(Kate Becker / The Visible Universe)

As the parent of a 5-year-old and a 2-year-old, I consider myself something of an expert on noise.

There's the pleasant buzz of children putting their tiny button noses to the Duplo grindstone. There the four primary screams: happy ("Eee!"), empty juice box ("Eeee!"), stolen toy ("Eeeee!"), and total meltdown ("Eeeeeeeeee!"). There's complex, multi-frequency soundscape of the birthday party: bouncy-house blowers on the bass, squealing kids on the treble, parents murmuring about sleep schedules and kindergarten readiness and where's-the-nearest-Starbucks somewhere in the middle.

But there's one kind of noise that most people rarely think about: radio noise. I say "most people," because radio astronomers actually think about radio noise a lot. Like optical astronomers, who need dark skies to pick out the faint light of distant stars and galaxies, radio astronomers need radio-quiet skies to "listen" to cosmic objects that give off radio waves.

But that kind of silence is hard to find: Ordinary household stuff — Wi-Fi routers, car starters, food processors, electric blankets — kick up radio waves, as do systems, such as radio transmitters and radar, that make radio waves for a living.


A few narrow slices of the radio spectrum are so important for radio astronomy that they are, by law, off-limits to electronics and transmitters. But astronomers taking data across wider swaths of the radio band have to surgically excise interference from their observations. They've developed clever ways to do this, but the methods don't always work and sometimes require throwing out a lot of data.

And it isn't always easy to tell the difference between mundane interference and extraordinary cosmic happenings. Take the case of the "Wow!" signal: a radio blast picked up in 1977 and considered so extraordinary that the discoverer marked the computer printout with big red "Wow!" Nothing like it has shown up since and now, 40 years later, astronomers still don't know whether it was caused by a cosmic object, human interference or (as those bullish on E.T. want to believe) aliens.

More recently, research on mysterious events called fast radio bursts was muddied by the detection of about a dozen superficially similar radio-wave spikes that were definitely coming from Earth. It took four years for astronomers to track the earthly radio emission to microwave ovens used by telescope staff and visitors. (The hunt was complicated by the fact that the microwaves only produced the suspicious signals when someone opened the door before the beep.)

The search for (radio) peace and quiet has taken radio astronomers to some very remote, unpopulated places. The Green Bank Telescope in West Virginia — the world's largest fully steerable radio telescope, as they like to say — even sits inside a National Radio Quiet Zone, established 60 years ago by the FCC. Close to the telescope, cellphones, Wi-Fi, Bluetooth and the like are all off-limits. It's a low-tech haven for a high-tech telescope (and, incidentally, for a community of "Wi-Fi refugees" fleeing wireless technology for, they say, health reasons).

But in the world of smart gadgets, radar auto safety systems and can-you-hear-me-now cell service, true radio quiet is getting harder to find here on Earth. So why not pull up stakes and head somewhere quieter — say, the moon?

Astronomers have been making the case for a lunar radio telescope for years now. The idea is to put the telescope on the far side of the moon, turning the moon itself into a giant shield from terrestrial radio interference. Another reason radio astronomers are keen on the moon: A lunar radio telescope would be able to pick up extremely low-frequency radio waves from the early days of the universe. Because of interference and atmospheric effects, these frequencies are very difficult for earthbound radio telescopes to tease out.

Now, that dream is a little closer to reality: Earlier this week, China launched a new satellite, Queqiao, that will lay technical groundwork for a future lunar radio scope. Queqiao's "day job" is relaying data to and from a soon-to-launch lunar lander and rover combo called Chang'e 4. But once Chang'e 4 has a chance to do some exploring, the satellite will open up three radio antennas and start its proof-of-concept listening campaign in the tranquil hush of the moon's shadow.

As for me? Noise-canceling headphones and Tylenol will have to suffice.

Kate Becker is a science writer living in Boston. Contact her at spacecrafty.com, or connect via facebook.com/katembecker or twitter.com/kmbecker.