One Lifetime Is Not Enough for a Trip to Distant Stars
One Lifetime Is Not Enough for a Trip to Distant Stars
NATALIE ANGIER . NY Times . 05 march 2002
Nobody knows why our early ancestors decided to get off their knuckles and stand upright. Maybe they just wanted a better view of the stars.
And when sky gazers finally realized that the heavenly lights were not the footprints of the gods, but rather millions of blazing stars like our Sun writ far, they began to wonder, How do we get there? How can we leave this world and travel, not merely the 238,000 miles to the Moon, or 35 million miles to Mars, but through the vast dark silk of interstellar space, across trillions and trillions of miles, to encounter other stars, other solar systems, even other civilizations?
According to a group of scientists for whom the term "wildly optimistic dreamers" is virtually a job description, it will indeed be very difficult to travel to other stars, and nobody in either the public or private sector is about to try it any time soon. But as the researchers see it, the challenge is not insurmountable, it requires no defiance of the laws of physics, so why not have fun and start thinking about it now?
At the annual meeting of the American Association for the Advancement of Science, held last month in Boston, scientists discussed how humans might pull off a real-life version of "Star Trek," minus the space Lycra and perpetual syndication rights.
They talked about propulsion at a reasonable fraction of the speed of light, a velocity that is orders of magnitude greater than any space ship can fly today, but that would be necessary if the light-years of space between the Sun and even the nearest star are ever to be crossed.
They talked about the possibility of multigenerational space travel, and what it might be like for people who board a space ship knowing that they, their children, grandchildren and descendants through 6, 8 or 10 generations would live and die knowing nothing but life in an enclosed and entirely artificial environment, hurtling year upon year through the near-featureless expanse of interstellar space.
They talked about how big the founding crew would have to be to prevent long-term risks of inbreeding and so-called genetic drift. They talked about how the crew's chain of command would be structured, what language people would most likely speak, and what sort of marital and family policies might be put in place.
And they talked about food, all of which would have to be grown, cultivated and synthesized on board.
"One thing is almost certain," said Dr. Jean B. Hunter, an associate professor of biological and environmental engineering at Cornell. "You'll have to leave the steak, cheesecake and artichokes with hollandaise sauce behind."
Many of the subjects raised during the session were so fanciful that at times it felt like a discussion of how to clone a unicorn, and indeed half the presenters moonlight as science fiction writers.
Nevertheless, the researchers argued, human beings have shown themselves to be implacable itinerants, capable of colonizing the most hostile environments.
Dr. John H. Moore, a research professor of anthropology at the University of Florida, compared a theoretical crew of spacefaring pioneers to groups of Polynesians setting out tens of thousands of years ago in search of new islands to populate.
"Young people with food and tools would set out in large flotillas of canoes," he said. "Nobody knew if they would ever come back, the trade winds went in only one direction, and many of them perished in the ocean."
Yet over time, the Polynesians managed to colonize New Zealand, Easter Island and Hawaii.
Still, no human migration in history would compare in difficulty with reaching another star. The nearest, Alpha Centauri, is about 4.4 light- years from the Sun, and a light-year is equal to almost six trillion miles. The next nearest star, Sirius, is 8.7 light-years from home. To give a graphic sense of what these distances mean, Dr. Geoffrey A. Landis of the NASA John Glenn Research Center in Cleveland, pointed out that the fastest objects humans have ever dispatched into space are the Voyager interplanetary probes, which travel at about 9.3 miles per second.
"If a caveman had launched one of those during the last ice age, 11,000 years ago," Dr. Landis said, "it would now be only a fifth of the way toward the nearest star."
Dr. Robert L. Forward, owner and chief scientist of Forward Unlimited, a consulting company that describes itself as "specializing in exotic physics and advanced space propulsion," argued that rockets and their fuel would be so heavy that they would prevent a starship from reaching the necessary velocity to go anywhere in a sane amount of time. He envisions a rocketless spacecraft that would be manufactured in space and equipped with an ultrathin, ultralarge sail, its span as big as Texas but using no more material than a small bridge. A beam of laser light or high-energy particles from a source on Earth, in space or perhaps on the Sun- drenched planet of Mercury would be aimed at the sail, propelling it and its attached module to as much as 30 percent the speed of light or about 55,000 miles per second.
At that pace, said Dr. Forward, a crew would reach Alpha Centauri in under 50 years.
"You could get a bunch of 16-year- olds, train them and then send them out at the age of 20," he said. "They'd have a long, boring trip, reach Alpha Centauri when they're in their 60's or 70's, do some exploring, and send everything they learned back home."
