discovery, which I believe convincingly underscores the universality of the fundamental laws of physics as we know them.

  When confronted with questions about the universality of physical laws, scientists usually turn to the stars. The editors of Social Choice and other postmodern journals may suggest that the laws of physics would be different had they not been developed by dead white males, but I find comfort in objective reality when I look at the sky on a starry night. Around distant stars there may be planets where female symbionts inhabit and govern otherwise male bodies and minds, like the Trill in Deep Space Nine, but even there the laws of physics they develop will have to account for the fact that their Sun (or Daughter?) shines with exactly the same colors as ours. There is nothing more telltale—not even a fingerprint, or a DNA trace—than the spectrum of light emitted by an object when it is heated up. Every element emits its own unique combination of colors, and it was one of the great successes of twentieth-century physics to catalogue those spectral features that had already been observed and then to predict those that hadn’t. The fact that distant stars shine with the same set of colors emitted by hydrogen gas when it is heated in a lamp in a terrestrial laboratory not only tells us that the stars are made mostly of hydrogen, it also tells us that the very laws of electricity and magnetism, which (together with the laws of quantum mechanics) produce these spectra, must be the same there as here.

  So much for the stars, but what about the space between the stars. What about the universe itself? Well, thanks to NASA, we now have compelling direct evidence that the fundamental laws of physics as we know them apply on the scale of the entire visible universe and, moreover, have so applied for most of its lifetime. You may have heard of the Cosmic Background Explorer (COBE) sate
llite, which was launched in 1989 by NASA to measure the properties of the radiation left over from the Big Bang from which our universe emerged some 10 to 15 billion years ago. COBE famously succeeded in finding minuscule fluctuations in this so-called cosmic background radiation, constituting the “seeds” of the cosmic structures we observe today, but first it measured the spectrum of the primordial radiation and confirmed what had been predicted—that it was of the form known as blackbody radiation.

  All you really need to know at this juncture about the blackbody spectrum—so named because it is the spectrum emitted by a perfectly black object when it’s heated—is that the correct understanding of it was the driving force behind almost all the major results of twentieth-century physics. The investigation of blackbody radiation led to the development of quantum mechanics and the correct quantum-mechanical treatment of electricity and magnetism. More important, at the very basis of the blackbody spectrum is a profound and subtle understanding of the statistical behavior of myriad individual particles. This understanding, called statistical mechanics, is at the heart of almost every calculation done by theoretical physicists today and almost all observed phenomena. It was developed to explain why you can’t tell by looking at, say, a movie showing the collision of 2 billiard balls whether the film is running backward or forward, whereas when you observe the collisions of 16 billiard balls—as when the cue ball hits a freshly racked set—that symmetry is lost. The principles involved in statistical mechanics are so subtle that two of its developers killed themselves because of the initial resistance to their ideas.

  In any case, it turns out that the cosmic background radiation left over from the Big Bang not only exhibits a blackbody spectrum but it is the most perfect blackbody spectrum ever measured—closer to the theoretical prediction than anything we have been able to create in the laboratory. We can therefore use the universe itself to test the predictions of quantum mechanics. To turn it around for the argument at hand, we now know that even the most subtle and complex laws that lie at the foundation of modern terrestrial physics apply to a radiation bath that permeates the entire visible cosmos, in space and time. It would be hard to ask for a better reason to believe that if there are Twilight Zones they are well hidden, and therefore probably irrelevant.

  In spite of all of this—in spite of the evident impossibility of launching realistic spacecraft to make round-trip visits to other stars, the implausibility of alien visitation, and the universality of the roadblocks and effective speed limits marking interstellar travel—I am firmly convinced that our destiny does lie in the stars. We will, one day, travel beyond our solar system. How can I say this with a straight face, after all that I have argued here? Well, every obstacle I have described lies only in the way of making a round-trip, on a human timescale. But the key to our future in the stars is that neither of these conditions need be fulfilled when we do venture out into the galaxy, as I believe we one day must.

  CHAPTER SIX

  SEEING IS BELIEVING

  I believe I am the most fortunate sentient in this sector of the galaxy.

  —Data

  Fifty years ago, Martians were the prototypical extraterrestrials, with Venusians a close second. As we learned more and more about our solar system, however, our expectations for finding life (let alone intelligent life) lurking on Mars or Venus began to fade. With the exception of a few Hollywood stars, the rest of us accepted the fact that we lived on the only planet orbiting our Sun which had ever harbored intelligent life.

  How much has changed in the past year! The claim by a team of NASA and university researchers that a meteorite from Mars known as ALH84001, which fell to Earth some 13,000 years ago and was later discovered in Antarctica, showed fossil evidence of microscopic life-forms electrified the world. Perhaps the rest of the solar system is not barren after all.

