If you’re a fan of the Search for Extraterrestrial Intelligence (SETI) and the Fermi Paradox, then it’s likely you’ve heard of a concept known as the Great Filter. In brief, it states that life in the Universe may be doomed to extinction, either as a result of cataclysmic events or due to circumstances of its own making (i.e., nuclear war, climate change, etc.) In recent years, it has been the subject of a lot of talk and speculation, and not just in academic circles.
Stephen Hawking and Elon Musk have also weighed in on the issue, claiming that humanity’s only chance at long-term survival is to become “interplanetary.” Addressing this very possibility, a research team led by NASA’s Jet Propulsion Laboratory (JPL) recently created a timeline for potential human expansion beyond Earth. According to their findings, we have the potential of going interplanetary by the end of the century and intragalactic by the end of the 24th!
The paper that describes their findings was recently published in the July 27th, 2021, issue of Galaxies. The team responsible was led by Jonathan H. Jiang, a Principal Scientist and group leader with NASA JPL’s Earth Science Section. He was joined by Kristen A. Fahy, a member of the Earth Science Section at NASA JPL, and Philip E. Rosen, a retired energy industry engineer.
The Great Filter was proposed in 1996 by Robin Hanson, an economist and research associate at Oxford University’s Future of Humanity Institute (FHI). In an essay titled “The Great Filter – Are We Almost Past It?” he proposed that there must be something in the grand scheme of biological evolution that prevents life from emerging and/or reaching a state of advanced technological development.
This was Hanson’s proposed resolution for why humanity’s attempts to find intelligent life – despite its assumed statistical probability – have failed thus far (aka. Fermi’s Paradox). But as Hanson makes clear in his paper, the Great Filter Hypothesis also has immense implications for humanity. Depending on where the Filter is located – an early stage of development or a later one – humanity may have already passed it or is nearing it (neither scenario is particularly reassuring).
For the sake of their study, Jiang and his colleagues proposed that since the end of World War II (and the development of nuclear weapons), humanity has entered a “Window of Peril” from which it has yet to extricate itself. Essentially, from this point onward, human beings have had the capacity to destroy themselves, either as a result of nuclear war, biowarfare, or anthropogenic climate change – which Hanson suggested as possible examples of “the Filter.”
To determine if humans have the potential to spread beyond Earth before we ruin it, wiping ourselves out, they created a foundational model that predicts the earliest possible launch dates for human-crewed missions from cis-lunar space to selected destinations throughout the Solar System and nearby stars. As Jiang explained to Universe Today via email:
“Initially, we looked at the relationship between reach and complexity of deep space missions as they relate to the development of computing power, expressed quantitatively as transistors per microprocessor, within the timeframe of the Space Age. Knowing the trend of computing power expressed in this easily quantifiable manner, along with some necessary assumptions, that trend was then used to help project trends for deep space missions into the future.”
Graphic representation of the relative distances between the nearest stars and the Sun. Barnard’s star is the second-closest star system to the Sun and the nearest single star to us. Credit: IEEC/Science-Wave/Guillem RamisaThis raises another important concept, which is Moore’s Law, named for American engineer Gordon Moore. In 1965, Moore observed that the number of transistors on an integrated circuit (IC) could be expected to double every two years. Rather than being a “law” in the strictest scientific sense, this observation serves as a means of characterizing the exponential growth of computing in the latter half of the 20th century and into the 21st (coinciding with the Space Age).
As Jiang explained, their model was created with simplicity in mind and will hopefully become a “first layer” for a more complex model in the future – one that goes beyond computing power. Regardless, the model returned some rather encouraging results that suggest human civilization has a good shot at long-term survival. When considering specific destinations for robotic and crewed missions within the Solar System and beyond, the projected timing for potential launch dates was surprisingly positive.
For example, the model predicts the first human mission to Mars will occur sometime in the late 2030s, missions to the Asteroid Belt by the 2060s, to Jupiter (and the Jovian moons) by the 2070s, and Saturn by 2080 (or thereabouts). Meanwhile, robotic missions to extrasolar destinations like Proxima Centauri (4.2 light-years away) and its potentially habitable planet (Proxima b) would be ready to go by in just a few years (e.g., Breakthrough Starshot), but a crewed mission would have to wait to launch until 2250.
Similarly, robotic and crewed missions to the Sun-like star Tau Ceti (12 light-years) would take a few decades longer, with robots ready to launch by the 2030s and humans by 2270. Robotic missions to the TRAPPIST-1 system (~40 light-years), with its seven suspected rocky planets, would be ready for launch by ~2040 and a crewed mission by ~2300. Lastly, they considered robotic and crewed missions to stars located about 14,000 light-years from the center of the Milky Way, which could launch by 2050 and ~2400 (respectively).
