Beyond “Fermi’s Paradox” IX: What is the Brief Window Hypothesis?

Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that we haven’t heard from aliens because intelligent life only survives for so long.

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Since Fermi’s time, there have been several proposed resolutions to his question, which include the possibility that civilizations only have a “Brief Window” with which to communicate with the cosmos before going extinct.

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Beyond “Fermi’s Paradox” VII: What it the Planetarium Hypothesis

Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that we can’t see them because they have us all inside a massive simulation!

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the disparity between high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. Seventy years later, we are still trying to answer that question, which has led to some interesting theories about why we haven’t. A particularly mind-bending suggestion comes in the form of the Planetarium Hypothesis!

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Beyond “Fermi’s Paradox” V: What is the Aestivation Hypothesis?

Welcome back to our Fermi Paradox series, where we take a look at possible resolutions to Enrico Fermi’s famous question, “Where Is Everybody?” Today, we examine the possibility that the reason we’re not hearing from aliens is that they’re asleep and waiting for the Universe to get better.

In 1950, Italian-American physicist Enrico Fermi sat down to lunch with some of his colleagues at the Los Alamos National Laboratory, where he had worked five years prior as part of the Manhattan Project. According to various accounts, the conversation turned to aliens and the recent spate of UFOs. Into this, Fermi issued a statement that would go down in the annals of history: “Where is everybody?

This became the basis of the Fermi Paradox, which refers to the high probability estimates for the existence of extraterrestrial intelligence (ETI) and the apparent lack of evidence. But despite seventy years of looking, we still haven’t been able to answer Fermi’s question, leading to multiple proposals as to why this is. Today, we look at the “Aestivation Hypothesis,” which argues that aliens are not dead (or non-existent), they’re just resting!

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Calculate the Number of Alien Civilizations in the Milky Way for Yourself.

In recent years, the explosive nature of exoplanet discovery (over 4,164 confirmed so far!) has led to renewed interest in the timeless question: “are we alone in the Universe?” Or, as famed Italian physicist Enrico Fermi put it, “Where is everybody?” With so many planets to choose from and the rate at which our instruments and methods are improving, the search for life beyond Earth is really kicking into high gear.

At the same time, these discoveries have inspired a plethora of new studies regarding the ongoing Search for Extraterrestrial Intelligence (SETI). This includes the Alien Civilization Calculator, which is the brainchild of physicists Steven Woodling and Dominick Czernia. Inspired by recent attempts to address the statistical likelihood of advanced life in our galaxy, they offer a mathematical tool that can crunch the numbers for you!

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Could We Detect an Ancient Industrial Civilization in the Geological Record?

As a species, we humans tend to take it for granted that we are the only ones that live in sedentary communities, use tools, and alter our landscape to meet our needs. It is also a foregone conclusion that in the history of planet Earth, humans are the only species to develop machinery, automation, electricity, and mass communications – the hallmarks of industrial civilization.

But what if another industrial civilization existed on Earth millions of years ago? Would we be able to find evidence of it within the geological record today? By examining the impact human industrial civilization has had on Earth, a pair of researchers conducted a study that considers how such a civilization could be found and how this could have implications in the search for extra-terrestrial life.

The study, which recently appeared online under the title “The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record“, was conducted by Gavin A. Schmidt and Adam Frank – a climatologist with the NASA Goddard Institute for Space Studies (NASA GISS) and an astronomer from the University of Rochester, respectively.

Carbon dioxide in Earth’s atmosphere if half of global-warming emissions are not absorbed. Credit: NASA/JPL/GSFC

As they indicate in their study, the search for life on other planets has often involved looking to Earth-analogues to see what kind conditions life could exist under. However, this pursuit also entails the search for extra-terrestrial intelligence (SETI) that would be capable of communicating with us. Naturally, it is assumed that any such civilization would need to develop and industrial base first.

This, in turn, raises the question of how often an industrial civilization might develop – what Schmidt and Frank refer to as the “Silurian Hypothesis”. Naturally, this raises some complications since humanity is the only example of an industrialized species that we know of. In addition, humanity has only been an industrial civilization for the past few centuries – a mere fraction of its existence as a species and a tiny fraction of the time that complex life has existed on Earth.

For the sake of their study, the team first noted the importance of this question to the Drake Equation. To recap, this theory states that the number of civilizations (N) in our galaxy that we might be able to communicate is equal to the average rate of star formation (R*), the fraction of those stars that have planets (fp), the number of planets that can support life (ne), the number of planets that will develop life ( fl), the number of planets that will develop intelligent life (fi), the number civilizations that would develop transmission technologies (fc), and the length of time these civilizations will have to transmit signals into space (L).

