Round may be the preferred shape of baseballs, bubbles and Cocoa Puffs.
The universe, however, may favor the ellipsoid.
Italian scientists using data gathered by NASA's WMAP probe say evidence points to the universe having a shape somewhat akin to an egg, rather than the expected round kernel of puffed cereal.
This, say the authors of a paper published this week in the scientific journal Physical Review Letters, would explain some curious anomalies over the heavens' expanse.
WMAP -- the Wilkinson Microwave Anisotropy Probe -- was launched in 2001 to measure fluctuations in the cosmic microwave background radiation.
Looking at small chunks of the sky, the measurements agreed with a conventional spherical model of the observable universe. But when the data were measured on the largest scale, taking in the entire night sky, for instance, the radiation was too low, physicists say.
These anomalies may signal what Leonardo Campanelli of the University of Ferrara in Italy termed "a nontrivial cosmic topology" that is different from the sphere.
Campanelli and his colleagues found that the radiation discrepancies disappeared if the universe was shaped like an ellipsoid, with an eccentricity of about 1%.
That's not much, but it has some cosmologists scratching their heads.
"Generally, inflation would predict a spherical universe," said astrophysicist Gary Hinshaw, lead data analyst for WMAP.
Hinshaw said he was impressed by the research but not necessarily convinced the authors had found something real.
There is a 10% chance the results found by the probe would occur even if the universe is spherical.
Over the years, cosmologists have proposed other shapes for the universe, including a doughnut and saddle shape, said UCLA physics professor Edward Wright.
One theory is that the universe may really be quite small, and its apparent hugeness may result from a phenomenon like gazing into mirrors on opposite walls: The image goes on forever, but the walls remain fixed.
"I didn't like that [research] paper either," Wright said.