Voyager 1 launched in 1977. Its stated mission was to do flybys of Jupiter and Saturn. It did so with aplomb, discovering, among many other things, active volcanoes on the moon Io, and just how intricate Saturn’s rings are. But that wasn’t the end of its mission. Its trajectory after its last flyby was toward an even more ambitious destination.

Out.

 As in, leave the solar system completely. Which it accomplished in 2012 by passing out of the area known as the heliosphere, the area of local space more affected by our sun than whatever forces might lie outside it.

Not its primary mission, but possibly more significant in the long view. Our very first robotic foray into interstellar space. Aside from instruments, it carries the “Golden Record,” with greetings in fifty-five languages on the assumption that any aliens smart enough to find It are also smart enough to figure out how to play it. It would be to their advantage, because the record also includes music by Beethoven and Chuck Berry. Which inspired the long-running joke: What will be our first communication from an alien species? “Send more Chuck Berry.”

I have my doubts, with all due respect to Chuck Berry, and this is also due to one more new discovery from Voyager 1: the Hum.

No one was expecting new science from the probe once its primary mission was over, as both Voyager probes were designed and expected to be operational for only five years. If that had been the case, Voyager 1 would still have been the first man-made object to leave the solar system, but it would be a dead hunk of metal when it did so. After forty-four years Voyager 1 and its sister craft Voyager 2 are both still very much alive, and Voyager 1 was the first to hear the universe singing.

Well, okay, it’s more of a hum, which why they call it that. For those of us who grew up fussing at science-fiction in movies and television which almost always depict spacecraft rumbling very loudly through space when there’s no air to carry any sound, it was a bit humbling. Yes, there is no air to speak of in space, so we can’t hear sound there the way we were designed to hear it, but that doesn’t mean there isn’t any. It appears the spaces between the stars contain traces of ionized gas—plasma—vibrating in a narrow band. It’s far too faint for us to hear, but with the right instruments to detect, amplify and interpret the wave forms, it becomes sound.

So it turns out the universe is humming to itself.

So much for the emptiness of space and the silence of the stars, both are illusions based on a misapprehension—ours. We just had to learn how to listen.