There is no gravity in space
Gravity exists throughout space and never truly reaches zero. Astronauts aboard the International Space Station experience roughly 90 percent of the gravity felt at Earth's surface, but they appear weightless because the station and everything inside it are in continuous free fall around Earth, the defining condition of orbital flight.
What we know
Gravity is a fundamental force that, according to Newton's law of universal gravitation, acts between any two masses and technically extends infinitely in range, weakening with the square of distance but never reaching exactly zero. This means the popular phrase "zero gravity," commonly used to describe the environment experienced by astronauts, is physically inaccurate as a description of the actual gravitational field present at the altitudes where crewed spaceflight occurs. At the roughly 400-kilometer altitude of the International Space Station, Earth's gravitational pull is still approximately 90 percent as strong as it is at the planet's surface, a substantial fraction, not a negligible one.
What astronauts actually experience is more accurately described by the term microgravity, or the sensation of apparent weightlessness produced by orbital free fall. An orbiting spacecraft is, in a very real physical sense, continuously falling toward Earth under gravity's pull. What makes this a stable orbit rather than a straight fall to the surface is the spacecraft's very high horizontal velocity, roughly 28,000 kilometers per hour for the ISS, which means that as the station falls toward Earth, the curve of its fall matches the curvature of the Earth itself, so it perpetually falls "around" the planet rather than into it. Because the astronauts inside are falling at exactly the same rate as the station surrounding them, they experience no relative force pressing them against any surface of the spacecraft, which produces the visual and physical sensation of floating that is commonly, if imprecisely, called "zero gravity" or "weightlessness."
This same principle, free fall producing apparent weightlessness, can be demonstrated on Earth using parabolic flight aircraft, sometimes nicknamed "vomit comets," which briefly follow a falling trajectory to simulate microgravity for astronaut training and scientific research, typically producing 20 to 25 seconds of weightlessness per parabolic arc. NASA and other space agencies use this method specifically because it reproduces the same physics, free fall under gravity, that produces weightlessness in orbit, underscoring that the phenomenon has nothing to do with an absence of gravity and everything to do with the relative motion between the observer and their surrounding reference frame.
True locations with meaningfully reduced gravitational field strength do exist, but they are vastly farther from any significant mass than low Earth orbit. Deep interstellar space, far from any star or planet, would have gravitational field strength approaching, though never mathematically reaching, zero. Even at the Moon's surface, roughly 384,000 kilometers from Earth, gravity is about one-sixth of Earth's surface gravity due to the Moon's own smaller mass, not because of increased distance from Earth, which by that point contributes only a small remaining pull.
NASA's own public education materials explicitly favor the term microgravity over zero gravity for exactly this reason, and the agency has published explanatory material specifically correcting the common misconception for students and the general public. The confusion persists partly because video footage of astronauts floating provides such visually compelling, intuitive "evidence" for an absence of gravity that the more complex and less intuitive true explanation, orbital free fall, requires active correction rather than emerging naturally from casual observation of the phenomenon.
Common claims
- There is no gravity in space.Not supported
- Astronauts float because they are far from Earth's gravity.Not supported
- Astronauts experience weightlessness due to orbital free fall.Accurate
- Parabolic flights can simulate weightlessness on Earth.Accurate