![]() ![]() In buildings, people would start floating gently upwards until they bumped into the ceiling. Things not attached to the Earth in any other way would fly off into space in a straight line that would take them away from the surface of the Earth. "Switching off" gravity is analogous to letting go of the string. If the circle is very big, then at first the straight line is almost the same as the circle - however, after a short amount of time, the two paths will be very different, since the circle bends around but the straight line does not. Now if you spin something around your head on a string, it goes around in a circle until you let go of the string. As you know, the Earth is rotating at quite a speed (you're moving at over a thousand miles per hour at the equator due to the Earth's rotation alone). ![]() What would happen to the things on Earth depends on how they are attached. Having said that, though, let's now imagine that we could magically turn off the gravity while leaving the Earth behind. But if the Earth didn't have mass, it wouldn't be there anymore! It is the Earth's mass that causes it to have gravity, and so in order to not have gravity the Earth would have to not have mass. The Earth has mass, just like every other solid object does (including you). We would like to start our answer by saying that we're sure you realize that this could never happen. We had a question: If the Earth no longer had gravity, would buildings and other structures attached to the Earth float away? In the same way, the astronauts are still in the clutches of gravity and only appear weightless because they are falling continuously around the Earth.Our third grade class has been studying gravity and the motion of objects. You would claim that gravity has ceased to act on the newspaper because it did not move away from you, yet gravity would still have you and the newspaper firmly in its grip. To you the floating paper would appear to be weightless. You and your newspaper both fall toward the earth at the same rate, and the newspaper would not fall away from you, but ’float’ beside you. ![]() You become frightened and release your newspaper. The elevator cable snaps and the elevator falls with you in it. You are in an elevator with your Jackson Sun. So, how does this produce apparent weightlessness? Consider another scenario. Shuttle astronauts are freely falling, just like the cannonball in the above example. The cannonball would perpetually fall toward the Earth but never get to it. The cannonball would leave the cannon and fall toward the ground but never land because it goes past the ’edge’ of the Earth! This happens because the Earth always curves away from the falling object. ![]() We normally ignore the curvature of the Earth, but we cannot here. As the cannonball travels away from the mountaintop, it falls in an arc-shaped path, and the Earth’s surface curves away from it. You orient the cannon to fire a cannonball parallel to the Earth’s local surface and fire it at very high speed. Suppose you take a cannon to the top of a high mountain. But, to answer that we need to use our imagination. The answer lies with the Shuttle’s orbit. In fact, at 125 mi the gravitational field experienced by the astronauts is 94% of what they would experience on Earth! A 150 pound astronaut here on Earth would, in the Space Shuttle, have a weight of 0.94 x 150 = 140 pounds! This is by no means weightless, so why do we refer to astronauts as being weightless? The Shuttle orbits about 125 mi above the surface, roughly the distance between Jackson and Nashville! When you consider the radius of the Earth is 3800 mi, you realize that Shuttle orbits are relatively close to the Earth in comparison to the Earth’s size. However, it does weaken as one gets further from the center of the Earth. The Earth’s gravitational field extends well into space it does not stop. But, are they truly weightless and is gravity zero? The short answer is no, the shuttle astronauts are certainly not weightless as they orbit the Earth, rather only apparently weightless. You commonly hear people refer to the weightlessness of the astronauts and zero-gravity. The Space Shuttle has proven to be a fine laboratory, particularly for experiments requiring a ’zero-gravity’ environment. The space shuttle astronauts are weightless when they are in orbit. Vocatio Center for Life Calling and Career.Office of Student Leadership & Engagement. ![]()
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