The ancient Greek philosopher Heraclitus once said that change is the only constant in life, and he may as well have been talking about the rules of sports.
The rules for college and professional sports have been constantly tweaked and adjusted for decades, so much so that it can be difficult to keep track. The now-infamous "Dez Bryant rule" regarding receivers catching a pass while falling to the ground has already been adjusted by the NFL following months of scrutiny. For a little refresher on other recent changes, we’ll take a look back at 20 of the biggest rule changes of the 21st century.