The moon, with automated probes dedicated to map every single inch of its surface, is probably less mysterious.

FORBES: Branding on the Moon: Marketing in The Middle East

Because interactions as a single metric is only the surface.

FORBES: SpongeBob SquarePants vs. The X Factor: A Social TV Throwdown In Infographics

The morning haze had burned off, and in the noon light the brackish water appeared deceptively lovely, its surface undisturbed except for a single Jet Ski carving a white wake whose exhausted wavelets lapped at the riprap at the side of the road.

NPR: In 'Challenger Park,' Mom Is an Astronaut

They persuaded their frogs to expose a single toe and then slowly moved the glass surface on which this toe was standing.

ECONOMIST: How tree frogs keep their grip

Coral reefs are home to 25 percent of the world's marine fish species, and cover 1 percent of the Earth's surface, making them the largest single living structure on Earth.

CNN: All About: Coral Reefs

On the surface it is just odd that a single debate would have produced such a big shift.

BBC: Obama's do-or-die debate

Murphy sliced six yards wide from a good position, losing his boot on the muddy surface in the process, but his single goal was enough to give Well victory for a second week in a row.

BBC: Jamie Murphy celebrates with Mark Reynolds

On their surface, the new rules would provide for a single EU passport for hedge funds.

FORBES: EU Punts Again on Question of Hedge Fund Passport

The streetlights, perhaps the single most important and overlooked part of this normally well-run city surface, were all out.

FORBES: New York City After Hurricane Sandy

Although the Met Office has 1998 as the single warmest year, that coincided with strong El Nino conditions - the warming of surface waters in the eastern Pacific that releases heat stored in the deep ocean into the atmosphere, raising temperatures globally.

BBC: This decade 'warmest on record'