The Rings of Saturn
The celebration of Pi Day raises the age-old question of whether perfect circles exist in the universe.
A look at nature's stunning circular creations, like the remarkable rings of Saturn seen here, seems to make a compelling argument that Greek philosopher Plato was mistaken when he first observed that no one has ever seen a perfect circle—only imperfect approximations.
But John Adam, a mathematics professor at Old Dominion University and the author of Mathematics in Nature: Modeling Patterns in the Natural World, said that no perfect circle can occur in nature "since a perfect circle is a geometrical idealization."
Though Saturn's rings appear to be circular thanks to the shepherd moons orbiting the planet, parts of the rings are bent by the pull of gravity from its other moons.
Here are some of nature's other (seemingly) perfect circles.