Pick a topic to preview real questions and start a free game — every answer comes with an explanation, so you learn as you play. Every topic carries easy, medium and hard questions, so beginners and experts both get a real game.
A mix of easy, medium and hard — questions run from warm-up to expert, so there's a real challenge at every level. Think you know the answers? Play to find out.
This long, buoyant piece of equipment is what surfers stand on to ride waves.
Difficulty: EasyThis four-digit code assigned by air traffic control allows radar to identify individual aircraft on their screens.
Difficulty: MediumThis phenomenon, where the magnetic compass needle dips toward the ground at high latitudes, makes compass navigation increasingly difficult near the poles.
Difficulty: HardThe technical term for a wave that breaks suddenly and violently over shallow reef or sandbar.
Difficulty: MediumThis dangerous oscillation occurs when a swept-wing aircraft experiences coupled yaw and roll motions, common in early jet transports.
Difficulty: HardThe 'Rule of Threes' states you can survive approximately three minutes without this essential element.
Difficulty: EasyThis Australian surfer won four consecutive world titles from 1979-1982 riding revolutionary twin-fin surfboards.
Difficulty: HardThese two brothers from Ohio achieved the first powered, controlled flight at Kitty Hawk in 1903.
Difficulty: Easy