This can be expressed mathematically as: N = R* x fp x ne x fl x fi x fc x L

The Drake Equation, a mathematical formula for the probability of finding life or advanced civilizations in the universe. Credit: University of Rochester

As they indicate in their study, the parameters of this equation may change thanks to the addition of the Silurian Hypothesis, as well as recent exoplanets surveys:

“If over the course of a planet’s existence, multiple industrial civilizations can arise over the span of time that life exists at all, the value of fc may in fact be greater than one. This is a particularly cogent issue in light of recent developments in astrobiology in which the first three terms, which all involve purely astronomical observations, have now been fully determined. It is now apparent that most stars harbor families of planets. Indeed, many of those planets will be in the star’s habitable zones.”

In short, thanks to improvements in instrumentation and methodology, scientists have been able to determine the rate at which stars form in our galaxy. Furthermore, recent surveys for extra-solar planets have led some astronomers to estimate that our galaxy could contains as many as 100 billion potentially-habitable planets. If evidence could be found of another civilization in Earth’s history, it would further constrain the Drake Equation.

They then address the likely geologic consequences of human industrial civilization and then compare that fingerprint to potentially similar events in the geologic record. These include the release of isotope anomalies of carbon, oxygen, hydrogen and nitrogen, which are a result of greenhouse gas emissions and nitrogen fertilizers. As they indicate in their study:

“Since the mid-18th Century, humans have released over 0.5 trillion tons of fossil carbon via the burning of coal, oil and natural gas, at a rate orders of magnitude faster than natural long-term sources or sinks. In addition, there has been widespread deforestation and addition of carbon dioxide into the air via biomass burning.”

Based on fossil records, 250 million years ago over 90% of all species on Earth died out, effectively resetting evolution. Credit: Lunar and Planetary Institute

They also consider increased rates of sediment flow in rivers and its deposition in coastal environments, as a result of agricultural processes, deforestation, and the digging of canals. The spread of domesticated animals, rodents and other small animals are also considered – as are the extinction of certain species of animals – as a direct result of industrialization and the growth of cities.

The presence of synthetic materials, plastics, and radioactive elements (caused by nuclear power or nuclear testing) will also leave a mark on the geological record – in the case of radioactive isotopes, sometimes for millions of years. Finally, they compare past extinction level events to determine how they would compare to a hypothetical event where human civilization collapsed. As they state:

“The clearest class of event with such similarities are the hyperthermals, most notably the Paleocene-Eocene Thermal Maximum (56 Ma), but this also includes smaller hyperthermal events, ocean anoxic events in the Cretaceous and Jurassic, and significant (if less well characterized) events of the Paleozoic.”

These events were specifically considered because they coincided with rises in temperatures, increases in carbon and oxygen isotopes, increased sediment, and depletions of oceanic oxygen. Events that had a very clear and distinct cause, such as the Cretaceous-Paleogene extinction event (caused by an asteroid impact and massive volcanism) or the Eocene-Oligocene boundary (the onset of Antarctic glaciation) were not considered.

Artistic rendition of the Chicxulub impactor striking ancient Earth, with Pterosaur observing. Credit: NASA

According to the team, the events they did consider (known as “hyperthermals”) show similarities to the Anthropocene fingerprint that they identified. In particular, according to research cited by the authors, the Paleocene-Eocene Thermal Maximum (PETM) shows signs that could be consistent with anthorpogenic climate change. These include:

 “[A] fascinating sequence of events lasting 100–200 kyr and involving a rapid input (in perhaps less than 5 kyr) of exogenous carbon into the system, possibly related to the intrusion of the North American Igneous Province into organic sediments. Temperatures rose 5–7?C (derived from multiple proxies), and there was a negative spike in carbon isotopes (>3%), and decreased ocean carbonate preservation in the upper ocean.”

Finally, the team addressed some possible research directions that might improve the constraints on this question. This, they claim, could consist of a “deeper exploration of elemental and compositional anomalies in extant sediments spanning previous events be performed”. In other words, the geological record for these extinction events should be examined more closely for anomalies that could be associated with industrial civilization.

If any anomalies are found, they further recommend that the fossil record could be examined for candidate species, which would raise questions about their ultimate fate. Of course, they also acknowledge that more evidence is necessary before the Silurian Hypothesis can be considered viable. For instance, many past events where abrupt Climate Change took place have been linked to changes in volcanic/tectonic activity.

