Scientists have discovered the biggest expanse (one billion light years across) of nothing. Inside the void, there are hardly any galaxies, planets, or black holes. For a long time, astronomers thought that matter—which makes up everything in the universe—was distributed fairly evenly through space, with only small empty spaces. The new find calls that assumption into question.

A cold puzzle

The discovery began with observations made by other scientists about something called cosmic microwave background radiation, or CMB. The CMB is a glow of radiation that flooded outer space about 13.7 billion years ago, after the Big Bang. The CMB still fills the universe, but it has changed. For one thing, it has drastically cooled. Just after the Big Bang, the glow was billions of degrees hot. Now it is just 3 degrees above zero kelvin (K). That’s equal to -270 Celsius. Calculations show that most of the radiation is about the same temperature in all directions. About three years ago, however, scientists noticed that there was a cold spot in the CMB radiation that was especially cold.

Radio clues

To get a closer look, scientists looked at pictures of the spot taken by the Very Large Array (VLA), a radio telescope in New Mexico. When they examined the VLA images, however, scientists counted 30 percent to 40 percent fewer radio galaxies than normal in the direction of the cold spot. The only explanation for the unexpectedly low number of radio galaxies in the strangely cold spot, the team decided, was that the spot was actually a huge expanse of empty space.