The Search for Extraterrestrial Intelligence (SETI) is regularly plagued by the fact that humanity has a very limited perspective on civilization and the nature of intelligence itself. When it comes right down to it, the only examples we have to go on are “life as we know it” (aka. Earth organisms) and human civilization. On top of that, given the age of the Universe and the time life has had to evolve on other planets, it is a foregone conclusion that any advanced life in our galaxy would be older than humanity. Luckily, this presents an opportunity to develop and test theoretical frameworks in the field.

To paraphrase Freeman Dyson, if we can conceive of a concept (and the physics are sound), an advanced species will likely have built it already. In this respect, imagining where humanity will be centuries or eons from now could provide potential “technosignatures” to look for. In a recent paper, a team from the Blue Marble Space Institute of Science (BMSIS) and NASA’s Goddard Space Flight Center modeled a series of scenarios that attempt to predict what humanity’s “technosphere” could look like 1,000 years from now. Their research could have implications for future SETI studies.

The research team was led by Jacob Haqq-Misra, an astrobiologist and Research Scientist at Blue Marble Space Institute of Science. He was joined by George Profitiliotis, an Affiliate Research Scientist with BMSIS and a co-founder of the Greek NewSpace Society, and Ravi Kopparapu, a Planetary Scientist at NASA Goddard Space Flight Center. The preprint of their paper recently appeared in Elsevier and is being reviewed for publication in the journal Technological Forecasting and Social Change. The paper is the first in a series titled “Projections of Earth’s technosphere.”

Searching for Technosignatures

When it comes to predicting what advanced civilizations might look like and the technologies they will employ, scientists are often marred by our limited perspective. When it comes right down to it, humanity is familiar with only one example of an advanced species relying on technological innovations to ensure food security, health and safety, transportation, defense, and other applications – i.e., ourselves! But as Freeman Dyson once related when discussing his theory of a Dyson Sphere, if we can conceive of an idea and the physics of it are sound, an advanced civilization may have already built it.

As they indicate in their paper, this process is similar to how astrobiologists rely on the study of Earth organisms to predict what biosignatures they should be searching for. As Haqq-Misra told Universe Today via email:

“Astrobiology has the entire history of Earth to draw upon as examples of how life has modified the planet. The search for extraterrestrial biosignatures can use Earth today or Earth in its past for ideas of what to look for. In the same way, the search for extraterrestrial technosignatures begins with the history of technology on Earth, although technology is much more recent in Earth’s history when compared to life in general. Our paper is an effort to provide a theoretical basis for technosignatures that is based on our undersstanding of life and technology on Earth.”

Similarly, SETI research has benefitted in recent years from anthropological studies that consider the totality of human activity on Earth. This collective activity is known as the “anthroposphere,” which corresponds to the concept of the Anthropocene—the current geological era in which humanity has become the largest driving force in environmental change. When considering this through the lens of technological activity and the technosignatures this would produce, the term “technosphere” is used.

Multiple SETI experiments have been mounted in the past sixty years, most of which searched for signs of extraterrestrial radio transmissions. This should come as no surprise since radio communications are a time-tested and validated technology that humanity has relied on for more than a century. But as Haqq-Misra explained, SETI also has a rich history of drawing upon various projections of future technology as well:

“[T]echnosignature studies begin with what exists on Earth, what could exist on Earth in the near-term, or what could theoretically be possible given known understanding of physics as places for extrapolations into the future. This approach does not assume that such projections are inevitable or even probable, but it at least provides a way to think about the astronomical tools that would be needed to remotely detect an extraterrestrial civilization with even greater technological capabilities than on Earth today.”

A New Approach

When it comes to predicting humanity’s future (and, by extension, advanced technosignatures), prior studies tend to have suffered from an inherent bias. In many cases, there is the assumption that a technological civilization will continue to grow exponentially. A perfect example is the Kardashev Scale, which predicts how advanced civilizations will invariably grow to occupy more space and harness more energy. This is an understandable assumption given human history and the exponential increase in the global population – from 1 billion in 1800 to 8.1 billion in 2024 (an increase of over 800%)

Similarly, global energy use also grew exponentially during this same period – from 5,653 terawatt-hours (TWh) in 1800 to 182,230 TWh in 2023 (an increase of more than 3200%). This model of continuous growth well into the future has motivated many observational and theoretical approaches for finding technosignatures. Among them is the search for possible megastructures around stars that experience periodic drops in brightness (like Boyajan’s Star) and “disappearing stars.” But as Haqq-Misra explained, this is merely one possibility for an advanced civilization.

