context: Hoping to rebound from their road loss to the Jaguars, the Titans went home for a Week 10 fight, as QB Vince Young went up against his predecessor (Steve McNair) and the Baltimore Ravens.  In the first quarter, the Titans scored first on a 21-yard field goal by kicker Rob Bironas.  Afterward, McNair completed a 65-yard TD pass to WR Mark Clayton to give Baltimore the lead.  Afterwards, Young got a 2-yard TD run to give Tennessee the lead, while DE Tony Brown sacked McNair in the end zone for a safety.  In the second quarter, the Titans increased its lead with TE Bo Scaife getting a 13-yard TD run and RB Travis Henry getting a 1-yard TD run.  However, the Ravens responded with McNair completing a 30-yard TD pass to FB Ovie Mughelli, followed up by kicker Matt Stover's 27-yard field goal.  After a scoreless third quarter, Baltimore wrapped things up against Tennessee with Stover getting a 40-yard field goal and McNair completing an 11-yard TD pass to WR Derrick Mason.  With the loss, the Titans fell to 2-7.
question: How many yards was the shortest field goal?
answer: 21