Low Earth Orbit
Great Ideas from Newton

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.


Transparency Master 		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.

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.

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


Transparency Master 		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.

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.

There are two very important points that should be made about Newton's idea.

    1. 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.
    2. 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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