It is remarkable that a single thought can give a purpose to our life, and sometimes allow our body to survive tremendous hardships. How many thoughts were born since the Big Bang?
Altogether, a total of 117 billion people lived on Earth, comparable by coincidence to the number of stars in the Milky-Way galaxy. The average life expectancy grew over time and peaks at about 80 years today in the U.S. and peer countries. It takes about half a second for external sensory information to be processed into a conscious experience in the form of a thought. This means that a typical human can process at most 5 billion thoughts over a lifetime. Considering all people who ever lived, there were less than a sextillion (10 to the power of 21) thoughts ever contemplated by humans, comparable by coincidence to the total number of stars in the observable Universe.
Most of these sextillion thoughts were rather mundane, focused on survival through challenges and conflicts on Earth, as well as urgent bodily needs such as food or sex. A tiny fraction of these thoughts swayed away from Earth as a result of looking at the sky. And an even smaller fraction of those was dedicated to the aspiration of leaving earth towards the vast interstellar space out there. Such rare thoughts are often followed by a flood of counter thoughts, like: “We need to solve our problems on Earth first before going to the Moon, Mars or beyond.”
As a corollary, not many thoughts were dedicated to checking whether any technological debris from extraterrestrial civilizations might be floating near Earth among the familiar icy rocks of solar-system comets or asteroids. There are many more thoughts associated with self-fulfilling prophecies, like: “We are probably alone, because we had not noticed extraordinary evidence for extraterrestrial civilizations, and so mainstream resources should not be spent in searching for that evidence.” In April 2024, I dedicated 18 minutes of a TED talk with hundreds of thoughts to why this circular argument is misguided, and the approach taken by the Galileo Project makes more sense. Today I was notified that my time was not wasted, since this presentation ranked among the top ten most popular TED talks in 2024. With millions of views, the number of extraterrestrial thoughts triggered on Earth by this video might have exceeded a billion in 2024, comparable to the total number of thoughts in a single human lifetime. Still, it amounts to a tiny unimpressive fraction of a sextillion.
A more global question is how many thoughts existed in the entire cosmos over the past 13.8 billion years since the Big Bang? If every star hosted a planet like Earth with a hundred billion human-like creatures on its surface, then there could have been a sextillion squared thoughts altogether. This amazing number could have led not only to known unknowns, such as the development of a predictive theory of quantum gravity, but also to unknown unknowns that we cannot even imagine. It is still possible that most of these thoughts were wasted on local conflicts, food and sex, and arguments about why it makes more sense to focus on local rather than global cosmic matters. If so, intelligent life would appear as a missed opportunity in the grand scheme of the cosmos. The emergence of natural intelligence-as-we-know-it would be ranked as one star out of five in a critical review of the cosmic play. Rather than considering natural intelligence as a `rockstar’ in cosmic history, it would be regarded as an insignificant phenomenon on a rock orbiting a star.
But does the cosmic play have a “deus ex machina”? This phrase is Latin for “god from the machine,” referring to a plot device where an unlikely occurrence resolves a seemingly unsolvable problem in the storyline and leads to a happy ending. This technique was employed, for example, by the ancient Greek tragedian, Euripides, who used a dragon-drawn chariot sent by the Sun god Helios to transport his granddaughter Medea away from her husband Jason to the safety of Athens. The device triggered a dramatic sense of wonder and awe in the audience at the appearance of the gods.
Is there such a device in our own cosmic play? Yes, indeed: artificial intelligence (AI). This machine is endowed with the potential to show godlike abilities that will change our fate. Our hope to control the machine by aligning a device made of silicon chips with our flesh-and-blood brain, is like putting lipstick on a pig. As of now, AI is inferior to the human brain on some tasks. But to gauge its potential, consider the following detail. A gigahertz processor can perform a single operation in a billionth of a second (nanosecond). Even if it takes a few tens of CPU cycles to transfer the data from memory before processing, a computer can do a single operation, including data fetch, in about a few tens of nanoseconds, faster by a factor of a hundred thousand than a neuron in the human brain which collects inputs from a synapse, processes it and transfers it to the next neuron, in at least a few milliseconds.
In a preprint I wrote this summer with the brilliant Jacob Wilde from Oxford University, we showed that the number of neural parameters in AI systems could exceed that in the human brain in less than a couple of decades. Combining that with the much faster rate of operations means that the machine will produce many more `thoughts’ than humans did throughout history. This means that the machine could explore a much larger landscape of thoughts than humans did, as long as it will not be caged within the strict confines of human training sets. The experience of letting the machine run free would resemble traveling on an aircraft rather than by feet through a vast terrain.
Humans introduced a “deus ex machina” into their cosmic play. The fundamental question is whether it will lead to a happy ending or to a Greek tragedy. We tend to think that we are in control of our fate. But Euripides would have suggested that the happy ending of our violent plot might be delivered by a machine which was sent to us by the gods.
ABOUT THE AUTHOR
Avi Loeb is the head of the Galileo Project, founding director of Harvard University’s — Black Hole Initiative, director of the Institute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics, and the former chair of the astronomy department at Harvard University (2011–2020). He is a former member of the President’s Council of Advisors on Science and Technology and a former chair of the Board on Physics and Astronomy of the National Academies. He is the bestselling author of “Extraterrestrial: The First Sign of Intelligent Life Beyond Earth” and a co-author of the textbook “Life in the Cosmos”, both published in 2021. The paperback edition of his new book, titled “Interstellar”, was published in August 2024.