Admittedly, the astronauts would not make it home themselves. "It's a lifetime job," Dr. Forward said. "But it could be done in a single generation."
For longer journeys, designed with multigenerational crews in mind, an onboard engine and fuel source would be required, perhaps something powered by nuclear bombs, or the combining of matter and antimatter in a reaction that converts both substances into pure energy.
However the ship is propulsed, the researchers agree that it must be comfortable for long-distance travel. That means creating artificial gravity by gently rotating the craft; a spin no greater than one or two revolutions per minute would suffice.
It might also mean calling upon architects with Disney-esque sensibilities.
"The inside of one of these long- duration space habitats might feel like the inside of a shopping mall," Dr. Landis said. "Malls are carefully designed to use space efficiently, yet to give you the feeling that they're more spacious than they are."
And malls, of course, are a great place to bring the family. In Dr. Moore's view, the good old-fashioned family is the key to success in space.
"Over the past several decades, space scientists and writers of science fiction have speculated at length about the optimum size and composition" of an interstellar crew, he said. They have imagined platoons of Chuck Yeager-type stalwarts grimly enduring all hardships, or teams of bionic and vaguely asexual crew members overseeing freezers of embryos that can be defrosted and gestated as needed.
"Some of the scenarios proposed so far are downright alarming from a social science perspective," Dr. Moore said, "since they require bizarre social structures and an intensity of social relationships which are quite beyond the experience of any known human communities."
In deciding how to organize a star mission, Dr. Moore looks to the most "familiar, ubiquitous, well-ordered and well-understood" of social forms, the human family. "Virtually every human society in history has been structured along kinship lines," he said, "from small-scale foraging societies to empires comprising millions of people."
Lines of authority and seniority in a family are reasonably clear, and when they're not, well, there's always the time-out chamber.
In Dr. Moore's rendition, all recruits for an interstellar odyssey would be guaranteed the opportunity, though not the requirement, to marry and have children. Mate choice would be part of the bargain as well, with the population cannily structured so that each cohort of individuals, on reaching sexual maturity, would have about 10 potential partners of a similar age to select from.
Dr. Moore and his colleagues have developed a computer simulation called Ethnopop, in which they asked how large the crew must be in order to maintain genetic variability over time while still allowing crew members a choice of sex partners. They determined that a founding crew could be as small as 80 to 100 people and stay viable for more than a thousand years, assuming that two rules were followed: women waited until they were in their mid-30's or so before having children, and they had only a couple each. Counterintuitive though it may seem, said Dr. Moore, delayed childbearing and small families are known to help maintain genetic variability in a closed population.
Genetic diversity may be essential, but Dr. Sarah G. Thomason, a professor of linguistics at the University of Michigan, argued that the same could not be said for language. "You want everyone to be able to talk to each other as soon as they're on board," she said.
As Dr. Thomason sees it, the likeliest lingua franca for a starship will be gracias a Dios English. After all, she said, English is the language of the international air traffic control system, the scientific community and the educated class generally. English is the official language of 51 of the 195 nations of the world, and it is the second language of many others.
Yet, while crew members will be expected to speak English, their accents are likely to be quite diverse, and the English that their children and grandchildren end up speaking will have a rhythm and texture of its own Space English. And though Dr. Thomason believes that the basic structure of Space English is not likely to change much from that of the mother tongue, teenagers will, of course, invent words of their own and drop words of scant use. "I can imagine the loss of words like snow, rivers, winter, mosquitoes, if they're lucky," she said.
Another arena that will test the limits of human ingenuity is space cuisine. Without livestock on board or supply ships to restock the pantry, crew members will have to be entirely self-sufficient. Dr. Hunter of Cornell envisions crops grown in hydroponic gardens, in which plants are suspended in troughs like rain gutters, and water and fertilizer are trickled slowly over their roots. Among the possible food groups are wheat, rice, sweet potatoes, beans, soy, corn, herbs and spices.
In addition, space-minded agronomists are exploring the marvels of microbes. Plants take weeks to grow, but yeastlike micro-organisms replicating in vats can be used to churn out significant quantities of carbohydrates, sugars, proteins and fats in a matter of hours. Of benefit to a community in which recycling is not just a personal virtue but a public necessity, micro-organisms can live on the carboniferous waste products of plants and people.
"There's a protein product called quorn, which is made from filamentous mold," Dr. Hunter said. "Not to make a joke of it, but it does taste like chicken."
Some clichés, it seems, are truly universal.