A term popularized (although not coined, as many think) after being used by President Barack Obama in his 2011 State of the Union Address. It refers to a moment of challenge when a country (or person) realizes they must work harder to surpass their competitor. Caught on like wildfire that same night as Twitter users & others found the phrase catalyzed adolescent-like paroxysms of merriment for no absolutely discernible reason other than joyful immaturity.
Greg had his Sputnik Moment when he realized he was the same age as the dude who founded Facebook.
Jim: Dude, I just had my Sputnik Moment about Jenny.
Josh: What was it dude?
Jim: I caught her in a Sputnik Moment with Niles.