I realize that the title of this article is a bit confrontational. To be very clear, I’m going to be explicit in a few things that I might be able to take for granted: First, when I use the term skepticism, it refers to the positions taken by Martin Gardner, Ray Hyman, and James Randi when they formed Sanity in Research (SIR), which was later formalized as the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP), now the Committee for Skeptical Inquiry (CSI). Second, there are people who are prone to reaching conclusions that aren’t supported by the available facts. We often reach conclusions because we like them, even if the facts don’t support those conclusions. We are led astray by cognitive biases and illusions and other flaws that are built into the ways we think. Skepticism tells us that the use of science and reason is vital to overcome these tendencies. This was simplified and popularized by Carl Sagan in the well-known phrase “extraordinary claims require extraordinary evidence.” This has been distilled to its core in the phrase “I Doubt It” from CSI.

I think it is useful for any group to check how well it is doing in reaching its goals. I see one of the goals of modern, or scientific, skepticism as the evaluation of as many claims as possible to see if they are supported by the evidence. We’ve been doing this in a wide variety of areas, and a few of them have been quite successful recently. The recent interest and publicity around UFOs (or unidentified aerial phenomena [UAP], as they are now being called) has seen the skeptical view presented quite prominently, for example by several articles and online appearances by Mick West. We can also include the domain of alternative medicine. The current pandemic has focused much needed attention on the fact that bogus medical advice exists, and skeptics have been adept at showing some of the techniques that can determine whether a treatment should be trusted. If more people had embraced the skeptics’ view of reality, I think the death toll of these past months would have been much lower.

One of the things I’ve come to realize after being involved with skepticism for quite a while now is that all of us are susceptible to these flaws. Even in skeptics meetings, I have encountered people who seem to think that this doesn’t happen to them. They’re wrong. By being aware of the problems built into our cognition, we can reduce the mistakes we make or correct them quickly—but only sometimes. All of us fail in some areas and accept ideas that are not supported by the available evidence.

Think about the following assertions: viruses are a source of human disease; homeopathic principles lead to effective medical treatments; quantum mechanics allows cats to be dead and alive at the same time; with one trillion planets in our galaxy, it is certain that life is present on other planets because the chemical elements that form the building blocks of life are ubiquitous in the universe.

I’m pretty sure that most people would say that three of these assertions are scientifically sound—or they would as long as they hadn’t seen the title of this article. You skeptics might be surprised, however, that only the first one is true. I’m confident that all of you knew the second is false. The third is a topic I’m doing some writing on at the moment.

The last one, however, is a pretty widespread belief. In fact, the conclusion that life is found throughout our galaxy was quite popular even before we knew that there were a trillion planets in our galaxy. Not only is it common in our culture in general, it is also common among skeptics. I’ve asked a lot of people at skeptical conferences (remember those?), and most would express the belief that life was common throughout the galaxy. It is also a widely held belief among prominent figures in skepticism. For example, Brian Dunning has said, “It’s practically a mathematical and statistical certainty that life exists elsewhere.” Bob Novella frequently says similar things.

The first part about the components of life being ubiquitous is true. We know from spectroscopic observations that the elemental composition of other stars and, by reasonable extrapolation, other planetary systems is very much like our own. Even more telling, we have the observations of amino acids in many dust clouds in our galaxy. This eliminates many of the arguments that could be made to show that life on Earth is unique or at least unusual. But it is important to realize that it doesn’t support the assertion that life is “a mathematical and statistical certainty.”

A very useful framework to look at these questions was developed by Frank Drake with his Drake Equation:

                         N = R f_p  n_e  f_l  f_i  f_c  L

The first factor, the rate of star formation, is well known and not relevant to this discussion.

The next two, the fraction of stars with planets and the number of planets that could support life per star, are far better known now thanks to recent advancements, primarily the Kepler Space Telescope and the HARPS spectrograph. This is the reason we can confidently say that there are a trillion planets in our galaxy.

The Kepler Space Telescope has gotten a lot of coverage, and I suspect most of you are familiar with it and the transit method it relies on. This is not true of HARPS. The acronym stands for “high accuracy radial velocity planet searcher.” It is located in the La Silla Observatory operated by the European Southern Observatory (ESO) in the Atacama Desert in Chile and mounted on a 3.6-meter telescope. It detects planets, as indicated by the acronym, by measuring the radial velocity of a star as it moves around the center of mass of the star-planet system. This method is responsible for the second largest number of confirmed planets as shown in the accompanying graph.

 

The transit method data points are in green; the radial velocity ones are in red. It is interesting to note that this method is far more sensitive to planets with longer period orbits, so it finds planets that the transit method isn’t that sensitive to.

