Remember static?
That thing you heard when you were fiddling the dial between radio stations, or saw when you tuned your TV between channels? Our digital world is static-less. There’s no static on Spotify or iTunes. Netflix gets pixelated but never goes snowy. Even my car radio automatically flips to the next station, bypassing the noise in between. And if you needed more evidence that static is a museum piece, there’s a YouTube video out there with 10 hours of simulated TV static. It has a million views.
One thing about static: If you looked at it for more than a few seconds, you started seeing patterns. They were probably meaningless — jiggling electrons inside the TV’s own electronics, electromagnetic interference from other devices in the house, sky noise. But every encounter with those phantoms in the static made you wonder: Is that really there?
That’s the question astronomers are asking themselves as they look at the universe’s original static, the cool hum of electromagnetic radiation laid down shortly after the Big Bang. Astronomers call this radiation the cosmic microwave background, or CMB: “microwave” because it is brightest at about 160 Gigahertz, which is in the microwave portion of the electromagnetic spectrum, and “background” because it’s the most distant observable light in the universe and covers the whole sky. No matter where you point your telescope, it’s there, buzzing away.
The first thing to know about the cosmic microwave background is that it is almost exactly the same temperature everywhere. The second thing to know is that it “almost” contains the seeds of every structure in the universe. Over the course of almost 14 billion years, tiny blips in the density of the early cosmic froth have grown galaxies, stars, planets, and all the rest. So, astronomers have put a lot of effort into analyzing minute deviations in the CMB, looking for patterns and anomalies that could help explain how the universe’s ornate architecture evolved.
One of those anomalies has been vexing astronomers for more than a decade: a “cold spot,” about 0.00015 Kelvin colder than the CMB average, covering an area of sky many times larger than the full moon. Researchers think there’s a 1-in-50 chance the cold spot is the product of random quantum fluctuations: slim but not impossible odds. But if it’s not just noise, what might it be?
The most extravagant possibility is that the cold spot is a “bruise” left behind by a collision with another universe. But a soberer explanation is that the cold spot is really just a trick of the light caused by a “supervoid” — a zone of space that’s underpopulated with galaxies. Photons lose energy when they cross supervoids, so a supervoid along our line of sight could create the illusion of a cold spot in the CMB.
Now, a new study claims to rule out the supervoid hypothesis. After surveying some 7,000 galaxies that lie between Earth and the cold spot, a team of astronomers concluded there is no supervoid that can explain the cold spot. They did find some voids along the way, but those sparsely populated areas were offset by denser regions. Plus, the distribution of the galaxies the astronomers surveyed was very similar to a “control” area of sky, where the CMB was a perfectly ordinary temperature. Whatever is causing the cold spot, they argue, it isn’t a supervoid.
Could this strange fluctuation in the CMB really be a clue to strange new physics? It seems farfetched. But the CMB itself was once dismissed as just noise. You never know what you might find when you look hard at the static.
Kate Becker is a science writer living in Boston. Contact her at spacecrafty.com, or connect via facebook.com/katembecker or twitter.com/kmbecker.
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