“Are We Alone?” Top Scientists at Cambridge Science Festival Weigh In
published during a waning crescent moon.

Originating in 1994, the Cambridge Science Festival (CSF), the first science festival in the U.S., has provided over a week of science-related events in the greater Boston area. This year, its opening night event, “Are We Alone?” brought together experts in astronomy, chemistry, biology, neuroscience, physics, astrobiology, and more, to weigh in on one of the humanity’s biggest questions.

Each presentation revolved around the Drake Equation. Devised by astronomer, Frank Drake, in 1961, the Drake Equation estimates the likelihood that intelligent, communication-capable species exist in the cosmos.

The Drake Equation looks like this:


SETI Institute provides a rundown of the equation’s variables:

N = The number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable.
R* =The rate of formation of stars suitable for the development of intelligent life.
fp = The fraction of those stars with planetary systems.
ne = The number of planets, per solar system, with an environment suitable for life.
fl = The fraction of suitable planets on which life actually appears.
fi = The fraction of life bearing planets on which intelligent life emerges.
fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = The length of time such civilizations release detectable signals into space.

Since there are no definite values for any of these variables, each expert provided their thoughts about the variable corresponding to their area of expertise.  But before they began, Frank Drake himself kicked off the event, taking the stage amidst a standing ovation in the crowded Sanders Theater.


Drake told the story behind his famous equation, which started in the 1950s in Harvard, Massachusetts, where he worked at the Agassi Radio Station with (what was then) the most sensitive radio telescope in the world. One night, he received a signal with such a narrow frequency that he knew it wasn’t natural—he thought it was coming from the Pleiades constellation. It turned out he was picking up the transmission of a ham radio operator, but the experience gave him the idea for devising an equation that would help astronomers figure out how and where to search for signs of life. He convened a meeting at the National Academy of Sciences to discuss his idea—Carl Sagan was there, among other prominent astrophysicists.

Following Drake, Sara Seager, MIT Professor of Planetary Science and Physics, took to the stage to tackle two variables of the famous equation (R* and fpby estimating the number of habitable exoplanets in the Milky Way. She narrowed down the total number of stars in our galaxy to include only those that have Earth-sized planets located within a “Goldilocks” zone. From there, she calculated the number of existing habitable exoplanets in the Milky Way, arriving at an estimate of ~40 billion planets. Of course, Seager knew that the rest of the panel following her would chip away at this enormous number.

Cambridge Science Festival


The next speaker was Dimitar Sasselov, Harvard astronomer professor, director of the Origins of Life Initiative, and Seager’s former thesis advisor. He addressed variable ne, the number of planets in a solar system that could sustain life. He explained while many planets can technically support life, the number of planets with conditions that actually allow life to emerge is far fewer.  Ocean planets have too much water, and dry planets have land, but they, like Earth, need some amount of water.

For life to develop, a planet also needs the right kind of atmosphere and the right kind of host star (probably a hydrogen-rich G-type main sequence yellow dwarf star like the sun, rather than the smaller, cooler red dwarf star). Instead of providing a raw number for ne, Sasselov instead gave an fe value—the fraction of exoplanets that can support life: eight percent. He pointed out that the number excludes moons. Given what we’ve recently learned about Enceladus, the number of celestial bodies on which life could emerge may be significantly higher.

Next up was Jack Szostak, Nobel Prize winner and Professor of genetics, chemistry, and chemical biology at Harvard, who tackled fl, or what fraction of the planets identified by Sasselov could develop life. Szostak argued that some of the steps necessary to the emergence of life seem complicated, but are, in fact, simple, such as cell division. He asserted that it’s not difficult to generate biological building blocks and used hydrothermal vents (like the kind recently discovered on Enceladus) as an example. He didn’t offer a solid number for his variable, but his takeaway was clear: life will emerge. Probably.

Cambridge Science Festival

Enceladus South Pole plumes. Credit: NASA/JPL

The next speaker wasn’t an astronomer, chemist, or astrobiologist. Lori Marino is the Founder and Executive Director of the Kimmela Center for Animal Advocacy and she taught ethics at Emory. She’s studied dolphin and primate brains and likely has a different perspective than most about what intelligence is or means, which made her the perfect person to speak about variable fi, the fraction of planets with life on which intelligent life evolves. She opened with an evident yet profound statement: “that depends on your definition of intelligence.” Fair point.

Morino offered a working definition of intelligence that revolves around how an entity “acquires, processes, stores, analyzes, and acts upon information.” The first question she addressed was whether single-celled organisms satisfy this definition or whether intelligent organisms need to be multi-cellular. If one goes with the former, then intelligent life on Earth began between 3.8-4 billion years ago; if one goes with the latter, then intelligent life started with the first neurons, roughly 600 million years ago. From there, neurons became brains, which then evolved circuits and developed the structure characteristic of vertebrate brains. Her takeaway was this: intelligence evolves early.

Seth Shostak, SETI Institute senior astronomer and former SETI Director of Research, spoke next to shed light on fc, the fraction of civilizations advanced enough to develop technology that would make its existence known to others. Shostak, the most dynamic of all the speakers, crammed tons of information into ten minutes, often talking at light speed so as not to leave anything out. “How does life make itself known?” he asked. Radio wave technology is the most obvious answer, and Shostak believes 100% of advanced civilizations would have this technology. After all, he reasoned, “if the Greeks can build science, anyone can.”

