I dined the other night with a college buddy visiting from the US.
He told us that he recently spat into a bottle and sent the results to a company called 23andMe. You’re gagging, but hear me out. Using a saliva sample like this, 23andMe does some DNA analysis and can tell you about your extended family and your origins.
Thus it was that my buddy, a Tamil speaker who grew up in Hyderabad, learnt that he has ancestral roots in—ready for this?—Ukraine.
It had me wanting to spit, I’ll say that. What might I learn about my ancestors? That they were from Japan? Dombivli? The Kerguelen Islands?
Some unknown planet that orbits the star Alpha Centauri, perhaps?
Only, 23andMe cannot take samples from India, so that’s the end of that. Still, if Ukraine was unexpected, you’re probably furrowing your brow about Dombivli, maybe about Alpha Centauri as well. But hear me out, nevertheless.
One of these years, I’m guessing many of us humans—enough to populate a small town—will pile into spacecrafts and leave our planet. Why? Because this is a small planet with finite resources that must support ever more of us. Our population is rising today at a pace that doubles it about every 48 years (imagine, all of human history got us to 7 billion, but by 2060 we could be at 14 billion). With that, and the rate at which we consume our resources, they may be gone one day. Then what?
Used to be, when a group of humans exhausted the resources in a particular spot, they’d simply move on. Not so easy today, when Homo sapiens are to be found wherever there is land. So just for our species to survive, there may come a time when some of us will think to leave the earth. Don’t start packing yet, but it’s intriguing to think how that emigration will happen.
One idea is to produce large colonies that roam through space, searching for the best place to live. Such a colony will be solar-powered, for that’s about the only feasible source of abundant energy. Since it will carry humans, it will need water and oxygen and gravity, all fundamental to life as we know it.
Where would we build such a colony? Probably not on earth, and not just because of limited resources. Ferrying anything into space from earth needs vast energy just to escape gravity. But we have a celestial neighbour whose surface contains plenty of oxygen, titanium, aluminium and silicon. Mine the moon, then. Not least because gravity there is much weaker than on earth, and so it would be easier to carry all we need to a colony-building site somewhere in space.
Gerard O’Neill, a physicist at Princeton University, suggests using titanium and aluminium from the moon to make a cylinder 30km long, 6km in diameter. Its inner surface has alternating strips of “land” and windows. Enormous shutters on the windows control the light, simulating night and day and the seasons. To produce earth-like gravity, it rotates once every two minutes.
This contraption, O’Neill estimates, can support and transport more than 200,000 people.
That’s a lot to dispatch into space. Why so many? Consider that in the time it takes to reach even nearby stars, those who started the journey will have died, as will plenty of their descendants.
Therefore, the colony must be self-sustaining, even a viable economic entity on its own. So it makes no sense to send out only a handful of our kind on this mission.
Imagine that we make this gargantuan can of Pepsi accelerate, over several months, to 1% of the speed of light, or about 3,000km per second. Scudding along like that, it will reach Alpha Centauri, the star that’s nearest to us, in about 400 years. A long time? Yes, but that’s only about six human lifetimes.
Let’s say we send out several such colonies. Centuries later, one arrives at a star that has planets, one of which can sustain life. The descendants of the original 200,000 settle there. Later, they build a new colony and launch another set of brave explorers into the unknown.
Hopping from star to star like this, Homo sapiens could colonize our entire Milky Way in about 12 million years.
Twelve million years. OK, don’t hold your breath. Still, that’s a mere tick compared with how long it has taken life on earth to evolve intelligence and begin dreaming about colonizing space. In cosmic terms, we can fill our galaxy very quickly indeed.
Which means some other civilization might have done exactly the same thing by now. If colonization can happen so quickly, why shouldn’t it have happened already? Maybe members of an extra-terrestrial intelligence are already everywhere in our galaxy. In our solar system. Here on earth.
In fact, are some of us ourselves members of an extra-terrestrial intelligence that landed on Earth? Do I have roots near Alpha Centauri?
Once a computer scientist, Dilip D’Souza now lives in Mumbai and writes for his dinners. A Matter of Numbers will explore the joy of mathematics, with occasional forays into other sciences. Comments are welcome at firstname.lastname@example.org
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