Are we alone in the universe? It’s one of the biggest questions that haunts our imaginations. Astrobiologist Adam Frank argues in his new book Light of the Stars that we have never been in a better position to answer that question, thanks to a revolution in our knowledge gained by powerful telescopes like Hubble and space probes like Voyager. Indeed, the chances that there has never been another civilization in the universe are as low as one in ten billion trillion. But whether there is still one out there today is a more complicated question.

Speaking from his home in Rochester, New York, Frank explains how, after being rejected because of its New Age connotations, the Gaia Hypothesis has gained acceptance in the scientific community; how climate change is an inevitable feature of civilization building; and why we need to grow up as a civilization if we are to survive climate change.

Your book centers on a relatively new field of study known as astrobiology, which you call revolutionary. Explain what it means and why it is giving us new insights into our place in the universe.

Astrobiology is the study of life in its planetary or astronomical context. People will say we have only one example of life—here on Earth. But, if you take that position, you miss three revolutions that have happened in the last 30 years.

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The first revolution is that we have been visiting other planets in our solar system. We have now sent probes to pretty much every kind of object in our solar system, including Mars. And from this we’ve learned about climate and how planets work in a generic sense. There’s an app you can pull up that will give you the weather on Mars. We have climate models for Mars, Venus, and Saturn, and we know a huge amount about climate as a generic planetary phenomenon, not just on Earth.

The second revolution is studying the Earth’s history going back 4.5 billion years. We have been able to unspool in some detail the long history of the Earth and its life co-evolving over that time. We see that Earth has been many different kinds of planets, sometimes a snowball world, sometimes a hothouse world without ice. In the beginning there were no continents; it was pretty much a water world.

The last big revolution is the exoplanet revolution. When I was a graduate student in 1985 I did not know whether there were any stars in the universe with planets around them. Now we know that the universe has ten billion trillion planets that are in the right place for life to form. Those three revolutions completely changed not only how we think about life and planets, but also leads us to think very differently about exo-civilizations.

The big question we all want to know is are we alone? What’s your view, based on the evidence?

In 2016, Woody Sullivan and I wrote a paper where we took all of the data from the exoplanet revolution and asked ourselves: What can we say with this data about exo-civilizations or aliens, as people like to call them? With science you have to tune the question to the data you have. And the question we could answer with that data was: How bad does the probability of forming a civilization on a random planet have to be for us to be alone, for us to be the only time in the entire history of the universe that there’s ever been a civilization? That number is 1 in 10 billion trillion.

That number tells me that the only way that we can be the only civilization in cosmic history is if the odds are that low or lower. As long as there’s a probability larger than that, then it has happened before. So unless nature is really perversely biased against forming civilizations then there have been others.

Whether there are others in existence today, I cannot answer. It all depends on this important factor in the Drake Equation, the average lifetime of a civilization. You could have planets creating civilizations all the time, but if nobody makes it to more than, say, 200 years, then right now we would be living in a sterile galaxy. We can say that, yes, there have probably overwhelmingly been civilizations before us. The next step is, does anybody last long, particularly when climate change is going to be a natural consequence of civilization-building?

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Carl Sagan said that we were “cosmic teenagers.” Explain that idea and how important Sagan is in our understanding of the cosmos.

I grew up reading Carl Sagan’s books. He was enormously influential in my decision to become an astronomer and my decision to write about astronomy. But even I didn’t realize how deeply woven he was into every aspect of the story I was telling.

The “cosmic teenager” idea is that we’re a very young species that’s just coming of age. What I argue is that climate change is our coming of age. I argue that there have been many civilizations before and, if you are a technological civilization like ours, you can’t help but trigger climate change. Every young civilization is going to trigger their version of the Anthropocene and that is what makes us cosmic teenagers. We have enough power over ourselves and the planet to change the planet, but it’s not yet clear that we have the wisdom to navigate the difficult transition through climate change.

Venus offers a model for what is known as the greenhouse effect. Explain that idea, and what Venus can tell us about our own climate problems.

In 1962, we sent the first probe to another planet, which happened to be Venus. There was already debate raging. People using telescopes had determined that Venus had this very high temperature, 700 degrees, which was way higher than expected because, even though it is closer to the sun than the Earth, it shouldn’t be that much hotter! The probe confirmed that, yes, those temperatures were real and it was Carl Sagan who realized that the reason Venus is so hot is that there is what we call a “runaway greenhouse effect.”

