Astronauts Cannot Cry in Space

The simple act of shedding a tear is profoundly different without Earth's gravity. Here on the ground, gravity is the force that pulls tears from our eyes and down our cheeks. In the microgravity environment of the International Space Station, however, that downward pull is virtually absent. Instead, the powerful force of surface tension takes over. The water molecules in the tear cling tightly to one another, creating a cohesive ball of liquid. This liquid has nowhere to go, so it wells up and sticks to the astronaut (Review)'s eye, lashes, and surrounding skin, forming a quivering, uncomfortable blob.

This phenomenon is more than just a curious quirk; it's a significant discomfort. Astronauts like Andrew Feustel have described the experience after getting irritants in their eyes during spacewalks. The resulting ball of tears doesn't offer relief; it just sits on the eye, stinging and blurring vision until it's manually wiped away with a towel. Whether caused by emotion or a stray piece of dust, the inability for tears to fall naturally transforms a simple human reflex into a challenging and uncomfortable physical problem that must be actively managed in orbit.