What the Search for Extraterrestrial Intelligent Life Means for Us
During my graduate school days at the University of Toronto (late 1960s) I took a short summer course, Advances in Planetary Physics, taught by astronomer Carl Sagan. Sagan was a rising star then and well on his way to becoming the science popularizer and communicator for which he later became famous. Most of the course and nearly all of the informal evening discussions focused on the possibility that extraterrestrial intelligent life existed and on the kinds of civilizations such beings would have established. In Sagan's mind, there was absolutely no doubt that extraterrestrial intelligent beings (ETI) existed. Furthermore, he was convinced that on many planets in our galaxy ETIs had developed civilizations far more technically advanced than ours.
Sagan finished the course by listing over a dozen currently existing problems on earth that could bring about the end of human civilization. He then pointed out that the nations of the world had failed to develop, or even to propose, a single viable solution to even one of the problems on his list. Therefore, he asserted, mankind's only hope was to get counsel from an ETI civilization far more advanced than ours. Such a civilization, he was sure, would have produced something on the order of an Encyclopedia Galactica, which—as he was also confident that the civilization must be benevolent—it would be motivated to broadcast to beleaguered planets like ours.
Sagan devoted much of the rest of his life to the search for extraterrestrial intelligent life (SETI). He tirelessly promoted SETI as mankind's top priority.
Searching for Signals
Even before Sagan started publicly promoting SETI, a few astronomers had obtained time on some large radio telescopes to search for signals sent out by extraterrestrial intelligent civilizations. They failed to detect any signals, but their failures did little to blunt the growing enthusiasm for finding ETIs.
Thanks to Sagan's encouragement, the SETI (Search for Extraterrestrial Intelligence) Institute was founded in 1984. In 1995-1996 the SETI Institute's Project Phoenix obtained four months' observing time on the Parkes radio telescope in New South Wales, Australia, the southern hemisphere's largest radio telescope, to check out all 202 of the approximately solar-type stars within 155 light years of Earth for intelligence-generated electromagnetic signals. The results effectively ruled out the existence of any intelligent species as advanced as the current human race that might be broadcasting their presence.1 From 1996 to 2004 Project Phoenix was extended to include 800 stars out to 200 light years away. Still no signals indicative of an intelligent civilization were detected.2
Once again, none of these failures dampened the enthusiasm for SETI. So, thanks to generous donations from Microsoft cofounder Paul Allen, the Allen Telescope Array of 42 radio telescopes was built and is dedicated to SETI observations.
Recently, astronomers have adopted a new approach to finding intelligent civilizations. Rather than looking for communication signals that may or may not be aimed at us, these astronomers are attempting to detect the energy-processing activities of such entities. This approach is based on the correlation between a civilization's level of technological advancement and the amount of energy such a civilization needs to consume and process in order to maintain its technological capability.
Kardashev's Categories
In 1964 Russian astronomer Nikolai Kardashev, after a failed search for ETI, defined three categories of advanced civilizations, as shown in the following chart:
American physicist Freeman Dyson explained how an intelligent civilization would go about harvesting most of the energy output of a star: it would surround its star (or other stars) with energy-capturing structures not dissimilar to the solar panels a homeowner might put on his roof here on Earth. Such structures have been labeled "Dyson spheres."
Whereas previous generations of astronomers lacked the telescope power needed to detect operating Dyson spheres, today's astronomers possess that capability. Four Swedish astronomers noticed that if Dyson spheres surrounded a large number of stars in a galaxy, both the apparent luminosity and the color of those stars, as seen from Earth, would change, while the galaxy's gravitational potential would remain unchanged.3 The team proceeded to search for records of such changes in the latest galaxy survey databases. But out of a sample of 1,359 spiral galaxies searched (only spiral galaxies are candidates for hosting advanced life4), the team failed to detect the existence of a single Kardashev III-level civilization.
I am sorry to disappoint Stars Wars fans (or Star Trek fans), but apparently there is no faraway galaxy hosting a confederation of intelligent civilizations on thousands of planets.
A "Dimmer" of Hope
The ruling out of Kardashev III civilizations led SETI astronomers to turn their attention to searching for Kardashev II civilizations. Some members of a team of 29 American and European astronomers now speculate that they may have found one. In September 2015, the entire team submitted a paper to the Monthly Notices of the Royal Astronomical Society,in which they report on an observed anomalous dimming of the star KIC 8462852.5
The dimming is not characteristic of a transiting planet or brown dwarf star. It is irregular, and one of the dimmings was about fifteen times greater than what one would expect to see in the case of a very large gas-giant planet passing in front of the star. In their paper, the team considered seven possible explanations for the dimmings:
1. instrumental effects or data reduction artifacts,
2. intrinsic variability in the star's light output,
3. variability of KIC 8462852's companion star,
4. variability in light absorption by dust clouds and clumps surrounding the star,
5. the aftermath of catastrophic collisions in an asteroid belt,
6. the aftermath of a giant impact in the planetary system, or
7. a breakup of one or more large comet bodies that resulted in a cloud of disintegrating comets.
