For several decades we have been listening to the cosmos. Giant radio telescopes first scanned all nearby stars, then stars within 100 light years from Earth, then we started checking the entire sky—only to hear nothing. This has been dubbed "eerie silence"—because, clearly, if someone is out there, we would hear from them by now. We never wanted to be alone.
But besides listening, some tried to speak. Sending high-energy radio signals into space requires lots of energy and is much more expensive than receiving, besides, some think that revealing our presence and location to the galaxy might be dangerous. However, over the last few decades a few messages were sent to the stars.
Probably the most notable one was the so-called Arecibo message sent in 1974 from the Arecibo radio telescope (hence the name). In an encoded format the message contained some general information about humanity, biology of life on Earth, a schematic image of a human, and even the chemicals that our DNA consists of. The whole idea was seen as mere scientific exercise or even a joke. Nobody really expected to receive a response.
Until now.
Roughly 46 years after the Arecibo message, Earth's biggest radio telescope, the enormous 500-meter Tianyan telescope in China, received a modulated signal from the same direction where the original message was sent. The signal was clearly artificial:
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Scientists quickly determined that it represented a string of bits, just like the original Arecibo message. This was a response!
It was shorter that the original (only 341 bits as opposed to 1,679) but its significance was enormous. It turned out, the aliens sent a package to Earth and now revealed its location in the radio message. Can you decode the message and make the most important discovery in human history?
You can validate your puzzle solution with certitude.