But, he said, that’s not the most important number. The real question is how many of those civilizations would want to broadcast evidence of their existence? Intelligent alien life may not want to alert other aliens on the cosmic block of its existence. He argued convincingly that intelligent aliens might go to great lengths to not be detected, and if their technology is more advanced than ours, they would probably succeed.

Shostak also pointed out something the other speakers neglected—that everything involved in our search for extraterrestrial life is anthropocentric. We extrapolate from what we know about life on Earth and human civilization and apply it to other planets and life forms. But who knows if aliens are like us or even have the same requirements for life? Who knows if we would recognize their signatures even if we somehow stumbled upon them?

MC Chris Impey, Associate Dean of the University of Arizona’s College of Science and a professor in the astronomy department, summarized and reflected on what each speaker said before the next presenter’s turn. After Shostak’s talk, Impey addressed Shostak’s observations about humanity’s scientific trajectory: “Most people think once you have science, you never go back. Not to get political, but…look around. Clearly, you can go back.” This was the first of two explicit references to the current administration, and Impey’s comment drew the second-loudest applause of the evening.

The final speaker was Martine Rothblatt, United Therapeutics CEO, creator and former CEO of Sirius XM, and author of Virtually Human, a book about cyber-consciousness. Rothblatt commissioned Bina48, a robot designed by Hanson Robotics and a “mindclone” of Rothblatt’s wife. You might wonder what someone who focuses on consciousness uploading and robots has to offer to the “Are we alone?” question, but Rothblatt demonstrated her insight as she took on the final part of the Drake Equation, L: the lifetime of communicative civilizations.

Rothblatt addressed a question I have become increasingly obsessed with since I first read Susan Schneider’s paper “Alien Minds,” in which she argues that intelligent life forms are probably digital, not biological. Rothblatt argued that advanced civilizations are probably “substrate free” or digital. It makes sense—many in the scientific community believe in the technological singularity, the point at which artificial intelligence exceeds human intelligence. The term “singularity” comes from physics—it’s the center of a black hole, “the point where all laws of physics break down,” according to physicist Kip Thorne. Scientists predict that the technological singularity will render our current existence obsolete and will change humanity forever, probably by merging humans and machines. While 2045 is commonly predicted for when we might reach the singularity, no one knows for sure when it will happen, though most agree that this point in technological advancement is inevitable.

Given that Earth is a relatively young planet, it stands to reason that other advanced civilizations have already reached a technological singularity and perhaps crossed that threshold some time ago. That being the case, it’s entirely plausible that older, more technologically advanced civilizations transitioned from biological lifeforms to hybrid/cyborg life forms and then to substrate-free ones. This is the concept behind virtual immortality.


Serial section of the brain: a possible method for mind uploading where frozen brain tissue and parts of the nervous system are scanned and analyzed layer by layer, thus capturing the structure of the neurons and their interconnections.

“Consciousness is to brains as flight is to birds,” Rothblatt argued, suggesting that an entity doesn’t need a brain (or human-likeness) to be conscious: “Similar functions arise from diverse forms.” Rothblatt dispensed of the evil robot/AI theory that typifies so much of Western sci-fi by reasoning that humans will increasingly be in charge of our own evolution and that humans won’t create evil robots because there’s no market for them. But there is a market for friendly, human-like robots and such “buying power creates a Darwinian environment.” Whether or not she’s right about the disposition of future AI, her point about the eventual transition from biological to digital or cybernetic makes sense. Rothblatt gave an unwavering answer to the “L” part of the equation: “once a race goes trans-atmospheric, it goes forever.”

Rothblatt earned the biggest applause of the night with the conclusion of her talk in which she advocated for civil rights and fairness for all. “We’ll all be immigrants ourselves,” she said, “whether in cyberspace or actual space.” From the sound of it, no one in the auditorium disagreed.

“They’re already here.”

The brief but spirited roundtable following the talks focused primarily on the Fermi paradox that states, “if it’s likely advanced civilizations exist, where are they?” Shostak supported Rothblatt’s argument and pointed out that if aliens have gone digital, then it makes sense why we haven’t detected any biological life signatures from elsewhere.  Someone in the audience asked about the possibility that aliens have visited or remained among us but we don’t recognize them. Szostak said that if aliens were aware of our presence, they wouldn’t have “allowed us to evolve,” a comment which elicited some disagreement from the rest of the panel. Shostak argued that we’ve simply looked at too little of space, and that evidence of alien civilizations might well be out there, just as the two Voyager spacecraft are representative of proof of our civilization, but that aliens “finding Voyager is like finding a bacterium in the Pacific Ocean.”

Cambridge Science Festival

CubeSats being launched from the NanoRacks CubeSat Deployer on the ISS on February 25, 2014.

Sasselov provided a physical demonstration for why he believes our future is not biological. He held up a nanosat that holds more circuits than a human brain. “They’re already here,” he said, referring to advanced, substrate-free aliens. “And we can see them.”

The talks made an impact on the audience. Before the event, attendees voted via smartphone to answer the question, “How many active, communicative alien civilizations are there in our galaxy?”

15% said zero, 20% guessed over a million, and 32% said between 1-100.

After the event, attendees voted again, and 38% of them believed there are more than a million.

It’s both arrogant and ludicrous to believe that humans are the only intelligent life form in the cosmos, and there are likely more alien civilizations out there than we’ll ever know. As cosmologist Martin Rees was famous for saying, “absence of evidence isn’t evidence of absence.”