The message includes 33 musical pieces, each lasting 10 seconds long, that were commissioned for the project. It also contains a mathematical and scientific tutorial created by METI that starts with basic principles and builds up to more complex concepts, to show our intelligence.
For example, it describes the key characteristics of electromagnetic waves, by pointing to the frequency and direction of radio waves. The message was transmitted nine times over three days, which means that any aliens who happen to be listening have time to confirm that the signal is coming from our planet.
The scientific part of the message also contains a “cosmic clock” that tracked the passage of time over the three days of transmissions. The goal of this is to show the aliens how we measure time, and help any potential observers work out that we're real.
"If an astronomer on GJ273b detects our signal, they’ll need to follow-up to confirm it’s artificial, and not created by nature," said Vakoch. "We transmitted our message on three successive days, giving extraterrestrials an opportunity for repeated observations."
In April 2018, the plan is to send another message to the star, with even more information about our scientific understanding. This second message will end with a clock time, which will tell the aliens that we are expecting to hear a reply from them in 25 years – roughly the time for a round-trip of communications – on June 21, 2043.
Whether anyone is out there, let alone on this specific planet, well that’s anyone’s guess. But projects like these always instill a bit of public excitement as a talking point at the very least. And you never know, we may just get the reply we’re hoping for.