What’s exciting about this finding is that Proxima Centauri is only 4.2 light years away from us. As the lead author of the study, Guillem Anglada-Escudé, states, “It's not only the closest terrestrial planet found, it's probably the closest planet outside our solar system that will ever be found because there is no star closer to the solar system than this one.”

Furthermore, Proxima b falls within the “Goldilocks zone” around its star, meaning that it’s surface could contain water in the liquid phase. If it has an atmosphere, it’s surface temperatures could range between 86 and 104 degrees Fahrenheit, although scientists aren’t sure Proxima b has an atmosphere. There are also questions about whether is is “tidally locked” with its sun, and the effect of much stronger X-ray and ultraviolet flares that are estimated to be roughly 100 times those experienced on Earth.

Space Exploration

Nonetheless, Proxima b has generated quite a bit of excitement, and for good reason: it’s the most extraordinary discovery in an ongoing effort to identify Earth-like “exoplanets” throughout our galaxy and other cosmic neighborhoods. In addition, the discovery of habitable exoplanets elsewhere has direct implications for our species’ future survival in the universe.

As the former NASA administrator Michael Griffin put it 10 years ago, “human expansion into the solar system is, in the end, fundamentally about the survival of the species.” Stephen Hawking echoed this same idea when he claimed that “the human race [won’t] survive the next thousand years, unless we spread into space.” And similarly, the CEO of SpaceX, Elon Musk, more recently claimed that “there is a strong humanitarian argument for making life multi-planetary in order to safeguard the existence of humanity in the event that something catastrophic were to happen.”

In concert with these statements, I would argue that of all the macro-strategies that have been proposed to mitigate existential risk, the colonization of space offers one of the best options. This is because it wouldn’t require us to curb technological development or redesign the human form (for example, through cognitive or moral bioenhancement) — both of which appear either difficult or impossible. Simply put, the wider we spread throughout the world, the less likely it will be for a single catastrophe to have world-wide consequences.

So, Proxima b and other “Earth-analogs” offer some hope for one day spreading our population to other regions of the universe and thereby increasing our species’ probability of survival in the event of a planetary disaster.

(This being said, there are some disaster scenarios that space colonization wouldn’t protect us against, such as a catastrophic vacuum decay. In this case, a bubble of total destruction would expand at the speed of light and obliterate everything in its path — including other galaxies, solar systems, and planets.)

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Alien Life

On the other hand, the discover of Proxima b could offer the opposite of hope: it could indicate that our species is very likely to go extinct soon. Why? The reason concerns the notion of a “Great Filter.” The fact that we see no credible evidence of alien species calling out for cosmic companionship suggests that there must be a Great Filter somewhere between dead matter and interstellar civilizations. The question for us is where this filter is located: somewhere in our evolutionary past, or looming ominously in our technological future.

Imagine for a moment that we find the universe to be utterly barren. No traces of life — other than us — anywhere. This would suggest that the Great Filter lies between dead matter and single-celled organisms, i.e., that this is the highly improbable step that explains why we appear to be alone in the cosmos. And if the Great filter is behind us, this would be very good news indeed.

Now imagine that we find vertebrate-like species on another planet. This would imply that the Great Filter isn’t between dead matter and single-celled organisms, but much further along on the evolutionary timeline. As Nick Bostrom puts it, such a discovery would “shift the probability more strongly to the hypothesis that the Great Filter is ahead of us, not behind us.” Following this line of reasoning, the more complex the organisms, the more probable the claim that we haven’t yet cross the Great Filter. In other words, there’s great hope in cosmic loneliness.

Tying these loose ends together, the point is that Proxima b is a good candidate for harboring life, given its potential habitability. And if life were someday discovered on it — or Mars, or Kepler-186f, and so on — then this would be extremely bad news for humanity. As further exploration of our cosmic backyard continues, we should all wish for only two results: (a) the continued discovery of more habitable exoplanets to which our descendants (some of whom might already have been born) could someday migrate, and (b) a complete lack of evidence that life has inhabited any planet other than our own pale blue dot.

If both of these wishes come true, we might just have reason for optimism about the future of humanity.