As one of our weekend features, we thought it would be interesting to revisit Carl Sagan's question: "What does it mean for a civilization to be a million years old? We have had radio telescopes and spaceships for a few decades; our technical civilization is a few hundred years old ... an advanced civilization millions of years old is as much beyond us as we are beyond a bushbaby or a macaque." 

Michio Kaku, professor of theoretical physics at City University of New York believes that Sagan's question is no longer just a matter of idle speculation. Kaku writes that that "one day, many of us could gaze at the encyclopadia that contains the coordinates of perhaps hundreds of Earth-like planets in our sector of the galaxy. Then we will ponder with wonder, as Sagan did, what an intelligent civilization a millions years ahead of ours will look like."

Soon, humanity may face an existential shock as we discover Earth-sized twins of our planet orbiting nearby solar systems. This may usher in a new era in our relationship with the universe, so that we will never see the night sky in the same way. Realizing that scientists may eventually compile an encyclopedia identifying the precise coordinates of perhaps hundreds of Earth-like planets, gazing at the night sky, we will forever after wonder if someone is gazing back at us.

Kaku takes up where some/one of the world's pioneer astronomers left off with a definition of civilizations in the universe that mimics the work of Russian astrophysicist Kardashev. Inspired at the age of five by a Moscow Planetariumshow about Giordano Bruno, Kardashev definined three levels of advanced civilizations based on how they harness energy to fuel their societies.

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