Read Beyond: Our Future in Space Online
Authors: Chris Impey
Beyond: Our Future in Space (34 page)
Figure 56. The human past becomes primitive viewing history in orders of magnitude of time. Landmarks in the past are labeled, along with speculations about the next thousand years. If humans persist for millions of years, our capabilities could be profoundly more advanced than they are now, and very difficult to predict.
When we finally leave the Solar System, those voyagers will represent a slender green shoot from the sturdy human tree. There’s no need to break laws of physics, or even to travel at a substantial fraction of the speed of light. They will never rejoin the tribe. Once they leave home, there’s no returning. The first European settlers to America knew that they would never go home; the commitment of the first star travelers will be just as absolute. They will, however, need to be kept alive for the duration of the trip.
Exploration of space beyond the Solar System is only possible if we persist as a species. It will also require innovations to extend the lives of the travelers.
The pig is named 78-6. She’s ruddy pink and weighs 120 pounds, and her beating heart is exposed in the operating theater. The surgeon cuts the aorta, watches the EKG flatline, and connects external tubes to replace the pig’s blood with a chilled saline cocktail. With her vital organs preserved, 78-6 isn’t quite dead. She’s in a state of cryogenic suspension or suspended animation at Massachusetts General Hospital in Boston. This surgeon has suspended 200 pigs for one or two hours each, and they all survived as long as they were given optimal treatment. A few hours later, 78-6 will wake up in a recovery room with classical music on the radio and a healthy pig in an adjacent stall for company. Postmortem exams on other pigs showed no cognitive damage from the procedure.
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Research in suspended animation is in its early stages. Pigs are critical test subjects because their physiology is close to that of humans. Also at Mass General, mice have had their metabolisms slowed by factors of ten or twenty. In other research labs, dogs have been revived after hours of being clinically dead. In a few cases, humans have survived being subjected to extreme hypothermia and near death for several weeks.
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But we’re taking the long view now, so let’s assume that we eventually master the art of suspended animation. This finesses the obstacle of long travel times—these starship Rip Van Winkles would wake up and continue with their new lives, oblivious to the centuries it took to get to their destination. Suspended animation would create an irrevocable rift between the voyagers and the Earth. Everyone they knew and loved, and their descendants, would have lived and died while they silently sailed through the void.
Let’s also assume that human cloning will one day be perfected. Since the pioneering experiment that gave birth to Dolly the sheep in 1996, cloning has been performed uneventfully on rabbits, goats, cows, cats, and fifteen other species.
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Primate reproductive biology appears to be more complex, but it’s only a matter of a few years before humans are cloned. Cloning is ethically fraught, but it would provide a way for us to propagate in the vastness of space. Instead of one set of colonists, chosen to be a minimum viable population with a good genetic mix, there would be a suite of colonies, each composed of the same set of cloned individuals. Each cloned colony would disperse to a different destination. Each would grapple with a different environment. Despite identical DNA, the evolutionary paths of the colonies would diverge. Taken together, they would play out natural selection on a new cosmic stage.
How then will we head for the stars?
Conceptually, there are four approaches: The travelers live and die on the spaceship, they travel in suspended animation, they’re carried as embryos or single cells, or they’re transported digitally at the speed of light. These four scenarios are ordered in increasing level of technical sophistication but decreasing order of resources required for the trip.
We’ve seen that vast Gerard O’Neill pinwheels loaded with thousands of passengers are ruinously expensive, and teleportation is far beyond current and projected technology. Suspended animation is promising, and it need not be for the whole trip. Subsets of the crew could be revived periodically to monitor life-support systems and carry out routine maintenance. Embryo transport may also be possible one day.
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Echoing Arthur C. Clarke, we’ve imagined the emotional impact of the cry of the first off-Earth infant. But what if that baby is animated after a journey of millennia and tens of light years? It would have traveled as a frozen zygote, the earliest developmental stage of an embryo. It would then have been brought to term in an artificial womb, and reared to self-sufficiency by robotic nannies, all to be part of a new human colony. The starship would also carry frozen cells of useful livestock and crops, serving as a miniaturized Noah’s ark.
Living in the Multiverse
We leave a tiny footprint in the universe. The sum of all our industry and striving is a spherical ripple moving out into the void. We’ve had powerful radio and TV transmitters operating for fifty years, and in principle that expanding sphere of radiation has swept over thousands of habitable worlds. In practice, all the pop-culture messages carried by these waves are diluted to a level below the hiss of the cosmic background radiation before they exit the Solar System. The Pioneer and Voyager spacecraft carry information about our civilization, and they’re our first artifacts to reach interstellar space, but it will be hundreds of thousands of years before they reach another star.
Other creatures to have left their planet are likely to be considerably more advanced than us. What would that imply?
