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Image shows the extent of human radio broadcasts

Click to enlarge (Image credit: Adam Grossman of The Dark Sky Company)

(Source: Popular Mechanics)

Carl Sagan’s famous line from his 1990 speech about the Pale Blue Dot image—”Our planet is a lonely speck in the great enveloping cosmic dark”—is an understatement. We might consider our Milky Way, with its estimated 100 to 400 billion stars, a significant fixture in the cosmos. But there are some 100 billion galaxies just like it in the observable universe. It’s a daunting reality to consider when we’re thinking about the possibility of making contact with any intelligence that might be out there.

This map designed by Adam Grossman of The Dark Sky Company puts into perspective the enormity of these scales. The Milky Way stretches between 100,000 and 180,000 light-years across, depending on where you measure, which means a signal broadcast from one side of the galaxy would take 100,000 years or more to reach the other side. Now consider that our species started broadcasting radio signals into space only about a century ago. That’s represented by a small blue bubble measuring 200 light-years in diameter surrounding the position of the Earth. For any alien civilizations to have heard us, they must be within the bubble.[…]

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