Climb up a 23-foot-tall ladder and step onto a platform, grab the monkey bar, look down at the porous net that’s supposed to catch you, feel your knees get weak as you imagine falling through, hold tight and jump despite the shortness of breath. Swing through the air like a chimpanzee and let that humid Hudson air roll over your body as some beefy man in tight pants catches your wrists and you become the circus act you always watched with awe as a kid under a big tent. Twenty thousand people have faced their fear (or indulged in their penchant for an adrenaline rush) since Trapeze School opened five years ago. The rig sits atop Pier 40’s Astroturf roof; as you swing, your peripheral vision will pick up a beautiful blur of blue and brown . (Don’t worry, other color schemes—like black and blue—rarely happen.) Listen for the command—Hup!—that tells you to drop from the bar to the net below. Some flyers dismount quaking, some in tears, others with teeth shining as white as the clouds in the sky, but within minutes everyone climbs the ladder and does it all over again. Thirty of the school’s students have gone on to circus careers.