“The same thing is to be understood of all bodies, revolved in any orbits. They all endeavour to recede from the centres of their orbits, and were it not for the opposition of a contrary force which restrains them to and detains them in their orbits, which I therefore call Centripetal, would fly off in right lines with a uniform motion.”
- January 4, 1643 – March 31, 1727
- Born in England (UK)
- Natural philosopher, mathematician, physicist, astronomer, theologian
- Proposed the laws of universal gravitation and motion, built the foundations of modern science, and systematized theories of natural philosophy and mathematics.
Quote
“The same thing is to be understood of all bodies, revolved in any orbits. They all endeavour to recede from the centres of their orbits, and were it not for the opposition of a contrary force which restrains them to and detains them in their orbits, which I therefore call Centripetal, would fly off in right lines with a uniform motion.”
Explanation
In this quote, Isaac Newton is describing the fundamental forces at play in orbital motion, specifically the concept of centripetal force. He explains that objects in orbit, whether planets or moons, are constantly trying to move in a straight line due to their inertia. However, they are kept in their orbits by a contrary force, the centripetal force, which acts toward the center of the orbit and keeps the object from flying off into space. This insight was crucial for Newton’s formulation of universal gravitation, where the gravitational force between two bodies is the centripetal force that governs their orbital motion.
Newton’s laws of motion and universal gravitation, developed in the late 17th century, revolutionized the understanding of celestial mechanics. Before his work, the motions of celestial bodies were often explained through more mystical or philosophical ideas. By showing that forces of nature could be described mathematically and were universal in application, Newton placed gravity at the center of understanding how everything from earth-bound objects to planets in orbit behaved according to predictable laws.
In modern times, Newton’s explanation of centripetal force continues to be a foundational concept in both astronomy and engineering. The motion of planets, satellites, and spacecraft still follows the principles he described. For example, when sending a spacecraft into orbit, engineers calculate the necessary speed and trajectory to balance the centripetal force with the pull of gravity, ensuring the spacecraft remains in its designated orbit. Similarly, Newton’s laws help explain natural phenomena such as the tides, caused by the gravitational pull between the Earth and the Moon, or the precise orbits of artificial satellites around Earth.
