Where is there no gravity in space?

The law of gravitation states that the attraction between two masses decreases with the square of the distance. It is a function that tends toward zero but never reaches it: at any finite distance there remains a force, however tiny. That is why there is no point in the universe where gravity can be said to equal exactly zero. Probes that have left the solar system are still subject to the Sun's pull and, beyond that, to the pull of the Milky Way as a whole.

At 400 km altitude, where the International Space Station orbits, Earth's gravity still retains close to 90% of its surface value. The crew floats because the station is in free fall around the planet, not because gravity has ceased; the correct term for that environment is microgravity.

The closest thing to a "zero-gravity zone" are the Lagrange points, five positions in a two-body system where the pull of both bodies and the centrifugal force of orbital motion balance out. A spacecraft placed there can maintain its position with minimal fuel corrections. The James Webb Space Telescope occupies the L2 point of the Sun-Earth system, about 1.5 million kilometers from our planet, in the direction opposite the Sun.

There is also a neutral point between Earth and the Moon, about nine-tenths of the way there, where the pull of both bodies is equal. Apollo spacecraft crossed it on every trip. But even there gravity is plentiful: what happens is that two opposing pulls cancel each other out, an unstable equilibrium very different from a true absence of gravitational field.