11_16_sonar calling

The messages were sent from the EISCAT antenna in Tromsø, Norway.


Any civilization that could travel to Earth to do us harm could already pick up our leakage television and radio signals. So there’s no increased risk of alerting them of our existence. Earth’s atmosphere has been giving off evidence of life’s existence for two and a half billion years, thanks to the oxygen in our air. So any civilization that’s paranoid about competition has had plenty of time to come to Earth and wipe us out. That hasn’t happened. 

How did you decide what to say in the messages?

Extraterrestrials won’t speak English or Spanish or Swahili. So we need to look for a truly universal language. Our message is written in the language of math and science. Over the centuries, scientists and mathematicians have repeatedly taken a vote on the most essential concepts needed to explain the nature of the universe. Those are the ideas that are at the core of our message.

If there is alien life on GJ273b, how soon could they feasibly respond?

It will take a bit more than a dozen years for our message to reach GJ273b, and the same amount of time for their response to travel back to Earth.

What is the precise date that has been selected for when we will be listening for a reply? How was this date chosen?

We’ll be listening for a reply on June 21, 2043. As we make plans for listening for responses, we should look for dates that will have significance even with changes in nations and cultures. By asking for a response that would arrive on the summer solstice, we’re setting a time that’s connected to the cycles of the Earth. 

Are you hopeful we will hear back then?

The only way we’ll get a reply back from GJ273b is if the entire galaxy is filled with life. It’s certainly possible we’ll get a reply, but more likely we’ll need to ping many, many more stars before we get a response.

My hope for first contact operates on longer timescales. If we can mount a sustained transmission campaign that targets not a single star—but hundreds, then thousands, then millions of stars—then I have hope that sometime in humanity’s future, we’ll finally receive a reply.

What sort of dialogue could we expect to have with an alien civilization?

We won’t be having a snappy back-and-forth with aliens. Given the distances between the stars, even when our signals travel at the speed of light, it’s guaranteed to take at least several years for each exchange, and it could well take centuries or millennia. 

This story has been updated to include more information on the role Sónar played in the project.