This is how the first planets around regular stars were found. The first such exoplanet to be discovered imparted a velocity of 53 m/s, or about 120 miles/hour, to its star, 51 Pegasi. HARPS can detect radial velocities of less than 1 m/s. This would allow it to see the radial velocity imparted on our sun by Jupiter, Saturn, and Uranus. A couple of the more significant results from HARPS include finding that about 40 percent of red dwarfs have planets in the habitable zone and discovering a planet around the closest star to our sun.¹

The next factor, f_l, is the last one relevant at this point. It is the fraction of planets that could support life that in fact develop life. It is basically the fraction of planets upon which abiogenesis occurs.

Abiogenesis—the natural process by which life has arisen from nonliving matter—is an active research area. Although there have been many proposals made to describe the process, or components of it, we still don’t have detailed knowledge of how it happened on Earth or even how it might have happened. The fact that life began on Earth in a geologically short time is often cited as evidence for estimating f_l as near 1. If we use the Copernican Principle, otherwise known as the Principle of Mediocrity, we are led toward the idea that f_l is near 1. If it happened here, it could happen other places. However, estimates based on the probability of self-replicating nucleic acid chains randomly forming give results near 0.

Our ignorance of the value of f_l is essentially complete. We just don’t know. I think there is only one appropriate reaction. No matter what the other factors are that go into our estimates, if the best we have for one of them is “I don’t know,” then the product is also “I don’t know.” (I’d like to credit my friend Jay Diamond for introducing me to the mathematics of “I don’t know” in a talk of a similar nature.) I don’t see any other conclusion that can be supported by what we know. So saying either f_l is high or low isn’t well supported by actual knowledge. I see asserting any conclusion about f_l as a failure of skepticism.

If life happened quickly on Earth and there are many planets out there, it seems quite reasonable to think that it exists on some of those planets. There is good evidence that life doesn’t need to be rare. But to conclude that life is common ignores what I think is the only scientifically justifiable answer: “We don’t know.” To put this in the context of Carl Sagan’s maxim, I think that part of the reason that this failure occurs is that the claim of extraterrestrial life doesn’t seem like an extraordinary one. We have good reason to think that life may be common, and when we combine this with the familiarity all of us have with living beings, we are lulled into a conclusion. We are swayed more by the availability heuristic than solid reasoning.

So what does this say about SETI, the Search for Extraterrestrial Intelligence program? The rest of the factors in the Drake equation don’t matter at this point; “I don’t know” is still the answer. In the interest of full disclosure, I’m a big fan of SETI, and I serve on one the SETI Institute’s advisory boards.

This might make some of you wonder why I would work with the SETI Institute given the highly speculative impression I have of SETI. There are a couple of reasons for this. First, I’m not opposed to highly speculative efforts. The question “Are we alone?” is an old one. It has captured the attention of both experts and lay people for millennia. If SETI succeeds, just imagine what we could learn. At this point, one of the most profound questions the program might be able to answer is “How did you not destroy yourselves?” We might also be able to learn new scientific ideas, possibly in areas we don’t even know we are missing. We will also learn what it means to exist from another, probably very different point of view.

On the other hand, if after a search far more extensive than we have done to date SETI doesn’t succeed, we will know that we are very rare, if not unique. We will confirm that we are precious. As Jill Tarter said in her TED talk, when she was given the Ted prize, “We live on a fragile island of life.” If that island isn’t one of many, we need to protect it.

First, let’s see what some other SETI folk say about it. Seth Shostak, senior astronomer at the SETI Institute, has often repeated that he will bet that we’ll find intelligent life within twenty years. That sounds like a pretty bold statement … at least until you see that the bet is for a cup of coffee. In Jill Tarter’s TED talk, she also said, “SETI doesn’t presume the existence of extraterrestrial intelligence; it merely notes the possibility, if not the probability in this vast universe, which seems fairly uniform.” On several other occasions, she has said, “If intelligent life isn’t common in our galaxy, given the large number of planets, it is a terrible waste of space,” echoing the words of Ellie Arroway, the protagonist of Carl Sagan’s novel Contact, who is widely regarded as being, at least partly, based on Tarter. It strengthens the plea of Carl Sagan regarding the Pale Blue Dot: “This image of our tiny world … underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”

But there is more to it than that. As SETI searches utilize new techniques, the knowledge gained adds to humanity’s store and helps all of science. For example, with current technology we can produce very short, very narrow bandwidth optical signals that exceed the brightness of the Sun during the pulse. We can also detect these with the fairly new field called optical SETI. When we build new ways to view the universe, we find things that weren’t expected. Who knows what will be discovered as a result of these new detectors?

The SETI Institute is currently deploying a set of detectors called LaserSETI that are looking for the brightest and longest of these signals. Will it find a new class of astronomical object? I look forward to finding out.

