What might we find: little green men or microbes? How might we find them: radio waves or strange chemicals in the planet's atmosphere? Something no one has even thought of yet?
Over the decades, scientists considering the possibility of life beyond Earth have pondered what such life might look like, how humans might be able to identify it from afar — and whether communication between the two worlds might be possible.
That thinking has included developing classification systems ready to fill with aliens. One such system is called the Kardashev scale, after the Soviet astronomer who proposed it in 1964, and evaluates alien civilizations based on the energy they can harness.
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