If you stood beneath both Landscape Arch in Arches National Park and Kolob Arch in Zion National Park, could you tell which span is longer? Probably not, but a group has come up with a standardized way to measure arches and says Landscape is the longer span of stone.

The Natural Arch and Bridge Society long has pondered this question, and using lasers and an agreed upon definition of what should be measured says Landscape Arch is the world's longest stone arch. But don't be surprised if the debate continues.

The definition used by the society centers on the "maximum horizontal extent of the opening." That opening beneath Landscape Arch measures right around 290.1 (plus or minus 0.8 feet) feet across.

The opening beneath Zion National Park's Kolob Arch, which long had been in the running for world's largest, measures 287.4 feet (plus or minus 2 feet), according to the group.