Super Bowl Physics!

Are you getting excited for this Sunday's Super Bowl?  If you like the merging of science and sports, check out the premier episode of Season 4 of StarTalk's Playing with Science.

• Season 4, Episode 1 (January 30, 2019):  SEASON PREMIERE:  2019 Big Game Special, with Neil deGrasse Tyson

I talk about the physics of football during the first portion of the episode.  I also had a pretty nerdy way to predict the winner!

Danger Among the Thrills

If you're like me, you watched the two NFL conference championship games yesterday, thinking perhaps you were watching the most thrilling back-to-back football games you'd ever seen.  Both games were decided in overtime.  Both games saw the visiting team as the victor.  Both games had a terrible official mistake (a non-call in the first game and a call in the second game) that could have given the victory to the home team.  As thrilling as both games were, something unsettled me late in the first quarter of the first game.

With less than six minutes to go in the opening quarter, the Saints enjoyed a 6-0 lead over the Rams.  They were looking to extend their lead on a drive that had them with 1st and 10 on their own 32-yard line.  Saints quarterback Drew Brees (#9) threw a short pass to tight end Josh Hill (#89).  Hill caught the ball near the line of scrimmage and ran for a first down and more.  The play netted the Saints 24 yards.  But I cringed at the hit Hill received from Rams linebacker Cory Littleton (#58).  Check out the screen capture below (click on image for a larger view).

I could tell from the sound of the collision that Hill's helmet and Littleton's helmet collided with a great deal of force.  Hill was slow to get up, and Littleton could be seen waving for help for Hill.  Below is another view of the collision, but if you'll have to watch the video if you desire to see and hear just how violent the collision was (click on image for a larger view).

Hill reached a speed near 15 mph on his run, and only slowed a little prior to the collision.  The Saints removed Hill from the game and entered him into concussion protocol.  It was later determined that Hill did indeed suffer a concussion.

Josh Hill weighs 250 pounds and Cory Littleton weighs 226 pounds.  Throw in more than 20 pounds per player for pads, gear, and helmet, and yesterday's collision involved more than 500 pounds of total weight.  The average force during a collision like that is comparable to that 500-pound weight.  The maximum instantaneous force can be three times that average force.

Acceleration is the real concussion culprit.  The brain sits in cerebrospinal fluid, which provides cushioning during normal, every-day accelerations.  But if the brain is subjected to an acceleration of about 100 times the acceleration due to gravity, a concussion will be the likely result.  Usually, the torso takes the brunt of that acceleration during a tackle, but a hit to the head means the brain will feel the full acceleration.  Really hard hits to the helmet can actually lead to accelerations as large as 150 times the acceleration due to gravity.  Keep in mind that a fighter pilot only feels one tenth of that acceleration while executing some maneuvers (though the fighter pilot deals with the large acceleration for much longer than the football player does). A severe car crash may have one third the acceleration of a dangerous hit to the helmet in football.  Collision times in football are very short, and the time of the large instantaneous accelerations is even shorter.  But the time is long enough for the brain to hit the skull and leave the player with a concussion.

Today's helmets do a decent job with linear accelerations.  Padding and helmet design help extend collision times (think air bags and catcher's mitts!), which reduces collision forces.  But modern helmets have still not solved the problem of large angular accelerations.  Look at the second screen shot above.  The two players were nearly coming at each other perpendicularly.  The hit to the top of Hill's helmet caused his head to rotate to toward his right shoulder.  Padding does little to help prevent large rotational accelerations.

The football action yesterday was thrilling to say the least.  I just hate to see the darker side of the sport, a side that leaves a player with brain trauma.

Can't Blame Coriolis!

The Chicago Bears lost a heartbreaker at home yesterday to the Philadelphia Eagles, 16-15, in an NFC wild card playoff game.  Cody Parkey missed a 43-yard field goal at the end of the game that would have given the Bears the victory.  The ball he kicked first hit the left upright, then hit the crossbar on the way down, bouncing off in the wrong direction for the Bears.  Check out the the ball hitting the left upright (click on image for a larger view).

The Bears play their home games at Soldier Field, which is at a latitude of 41.8632 degrees north, according to Wikipedia.  A closer look at the stands in the background shows section 151 (click on image for a larger view).

I looked at the seating chart for Soldier Field, and then checked that the field does indeed run south to north.  Section 151 is behind the north end zone, which means Parkey's kick left his foot traveling north toward the left goalpost.

The Coriolis effect arises because the Earth turns on its axis, which means we here on Earth's surface are not in an inertial reference frame.  Earth turns once on its axis in 24 hours, which gives a rotational speed of about 0.73 microradians per second or 15 degrees per hour.  Just after the kick and before the ball hit the upright, the ball was in the air for 2.33 seconds.  At the latitude of Soldier Field, Parkey's kick would have only deflected about a tenth of an inch due to the Coriolis effect.  But what's really important is that a ball kicked to the north in the northern hemisphere will be deflected to the right, i.e. east.  That means that the Coriolis effect actually helped Parkey's kick!  Without the added tenth of an inch to the right, the ball still would have hit the left upright, but just a tiny bit closer to the center of the upright.

I feel bad for Cody Parkey.  His kick would have won the game for the Bears.  The snap was perfect, and the hold was perfect.  Parkey just missed the kick.  He even got a little push in the right direction from the Coriolis effect.