Because SETI, and in particular the SETI Institute, is a science-based endeavor, the questions it investigates haven’t been limited to “Are we alone?” The mission of the Institute is to “explore, understand, explain the origin and nature of life.” This is very close to the usual definition of astrobiology, which is generally defined as the study of the origin, evolution, distribution, and future of life in the universe. Most scientists and activities of the SETI Institute are part of the Carl Sagan Center for Research.

SETI’s activities span a huge range. Some of it has an obvious SETI connection. For example, much of the data analysis for the Kepler and the Transiting Exoplanet Survey Satellite (TESS) planet-finding missions was, and continues to be, done by SETI scientists. SETI scientists also work on the Gemini Planet Imager. There is also work being done on a wide range of solar system planetary science. SETI scientists were involved in site selection for the most recent NASA Martian rover missions and have been producing papers on a wide range of topics about Mars and other planets.

There is also work done on smaller bodies in the solar system. Quite recently, there was announcement of the 3D modeling of the asteroid Kleopatra; the lead author is a SETI scientist. This analysis is a really deep rabbit hole; not only does this asteroid look like a dog bone, but it also has a couple of moons. The process of combining all the available data, some of it obtained by the now-destroyed Arecibo radio telescope, was, let’s say, complex.

Another area is work done by CAMS (Camera for Allsky Meteor Surveillance). This system uses multiple sets of video cameras to determine the orbits of meteors. This work is based on previous data taken with a set of 35 mm cameras. I’m particularly interested in this because I helped operate one such 35 mm camera system. That involved staying up all night during a meteor shower, cranking the film advance, and pressing the shutters on several cameras at regular intervals. It was a particularly frustrating thing for me to do because it meant I couldn’t star gaze or meteor count. The sky conditions were great that night, and it felt wrong not to take advantage of the opportunity.

This has led to new information about meteor showers and the bodies that cause them. The parent bodies of some showers have been identified by this work. This is putting real-world constraints on models of solar system formation. The same team has collected samples of meteorite falls from around the world. Asteroid 2008 TC was the first case where a known object was observed in space and then had samples retrieved. By going to those locations, it was possible to use on-site data and photographs taken by residents to determine the orbit of objects, such as the one that caused the Chelyabinsk impact, which weren’t previously known. Another class of small solar system bodies that most people don’t think of that way is planetary rings and moons. The Ring-Moon Systems Node of NASA’s Planetary Data System is managed at the SETI Institute. This group worked to ensure flight path safety for the New Horizons spacecraft and also the discovery of several moons in the solar system and ring systems of the outer planets.

My background is in physics, so that’s the subject that most immediately comes to mind for me. But astrobiology has, as the name suggests, a large biology component. SETI scientists do field studies all around the world in extreme environments, such as high mountain lakes, geysers, and isolated sub-ice lakes in Antarctica, to collect and study the ways life has evolved to adapt to these conditions.

They are also involved in crewed space flight efforts in projects such as the Haughton Mars Project (HMP), part of a research facility located on the world’s largest uninhabited island, Devon Island. This harsh climate mimics the environmental conditions on Mars and other planets. Devon Island’s barren terrain, freezing temperatures, isolation, and remoteness offer scientists and personnel unique research opportunities. The arctic day and night cycle and restricted communications capabilities offer fitting analogs for the challenges of long-duration space flights. There is also work into animal language. This has, of course, a SETI connection because it provides a path for learning about some of the ways nonhumans communicate.

The Institute also has a large outreach effort, which is where most of my direct involvement has been. They have produced science curricular materials, have the Education and Public Outreach contracts for several NASA missions, work with many outside groups to increase understanding and appreciation of science, and have a lecture and talk series that goes back many years and continues to this day.

This has barely scratched the surface of the work done at the SETI Institute.

But I want to end by going back to the SETI search itself.

As I have hopefully made clear, the search has stimulated a lot of really solid science in a wide variety of areas, but it also provides a vision that ties it all together. The search is an attempt to answer a profound question. And no matter what the answer turns out to be, it is well worth knowing. We will either have discovered a source of information that may be superior to everything we have ever had, or we will have even more evidence of how precious our pale blue dot really is. It reminds me of a comment made to a U.S. Senate committee about what became the Fermi National Accelerator Laboratory by its first director, Robert R. Wilson: “It has nothing to do directly with defending our country, except to make it worth defending.” SETI is that kind of activity. It inspires. It forces us to think about the universe and our, possibly very fragile, place in it. It brings out, in the scientific direction, the best in what it means to be human. When I was asked to make the case that SETI was worthwhile, the first thing I thought of was “Truth matters, and profound truths matter even more.”

Note

1. As an interesting aside, I’ll note a new instrument, the echelle spectrograph for rocky exoplanets and stable spectroscopic observations (ESPRESSO). ESPRESSO increases sensitivity to around 50 cm/s or less. This will allow us to detect even more planets and characterize the types of solar systems in our galaxy.

This article is based on an online talk to the New York City Skeptics.