Instead of predicting a single evolutionary pathway, Haqq-Misra and his colleagues adopted the “futures studies” approach. This interdisciplinary field relies on various systematic methodological approaches for predicting self-consistent future trajectories. Said Haqq-Misra:

“The plural “futures” is used to indicate that the actual future is unknown and cannot be predicted; instead, futures studies develops systematic projections of multiple contrasting futures that can provide insight into the range and diversity of possible outcomes. Most attempts at making informal projections in technosignature science inevitably succumb to biases based on internal assumptions or prevailing cultural narratives, which can limit the possibility space of imagined futures. The methodological approaches developed by practitioners of futures studies are designed to minimize such biases and enable much more robust exploration of possibilities for the future —in our case, the future of civilization.”

Our Possible Futures

Their approach involved a method known as a “general morphological analysis,” a means of exploring possible solutions to multi-dimensional, non-quantified problems. This method is intended to minimize the bias in underlying assumptions and encompass a wide range of possibilities. From this, the first step for Haqq-Misra and his colleagues was to ask the question:

“What are the technological phenomena of the future anthroposphere,
and how can they be described?”

They then defined a large set of scenarios based on different political, economic, societal, and technological factors, each with different values corresponding to different possible futures. This yielded almost 5,800 scenarios, but the team eliminated many based on logical inconsistencies while clustering others based on similarities. The team also used the Claude large language model (LLM) to assist with analyzing, comparing, and clustering. This allowed them to work their way down to ten future scenarios.

The next step was to develop a novel worldbuilding “pipeline” based on an assessment of human needs in all ten scenarios. This allowed them to incorporate details for each scenario that would define observable properties for the corresponding technosphere. As Haqq-Misra explained:

“The underlying assumption in our worldbuilding process is that technology is intended to fulfill basic human needs. This means that any future technosphere must be reflective in some way of the needs of humans in a given future scenario. We do not assume that any given technosignature will exist for an arbitrary reason, but any feature of the physical technosphere in our scenarios is the outcome of political, social, or economic factors that drive human needs. We likewise expect that any technosignatures we find in extraterrestrial settings will exist because they are indicative of or derivative from processes that relate to extraterrestrial needs.”

One interesting finding was that only one of the ten scenarios involved the kind of rapid growth predicted by the Kardeshev Scale, Haqq-Misra added. Others showed slower growth, no growth at all, while another oscillated between growth and collapse. “This suggests that focusing the search for technosignatures on the idea of advanced, energy-intensive, and expansive extraterrestrial civilizations may be too limiting,” he said. “Numerous possibilities exist from our modeling alone that show alternative possibilities for long-term futures, and such civilizations could even be more likely or more numerous than longer-lived or galactic-spanning civilizations.”

Among the potential technosignatures these scenarios predicted, nitrogen dioxide emerges as a possible means of distinguishing between modern-day Earth, Earth before the introduction of agriculture, and a more industrial Earth in the future. They also found that the atmospheric spectra produced in three scenarios were “indistinguishable from nature,” meaning there was no discernible distance between a pre-agriculture and a more technologically advanced Earth.

“These three scenarios still include expansive technosphere, but much of the detectable technology is on Mars and other parts of the outer solar system,” said Haqq-Misra. “This raises an important possibility for false negatives in the search for technosignatures: a planet with no obvious technosignatures may not necessarily be devoid of technology, and the best places to look may even be elsewhere in the system.”

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As always, the field of SETI and technosignature searches are constrained by the limits of our knowledge, where scientists must speculate about what we don’t know based on what we do. However, the process is becoming increasingly sophisticated thanks to advanced modeling and simulations that can account for various possibilities. In addition, scientists are questioning underlying assumptions regarding advanced civilizations and their motivations. The work of Haqq-Misra and his colleagues represents a first in a key way.

As he explained, futures studies methods tend to be applied to short-term projections of a few years or decades, while some climate science studies have looked ahead a few centuries:

“Our study is the first to use futures studies methods to develop projections across a 1000-year timescale, which requires us to focus on the longer-term trends that could shape different outcomes for civilization on Earth. This provides a solid theoretical basis for thinking about the range of technosignatures in planetary systems, and how to search for them, and much more work can be done from these scenarios alone to develop new search strategies. These scenarios also help us to imagine a broader range of possibilities for Earth’s future, which include numerous optimistic outcomes that avoid collapse or extinction. Our civilization may face numerous challenges, but studies like ours are important to remind us that the future remains open.”

Further Reading: arXiv