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How long does the human civilization need to last in order to observe another advanced intelligence in the Universe?
Paper Details
Published: 2025/07/31
Journal: Journal of the British Interplanetary Society
Volume: 78
Number:
Pages: 230-237
Paper Links
HTMLWhy do we appear to be alone in the Universe? We argue that even if an advanced civilization in another galaxy evolved to be remarkably similar to us-using radio waves for communication-it would still be highly unlikely for us to detect them. For instance, if such a civilization were located 10 6 light-years away, by the time our radio signals reached them, their civilization (and possibly ours) may no longer exist. The central idea is that the spatio-temporal separation between intelligent civilizations may be so vast that, even if a radio-transmitting civilization does emerge, it is unlikely to be noticed by others. This is because, at any given moment, there may be no other civilizations both advanced enough and close enough to detect its presence. We present a mathematical model for estimating the probability of detecting radio-transmitting advanced civilizations. This model highlights the profound difficulty involved in such detection. A further important consideration is that other civilizations may not communicate using the electromagnetic spectrum or think in symbolic terms as we do. For example, birds display high levels of intelligence but likely do not use symbolic representations of the world. While symbols shape how we think and communicate, other life forms-on Earth or elsewhere in the Universe-may rely on entirely different mechanisms for cognition and communication. We may need to open our minds to alternate forms of life which may be more abundant in the Universe but may not look like life as we know it, and may not communicate (or think) like us. Our work suggests that, in order to detect or be detected, advanced civilizations must endure for very long periods. This mathematical perspective not only underscores the challenges of discovering extraterrestrial intelligence, but also invites us to reflect on the uniqueness of our planet and the conditions necessary for mutual detection in the cosmos.
