Imagine a world where a trip to the moon is as easy as running to the grocery store. Visiting nearby stars might be a routine cross-galaxy flight, and you may even have a layover at a galactic travel hub on a place like Batuu from Star Wars. In this imaginary universe, many stars and planets would be connected, and their societies could communicate as a part of a galactic civilization.
Given our limited spaceflight capabilities, it might seem obvious at first why this hasn’t happened. It took even one of our fastest small probes (New Horizons, which visited Pluto in 2015) almost 10 years to get to the outer solar system, and we haven’t yet sent humans any further than the moon (and that was back in the 1970s). With our current technology, it would take around 100 human lifetimes to cross the unimaginably large four light years to our nearest neighbor star, Proxima Centauri.
But, even if we’re incapable, why hasn’t another alien life form managed to accomplish interstellar travel and populate the galaxy? The odds seem to be incredibly high that there is other intelligent life out there, given that there are over 200 billion stars in our galaxy alone, each with at least one planet, on average. There’s also been more than enough time in the 13.8 billion year lifetime of the universe for a civilization to traverse the whole Milky Way, even at the slow speeds we humans travel now. In fact, there’s been enough time for the galaxy to have been colonized hundreds of times over. This dilemma—where is everyone? why haven’t we heard from them?—is known as the Fermi paradox.
Although this may seem like an unanswerable question, we can learn a great deal about our own planet’s destiny by exploring the possibilities. Imagining the outcomes for other life forms on other planets is like looking at a crystal ball of our own possible futures. Let’s first assume that there is intelligent life elsewhere. This would eliminate solution one to the Fermi paradox—that we actually are sadly completely alone in this galaxy.
If we’re not alone, then the remaining possibility is that life on other planets exists and has had some reason not to colonize the galaxy. Knowing life-forms on Earth, it’s hard to imagine us developing the technology for interstellar travel and not wanting to explore, spreading our species and taking the resources of planets beyond our own.
As a species, we certainly have a track record of this problematic and exploitative behavior throughout our short history. Our history is fraught with missteps and injustices, the growing pains of a species becoming more self-aware and technologically advanced. And news today shows us that we clearly still have catastrophic problems to deal with: threats of nuclear war, the impending doom of climate change, income inequality, systemic oppression of many groups of society, and more. Although we are continually improving our computing power, space infrastructure, and communications capabilities, we don’t always know how to apply this technology for good. With great power comes great responsibility, and we must learn how to use all the tools at our disposal.
This is the idea of technological adolescence: as a species grows and advances their control over the world around them, they must figure out how to do so peacefully and avoid destroying themselves. It’s not an easy or smooth process, or at least it hasn’t been for us so far. We can imagine that other civilizations were like us at some point, fumbling through their growth. There are only two outcomes: either you make it through, or you go extinct from your mistakes.
If civilizations can’t make it through this phase of evolution, then that solves our paradox. Or, they could make it through, and just find out that interstellar travel isn’t actually possible within the laws of physics and nature after all. If the technology could exist, though, there has to be some other reason why they haven’t reached us; maybe, they just don’t have the drive to colonize or exploit once they’ve matured. If the only way to survive technological adolescence is to outgrow any hostile warring drives, the only interstellar civilizations would be peaceful, without any harmful colonizing instincts pushing them to explore the galaxy and interrupt the happenings on our planet.
Of course, there is the possibility that a galactic civilization exists all around us, purposefully kept from our sight. Since we are still barely teenagers in our own technological development, the more advanced gatekeepers of the galaxy might be waiting for us to grow up. Two ideas—the sentinel and zoo hypotheses—provide two scenarios for us (and there could be more). Just like the black obelisk in 2001: A Space Odyssey, there could be a piece of machinery (a sentinel) on Earth that will notify the intelligent aliens when we are mature enough to be contacted. Alternatively, we could be (comparatively) primitive animals roaming a wildlife preserve for our own protection, or unknowing participants in a zoo for the entertainment of more powerful lifeforms.
Some scientists are searching for clues of these intelligent extraterrestrials, listening for radio signals indicative of technology. Although there hasn’t been a successful detection yet, we have the machinery (large radio telescopes, like the Green Bank Observatory in West Virginia) to systematically survey the sky for ET. Simultaneously, other researchers are approaching this problem by looking for biology—looking for indicators of habitable exoplanets, using large space telescopes such as the James Webb Space Telescope (JWST), launching soon in 2021. Either way, the search for life is a major research area in modern astronomy; some people even think we may soon get results that tell us we’re not alone in the universe. We may even someday soon know a little better how common biological life is in our corner of the galaxy, a critical piece of information in considering the Fermi paradox.
All in all, what does this mean for us, living on Earth now? These hypothetical scenarios can broaden our perspective, reminding us that we exist in this precarious turning point of Earth’s history, where the next few decades may determine the fate of our entire species. What would our “adulthood” even look like? World peace, a sustainable solution to our climate woes, and a more equitable society may be what we need.
Self-awareness of our immaturity (and our danger to ourselves) can motivate us to improve, to strive for peace and harmony, so that we too can save our species and our planet. Only then—once we’ve become fully-fledged adult members of the galactic “society”—can we truly find answers to the Fermi paradox, and become the Star-Trek-esque interstellar civilization of our wildest sci-fi dreams.
Briley Lewis is a graduate student and NSF Fellow at UCLA, studying Astronomy & Astrophysics. Her research interests are primarily in planetary systems—both exoplanets and objects in our own solar system, how they form, and how we can create instruments to learn more about them. She has previously done research at the American Museum of Natural History and at Space Telescope Science Institute.