It is 3 a.m., and I am listening to static on the radio.
To my 6-week-old baby, radio static is the sound of sleep. We try to sooth her to sleep with lullabies, ocean waves or the drizzle of the rainforest (the options on our baby sound machine), but she'd just as soon snore her sweet snores to the hum at the bottom of the FM dial.
So why am I awake while she dozes? It's because every few minutes, something breaks through the radio noise: a snippet of Top 40, the singsong voice of a DJ or a jingle for the local car dealership. My ears perk up, trying to pick out signal from noise.
Radio astronomers have a similar task, though they tune in with enormous dishes, not clock radios, and they use computers, not their ears, to sift real astrophysical signals from earthly interference and the background hum of the cosmos.
Now their search has turned up four examples of a new class of cosmic mysteries: radio bursts that last just milliseconds, but which, for that brief time, are brighter than any other such radio sources in the sky.
What are they? To answer that question, astronomers start with a somewhat more approachable mystery: Where are they?
The universe gives us a helping hand in figuring this out. As radio waves travel across the cosmos, they run into free electrons that slow them down. Low-frequency waves slow down more than high-frequency waves. By analyzing the delay across frequencies, astronomers can determine how many electrons the waves encountered as they made their way toward Earth.
From that, they can deduce the distance to the source of the radio waves.
These radio bursts seem to be coming from somewhere beyond our galaxy, based on the major delay between their low-frequency and high-frequency waves.
But this method of measuring distance leaves plenty of room for error. After all, free electrons aren't distributed evenly across the cosmos. They are sparse in the space between galaxies and dense within them, thronging in the dense galactic cores. So waves coming from the center of a nearby galaxy might be delayed even more than waves that originate at the outer edge of a far more distant galaxy.
Astronomers do have a few guesses as to the nature of these radio bursts. They could come from the collision of two outrageously dense dead stars, called neutrons stars. They could be screams from dying black holes or supernova explosions. They also could be nearby radio interference masquerading as cosmic events.
Or they could be something entirely new -- something we haven't even thought of yet.
Whatever they are, each seems to be a one-and-done event, suggesting that they are probably destructive: the sounds of guitars being smashed, not played.
And though it might seem odd, as we're only now discovering these blasts of radio waves, they are probably happening 10,000 times a day across the universe. That means that every 10 seconds or so, one of these tremendously powerful cosmic firecrackers goes off somewhere in the universe.
That's a lot of smashed guitars.
As astronomers build telescopes that can "listen" to broader swaths of the sky at once and dissect their data down to the millisecond, they likely will find more bursts like these, plus even stranger signals from still unimagined exotic objects.
It is a new picture of the cosmos: One we are just waking up to.