<p><strong>The <a href="http://news.nationalgeographic.com/news/2013/03/031314-pi-day-exploratorium-mathematics-pie-science/">celebration of Pi Day</a> raises the age-old question of whether perfect circles exist in the universe. </strong></p><p>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.</p><p>But <a href="http://ww2.odu.edu/~jadam/index.html">John Adam</a>, a mathematics professor at Old Dominion University and the author of <a href="http://press.princeton.edu/titles/7686.html"><em>Mathematics in Nature: Modeling Patterns in the Natural World</em></a>, said that no perfect circle can occur in nature "since a perfect circle is a geometrical idealization."</p><p>Though Saturn's rings appear to be circular thanks to the&nbsp;<a href="http://saturn.jpl.nasa.gov/faq/FAQSaturn/index.cfm#q13">shepherd moons</a> orbiting the planet, parts of the rings are bent by the pull of gravity from its other moons.</p><p>Here are some of nature's other (seemingly) perfect circles.</p><p><em>—Linda Poon</em></p>

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.

—Linda Poon

Image courtesy SSI/NASA

Pi Day Pictures: Nature's Near-Perfect Circles

On Pi Day, we explore the universe of naturally occurring circles.

Read This Next

225-year-old working warship sustained by a Navy forest
Can today's youth overcome widespread climate anxiety?
To discover wild America, follow Bigfoot’s mythical steps

Go Further

Subscriber Exclusive Content

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet

Why are people so dang obsessed with Mars?

How viruses shape our world

The era of greyhound racing in the U.S. is coming to an end

See how people have imagined life on Mars through history

See how NASA’s new Mars rover will explore the red planet