This question is more science fiction than science, as, thankfully, we can’t just turn off gravity. But it is a question I get asked a lot, so hypothetically speaking, this is what we could expect.
WHAT WOULD HAPPEN FIRST?
If the Earth’s gravity did just suddenly disappear we would no longer have a force keeping us on the ground. The Earth would keep spinning, as it does, but we would no longer move with it; instead we would move in a straight line, upwards.
However, we wouldn’t so much feel like we are floating away from the Earth, but more that the Earth is dropping away from us.
Anything not stuck would move upwards too, just like us, float off into space.
WHAT WOULD HAPPEN TO THE AIR?
The lack of gravity would not just affect solid objects though. All the gases that make up our atmosphere would float off into space too. This would leave anyone still left on Earth in need of an oxygen tank, in order to keep breathing. The air supply in some buildings might last for a short while, but that too would soon be drawn off into space.
WHAT ABOUT THE LAKES, RIVERS AND SEA?
Liquids would leave the Earth’s surface too, so all the water on our planet, in lakes, rivers and seas would start to float off, probably as large blobs initially. The temperature of the Earth would rapidly start to rise once our atmosphere had disappeared. Without our atmosphere we have little protection from the Sun’s heat. It would penetrate to the Earth’s surface and cause the water to start boiling off into steam that would float off into space.
WHAT WOULD HAPPEN TO THE WHOLE EARTH?
Buildings and solid structures would start to break up, as would mountains, land and rocks until eventually the whole Earth would break apart and float away into space. That would have little impact on us as we would already be long gone by then.
THE REALITY OF ZERO GRAVITY
While scientists can only predict what would happen if we suddenly lost gravity on Earth, they can tell us the short term effect that lack of gravity would have on our bodies through their studies examining what happens to astronauts while in space. Initially astronauts lose their sense of orientation. This can make them feel sick for a while. They also report feeling like their arms and legs are disconnected from their body. The change in air pressure can sometimes affect their vision; this may be due to the altered pressure on the eye ball, brain and spinal fluid.Due to the lack of weight on their bodies, their muscles and bones begin to weaken; to counteract this they spend a lot of their time exercising.
An astronaut will actually grow while in space; without the pressure of gravity, their bodies can stretch about an inch or more. This too is only temporary and they soon return to their usual height on Earth.
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