快猫短视频

An initial crew of just 98 people might be all that is needed to survive a trip to another star. It turns out this is the minimum number needed to maintain a healthy population during a six-millennia-long trek to Proxima Centauri b, the closest Earth-like exoplanet.

Imagining such a mind-bending scenario led Fr茅d茅ric Marin, an astronomer at the University of Strasbourg, France, to simulate the long-term population dynamics of people living in a starship.

His computer model takes into account biological factors like fertility rates, life expectancy, and even the odds of an ecological catastrophe such as a major plague. 鈥淵ou have in the code a population that is living, reproducing, and dying,鈥� Marin says.

Slow going

Marin and his colleague Camille Beluffi, a physicist who works for Casc4de, a data firm in Strasbourg, assumed their colony ship would be built with current propulsion technology.

The fastest vehicle humans have built is NASA鈥檚 Parker Solar Probe, set to launch later this year and eventually achieve speeds greater than 700,000 kilometres per hour. At that rate it would take 6300 years to reach Proxima Centauri b, which is around 4 light-years away.

Such a mission risks running out of resources, so strict social-engineering would be necessary to enforce a population cap of 500, say the pair. Women would only be allowed a maximum of two children and be limited to procreating between the ages of 35 and 40, so as to space out the generations.

Of course, at this age women might encounter fertility issues 鈥� a recent study found that women aged 34 only have a 75 per cent chance of successfully building a two-child family.

By running thousands of simulations, Marin and Beluffi discovered that 49 women and 49 men is the minimum starting crew needed to guarantee the population doesn鈥檛 crash or succumb to the effects of inbreeding before they reach their destination.

Hardy crew

This crew would even be resilient against a disease outbreak that takes out a third of its members, provided the catastrophe doesn鈥檛 happen too early in the journey.

The simulations also revealed that although strict enforcement of the rules is important, it must also be possible to vary them during the lengthy voyage.

For instance, if the population falls too low, the limit on the number of children or the age range in which women could get pregnant would have to be lifted. 鈥淭he rules must be logical with the mission and the resources inside the vessel,鈥� says Marin. 鈥淏ut they must be flexible.鈥�

Wayne Getz, a wildlife ecologist at the University of California, Berkeley, questions the assumption that an initially equal division between the sexes is 聽the best strategy.

Since a few men can impregnate many women, it seems better to include greater numbers of female settlers from the start, says Getz, though the ideal ratio would have to be investigated further. To ensure that the population maintains genetic diversity, he suggests stocking the spaceship with a sperm or embryo bank.

Many unknowns

Cameron Smith, an archaeologist at Portland State University in Oregon, has previously proposed that would be needed to start off a multi-generational starship.

He based his estimate on studies of how natural populations of animals such as primates and other mammals maintain healthy demographics, but says he welcomes the new approach. 鈥淭his is an early exploration of a topic in science,鈥� he says. 鈥淎nd I think it鈥檚 entirely natural we have diverging opinions.鈥�

Many unknowns remain, including what would happen psychologically and socially to people confined in a spacecraft. 鈥淎fter the first generation of leaders die, who is there to enforce the social engineering rules?鈥� asks Jade Zhang, also at University of California, Berkeley.

Marin and Beluffi are aware of such issues and hope to include more input from social scientists for their thought experiment spanning six millennia. 鈥淚t鈥檚 almost as long as civilised human life,鈥� says Marin. 鈥淚鈥檓 quite sure you would see new religions and beliefs.鈥�

搁别蹿别谤别苍肠别:听