the.com/weightlessness
the body's vacation from gravity, where your spine grows and your heart shrinks in protest
means The state of experiencing no apparent gravitational force, so that the body and everything around it floats freely, as astronauts do in orbit.
from A plain English assembly: 'weight' (Old English 'gewiht,' the heaviness of a thing) plus the negating '-less' (Old English '-leas,' meaning 'without' or 'free from') and the noun-making '-ness.' So at root it simply names the condition of being without weight. The word only became truly useful in the 20th century, when rockets and orbit gave humans an actual place to be weightless rather than merely a thing to imagine.
tallerAstronauts gain up to two inches in orbit
not zero gIt's actually constant freefall, not absent gravity
weak heartHearts shrink without gravity to pump against
puffy facesFluids float upward, swelling astronauts' heads
vomit cometPlanes simulate it via stomach-churning parabolic dives