Since it’s impossible to anticipate the function and form of an alien species, the simplest way to categorize hypothetical civilizations is by their energy use. This was first done by the Russian Nikolai Kardashev. Kardashev studied astronomy while both of his parents were in Stalin’s slave-labor camps in the 1950s. He heard about Frank Drake’s Project Ozma, which inspired him to write his influential paper “Transmission of Information by Extraterrestrial Civilizations.”
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In it, he defined three levels based on the amount of power available to a civilization. Type I civilizations utilize all the solar energy arriving at their planet’s surface, about 10
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watts for a planet like the Earth and a star like the Sun. The next tier is 10 billion times higher—a Type II civilization harnesses all the energy from its star, about 10
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watts. A Type III civilization is 10 billion times hungrier, consuming energy at the phenomenal rate of 10
37
watts, the luminosity of a galaxy like the Milky Way. Beyond the original Kardashev scale is Type IV: masters of the universe (
Figure 57
).
Kardashev created his scale to categorize technologically mature civilizations. We’re so feeble that we don’t even make it onto the scale. Stuck getting energy from dead plants, our vaunted civilization runs on a measly 0.001 percent of the energy that arrives gratis from the Sun. Theoretical physicist Michio Kaku has noted that with our energy consumption growing at 3 percent per year, we’ll rise to Type I status in a few centuries, Type II status in a few millennia, and, if we make it that long, Type III status in a million years.
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Type I civilizations will elude detection, giving off extra waste heat but not enough to be detected from many light years away. Civilizations that harness most of their star’s energy might be detectable because they would have to build something like a Dyson sphere.
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Freeman Dyson published this thought experiment in 1960, based on a 1937 Olaf Stapledon science fiction novel. The idealized concept of a hollow sphere around a star is physically unstable (in Larry Niven’s
Ringworld
series of science fiction novels, this instability causes a collapse of the civilization), but a civilization might build a swarm of orbiting satellites to envelop the star and capture most of its energy. The visible light is captured and reradiated as infrared emission, so Dyson spheres are detectable as excess infrared emission from an otherwise normal star. Several SETI projects look for anomalous infrared radiation. Researchers at Fermilab, near Chicago, sifted 250,000 stars down to seventeen candidates, of which four were declared “amusing but still questionable.”
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Figure 57. A Dyson sphere is the theoretical concept of an energy collection system that can harvest all the radiation from a star. Nikolai Kardashev imagined a scale of increasing energy usage as a civilization matured—from using the energy falling on a planet (I) to using the energy of a star (II), a galaxy (III), and the universe (IV). A Dyson sphere is the technology of a Type II civilization while we are currently less than a Type I civilization.
The existence of Dyson spheres allows for passive SETI, where no intention to communicate is needed. The premise is that any highly advanced civilization will leave a much larger footprint than we will. Type II or later civilizations may employ technologies that we’re tinkering with or can barely imagine. They might orchestrate stellar cataclysms or use propulsion by antimatter. They might manipulate space-time to create wormholes or baby universes, and communicate via gravity waves. We can look for artifacts as well as messages. Extrapolation is addictive, so some scientists have proposed adding the category of a Type IV civilization that controls space-time well enough to affect the entire universe.
Why stop at one universe?
Modern cosmology involves the idea of quantum genesis—tracing back the cosmic expansion projects to an origin in a singularity where the space that now contains 100 billion galaxies was smaller than an atom. The inflationary scenario is an adjustment of the standard big bang to include an extremely early phase of exponential expansion. The idea was developed to explain why the universe now is very smooth and geometrically flat. Inflation has tentative support from the nature of small temperature variations in the cosmic background radiation. If inflation is correct, the universe began as a quantum fluctuation. The precursor state would have been an ensemble of quantum fluctuations, perhaps infinite in number, each with randomly different initial physical conditions. Some of them inflated into large space-times like our own. Others were stillborn. This process can be timeless and eternal (
Figure 58
). The laws of nature in these parallel universes would differ from the laws with which we’re familiar.
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This, in a nutshell, is the multiverse.
Figure 58. In chaotic inflation, the precursor state was an endless series of space-time quantum fluctuations. Some of these fluctuations might inflate into macroscopic universes, while others would not. This is the multiverse concept.
The multiverse is connected to another issue that has been perplexing physicists for several decades: fine-tuning.
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Albert Einstein fervently believed that the laws of physics, when they were fully understood, would be inevitable, elegant, and self-contained. This quality, called naturalness, has been a touchstone in theories of nature ever since. But nature isn’t cooperating. The “standard model of particle physics” precisely explains the interactions of fundamental particles, but the model is governed by more than two dozen parameters, so it’s not elegant or simple and the parameters don’t emerge naturally from an underlying theory. Some quantities—like the mass of the Higgs particle and the value of the dark energy that controls cosmic acceleration—are much lower than physicists expected. They’re dismayed that laws of nature seem to be an arbitrary and messy outcome of random fluctuations in the fabric of space-time.
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