Science
What If Gravity Stopped?
If g went to zero everywhere, what already-moving things would do next?
Gravity is the reason you have a weight, the reason air has a scale height, and the reason Earth falls around the Sun instead of going straight. Set it to zero and none of those jobs get done. Velocity, though, is not a job of gravity. Whatever was already moving keeps moving. Earth at 30 km/s goes tangent. You, standing still relative to the ground, do not fall; there is nothing to fall with. The atmosphere is a pressure vessel that suddenly lacks the weight that used to hold it down, so it expands. The planet itself is no longer bound. That last one is slow on a 60-second slider and decisive on an hour. This is Newtonian gravity set to zero, with inertia left on — a knob the universe does not offer.
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Your result
1,787 km
Earth along the old tangent
inertia, not a new force
- Time since g = 0
- 1 minutes
- Missed fall toward the Sun
- 11 m
- Tangent distance
- 1,787 km
- Air thermal-speed scale
- 30 km
- Weight
- there is no downward acceleration in this model
~500 m/s × t
What does that mean?
At t = 60 s, Earth has travelled 1,787 km along the old orbital tangent and has missed 0.01 km of solar 'fall.' After 60 s you still have not 'fallen' — there is no downward acceleration in this model. Relative to the local ground you were at rest, so you float, until the ground itself starts to fail as a planet. Air molecules at ~500 m/s thermal speed could be 30 km into an expansion they never had to fight weight for — an order of magnitude, not a weather map. Planetary unbinding lives on a ~42 minutes 12 seconds clock (the gravity-train half-period family). This knob does not exist in known physics.
Timeline
0 s
g = 0
Weight vanishes. Velocities stay. This is the fictional switch.
Seconds to a minute
Hovering, leaking air
People do not fall. Pressure-driven atmosphere starts to puff. Oceans are un-weighted water.
~40 minutes
A planet's free-fall clock
Without self-gravity, a ball of rock is not obliged to remain a ball. Order of the gravity-train time.
An hour
A straight-line Earth
Tens of thousands of kilometres along the old tangent (107,225 km if you wait the full hour).
Compare scenarios
People float; they do not 'fly off' at minute one
A body at rest on the ground has zero vertical speed. Remove g and the ground's normal force goes to zero because there is nothing to cancel. You hover relative to the local dirt, until the dirt itself misbehaves. The flung-into-space picture confuses this with a spinning-off story, which is about rotation providing the only centripetal force. Rotation is still here, and without gravity the large-scale Earth is unbound, but chemical solids do not evaporate in a second. The first minute is weightlessness plus confusion, not a cartoon catapult.
Earth's year becomes a straight line
Orbital acceleration toward the Sun is about 6 mm/s². After gravity stops, that inward fall stops. In 60 seconds the 'missed fall' is only metres; in an hour, tens of kilometres. Meanwhile the 30 km/s tangent continues, so Earth is a free particle with a very large business card. The Sun-disappeared experiment is a relative of this, with an 8-minute light-time. Here the switch is local and immediate by assumption, which is extra hypothetical. Known physics does not let you mute gravity and keep the rest of the furniture.
Air, oceans, the planet
Scale height exists because mg pulls a molecule down and kT pushes back. Without mg the atmosphere is an expanding gas. Thermal speeds for nitrogen are hundreds of metres per second, so in a minute the column has started to puff; in an hour it is not a climate, it is a dispersal. Oceans are a mass with pressure but no weight — they do not stay in basins. Earth's self-gravity, gone, means the free-fall time of the planet (~tens of minutes) is the clock on which a ball of rock stops being a ball. The slider will say where you are on that clock without animating a debris cloud.
How we calculated this
g = 0 at t = 0 by fiat. Orbital missed-fall is ½ a t² with a = G M_sun / AU². Tangent distance is v_orbit t with v_orbit = 2π AU / year. Thermal expansion of air is described with ~500 m/s as an N₂ thermal-speed order of magnitude, not as a hydrodynamic solve. Planetary unbinding uses the same timescale family as the gravity train (order sqrt(R/g)). People are given zero initial vertical speed. Not GR, not a movie.
Go further
A curated rabbit hole from this question. Each link is a real experiment, not a random suggestion.
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