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That's a very good question, but unfortunately, one that is unanswerable. Technically speaking, you can never escape the Earth's gravity. How can this be? A little lesson in physics may explain. Gravity is the force of attraction that exists between any two objects. You've probably heard the story about Isaac Newton and the falling apple. Newton devoted much of his time to studying gravity and developing theories to explain the mysterious and powerful force. His law of universal gravitation states that "the gravitational attraction between any two
objects is directly proportional to the product of their masses and inversely proportional to the distance between their centers." Basically, this means two things: - the more massive two objects are, the stronger the force of gravity between them
- the farther apart two objects are, the weaker the force of gravity between them
Relatively speaking, the Earth is a fairly massive object and exerts a strong gravitational pull. If an object is launched from the surface of the Earth, it needs to reach a certain speed called the escape velocity in order to break free of the Earth's gravity. This speed is about 7 miles per second, or 25,000 miles per hour. If the object doesn't reach escape velocity, it will either
crash back into the Earth, or enter into orbit around it, as satellites or the space shuttle do. Returning to the question at hand, the farther an object is from Earth, the smaller the effect of the Earth's gravity upon it. As a page from NASA explains: To reach a point where Earth's gravity is reduced to one-millionth of that on Earth's surface, one would have to be 6.37 million kilometers [3.73 million miles] away from Earth (almost 17 times farther away than the Moon). Even at that point, you still have not totally escaped the Earth's gravity, it is merely
too weak to have much of an effect. In fact, as another NASA site explains, "The effect of gravity extends from each object, indefinitely into space in all directions." The key word here is "indefinitely." No matter how far you go, you can never fully escape the pull of the Earth, a somewhat comforting thought when faced with the vast and endless expense of space.
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