They concluded that it involves a process that balances two forces, gravity and inertia. The tip of the tongue rapidly skims the surface, which draws a column of liquid into the cat’s mouth. The cat then snaps its mouth shut and captures the drink.
Timing is so critical to the process that without an established rhythm cats wouldn’t be able to drink. Domestic cats manage about four laps per second, and each lap brings 0.1 milliliters of liquid into the mouth. Bigger cats have a slower rate of lapping in order to balance gravity and inertia with their size (Richard Alleyne, “How Cats Drink Milk Without Getting Their Chins Wet,” Telegraph.co.uk, Nov. 11, 2010).