  The search for life on Mars has its roots in the search for the origins of life on Earth. Until perhaps a decade ago, it was felt that in order to flourish, organic life, like Goldilocks, needed conditions that were “just right”—enough water, warmth, and light, but not too much. But scientists exploring remote and inhospitable locations ranging from boiling vents in the deep seafloor to the frigid, wind-scoured valleys of Antarctica, from the burning sands of the Gobi desert to the sulfuric ooze from oil wells, have discovered that various forms of primitive life (like various forms of less primitive life such as race-car drivers and mountain climbers) choose to live on the edge. These extremophiles, as they are called, exist in all the wrong places. They may not flourish (indeed, some of them just barely hang on), but they survive, sometimes without light, heat, oxygen, or water—all the standard ingredients we once thought necessary to life.

  The evidence in favor of possible primeval life on Mars is controversial, but it does point to several interesting possibilities. The fossilized microbes that investigators claim to have found in ALH84001 would be more than 3 billion years old. They date to a time when the Martian surface was warmer and wetter, and thus more hospitable to life. Why Mars became barren and Earth did not is not fully understood. However, perhaps what is most significant about the claimed discovery is that the discoverers did not have to go to Mars to find the rock; it was sitting there, waiting to be found, on the windy ice-covered plains of Antarctica.

  Equally significant, perhaps, is the fact that this same location is where scientists have discovered primitive terrestrial life-forms called cryptoendoliths living inside frozen rocks. And deep underground in the frozen permafrost of Antarctica and Siberia, microbes have been discovered in various states of activity, some of them having lain virtually dormant for over 3 million years.

  It is now clear that meteor, comet, and asteroid impacts on planetary surfaces impart enough energy to kick projectiles into interplanetary space. This means that the Earth is not a closed ecosystem! If matter is exchanged between planets, then certainly organic materials might be, too—including, perhaps, primitive self-reproducing life-forms. (It is highly unlikely that any advanced form of life would survive the catastrophic ejection and subsequent interplanetary voyage.) Moreover, if primitive life-forms can remain dormant for millions of years until conditions are appropriate for them to “turn on,” then it’s perhaps possible that life on one planet could seed life on another.

  This is reminiscent of the panspermic theory that Francis Crick proposed, not altogether facetiously, a while back. Similar ideas have been proposed in science fiction novels and movies, with the source of the “seeds” usually being alien intelligences who later return to see how their offspring are doing. In a particularly creative use of this idea, the writers of Star Trek were able to explain why a great many of the extraterrestrials the Enterprise crew encounters are humanoid. Jean-Luc Picard, carrying on the work of the archaeologist Richard Galen, discovered that the primordial seas of many different planets had been seeded with DNA provided by a long-dead civilization.

  In any case, the discovery of what might be fossil evidence of Martian life, combined with interplanetary transport afforded by cataclysmic planetary collisions, suggests that the discovery of extraterrestrial life in our solar system may in fact be nothing of the sort. Who is to say that such life will be unrelated to our own? We may discover only our distant cousins! In fact, it appears that non-intelligent life-forms can survive processes that eventually lead to the demise of their home planets. The frozen bacteria in the Siberian permafrost demonstrate that primitive life-forms are capable of outlasting devastating climatic change. Could such microbial life survive long enough to be ejected and seed another world?

  The notion that life on Earth may well not have originated on this planet received further support from observations of the Hale-Bopp comet. (No, I am not referring to the observation of an alien spacecraft carrying members of our mother civilization!) Spectroscopic data indicate the presence of over 100 different types of relatively complicated organic molecules on the comet, including glycine, an amino acid. It has been argued t
hat enough organic material—and water, as well—could have been delivered to the Earth’s surface by cometary impacts during its early history to provide the wherewithal for all organic life on our planet. This is supported by recent evidence that the Earth is being continually bombarded by up to 30 small, water-bearing comets per minute, and by observations of the impact of comet Shoemaker/Levy on Jupiter, which indicate that some water from the comet made it down into the planet’s atmosphere. Perhaps—in a classic reversal of the typical scenario wherein we colonize the solar system—the solar system colonized us.

  This colonization might explain the relatively early appearance of life-forms on Earth, an event now thought to have occurred within 100 million years of the time the planet cooled and became habitable. The evidence also suggests that life evolved rapidly after its first appearance. Perhaps the discovery that life is robust enough to adapt to environments previously thought to be sterile—in boiling water full of organic solvents and heavy metals, for example—may explain this rapid burgeoning. Or perhaps some of those life-forms were delivered by interplanetary mail.

  This process need not have been restricted to our solar system. After all, how did the organic molecules on Hale-Bopp get there in the first place? One possibility is that they were cooked up in the comet itself. Hale-Bopp’s large tail, extending almost 30 degrees across the sky, so far from the heat of the Sun, suggests that there may be internal energy sources in the comet itself. Perhaps the material inside its frozen shell is liquid. In such a primordial soup, might something akin to the classic Urey-Miller experiment of 1953—in which a primitive atmospheric “soup” of methane, ammonia, hydrogen, and water was zapped with an electrical current to produce various organic compounds including two of the constituents of proteins, glycine and alanine—have been carried out on a cosmic scale?