premise: The largest thing in the universe More than ten years ago, while taking the temperature of the universe, astronomers found something odd. They discovered that a patch of sky, spanning the width of 20 moons, was unusually cold. The astronomers were measuring the thermal radiation that bathes the entire universe, a glowing relic of the big bang. To gaze at this cosmic microwave background, or CMB, is to glimpse the primordial1 universe, a time when it was less than 400,000 years old. The CMB blankets the sky, and looks pretty much the same everywhere, existing at a feebly cold temperature of 2.725 kelvins - just a couple degrees warmer than absolute zero. But armed with the newly launched WMAP satellite, the astronomers had set out to probe temperature variations as tiny as one part in 100,000. Born from the quantum froth that was the universe a half-moment after the big bang, those random fluctuations help scientists understand what the cosmos is made of and how it all came to be. And standing out amidst those fluctuations was a cold spot. Over the years, astronomers have come up with all sorts of ideas to explain it, ranging from instrumental error to parallel universes. But now, they're homing in on a prime suspect: an enormous cavern of emptiness called a cosmic supervoid, so big that it might be the largest structure in the universe. According to theory, such a vast void, in which nary a star or galaxy exists, can leave a frigid imprint on the CMB. The answer to the mystery, then, might simply be a whole lot of nothing. Yet puzzles remain, and the case is far from closed. Primordial1 - ancient, existing a very long time.
hypothesis: Investigation of fluctuations of temperature in the space help scientists to understand what the cosmos is made of.