Space exploration missions as a function of launch timing and logarithmic distances. Credit: MDPI/Jiang, J.H., et al. (2021)From the dates and the logarithmic nature of the distances involved (shown above), it is evident that it will take humanity much longer to “go interstellar” than it will to become an interplanetary species. As Jiang and co-author Rosen indicated, if these distances could be represented on a much smaller scale, Proxima Centauri would still be over 1 million km (700,000 mi) away, while Mars and the Moon would be just 1.6 km (1 mi) and 11 m (12 yards) distant:
“Obviously, going interstellar will take technologies we have yet to develop – from propulsion systems that can achieve at least a modest percentage of the speed of light to life support systems that can keep a large crew alive and healthy during many years to decades in deep space to computing capability which can manage the operations of such grand designs with limited human input.
“Intergalactic travel, such as to the Milky Way’s nearest large galaxy neighbor, Andromeda, is still very much the stuff of fiction. There are, however, approximately 400 billion stars right here in the Milky Way – many having planetary systems of their own – to keep us busy for some time to come.”
Missions to the central region of the Milky Way might even entail the possibility of making contact with one or more extraterrestrial species. This is based on recent research that was also conducted by Jiang and his associates, which suggests that a region near the center of the Milky Way is the most likely place to find complex life and technological civilizations (based on statistical modeling).
This was further indicated by research led by Jason T. Wright, a Professor of astronomy and physics and the director of the Penn State Extraterrestrial Intelligence Center, which simulated the likely pathways of expansion for spacefaring civilizations. In any case, these results are by no means an indication that humans have escaped “the Filter” or that the “Window of Peril” will ever be entirely closed.
“The short answer is that we are not out of the woods yet,” said Rosen. “We, as a species, have yet to establish even the first permanent off-world colony. It is heartening, however, that some noteworthy efforts are being made in this direction even as we speak. The technological potential and, in some quarters like JPL/NASA, the will is clearly there.”
What’s more, the prospect of becoming an interplanetary species (or interstellar) entails far more in the way of benefits than just mere survival. Granted, the appeal of not having all of our eggs in one basket, thereby ensuring the survival of humanity and countless other Earth species from any human-caused or natural calamities, is arguably the best reason to expand the human presence beyond the “Pale Blue Dot.”
But there’s also the potential for scientific breakthroughs, the commercialization of cis-lunar space, asteroid mining, the relocation of manufacturing into space, abundant energy, and vastly accelerated development as a species. Said Rosen:
“As well, some critical resources in short supply on Earth could be supplemented from elsewhere such as metals mined from the asteroid 16 Psyche, which is thought by some astronomers to be a remnant of a planetary core. The Moon has been suggested as a possible nearby source of extractable Helium-3, an isotope of Helium that is exceedingly rare here on Earth and could help make relatively clean nuclear fusion a reality.”
The Very Large Array (VLA) at night. Credit: NRAO/AUI/NSF; J. HellermanEstimating whether or not humanity will ever get past the Great Filter is a lot like answering if and when we’ll ever find evidence of intelligent life beyond Earth. Nevertheless, there is merit to creating models that can give us a better sense of when important milestone missions can happen. In much the same way, theoretical studies that consider how and where life could emerge can help us narrow the search for extraterrestrial intelligence.
In this sense, the model created by Jiang and his associates constitutes a good first step that could eventually lead to more in-depth predictive models. Beyond the exponential increase in computing power, there are many more variables that could play an important role in the future of space exploration that merit investigation. Climate change could certainly be one of them, though there are many others worth considering. As Fahy explained:
“We used computing power because it had prior data, but it was just a starting point. In the future, we could make a more robust model using other factors. These include human factors, propulsion, and technological advancements. There is some data about [human factors], how the lifespan of humans has increased due to medical advancement. If we have humans who live past 100, 150, or 200 years old, maybe there is more of a chance that people will be able to advance technology in their fields. Maybe in the future, there’s another Einstein that we are waiting on.”
“We face many threats here on Earth, climate change, biowarfare, nuclear, and natural threats that we may not be able to do anything to counteract – like an asteroid strike, extreme volcanic action,” added Rosen. “We’ve got all our eggs in one basket. It’s a very good basket, but it’s still only one. If you wait long enough, a natural calamity will occur. The Universe is unforgiving, as the dinosaurs found out. So the best bet for survival is to diversify where our species and other Earth species live.”
That, perhaps, is another potential takeaway from this research. If expanding our presence beyond Earth and cis-lunar space dramatically increases the odds of our survival, then we ought to consider doing everything we can to move the timetable up. So, in addition to being a possible stepping stone towards more highly constrained predictive models, we might also consider this research to be a call to action.
