The Arecibo radio telescope broadcast a single 3-minute message toward star cluster M13 in 1974, and because M13 is 25,000 light-years away, any reply would take 50,000 years to arrive, meaning the people who sent it knew with certainty no one alive would

The Arecibo radio telescope broadcast a single 3-minute message toward star cluster M13 in 1974, and because M13 is 25,000 light-years away, any reply would take 50,000 years to arrive, meaning the people who sent it knew with certainty no one alive would

On November 16, 1974, a 305-meter dish set into a sinkhole in the karst hills fired a narrow beam of radio waves toward the constellation Hercules for two minutes and 49 seconds. The signal carried 1,679 bits of binary data aimed at a globular cluster called M13, roughly 25,000 light-years away in the constellation Hercules. The people in the control room understood the math. Even at light speed, the message would take 250 centuries to arrive, a…