Could advanced alien civilizations, if they exist, actually see us? A recent journal article delves into this captivating aspect of the search for extraterrestrial intelligence. The paper, authored by Z.N. Osmanov from the E. Kharadze Georgian National Astrophysical Observatory, examines this question by considering various levels of alien technological advancement.
Osmanov posits that if advanced alien civilizations exist and have the technology to build incredibly large telescopes, they might be able to detect significant human-made objects on Earth. The actual possibility of this happening depends on several factors, including the number of such advanced civilizations in our galaxy.
The study discusses the use of advanced astronomical techniques for detecting objects in space. Optical interferometry involves combining light from multiple telescopes to create a more detailed image than what one telescope can achieve alone. This method significantly improves the angular resolution, allowing distant objects to be observed in greater detail. Mega-telescopes are extremely large telescopes, much larger than any currently in existence, capable of observing very distant objects.
Turning to the visibility of Earth’s structures, the study calculates the maximum distance from which alien civilizations could detect large human-made objects. Interestingly, they estimate that structures like the Egyptian Pyramids could be spotted from as far as approximately 3,000 light-years away. However, smaller objects like satellites become undetectable beyond 60 light-years.
This distance is significant because it covers a large portion of our galaxy, potentially making many of our structures visible to civilizations within this range.
The study also explores the feasibility of building such mega-telescopes. Osmanov references the Kardashev Scale, introduced by Nikolai Kardashev in 1964, which classifies civilizations based on their energy consumption: Type-I civilizations use all energy available on their planet, Type-II harness the full energy of their star, and Type-III exploit the energy of their entire galaxy. However, this study narrows its focus to Type-I and Type-II civilizations, exploring the possibility of them detecting human-made objects like large ships, buildings, and satellites.
For Type-I civilizations, constructing telescopes capable of these observations would be extremely challenging due to their immense size. However, Type-II civilizations could potentially build such massive structures. The implication here is that only highly advanced extraterrestrial societies (Type-II) might have the capability to observe our planet’s large structures.
The article then examines the potential distribution of these advanced civilizations in the Milky Way using the Drake Equation. This famous formula estimates the number of civilizations capable of interstellar communication based on factors like star formation rates, the presence of habitable planets, and the longevity of communicative civilizations. “By analyzing the Drake equation, it has been found that if the number of civilizations is of the order of 650 they will be able to detect our artificial constructions,” Osmanov writes.
This suggests that if there are about 650 or more such civilizations, they would be capable of detecting our artificial structures. This number is speculative and hinges on many variables, but it provides a framework for understanding the likelihood of our being visible to extraterrestrial civilizations.
In essence, the research invites us to consider our place in the vast universe and the possibility that if there are advanced extraterrestrial beings out there, they might already know about our existence through the monuments and buildings we’ve constructed on Earth. It’s a thought-provoking perspective that bridges the realms of astronomy, technology, and the ongoing search for extraterrestrial intelligence.
Osmanov’s paper is published in the journal Acta Astronautica.