Scientists were able to gauge the rate of water loss on Mars by measuring the ratio of water and HDO from today and 4.3 billion years ago. Credit: Kevin Gill

Second, there is the fact that current changes in our climate are happening faster than in any other geological period. However, this is difficult to say for certain since there are limits when it comes to the chronology of the geological record. In the end, more research will be necessary to determine how long previous extinction events (those that were not due to impacts) took as well.

Beyond Earth, this study may also have implications for the study of past life on planets like Mars and Venus. Here too, the authors suggest how explorations of both could reveal the existence of past civilizations, and maybe even bolster the possibility of finding evidence of past civilizations on Earth.

“We note here that abundant evidence exists of surface water in ancient Martian climates (3.8 Ga), and speculation that early Venus (2 Ga to 0.7 Ga) was habitable (due to a dimmer sun and lower CO2 atmosphere) has been supported by recent modeling studies,” they state. “Conceivably, deep drilling operations could be carried out on either planet in future to assess their geological history. This would constrain consideration of what the fingerprint might be of life, and even organized civilization.”
Two key aspects of the Drake Equation, which addresses the probability of finding life elsewhere in the galaxy, are the sheer number of stars and planets out there and the amount of time life has had to evolve. Until now, it has been assumed that one planet would give rise to one intelligent species capable of advanced technology and communications.
But if this number should prove to be more, we may a find a galaxy filled with civilizations, both past and present. And who knows? The remains of a once advanced and great non-human civilization may very well be right beneath us!

Further Reading: arXiv

If We Do Hear Signals From Aliens, They’re Probably Long Gone

In 1961, famed astrophysics Frank Drake proposed a formula that came to be known as the Drake Equation. Based on a series of factors, this equation sought to estimate the number of extraterrestrial intelligences (ETIs) that would exist within our galaxy at any given time. Since that time, multiple efforts have been launched to find evidence of alien civilizations, which are collectively known as the search for extraterrestrial intelligence (SETI).

The most well-known of these is the SETI Institute, which has spent the past few decades searching the cosmos for signs of extraterrestrial radio communications. But according to a new study that seeks to update the Drake Equation, a team of international astronomers indicates that even if we did find signals of alien origin, those who sent them would be long dead.

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What is the Drake Equation?

Is there life out there in the Universe? That is a question that has plagued humanity long before we knew just how vast the Universe was – i.e. before the advent of modern astronomy. Within the 20th century – thanks to the development of modern telescopes, radio astronomy, and space observatories – multiple efforts have been made in the hopes of finding extraterrestrial intelligence (ETI).

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Maybe the Aliens Aren’t Hiding, they’re Sleeping, Waiting for the Universe to Get Better

When you consider that age of the Universe – 13.8 billion years by our most recent counts –  and that which is “observable” to us measures about 93 billion light-years in diameter, you begin to wonder why we haven’t found signs of extra-terrestrial intelligence (ETI) beyond our Solar System. To paraphrase Enrico Fermi, the 20th-century physicists who advanced the famous Fermi Paradox – “where the heck are all the aliens?”

Naturally, Fermi’s Paradox has attracted a lot of theoretical explanations over the years – which include ETI being very rare, humanity being early to the Universe, and the aliens being extinct! But a new study by a team of scientists from the Future of Humanity Institute (FHI) offers a different take on this age-old paradox. According to their study, the key to answering this question is to consider the possibility that the aliens are engaged in “aestivation”.

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Inside the Drake Equation: A Chat with Frank Drake

This interview with Frank Drake — sometimes called the Father of the Search for Extraterrestrial Intelligence – was recorded in 2012 but not released until now to celebrate the beginning of the 30th year of the SETI Institute. As interviewer Andrew Fraknoi says, “I don’t think anyone had a conversation like this that was recorded with Galileo or William Herschel or Edwin Hubble, but I get to do it with Frank Drake!”

This is a great conversation that alternates between Drake’s current work with SETI and the history of his work that led to the famous Drake Equation. Fraknoi and Drake have an interesting exchange about the value of N, which is the number of civilizations in The Milky Way Galaxy whose electromagnetic emissions would be detectable.

It was recorded in June 2012 at an event called SETICon, which featured a series of talks, panels, and events featuring scientists, authors, futurists, and film-makers.

Fraknoi is a professor of astronomy and also works with the Astronomical Society of the Pacific and they have made available a written history of Frank Drake and his equation.