It’s amazing how many people eagerly make the von Däniken leap from not understanding something to assuming an extraterrestrial or paranormal explanation. This goes for highly educated and/or experienced men and women as much as for ordinary rubes. In the twenties any medium could have told you how easy it was to fool scientists.
As for intelligent life (if that's what we are) existing elsewhere in the universe I suspect it’s likely but that as a species we’ll never know.
The
likely part is an inference based on the exponential increase in the discovery of extra-solar planets over the last twenty years. They were completely unknown when I was studying physics and astronomy almost fifty years ago, and now it seems like every rock you pick up has a planet under it.
The
never know part is based not just on the insurmountably immense distances George cited but also the time scale of creation. Just our crappy little galaxy dates back over 13 billion years; the universe is about twice as old. There has been almost infinite time for countless intelligent civilizations to rise, fall, and utterly disappear.
A neat thought experiment is to consider the possibility that intelligent life existed here on Earth an almost unimaginably long time ago. What traces if any would remain and would we recognize them if we saw them? This MIT article appeared just before the pandemic and is a fun read:
Fossils and objects are unlikely to survive more than a few million years. Searching for chemical traces of industrialization offers an intriguing alternative.
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