The most uncertain parameter in the Drake equation, L, represents the lifespan of a technological civilization like ours. We do not have any clue as to the order of magnitude of this parameter. Our modern science and technology emerged over the past century, and I personally lived through half of it. Given that I passed the midpoint of my personal lifespan, does this imply that our technological civilization has only a century left before it will end?
My personal life has no ambiguity about its inevitable end, because of the large statistical sample of people who lived and died before me. Our common internal organs have an expiration date. Does this metaphor extend to humanity as a whole? Are we seeing signs that the end is near through the decay of our shared societal organs, in the form of the toxicity and pervasive polarization on social media, the exponential growth of artificial intelligence (AI) that could endow bad actors with unprecedented destructive powers, the possibility that the COVID-19 pandemic might have been a biological counterpart of a Chernobyl leak from gain-of-function experimentation, or the possible use of nuclear weapons by unpredictable leaders with an irrational agenda?
If we had access to the history of dead civilizations on some of the hundreds of billions of exoplanets within the Milky Way galaxy, and viewed the statistical distribution of their lifespan L, we would have had a better idea about the remaining time for our civilization on Earth. Of course, there is always a possibility of becoming an outlier, but there is little chance that I will live longer than twice my current age, 62.5, because no one among 117 billion humans did it before me. The oldest known person, Jeanne Calment, lived for 122.5 years, from February 1875 until August 1997, which is less than double my current age, 125 years.
What will be the nature of the event that will bring us to our knees? Mass extinction could have a natural cause, such as a nearby supernova shock or a giant solar flare that rips unexpectedly the Earth’s atmosphere, an impact by a huge asteroid like the one that killed non-avian dinosaurs 66 million years ago, or a global warming event like the one that eliminated 96% of all marine species 252 million years ago. These catastrophes occur on timescales of million to billions of years. A self-inflicted wound from a technological origin could occur on timescales of decades to centuries and might therefore be more relevant
Given our current geopolitics, there are various possible scenarios. In one case, a country like North Korea or Iran ignites a global nuclear war. In the second case, computer-proficient members of a terrorist organization use artificial intelligence (AI) to design a biological weapon which gets out of hand and spreads a violent global pandemic.
In an email exchange before my morning jog, the bright astrophysicist Boaz Katz asked me: “What is the implication if it turns out that there is no life outside Earth? … Suppose in the distant future, we somehow scan the entire galaxy and discover that only earth has life. What does that mean?” This question can be extended beyond the present time to also the past, supposing that we became aware that intelligence never existed before us since the Big Bang, 13.8 billion years ago. My answer was short: “If we learn that there was no intelligent life elsewhere, we will have the responsibility to extend the longevity of our civilization and save it from a single-planet catastrophe. Without being observed by conscious beings, the Universe will be pointless.”
With knowledge comes responsibility. If we happen to be the only example of an advanced technological civilization, then our future would not be dictated by the statistics of others and we can shape it anyway we want. In particular, we can aspire to make the lifespan of intelligence-as-we-know-it infinite. This can be accomplished by seeding exoplanets with intelligent entities in the form of AI-assisted probes that replicate themselves using local raw materials in analogy to the way that humans replicate on Earth. This is an ambitious long-term project that could require a billion years to accomplish, the time it will take our chemical rockets to reach the opposite side of the Milky Way disk of stars.
Having global knowledge allows us to evaluate our existence in a cosmic perspective. It provides an opportunity to appreciate how fragile we are relative to the Universe at large. In the absence of a statistical census of L and our slow ability to spread the seeds of intelligence-as-we-know-it, the best we can do is to search remotely with our telescopes for more examples of the technological signatures we find on Earth. Until we find others, we must work to minimize existential risks from nuclear or biological wars triggered by local disputes here on Earth.
If we find no analogs of our intelligence among the stars, the ultimate value of L would be a matter of our choice. Here’s hoping that we will make the right choice and extend our lifespan beyond the next century.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. His new book, titled “Interstellar”, was published in August 2023.
