Galaxy-Spanning Civilizations –“Rare or Non-Existent in the Universe” (A ‘Galaxy’ Insight)





We recently reported that "a globular cluster might be the first place in which intelligent life is identified in our galaxy," according to Rosanne DiStefano of the Harvard-Smithsonian Center for Astrophysics. Globular star clusters at the outer edge of the Milky Way are extraordinary in almost every way. They're densely packed, holding a million stars in a ball only about 100 light-years across on average. They're old, dating back almost to the birth of the Milky Way. And according to new research, they also could be extraordinarily good places to look for space-faring civilizations.

In 1974 astronomer Frank Drake used the Arecibo radio telescope to broadcast the first deliberate message from Earth to outer space. It was directed at the globular cluster Messier 13 (M13) shown above. What are the odds that advanced civilizations actually exists there?

"What does it mean for a civilization to be a million years old?" Carl Sagan pondered. "We have had radio telescopes and spaceships for a few decades; our technical civilization is a few hundred years old … an advanced civilization millions of years old is as much beyond us as we are beyond a bushbaby or a macaque."

Sagan observed that the time to colonize an individual system is small compared to the travel time between stars. A civilization could engulf its galaxy on a time scale comparable to the rotation period of the galaxy, or every 225–250 million years, and perhaps shorter.

Nearly 14 billion years ago, our universe was born from a swirling quantum soup, in a spectacular and dynamic event known as the Big Bang. After several hundred million years, the first stars lit up the cosmos, and many hundreds of millions of years later, the remnants of countless stellar explosions coalesced into the first planetary systems. Somehow, through a process still not understood, the laws of physics guiding the unfolding of our universe gave rise to self-replicating organisms – life. Yet more perplexing, this life eventually evolved a capacity to know its universe, to study it, and to question its own existence. Did this happen many times? If it did, how? If it didn't, why?




Everything that we believe was necessary for life to begin on Earth is now known to be ubiquitous throughout our galaxy and beyond. Knowing that extraterrestrial life could exist, the race is on to discover whether or not it, in fact, does exist.

SETI experiments seek to determine the distribution of advanced life in the universe through detecting the presence of technology, usually by searching for electromagnetic emission from communication technology, but also by searching for evidence of large scale energy usage or interstellar propulsion. Technology is thus used as a proxy for intelligence – if an advanced technology exists, so to does the ad advanced life that created it.

Although natural astrophysical sources produce a diverse array of electromagnetic, gravitational and high energy particle emission, there are particular types of emission that, as far as we know, could only be generated by an advanced technology. For example, technology constructed by human beings has been producing radio emission for more than 100 years that would be readily detectable at dozens of light years using receiving technology only moderately more advanced than our own. Some emission, including that produced by the planetary radars at Arecibo Observatory and the NASA Deep Space Network, would be detectable across our galaxy.

Technologies far more advanced than our own could potentially produce even more dramatic evidence of their presence. Large stellar-scale structures could cause apparent modulation in starlight as they orbited their host, and massive energy usage by a super advanced civilization might be revealed by its thermodynamic signature, even from millions of light- years away.

Although we know of only one example of life anywhere in the universe, we have reasons to be optimistic about the possibility of life beyond Earth. Earth-like planets, water and complex chemistry have now been found in abundance throughout our galaxy. Everything that we believe was necessary for life to begin on Earth is now known to be ubiquitous throughout our galaxy and beyond. Knowing that extraterrestrial life could exist, the race is on to discover whether or not it, in fact, does exist.

Yet more compelling is the possibility that extraterrestrial life may have followed a similar developmental process as life on the Earth, and given rise to a life form possessing intelligence and a technological capability similar to, or perhaps far exceeding, our own. Conducting direct searches for advanced extraterrestrial life is the sole means of determining the prevalence of such life in the universe, and answering one of our most fundamental questions: Are we alone?

Researchers at Penn State University, led by Jason Wright, have recently under taken a significant effort to search for evidence of massive energy usage by very advanced civilizations using data from NASA's WISE space telescope. Although so far this work has produced only negative results, it has placed significant constraints on the presence of extremely advanced galactic-scale civilizations.