There was so much CO2 in the atmosphere of Venus that the temperatures got high enough and it lost all its water. It was a feedback loop. CO2 built up in the atmosphere to the point where it acted like a blanket in the atmosphere—the sunlight that hits the surface warms it, and if there weren’t CO2 in the atmosphere, that warmth would just radiate back into space.

This is starting to sound familiar….

Exactly! [laughs] The Venus greenhouse effect was so important because it was the first time we recognized that physical processes happening on Earth were universal. There are generic laws of planets, and once you learn those laws they are good for any planet, planets 10,000 light-years away, or for the Earth. That’s part of my story. We have to learn how to think like a planet now that we know the laws of planets, if we’re going to be able to make it through climate change.

A key figure in these debates is James Lovelock. Tell us about the man and his vision of Gaia, and how, while not taken too seriously in the scientific community, he gained a huge following in popular culture.

Lovelock is an interesting character because he’s been an independent scientist his whole life. He didn’t have an appointment at a university. He’s this mix of an inventor and a scientist, trained in chemistry, who also knew a lot of physics and created a device for measuring small concentrations of chemicals in the air that made him enough money that he could be semi-independent.

In the early 1960s, the Jet Propulsion Laboratory invited him to work on experiments looking for life on Mars. The people at JPL thought they were going to go to Mars, dig up some earth and look for microbes. Lovelock said, “No, that’s the wrong way to do it! You should look at the atmosphere because, if there’s life, the atmosphere will be changed.”

Lovelock builds on that idea over the years when he recognizes that not only has the atmosphere been changed by life, but that the atmosphere is being regulated by life—that the concentration of oxygen and other compounds are being kept exactly where they need to be to keep life healthy on the planet.

At the same time Lovelock was thinking about this, the famous biologist Lynn Margulis was thinking about how microbes could regulate how the Earth behaved. She happened to be Carl Sagan’s first wife! [laughs] It was not a happy divorce, but they stayed in contact, and at some point in the early 1970s she contacted Sagan and said, “Hey, I’m working on this idea but I need a chemist, is there anybody you could recommend to me?” He introduces her to James Lovelock and together they put together the Gaia Theory.

Lovelock wanted to call it something boring like Earth’s Systems Dynamics Theory. But his neighbor, William Golding, who wrote Lord of The Flies, said, “No! That’s a terrible name! You should name it after the Greek God of the Earth, Gaia.” It then became this hippie-dippy thing. People would have Gaia church services, Gaia music and Gaia new age priests. And this outpouring of whack-a-doodle support made many scientists queasy about the idea.

Eventually, the name Gaia was dropped and people picked up the term Earth Systems Science. This recognized that there were a bunch of systems operating on the planet—the atmosphere, water, ice, rocks, and life—and that they were all strongly interdependent.

Easter Island has haunted generations of scientists and writers as an example of a failed civilization. Give us a snapshot of the theories, and what this remote rock can tell us about our future.

Easter Island is an island in the Pacific that’s a long way from anywhere. In that sense, it’s a perfect metaphor for a planet in space. Somewhere around 400 A.D. the island was colonized by Polynesian sailors, and probably started off with a few hundred individuals. But at the peak of the civilization there were probably 10,000-12,000 people on the island.

It was a complex society, with the capacity to dig those giant rocks out from the central volcano and make those iconic statues. But after some time the population collapsed, so that when the Dutch found the island at Easter, in 1722, there were only about 2,000 people living meagre, subsistence lives. One of the dominant ideas—it’s complicated—is that that there was some form of ecocide, that people over-used the resources on the island and destroyed the environment. That is a metaphor for what we are doing on the Earth today.

You write, “We urgently need to adapt civilization so that it can become fully and globally sustainable.” Map out the challenges facing us, especially from climate change, and how we can achieve that goal.

What’s funny about this is that, on a certain level, it’s not hard at all. One of the messages I want people to understand is that the primary difficulty about making this change is in our head. Because, fundamentally, the step we need to take to create a sustainable future is change energy infrastructures. It’s really that simple! [laughs]

The real problem is the way we look at the problems. We’re still stuck in this argument about whether or not climate change is even happening, certainly in the U.S. That comes from not having what I would call the astrobiological perspective. We don’t recognize ourselves as cosmic teenagers. If you’re 12 years old, you know adolescence is coming. But because we have the wrong view about ourselves and our place in the universe, we don’t see that, of course, climate change is coming! That inability to see the reality of what climate change means—its inevitability—keeps us from understanding the urgency and importance of acting on it.

This interview was edited for length and clarity.