Nothing Lasts Forever

Avi Loeb
5 min readMay 22, 2023


An astronaut tethered to the International Space Station during a spacewalk to a dark matter and antimatter detector in 2020. Credit: NASA/ESA

Sometimes, life feels like running a marathon. You fight your way through the beaten path with bruises to prove it. But when reflecting upon your journey, you realize that the destination is somewhat arbitrary.

After my parents passed away, I decided to focus on a destination that I care about: seeking evidence for extraterrestrial technological objects near Earth that could inspire the future of humanity.

It is easy to express an opinion on this matter, especially in the company of like-minded people. But it is harder to seek evidence through a journey that deviates from the beaten path. In summer 2023, I will lead such a journey to the Pacific Ocean. The expedition’s goal is to find out whether the first interstellar meteor was artificial in origin, given its exceptional material strength relative to all other 272 meteors in NASA’s CNEOS catalog of fireballs.

It is easy to believe in science fiction or the multiverse in theorized extra dimensions, but it is a harder task to separate fiction from science based on evidence derived in the real universe. Unrealistic illusions were the trademark of past civilizations that perished on Earth. Adaptation to reality based on evidence places a higher bar for our long-term survival.

Some argue that recognizing the limiting constraints imposed by reality would make us unhappy and humanity better enjoy its short lifespan by imagining virtual realities. But I argue that accepting humanity’s lifespan as short is premature since we have reached a technological level that provides us with the opportunity to preserve what we care about for billions or maybe even trillions of years.

Indeed, improving our terrestrial infrastructure will not prevent life-as-we-know-it from going extinct once the Sun will boil off all liquid water on the surface of Earth in a billion years. But artificial intelligence (AI) systems could outlast biological brains. And a space-based platform could adjust our distance from the solar furnace as it gets hotter.

Ultimately, the furnace will run out of fuel when the Sun dies. At that time, we may choose to move to the vicinity of a dwarf star, like our closest neighbor Proxima Centauri, which constitutes a fusion reactor that would last for trillions of years.

Before one of my annual eye exams, I told the receptionist: “My vision may have changed over the past year since everything changes. After all, even the Sun will die!” She responded with shock: “What did you just say … the Sun will die? This is contrary to my religion.” I replied calmly: “Well, the Sun is a nuclear fusion reactor that will consume its nuclear fuel in 7.6 billion years. After that, the Sun’s core will cool to become a white dwarf, namely a metallic ball roughly the size of the Earth.” Upon further reflection about her surprise, I realized that the illusion of permanence stems from the long lifespan of the Sun, a hundred million times longer than a human lifetime. Given that Homo sapiens existed only for one part in a thousand of the age of the Sun, it is natural for humans to expect the Sun to shine every morning forever based on experience. However, astronomers monitored stars that formed billions of years before the Sun and realized that many of them had already turned into white dwarfs. The situation is similar to visiting a graveyard and realizing that your partner will die one day. I am filled with gratitude during my encounter with the Sun as I jog every morning at sunrise, because I know that both of us will eventually die.

Much of the life experience of humans is shaped by the knowledge that it will end. However, the ancient Greek philosopher Epicurus insisted that “Death is nothing to us, since while we exist, our death is not, and when our death occurs, we do not exist.” As it turns out, Epicurus died from a stone blockage of his urinary tract, a urinary calculus, after bravely suffering for a long time. This was nature’s way of reminding him that death is nearing.

Knowing about these near-death experiences and having a cosmic perspective, keep us humble. The long-term future of the accelerating Universe appears as dark as the death of Epicurus or the Sun. In short, nothing lasts forever.

This should motivate humanity to enjoy any prospects for life in the company of sentient neighbors, while low-mass stars like Proxima Centauri are still burning their nuclear fuel. To find new evidence for these neighbors, we must follow the scientific method.

Humanity can be saved from existential risks on Earth by becoming interstellar. I discuss this vision in my forthcoming book, Interstellar, to be published on August 29, 2023. Whereas biological life thrives on planets, AI astronauts could maintain the flame of our consciousness in interstellar space.

Other civilizations may have done so already. I lead the Galileo Project in search of extraterrestrial gadgets with the hope that finding them will inspire us to focus on what matters for the long-term future of humanity.

Here’s hoping that what matters to us as intelligent beings will propagate beyond our anecdotal existence on the surface of the rock we call Earth and seed the Galaxy for many years to come. Based on a new paper I just wrote, it would be difficult for us to reach distant galaxies because of the accelerated expansion of the Universe. For example, going beyond the Virgo cluster of galaxies requires a spacecraft launched at a speed of 3,000 kilometers per second, a hundred times faster than the chemical rockets we launched so far.

The best way to fulfill the optimism of Epicurus about life and death is to avoid death and maintain consciousness for as long as we can in interstellar space. Just as the new prescription for my eyeglasses helped me see better, finding interstellar gadgets may help us realize what lies beyond the solar system.


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 chairs the advisory board for the Breakthrough Starshot project, and 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. His new book, titled “Interstellar”, is scheduled for publication in August 2023.



Avi Loeb

Avi Loeb is the Baird Professor of Science and Institute director at Harvard University and the bestselling author of “Extraterrestrial” and "Interstellar".