In my latest class at the Harvard Astronomy department, I noted that what happens in stars was not always beneficial for promoting geopolitical peace and prosperity on Earth.
The Big Bang endowed the Universe with mostly hydrogen and helium, but life-as-we-know-it requires heavier elements like carbon or oxygen. These elements were assembled out of the building blocks of hydrogen and helium through nuclear fusion in stellar interiors. Iron is the most stable element and hence the heaviest one made by stellar fusion. Energy is gained by breaking heavier nuclei down to iron through nuclear fission. So how were heavier-than-iron elements made after the Big Bang?
Element like gold and uranium were assembled in rare neutron-rich environments, such as those realized during a collision of neutron stars. The rarity of such collisions makes gold economically precious. Uranium is used in atomic weapons and is a source of geopolitical instability on Earth.
One of the students raised his hand and asked: “What is the practical benefit of studying astrophysics? I am often told that studying the sky is of no practical use and we better focus on more pressing down-to-Earth matters.”
My answer was swift. First, we must remember that Isaac Newton’s laws of motion and gravity were derived by observing the motion of the planets around the Sun, and their generalization by Albert Einstein to describe the Universe at large enabled GPS navigation. We currently construct vehicles and surround the Earth with communication satellites based on this knowledge. In the future, understanding the nature of dark energy and quantum gravity based on cosmological data, might lead to novel propulsion systems that we cannot imagine today.
Second, we were always curious about our cosmic roots. The scientific study of how stars like the Sun formed in galaxies like the Milky-Way within an expanding Universe that started in a Big-Bang, offers many more details than those found in the first chapter of the book of Genesis. Knowing our origin story helps us appreciate the context of our cosmic existence. Spirituality founded on facts about the cosmos beyond what we can see on Earth, is much more valuable than a belief system which flatters our ego. Spiritual substance is inspired by factual details.
Earlier than sixty-six million years ago, non-avian dinosaurs were focused on down-to-Earth matters, in particular on ways to dominate their environment. Their sense of self-importance, based on their large body size, stemmed from looking down to Earth rather than up into the sky. This ideology was tarnished by a giant rock, the length of Manhattan Island, which hit Earth. Such existential threats can be avoided by advance warning from telescopes, allowing observers of the sky to proactively change the orbit of killer asteroids away from their home planet. But this historic lesson about placing life on Earth in a global perspective offers an even bigger takeaway.
In 1882, the philosopher Friedrich Nietzsche stated: “God is dead,” revoking the need for a superhuman entity as a source of awe in the human psyche. However, if we ever discover an extraterrestrial technological civilization with superhuman intelligence, it could restore the sense of modesty and awe to our mindset. By studying more advanced science and technology, we might gain new insights about physics that would have taken us many centuries to develop on our own. But most importantly, with a global perspective we might realize that all of us are in the same boat and this could inspire us to cooperate rather than engage in down-to-Earth conflicts. Many of the geopolitical problems we face stem from a narrow-minded state-of-mind. We might do better with a cosmic perspective. Moreover, if extraterrestrials arrive first at our doorstep, they might inspire us to venture into interstellar travel and visit their homes. In the long-term, a down-to-Earth focus will not be remembered in cosmic history as much as the technological monuments that we could launch to interstellar space.
Useful lessons can also be learned from students in our class of intelligent civilizations that performed poorly by focusing on their planet without monitoring their cosmic neighborhood and venturing to space. They left behind burned-up planets with piles of defunct technological debris. Their depressing relics will educate us about a future we want to avoid.
Nature will endure even the most dramatic cataclysms that we trigger by misbehaving on Earth. Our planet went through global warming and cooling events in the past, and its surface is doomed to burn into a desert, like Mars, by the brightening Sun. The energy source for life-as-we-know-it will become a source of death on Earth within a billion years. Long before that, giant solar flares could destroy our technological infrastructure in the next millennium, as I showed in a paper with my former postdoc, Manasvi Lingam. By studying habitability of exoplanets, we can get a broader perspective about the existential risks posed by natural astrophysical environments.
Without astrophysics, we would be as ignorant as the dinosaurs were about existential threats from the sky. Our written history over the past five thousand years documented only the last millionth of Earth’s history. If we focus our attention down to Earth, extraterrestrial historians would be completely justified in ignoring our transient existence.
In summary, astrophysics is an existential necessity, not a luxury.
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.
