Aliens did not visit Earth in the distant past. They didn't build the pyramids or rule ancient Greece from Mount Olympus or teach Mesoamericans how to plant corn. How do I know? Because they didn't do ...
The Why Files on MSN
Comparing Earth technology with alien civilizations: The Kardashev scale
The Kardashev Scale is one of the most widely discussed scientific frameworks for measuring the technological advancement of civilizations, from planetary energy use to controlling entire galaxies.
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