Observations of the star and planet formation models enabled the team to eliminate all but the last explanation. In their summary, they concluded that a comet swarm was the most likely explanation of the observed dimming.
But after submitting the paper, the lead author, Tabetha Boyajian, speculated that the dimming might have been caused by a Kardashev II civilization. Several interviews and internet articles later, Boyajian and two of her colleagues garnered two weeks' observing time on the Allen Telescope Array, hoping to catch some communication signals from the possible civilization in the KIC 8462852 system. Alas, they found none.
KIC's Disqualifying Characteristics
Boyajian and her colleagues could have saved themselves the long telescope hours, as well as the time and ink expended by many media reporters. KIC 8462852's own characteristics rule out the possibility that it could host a planet on which intelligent life exists. The spectral type of KIC 8462852 is F3V/IV, contrasted with the Sun's G2V. F3V/IV stars are nearly five times more luminous than the Sun; they burn through their nuclear fuel much more rapidly; they emit much more deadly ultraviolet radiation; and they manifest much more flaring activity. Any one of these distinctives would eliminate the possibility that a planet orbiting KIC 8462852 could sustain life long enough to provide the environmental conditions and biodeposits necessary for an intelligent species to launch and sustain a civilization.
Moreover, KIC 8462852's rotation period is only 0.88 days, meaning it rotates about thirty times more rapid than the Sun. Rapid stellar rotation is strongly correlated with high flaring activity—much too high for the survival of terrestrial animals. Also, rapid stellar rotation usually implies a stellar age much too young for the long life history required for the emergence of intelligent life.
It is also relevant that spectral measurements of KIC 8462852's light output reveal no significant infrared excess. The lack of excess infrared radiation contradicts the hypothesis that an intelligent civilization is using a Dyson sphere to harvest energy from KIC 8462852. Such harvesting would involve the capture of the star's ultraviolet and visible light to generate electricity or other forms of useful energy, and the dissipation of the heat (infrared radiation) resulting from such exploitation. But KIC 8462852 is neither anomalously dim at ultraviolet and visible wavelengths nor anomalously bright at infrared wavelengths.
What is true of KIC 8462852 is also true of all the other stars SETI astronomers have observed in the hope of detecting signals indicative of an intelligent species inhabiting a planet orbiting one of those stars. None possesses the characteristics needed to make possible the existence, let alone thriving, of a high-technology civilization on one of its possible planets. The telescope time was wasted on demonstrable non-candidates.
Looking in the Right Place
In many respects, SETI research is a waste of time, money, and talent. However, these latest SETI efforts are yielding greater insights into and appreciation for just how many plans, preparations, and preliminary steps—especially the carefully orchestrated introduction of certain forms of non-intelligent life—are needed to make possible a narrow time window during which an intelligent living species can exist on a planet, and how many more plans, preparations, and carefully orchestrated steps must be taken to enable such a species to launch and sustain a high-technology civilization. No such species and civilization are possible apart from the handiwork of a super-intelligent, super-powerful, super-benevolent Creator.6 If there is intelligent life elsewhere in the universe, it exists thanks to the miraculous interventions of that Creator.
So far, everywhere beyond Earth that astronomers have looked, they have only found environments extremely hostile to advanced life. In fact, in spite of more than fifty years of diligent searching, astronomers have yet to find one other star with characteristics close enough to the Sun's to make it a candidate for hosting a planet on which intelligent life could launch and sustain a civilization.7
It seems that we really are alone. However, I do agree with Carl Sagan that humans face intractable problems that threaten our long-term survival. I also agree that our only hope is to take counsel from the Encyclopedia Galactica. When Sagan waxed eloquent about that great text during the course he taught at the University of Toronto, I nudged some of my fellow students and commented, "Don't we already have an Encyclopedia Galactica? And isn't Carl's problem that he refuses to read it?" They all knew, of course, that I was referring to the Bible. •
Hugh RossPhD, is an astrophysicist and the founder and president of the science-faith think tank Reasons to Believe (RTB).
Get Salvo in your inbox! This article originally appeared in Salvo, Issue #36, Spring 2016 Copyright © 2024 Salvo | www.salvomag.com https://salvomag.com/article/salvo36/eti-in-the-sky
