Science
What If Gravity Stopped?
Short answer: you’d float rather than fly off, because nothing was pushing you upwards. Earth would carry straight on at 30 km/s instead of curving round the Sun, and the air would start to drift away into space.
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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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.
Common questions
Would we fly off into space if gravity stopped?
Not straight away. You’d float, because you weren’t moving up or down to begin with. The flung-into-space idea mixes this up with Earth’s spin.
What would happen to Earth if gravity disappeared?
It would stop curving round the Sun and carry straight on at about 30 km/s. The air would start to drift away, and the planet itself would no longer hold together.
How we calculated this
g = 0 at t = 0 by fiat. The distance Earth no longer falls towards the Sun is ½ × a × t², where a is the Sun’s pull at Earth’s distance (G × solar mass ÷ AU²). The straight-line distance travelled is orbital speed × time, with orbital speed = 2π AU per 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.
Assumptions and limitations
This is a simplified estimate. Actual results depend on factors the model does not include.
This is a simplified thought experiment. It uses transparent assumptions so you can see what changes — it is not a full physical simulation of the real world.
- Newtonian gravity is set to zero everywhere, instantly — extra hypothetical.
- Velocities at t = 0 are unchanged (inertia stays).
- Standing people have zero vertical speed relative to the ground.
- Atmosphere expansion is order-of-magnitude, not a CFD.
- This is not a physically available switch.
Sources
- NIST CODATA — standard acceleration of gravity
gn = 9.80665 m/s².
- NASA Earth fact sheet
Earth mass and radius for orbital and gravity-train numbers.
- IAU 2012 resolution — astronomical unit
AU is exact: 149 597 870 700 m.
Go further
Related experiments that pick up where this one leaves off.
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