Leif Podhajsky

Zheng He! Zheng He! Is there a better icon for interstellar voyaging?

Between 1405 and 1433, Zheng set out from China on massive naval expeditions that reached as far as Mecca and Mombasa, journeys with more than 300 vessels and 28,000 crew, excursions far bigger and longer than those of Columbus more than a half century later. Staggering in price, formidable in technical sophistication, unprecedented in level of national commitment—Zheng's voyages remain the closest functional equivalent to the cost, effort, and risk required to travel into deep space. Trying to picture what settling other planets might entail? One place to look is 15th-century China.

Zheng was an unlikely candidate for a life of far-flung adventure. At the time of his birth, China was torn by war between the Yuan dynasty and surging Ming rebels. Zheng was born into a Muslim family in the remote Yunnan province, then a battleground between Yuan and Ming. When he was about 10, invading Ming forces captured him and slaughtered most of his family. The boy was castrated. Forced to serve the Ming crown prince, Zheng eventually became his confidant and trusted adviser. After the last Yuan emperor fled in 1368, Zheng became part of an elite group of eunuch adventurers and troubleshooters at the Ming court in Beijing.

The Ming government backed Zheng for decades. Seven times the emperor arrogantly overruled his accountants and summoned the vast amounts of material necessary to provision thousands of people on years-long voyages. Ultimately, Zheng took the Ming banner as far as East Africa and the Middle East.1 These areas were poorer than China, but they were thriving and productive. Alas, traveling to Africa to buy its iron, no matter how high the quality, would be like driving a hundred miles to pick up a gallon of exceptionally good milk—not a sensible use of time, money, or effort. In 1433, the voyages abruptly ceased; Ming bureaucrats had finally convinced the elite that they didn't make economic sense.

Zheng He’s ship undertook one of mankind’s greatest explorations into the unknown. Chris Philpot

If we traveled to other worlds, could we avoid the Zheng He problem? Back in 1978, the Nobel-winning economist Paul Krugman, a science fiction fan, playfully laid out the basic economics of interstellar trade. To justify the cost, Krugman pointed out, would-be starfarers must bring back something worth more than what they would have made by putting the same money in an interest-bearing account and staying on Earth. Going to distant planets, in other words, means fighting one of the greatest forces in human affairs: compound interest.

Today, the cheapest rockets available charge a little less than $1,000 to send 1 pound of material into low-earth orbit. Sending that pound to other planets, let alone the stars, would cost vastly more. To be sure, time and expense might be reduced by building space elevators and (should the laws of physics permit) taking advantage of handy wormholes. But the lesson of Zheng He remains: Exploration of distant lands will be a short-lived venture unless it yields something really, really valuable.

If future space voyagers decided to exploit a barren, lifeless planet, few would be upset. But such an endeavor is unlikely. As far as we know, a world without life would be a world without oxygen, a stable climate, or the possibility of growing food. Barring the discovery of some immensely valuable substance that doesn't exist on Earth, there would be no reason to set up shop there, let alone despoil it. A world with functioning ecosystems would be more attractive. But if local species were valuable, it would be more sensible to carry back to Earth a snippet of their DNA than whole animals. The entire Alien series can be considered as a proof by negative example of this assertion.

The real jackpot, of course, would be finding a nonhuman civilization: a planetful of new ideas, techniques, and expression. Here the temptation to interact—that is, to intervene—would be enormous. China again provides an example. Travel costs today are low compared to those in the 15th century. Africa, meanwhile, is still full of valuable resources, products, and land, so Chinese ships are again going to Africa. In the past decade, the nation has shipped in a million or more migrants. Buying and leasing swathes of land to grow food for export to the homeland, grabbing deals to extract minerals, locking up local water supplies—the newcomers have been throwing their weight around. Even though the Chinese have built many badly needed roads, bridges, and power plants, their moves have created a furor. “Landgrab!” cry African newspapers. Chinese workers have been attacked in Zambia, Cameroon, Niger, Sudan, and Angola.

History suggests that if anything of value is involved, contacts between distant societies are fraught. Think of Spain and the Aztecs. Cortés could have traded peacefully for Aztec gold and silver, but that would have involved the expense of ferrying over goods from Spain for barter. Conquest was more attractive (economically, if not morally), and greatly abetted by an epidemic of smallpox introduced to the Aztecs by the Spaniards. Stuck at the end of a trillion-mile supply chain, voyagers from Earth might be less likely to replicate the triumph of Cortés than the fates of Thomas Drummond and William Paterson. The two men were leaders of Scotland's biggest mission to the Americas: the attempt to implant some 2,500 highlanders in Panama starting in 1698. A grandiose effort for a poor country, the expedition sucked up as much as half of the nation's available investment capital. It was that rarest of events, an unmitigated disaster. The locals in Panama weren't interested in trade. Unable to grow food in the unfamiliar ecosystem and beset by diseases they had no experience with, the Scots died by the hundreds. Drummond vanished; Paterson lost his wife. As the few survivors limped back to Edinburgh in 1700, Scotland's economy collapsed, forcing it to merge with England.

Is interstellar travel too risky and economically irrational ever to happen? Turn again to Zheng He. His voyages were sponsored by the brutally ambitious emperor, who ignored his flunkies' complaints about the cost. Key to most great leaps is at least one overconfident investor; in 15th-century Asia, the emperor played that role. Our society, vastly richer than early-modern China, has no lack of would-be successors. Look at the billionaires jumping into commercial spaceflight: Jeff Bezos with Blue Origin, Richard Branson with Virgin Galactic, Naveen Jain with Moon Express, Elon Musk with SpaceX. Eventually humankind will push into space no matter what the expected cost-benefit ratio. Those first adventurers will have one advantage over their early-modern predecessors. Future starfarers will know about Zheng, Cortés, Drummond, and Paterson. They will understand that the outbound voyage, no matter how complicated and expensive, is only the beginning.

Charles C. Mann (charlesmann.org) is the author of 1493: Uncovering the New World Columbus Created.

1Correction 11/24/14 11a.m.: An earlier version of this story identified East Africa as West Africa.