Bound by gravity and biology, we can’t easily step outside it, above it, or away from it. For most of us, Earth is inescapably larger than life. Even now, after nearly six decades of human spaceflight, precious few people have rocketed into orbit and seen the sun peeking out from behind that curved horizon. Since 1961, a mere 556 people have had this rarefied experience. Fewer, just 24, have watched Earth shrink in the distance, growing smaller and smaller until it was no larger than the face of a wristwatch. And only six have been completely alone behind the far side of the moon, cut off from a view of our planet as they sailed in an endlessly deep, star-studded sea.

It’s an inherently unnatural thing, spaceflight. After all, our physiology evolved specifically to succeed on this planet, not above it. Perhaps that’s why it can be difficult for astronauts to describe the experience of seeing Earth from space.

Italian space traveler Luca Parmitano says that we haven’t yet developed the words to truly convey the realities of spaceflight. The building blocks of modern human communication, words are necessarily constrained by meaning and connotation, no matter which language you choose (Parmitano speaks five). And until the mid-20th century, there was no need to express what it means to see our planet in the fiercely primeval essence of space. “We just don’t think in terms of spaceflight,” he says.

Clearly, a desire to protect the planet is common among those who have left it. Russian cosmonaut Gennady Padalka has logged more cumulative days in space than anyone else. The allure of spaceflight kept him on the job for 28 years, but something even more powerful than gravity kept bringing him home.

There really is no place like home.