The mysterious function of eyelashes has been revealed at last — thanks to science.

After measuring the dimensions of nearly two dozen mammal eyes, performing a series of wind tunnel experiments and engaging in some complex fluid dynamic modeling, researchers determined most mammal eyelashes are one-third the length of their eyes — just the right length to minimize the flow of air over the eyeball.

This reduction of airflow is important because less moving air across the eye keeps evaporation at bay and stops irritating dust from getting deposited on the eye surface, the scientists report in a study published this week in the Journal of the Royal Society Interface.

“All mammals have wet eyes, and airflow is the enemy of that,” said Guillermo Amador, a doctoral student at the Georgia Institute of Technology, and the first author on the paper.