In our daily lives, we rarely contemplate the depth of Earth's history. The planet we inhabit is about 4.5 billion years old, while modern humans appeared relatively recently – less than 5 million years ago. This means that 99.9% of Earth's history unfolded without us. What happened in those distant epochs? Astrophysicist Avi Loeb, known for his work on searching for extraterrestrial artifacts, offers an intriguing perspective on this question.
Loeb shares a simple yet telling anecdote from his own life. A few years ago, a stranger stood by his house for a long time. It turned out that he had lived there as a child. The visitor spoke of a cat named Tiger buried in the garden – and indeed, under a stone with that inscription, a beloved pet once lay. This story illustrates how 'guests' can reveal what remains hidden from current inhabitants. By analogy, humanity might be a relatively new 'tenant' on Earth.
Around 201 million years ago, when Earth was about 95.6% of its current age, the planet experienced a sharp global warming event. Temperatures rose by 4–15 Kelvin, leading to a mass extinction: up to 95% of plant species were affected, along with a significant portion of marine and terrestrial organisms. This event, known as the Triassic-Jurassic extinction, paved the way for the dominance of dinosaurs. Loeb poses the question: could such a large-scale change have been linked not only to natural processes but also to the activities of a hypothetical technologically advanced civilization?
Direct evidence, of course, is lacking. Geological processes – plate tectonics, weathering, subduction, and meteorite impacts – could have completely erased traces of any surface infrastructure over hundreds of millions of years. This aligns with the 'Silurian Hypothesis' by Gavin Schmidt and Adam Frank. However, in space, the chances of preservation are higher. Passive satellites at an altitude of over 2000 km could have survived for hundreds of millions of years with virtually no atmospheric drag. Active, self-repairing, or self-replicating probes could last even longer.
In this context, Loeb draws attention to Unidentified Anomalous Phenomena (UAP). Most cases are explained by natural causes or human technology, but a portion remains unexplained. The hypothesis that some UAP might be relics of an earthly, but pre-human, civilization seems more plausible to him than visits from other star systems: it does not require overcoming vast interstellar distances over billions of years. Technologies capable of functioning near a habitable planet for several hundred million years would suffice.
This perspective shifts research priorities. Projects like the Galileo Project, led by Loeb, and the UAP Science Advisory Council are focused on collecting robust data. If UAP turn out to be human-made, it contributes to national security. If they are linked to an ancient earthly civilization, we will learn more about our planet's long history. And if they are indeed of extraterrestrial origin, it will expand our understanding of the Universe.
Loeb's reflections serve as a reminder that science is not just about established facts but also about the willingness to ask difficult questions. Earth holds many mysteries, and new observation tools may eventually help lift the veil on what transpired here long before humanity's arrival. For now, it is important to continue observing, analyzing, and remaining open to unexpected yet well-founded conclusions.
