Alpha Centauri civilizationA world under three suns

Proxima Centauri b is 4.24 light-years from Earth. The game's "Alpha Centauri civilization" asks: if this planet held a civilization, it would face three suns, deadly flares and a 4.24-year communication delay all at once.

This page first covers the real astronomy of this star system, then the story the game imagines, and finally lists related real research. The civilization in the game is entirely fictional.

Are the three suns real?

Yes, but this is not the "three-body problem" of science fiction. Alpha Centauri A and B orbit each other once about every 80 years. Proxima is about 13,000 AU from them and takes more than 500,000 years to go around. The real triple-star system is actually quite stable. In Liu Cixin's The Three-Body Problem (2006), the three-body problem has no general analytic solution, and that part is correct. But the real Alpha Centauri is not chaotic.

Proxima b: a locked world

• Terminator line: on a tidally locked planet, the mildest place may be the ring along the line between day and night. Proxima b orbits Proxima in only about 11.2 days.
• Sea under the ice: if there is enough atmosphere and ocean, heat could be carried from the day side to the night side. Some models instead have the night side freezing into thick ice.
• Magnetosphere: a planet's magnetic field can deflect charged particles in the stellar wind. Earth's field blocks most of the solar wind. Whether Proxima b has a magnetic field is still unknown.
• Underground city: rock blocks ultraviolet light and energetic particles, so building cities underground is a reasonable idea.

Flares: the biggest threat

In March 2016, Proxima erupted in a superflare. Within a few minutes its brightness rose to about 68 times normal, bright enough to see with the naked eye. Researchers estimate about 5 such superflares a year. Worse, Proxima's frequent flares could strip 90% of the ozone from an Earth-like atmosphere within 5 years.

Our own Sun also has flares and coronal mass ejections. We can now warn of them a little ahead of time, which buys time for satellites and power grids.

Hearing, seeing and reaching

Humans have listened for alien signals for more than 60 years and have never confirmed one. Radio telescopes can pick up human-made signals from far away, and also pulsars and quasars.

To actually go there, the Breakthrough Starshot project proposes using ground-based lasers to push gram-scale light sails to 20% of the speed of light, reaching Proxima in about 20 years. In 2025 the Webb telescope imaged a possible gas giant near Alpha Centauri A. It has not been seen again since.

The problems that the speed of light causes

In the game, 1 light-year equals 1 real hour, and nothing goes faster than light. This setting magnifies several real consequences:

• Chain of suspicion: light-speed delay means neither side can confirm the other's intentions in time. You only ever know what the other side was thinking a little over 4 years ago. David Brin's 1983 analysis of the "Great Silence" starts from here.
• Dispersal: against a weapon arriving at close to the speed of light, there is almost no way to intercept it. The only realistic defense is not to keep everyone in one place.
• Kinetic weapons: a 1-ton object moving at 10% of the speed of light carries kinetic energy of about 100 million tons of TNT. One arriving at half the speed of light leaves only about 4 years between seeing the launch flash and being hit.
• Interstellar trade: in 1978 the economist Paul Krugman wrote "The Theory of Interstellar Trade", which seriously works out how interest should be calculated when goods undergo time dilation in transit.

The idea in the game

What follows is game lore. The channel is located at "Proxima b, 4.24 light-years", with the subtitle "Under three suns". The mechanic is flares: Proxima is a flare star, and a superflare burns away the "Spark" accumulated on the surface. The more protection nodes you unlock, the smaller the loss. It is discovered by being found by them in the interstellar-civilization era, or by finding them with "Technosignature search" and "Light sail".

In the scenario, the civilization lives underground, hides a sea beneath the ice, and builds antennas on the ice sheet to listen to the sky. They have also thought of light sails, only in the opposite direction. They send part of their population to the sea under the ice and to the asteroid belt, begin planning a move to the A star, and send out an agreement to a point 4.24 light-years away, where every sentence takes more than 8 years to get a reply. The channel has four endings: Alliance, Cold peace, Ruins and Victor. Play the game for the details of the story. This page is only an outline.

Two related novels

• The Three-Body Problem (Liu Cixin, 2006): see above. The three-body problem has no general analytic solution, while the real Alpha Centauri is stable.
• Proxima (Stephen Baxter, 2013): the author wrote it based on what was known about Proxima at the time. In 2016 an Earth-like planet was in fact found around Proxima.

Related real research

These studies concern the detection of nearby star systems. They are not evidence of a civilization on Proxima b.

• A giant planet was found around 51 Pegasi, orbiting its star in 4 days, so the Solar System was no longer the only one. The discoverers won the 2019 Nobel Prize (Mayor and Queloz, Nature, 1995).
• The Kepler telescope looks for new worlds by the faint dimming when a planet transits, and went on to find thousands (Borucki et al., Science, 2010).
• Seven Earth-sized planets crowd around a small red dwarf, and several of them may have liquid water (Gillon et al., Nature, 2017).
• Two physicists suggested using radio telescopes to listen for alien signals near the 21 cm frequency of hydrogen, which started SETI (Cocconi and Morrison, Nature, 1959).
• Using a ground-based laser array to push an ultralight sail could accelerate a probe to one fifth of the speed of light (Lubin, Journal of the British Interplanetary Society, 2016).