An interstellar journey

Last week, we signed off this column with the premise that Man would one day need to colonise other worlds beyond our solar system. It will happen one day, when our technologies are sufficiently advanced to propel a starship Star Trek style. Until then, we will have to speculate on the various aspects of colonising other worlds. One of the most interesting aspects is the size of the human population that will be needed to colonise another habitable world in another star system.

(We already know that plenty of such planets exist).

Back in 2002, John Moore, an anthropologist at the University of Florida, calculated that a starship could leave Earth with 150 passengers on a 2,000-year pilgrimage to another solar system, and upon arrival, the descendants of the original crew could colonise a new world there - as long as everyone was careful not to inbreed along the way.

It is indeed a vast undertaking. Even the nearest star systems - such as Proxima Centauri, which is ‘just’ 4.2 light-years away are so far away that it would take millions of years to reach them at current speeds. In any case, reaching them would require a so-called generational starship where entire generations of people would live, and die before the ship reached its destination. If you imagine how massive this mission is, simple logic tells us that more than 150 people would be needed.

Starship

According to a new study by Portland State University anthropologist Cameron Smith, any such starship would have to carry a minimum of 10,000 people to secure the success of the endeavour. A starting population of 40,000 or more would be even better, in case a large percentage of the population died during the journey due to various factors.

You might be forgiven for thinking that space travel is a bit far-fetched given that NASA or for that matter, any other space agency, has so far failed to send people even to Mars. However, the initiative for private space travel may be taken by private companies, as evident by Amazon's Blue Origin and Virgin's Galactic space travel/tourism plans. Indeed, private organisations including the 100 Year Starship project, plan to make manned interstellar travel possible at least within the next century. They will, of course, need a huge increase in propulsion speed, even if they cannot match the speed of light.

In fact, the aforementioned study was requested by Icarus Interstellar, one of the groups involved in the 100 Year Starship. The results are published in the April - May issue of Acta Astronomica.

“I did this study to materially help in putting together the millions of puzzle pieces that will be required to allow humanity to spread out from our earthly cradle,” Smith says. William Gardner-O'Kearney, who studied archaeology at Portland State, helped Smith build the simulations to calculate how many different scenarios would play out during interstellar travel. Gardner-O'Kearny calculated each population's possible trajectory over 300 years, or 30 generations. In manned space travel, physics matters. But biology matters even more. Genetic diversity keeps groups healthy, and larger populations tend to have more diversity. That is a basic fact of biology and evolution. The same rule should apply to space travel.

As Smith points out, “if you are going to seed a planet for its entire future, you want to have as much genetic diversity as possible, because that diversity is your insurance policy for adaptation to new conditions”.

A starting population of 40,000 people maintains 100 percent of its variation, while the 10,000-person scenario stays relatively stable too. So, Smith concludes that a number between 10,000 and 40,000 is safe when it comes to preserving genetic variation. This will be a mind boggling exercise - the ship will have to be very large and scientists will have to solve other problems such as food and water supply, sanitation, waste, ventilation, gravitation, communications with Earth etc. A star ship should necessarily be a self-contained unit which does not need any outside help except in emergencies. Diseases, collisions with celestial objects and mechanical failures could wipe out large numbers at any time. They will also have to prevent the negative health effects that arise from living in space. They will most probably carry several species of flora and fauna as well, so their needs too have to be addressed (who will not want to take at least cats and dogs, man's favourite pets, to the stars?).

Population

Scientists say that a population of 40,000 can survive such challenges and manage to stay within the range of a healthy population size.

There is another theory that tens of thousands of pioneers would not have to be housed all in one starship. Modular ships could dock together for trade and social gatherings, but travel separately so that disaster for one would not spell disaster for all.

In the event that we manage to go the stars, selecting the pioneers will be an onerous task replete with thousands of questions and difficulties. Will each nation on Earth be represented? What will be the criteria for selection as participants? What kind of professions should be represented?

Should there be equal numbers of men and women? Will older children be allowed in? How will they be educated? What kind of material (cultural, social etc) can be allowed to be taken from the Earth to the space ships? In which direction should the space craft go? Space travel is an inherently fascinating subject that has given rise to many science fiction stories.

Yet, it is distinctly within the realm of possibility. As we write, an unmanned space probe is on its way past the very edge of the solar system on a journey to distant galaxies. Man will one day repeat this feat with manned spacecraft. Despite the rumblings about the massive expenditure for space exploration at the expense of many urgent matters on Earth itself, it will be a wise investment - because one day, it will not be possible to live on Earth any more.