Additional work led by Erik Zackrisson in Sweden and Michael Garrett of the Netherlands Institute for Radio Astronomy (ASTRON) and Leiden Observatory has come to similar conclusions regarding the rarity of super-advanced civilizations, but this collected work represents a promising and growing new area of SETI research.

In 1964, Soviet astronomer Nikolai Kardashev, who was looking for signs of extraterrestrial life within cosmic signals, speculated that a civilization’s level of technological advancement could be measured based on the amount of energy that this civilization is able to utilize. Kardeschev searched for traces of the more advanced type 11 and 111 at the 920 MHz wave length creating an uproar of excitement thinking he had discover signals from a Type 11 civilization that later proved to be an ordinary quasar with a large red shift.

He identified three types of civilizations called Type I, II, and III. Kardashev Type III civilizations – galaxy-spanning civilizations that command power equal to all of the stars in their galaxy – are very rare or entirely absent from the local Universe, according to Garrett.

All three categories of civilizations, even the most advanced Type 111, would still be bound by the laws of physics that allow us to predict the behavior of the universe from the subatomic world to the large-scale structure of the universe, through a staggering 43 orders of magnitude (a factor of 10 million billion billion billion billion).

Type 1 civilizations would have a technological level similar to ours at present, as measured by total energy consumption. Carl Sagan estimated that Earth qualifies as a Type 0.7 civilization.Type 11 civilizations would be capable of harnessing the energy of their own star -constructing, for example, a Dyson Sphere. Type 111 civilizations would be able to utilize energy on the scale of their own galaxies. Kardeschev believed that there is an extremely low probability of detecting Type 1 civilizations and suggests that type 11 or 111 civilizations would make better targets. Kardeschev calculated that the energy consumption of these three types of civilizations would be separated by a factor of about 10 billion.

The human race is not even on this scale yet. We are a Type 0 civilization. Physicist Michu Kaku believes that, all things taken into consideration, we will reach Type I in 100 – 200 years time. A Type I civilization can manage the entire energy and material resources of a planet. A Type II civilization is capable of harnessing the energy and material resources of a star and its planetary system. A Type III civilization is able to marshal the energy and material resources of an entire galaxy..

Roger Griffith of Penn State University and colleagues compiled a catalogue of 93 candidate galaxies — culled from a total population of 100,000 objects — where unusually extreme mid-IR emission is observed. One problem is that although rare, this kind of emission can also be generated by natural astrophysical processes related to thermal emission from warm dust.

Garrett has used radio measurements of the very best candidate galaxies and found that the vast majority of these systems have emission that is best explained by natural astrophysical processes.

“The original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don’t exist in the local Universe,” said Garrett. "In my view, it means we can all sleep safely in our beds tonight – an alien invasion doesn’t seem at all likely.”

“In particular, the galaxies in the sample follow a well-known global relation that holds for almost all galaxies – the so-called ‘mid-IR radio correlation.”

“The presence of radio emission at the levels expected from the correlation suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust – for example, dust generated and heated by regions of massive star formation.”

According to Prof Garrett, his method could also be used to help identify less advanced, Kardashev Type II civilizations. “It’s a bit worrying that Type III civilizations don’t seem to exist. It’s not what we would predict from the physical laws that explain so well the rest of the physical Universe,” Garrett said.

“We’re missing an important part of the jigsaw puzzle here. Perhaps advanced civilizations are so energy efficient that they produce very low waste heat emission products – our current understanding of physics makes that a difficult thing to do. What’s important is to keep on searching for the signatures of extraterrestrial intelligence until we fully understand just what is going on.”

The rim of the blue galaxy AM 0644-741 shown at the top of the page , an immense ring-like structure 150,000 light years in diameter caused by an immense galaxy collision, is composed of newly formed, extremely bright, massive stars.

Source: M.A. Garrett. 2015. Application of the mid-IR radio correlation to the Ĝ sample and the search for advanced extraterrestrial civilizations. A&A 581, L5; doi: 10.1051/0004-6361/201526687

The Daily Galaxy via NASA, Penn State University, and and

Imaged credit: Hubble Heritage Team (AURA / STScI), J. Higdon (Cornell) ESA, NASA


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