A common obstacle when imagining the distant future is that we impose bold potential realities onto our contemporary world, with our current tools and psychological makeup. The former makes tomorrow seem impossible and the latter frightening. But we’ll be different then, in almost every way.

In a fascinating Aeon essay about the colonization of space, Paul Gilster doesn’t fall into that trap, extrapolating the whole world forward into a different age, when we can populate a plethora of planets. The writer believes such an arrangement will extinction-proof our species, but, of course, it will likely also change Homo sapiens in profound ways. We won’t really be us in the new arrangement.

Gilster envisions “worldships” that will be “huge future space ‘arcologies’ – self-sustaining, city-size ships of the kind once imagined by the US physicist and futurist Gerard O’Neill, with thousands of people living in artificial, Earth-like environments.”

An excerpt:

Our expansion into the galaxy will begin slowly, for the stars are immensely distant. Scatter 200 billion grains of salt – each representing a single star – into an approximation of the Milky Way and, in our neighbourhood, each grain of salt would be seven miles from its nearest counterpart. To reach Alpha Centauri, the triple-star system closest to our own, with a human crew we need to travel at least at 10 per cent of lightspeed (about 30,000 kilometres per second), making for a four-decade crossing. With the help of some form of suspended animation, the journey might be made easier.

Ten per cent of lightspeed is an attractive goal. It’s fast enough to reach the nearest stars in a single human lifetime, but not so fast that collisions with interstellar gas and dust cannot be protected against. We’ll need to tune up those technologies and learn to shield our crews from galactic cosmic rays. Deceleration at the destination is a huge problem, but possibilities exist. Perhaps the most plausible of these is using a magnetic field generated by a superconducting loop, a so-called ‘magsail’, that can open in the latter phases of the mission to brake over years against the stream of charged particles emitted by the target stars.

As to how to get to 10 per cent of lightspeed in the first place, numerous ideas are bruited about. If we had to make a choice right now, the technology with the highest likelihood of success is probably a vast sail. This would be a ‘lightsail,’ driven by a powerful laser or microwave station in close proximity to the Sun; it would ride photons from the beam, acquiring their momentum. Strategies exist to tighten, or ‘collimate’, the beam through a huge lens in the outer solar system, or through a series of smaller lenses that can keep the beam on the departing spacecraft long enough for it to reach its substantial percentage of lightspeed. There are other possible interstellar propulsion strategies, from antimatter to fusion to interstellar ramjets. To help the crew survive the journey, we can explore nanotechnology, artificial intelligence, and uploaded consciousness.•

An excerpt from “Distant Ruins,” Paul Gilster’s Aeon article about interstellar archaeology:

“Today, a small group of interstellar archaeologists is looking for evidence of those civilisations. They are tantalised by the possibility that the universe is not just a birthplace of alien cultures but also their necropolis.

We use the word ‘archaeology’ to describe this effort, because looking into deep space takes us deep into the past. The photons that strike our telescopes’ detectors take time to reach us: the light of Alpha Centauri, the nearest stellar system, is 4.3 years old when it arrives. It travels at 300,000 kilometres per second but has to cross 40 trillion kilometres to get here. Dig gradually into the soil and you push through layers accreted by wind, rain, construction, and flood. Dig deep into the sky, beyond local stars such as Alpha Centauri, and you push the clock back with the same inexorability. Epsilon Eridani, another nearby star, is seen as it was over 10 years ago. Light from the fascinating Gliese 667C, a red dwarf with three planets in its habitable zone, takes 22 years to make the journey.

In the cosmic scheme of things, these are trivial distances. Our green and blue world circles its star some 27,000 light years from the galactic centre. The glow we see at the Milky Way’s core began its voyage towards us at a time when prehistoric hunters were chasing mammoths across Europe’s ice sheets. The galaxy itself spans 100,000 light years, and its nearest equivalent, the great disc of Andromeda, is 2.5 million light years away. We see it as it looked when humanity’s ancestors walked the African savannah. When interstellar archaeologists tilt their telescopes to the sky, they are gazing into the deep history of the cosmos, but to find a civilisation more advanced than ours, they have to tilt their imaginations into the future. They have to plot out a plausible destiny for humanity, and then go looking for it in the cosmic past.”