Newton's cannonball
Encyclopedia
Newton's cannonball was a thought experiment
Isaac Newton
used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion
. It appeared in his 1728 book A Treatise of the System of the World.
In this experiment Newton visualizes a cannon on top of a very high mountain.
If there were no forces of gravitation or air resistance, then the cannonball should follow a straight line away from Earth
.
If a gravitational force acts on the cannon ball, it will follow a different path depending on its initial velocity.
Thought experiment
A thought experiment or Gedankenexperiment considers some hypothesis, theory, or principle for the purpose of thinking through its consequences...
Isaac Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...
used to hypothesize that the force of gravity was universal, and it was the key force for planetary motion
Planetary orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
. It appeared in his 1728 book A Treatise of the System of the World.
The experiment
If there were no forces of gravitation or air resistance, then the cannonball should follow a straight line away from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
.
If a gravitational force acts on the cannon ball, it will follow a different path depending on its initial velocity.
- If the speed is low, it will simply fall back on Earth. (A and B)
- If the speed is the orbital velocityOrbital velocityOrbital velocity can refer to the following:* The orbital speed of a body in a gravitational field.* The velocity of particles due to wave motion, in particular in wind waves....
at that altitude it will go on circling around the Earth along a fixed circular orbit just like the moonMoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
. (C) - If the speed is higher than the orbital velocity, but not high enough to leave Earth altogether (lower than the escape velocityEscape velocityIn physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
) it will continue revolving around Earth along an elliptical orbit. (D) - If the speed is very high, it will indeed leave Earth. (E)
Other appearances
- An image of the page from the System of the World showing Newton's diagram of this experiment was included on the Voyager Golden RecordVoyager Golden RecordThe Voyager Golden Records are phonograph records which were included aboard both Voyager spacecraft, which were launched in 1977. They contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form, or for...
(image #111).
See also
- Space gunSpace gunA space gun is a method of launching an object into outer space using a large gun, or cannon. It provides a method of non-rocket spacelaunch.In the HARP Project a U.S...
- PhysicsPhysicsPhysics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...