A Targeted Search for Extraterrestrial Intelligence Found Nothing, Part 2

Despite efforts to detect signals from selected Kepler objects that might indicate an intelligent source, no such signs have been found. Part 2 of this article series explains why a null result should not be surprising and why, if naturalism is true, additional searches have a negligible chance of success.


The discovery of numerous exoplanets (planets outside of our solar system) has narrowed the search for extraterrestrial intelligence (ETI) to those exoplanets thought likely to support life. Part 1 of this series laid out the parameters and methodology of a recent search for ETI by members of the Search for Extraterrestrial Intelligence (SETI) Institute, SETI at Berkeley, and several radio astronomers.1 The team attempted to detect narrow band radio signals from a technological civilization. The search returned a null result—which should not be surprising for two reasons.

173484783First, even if radio-transmitting civilizations inhabited one or more of the target planetary systems, the methods of detection used in the study would encounter severe technological challenges. For example, the orbital and rotational motions of an ETI transmitter would be unknown, thereby severely complicating corrections for Doppler frequency shifts. In addition, solar wind and the interstellar medium2 can cause significant spectral broadening on transiting narrow band signals. And, of course, the data analysis must discriminate against copious narrow band signals of terrestrial origins.

Then there is the power required for ETI to transmit a signal detectable by the equipment used in the study. The researchers generally assumed a transmitting power about eight times (or more) than that of the Arecibo Planetary Radar, the most powerful radio transmitter on Earth—but there’s no guarantee that would be the case. Finally, if the transmitter has a typical Earth-like duty cycle (on/off times), the overall probability of being in the radar beam during an observation is approximately 2 x 10-8. From these considerations, we can appreciate the enormous technological challenges that confronted these SETI investigations.

Second, it is now known that for a planet to host a technological civilization, it along with its moon, star, and planetary system, must meet a long list of prerequisites. This list goes far beyond the simple criteria used in the SETI study. For example, the planet must have finely tuned plate tectonics, the just-right amount of surface water, a unique moon that stabilizes the planet’s rotation, a magnetic field that protects the planet’s atmosphere, a star with the just-right metallicity,3 a planetary system that is stable over billions of years and a history of microbial activity that also spans billions of years. Even then, there is a high likelihood that astronomical or terrestrial catastrophes will wipe out any advanced life on the planet.

In his book Alone in the Universe, physicist John Gribbin spells out the details of why it is extremely unlikely that another technological civilization exists in the Milky Way Galaxy. He concludes:

The reasons why we are here form a chain so improbable that the chance of any other technological civilization existing in the Milky Galaxy at the present time is vanishingly small. We are alone, and we had better get used to the idea.4

If we are looking for galactic neighbors, as the SETI researchers are doing, we will increasingly feel alone in the cosmos. In his book Why the Universe is the Way It Is, Hugh Ross writes, “it seems doubly certain that the humanity of Earth is the only intelligent physical species in the observable universe.”5 At some point the advocates of SETI will have to acknowledge the realities of the universe that we live in. They are searching for something that recent scientific discoveries give us little reason to believe exists—unless there has been divine intervention.


The search for extraterrestrial intelligence will continue because its adherents believe human civilization is mediocre and unexceptional. They cling to that belief in the face of scientific discoveries that have dramatically diminished the realm of possible habitats for technological life in the Galaxy.

It is a great irony that, if naturalism is true then there is little hope for SETI’s success, no matter the degree of sophistication in detection technology. In the naturalist’s worldview, the universe has no purpose, no meaning, and no direction. Every outcome is the result of a combination of undirected natural laws and stochastic processes. Naturalism cannot explain why we are here, much less why there should also be human-like extraterrestrials. A supernatural Creator is the best explanation for what we observe (or don’t observe) in our galaxy.


1. Andrew P.V. Siemion et al., “A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets,” preprint, arXiv:1302.0845, http://arxiv.org/abs/1302.0845.

2. The interstellar medium is the matter that exists in the space between the star systems in a galaxy. The medium contains gas in ionic, atomic, and molecular form, dust, and cosmic rays.

3. Astronomers use the term “metallicity” for all elements that have an atomic weight heavier than hydrogen, helium, deuterium, and lithium. These “light” elements were produced by nucleosynthesis subsequent to the big bang, whereas all the heavier elements (the “metals”) are produced by nuclear reactions within stars. Thus, production of the metals requires a healthy ecosystem of birth, life, and death of generations of stars

4. John Gribbin, Alone in the Universe: Why Our Planet Is Unique (Hoboken, NJ: John Wiley & Sons, 2011), 205.

5. Hugh Ross, Why the Universe is the Way It Is (Grand Rapids: MI, Baker Books, 2008), 76.


By Otis F. Graf Jr.

Dr. Otis Graf received his PhD in aerospace engineering from the University of Texas at Austin in 1973. He worked at the NASA Johnson Space Center and for IBM Government Systems. Since retiring from IBM, he has served as an online instructor for Reasons Institute and is living in Katy, TX.


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