Humanity is sending out a musical, mathematical and scientific message for E.T. across interstellar space, and if any aliens happen to receive it and respond, first contact could happen as soon as 2042.

Of course, that's quite a huge "if."

Nonetheless, Doug Vakoch, president and founder of METI (Messaging Extra-Terrestrial Intelligence) International, is optimistic that his organization's detailed message encoded in radio waves could be received by an intelligent civilization.

The message is "distinctive because it's designed with extraterrestrial SETI scientists in mind. We sent the sort of signal we'd want to receive here on Earth," he told me.

Enlarge Image Sonar

METI is an organization dedicated to searching for and considering how to communicate with extraterrestrial intelligence. It was approached by Barcelona's Sonar Festival to help develop a message that could be sent across the cosmos to celebrate the music and technology festival's 25th year. The result is dubbed "Sonar Calling GJ273b," and if everything goes perfectly, we could receive a response in 25 years from now, when Sonar turns 50.

"Given the largely negative impact of humanity on our planet, perhaps this is the best time to reach out to -- hopefully superior -- extraterrestrial intelligence to solicit help and advice on what we can do to change things," Sonar directors Enric Palau, Sergio Caballero and Ricard Robles said in a statement. "Sonar Calling is an attempt to rekindle a sense of global consciousness and a shared reflection on our collective present, that we hope will lead to new ideas and new partners. Yes, even alien ones."

Sonar made its first public announcement about the transmissions on Wednesday. The Sonar Calling GJ273b signal was sent in the direction of GJ 273, also known as Luyten's Star, just over 12 light-years away, on three successive days in October from the Eiscat transmitter in Tromsø, Norway. It was embedded with a tutorial in basic math and science that also builds upon those fundamentals to explain concepts from physics like radio frequencies and our conception of time. This could help E.T.s not only understand a little about us, but also about the communication process, including making clear when we'll be listening for a response.

Each of the three transmissions also included six original pieces of music commissioned by Sonar. Brief, 10-second pieces by composers and musicians including Jean-Michel Jarre, Autechre and Matmos accompanied METI's tutorial on each transmission. The compositions and interviews with their creators can be found on the Sonar Calling website.

"In a reply message, I would first want to know that the extraterrestrials understood what we said in our first message," Vakoch said. "The easiest way to do this is to repeat our message, but in expanded form. We tell them that '1 + 1 = 2.' They could let us know that they understand that '10 + 10 = 20.'"

The message was repeated over three consecutive days to give any alien astronomers on GJ 273b, the potentially habitable exoplanet orbiting Luyten's Star, a chance to confirm the detection of an intentional signal.

"This sort of confirmation is essential to having a credible SETI signal," Vakoch explained. "The last thing we want to do is send the aliens a Wow! Signal that's seen only once, but never replicated."

Because it will take a little more than 12 years for a message to travel between Earth and GJ273b, it would take a minimum of about 25 years for our message to reach its target and for a response from there to then reach Earth.

Luyten's star was chosen because it's visible from the Northern Hemisphere, where the transmitter is located, unlike the closest known potentially habitable exoplanet, Proxima b, which is just four light-years away.

So what are the odds anyone or anything beyond Earth ever actually picks up the signal and gets the message? Vakoch is measured in his expectations.

"Practically speaking, if we get a signal from Luyten's Star, it will mean the Milky Way is teeming with life. It's certainly possible," Vakoch said, before hedging a bit. "It seems more likely that we'll need to target not just one star, but hundreds, thousands, or even millions before we get a reply back."

There have been a few other, similar signals sent into space, such as the Arecibo message. But Vakoch says this is the first signal he knows of that has targeted a nearby star system that is potentially inhabited.

The channel of communication will open up again next year, with a second transmission planned for April.

This follow-up message will include an expanded tutorial that will attempt to "turn the Eiscat antenna into a musical instrument transmitting pulses at several different frequencies, mimicking the tones of a musical scale," explains a release. "By sending basic melodies at multiple radio frequencies, METI will expand its tutorial for Sonar Calling to describe the physics and psychology of music."

This second round of transmissions will again include musical compositions from Kate Tempest, Daito Manabe, Juana Molina and several other musicians who have performed at Sonar in the past. The festival has also started an open call for music to be included in the April transmissions.

"The public is invited to send an original composition, in any genre or musical style, and conceived with an unknown, extraterrestrial audience in mind," reads a release.

Three selections from this open call will be included in the follow-up signal, which will end with a clock time marking the date that humanity will be listening for a reply 25 years from now.

"A wonderful reply would be to hear extraterrestrials develop these melodies into something more complex. I would love to hear what an interstellar symphony created by extraterrestrials sounds like," Vakoch says.

But what if the aliens aren't interested in making music with us? What if they're more interested in, say, making mince meat pies out of us? Not to fear, explains Vakoch:

"Any civilization that is capable of an alien invasion is already privy to our existence. Earth's atmosphere has been giving off evidence of the existence of life for two and a half billion years, by virtue of the oxygen in our atmosphere, so any paranoid aliens have had plenty of time to do us harm. There's no sign they've been here."

Oh, OK then. Let's begin composition of our interstellar, multispecies magnum opus.

First published, Nov. 16 at 3 a.m. PT.

Update, 7:32 a.m. PT: Adds information about the Sonar festival and Sonar Calling collaboration.

Crowd Control: A crowdsourced science fiction novel written by CNET readers.

Solving for XX: The tech industry seeks to overcome outdated ideas about "women in tech."