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Low Earth Orbit Great Ideas from Newton |
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Sir Isaac Newton (1624-1727)
Sir Isaac Newton was born in 1624, the year in which Galileo Galilei died. This
coincidence represents perhaps one of the most important turning points in the
history of science, for although Galileo had come to rely more on the results of
direct experimentation, it was Newton who presented science with a new way of
looking at the facts of observation.
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With Newton, the long-standing Aristotelian tradition of solving problems which
dealt with natural philosophy, (the study of light, motion, and sound), by
speculation and meditation gave way to dealing with those problems by
measurement and experiment.
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Newton's celebrated work on light and optics and the laws of motion and
gravity represented a transition from ancient methods to the modern manner of
scientific thought.
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In 1705, Newton was knighted at Cambridge by Queen Anne - the first time this
honour had ever been conferred for achievement in pure science. Sir Isaac Newton
died in 1727 and is buried in Westminster Abbey.
Very Fast Projectiles
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Newton hypothesized the possibility of artificial satellites. His knowledge of
ballistics lead him to reason that a projectile could be made to follow the
curvature of the Earth if it were given a sufficiently large initial velocity.
The drawing to the left illustrates Newton's reasoning. As the cannon balls
acquire increasingly larger and large initial velocities, their trajectories
increase in length.
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At very large initial velocities the curvature of the Earth becomes apparent
and the cannon balls are able to travel further because the Earth's surface
tends to curve away from the ball's trajectory.
At a high enough initial velocity, the curvature of the Earth matches the
curvature of the cannon ball's trajectory... which is equivalent to orbiting
the Earth.
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There are two very important points that should be made about Newton's idea.
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The height (distance from the Earth) of the orbiting object is not
important (provided the object is above the energy absorbing drag of the
Earth's atmosphere). It is the speed of the object that allows it to
attain orbit, not its height.
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The Earth's gravity is essential in keeping the object in orbit. An
orbiting object does not escape the Earth's gravity. It is, in fact,
trapped in a perpetual circular orbit by the gravitational attraction of
the Earth.
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Answer Key
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