Isaac Newton (1643-1727) is undouptedly one of the greatest physicists in history and his scientific contributions continue to shape much of modern science and everyday life. 

Newton challenged the beliefs of his time

In the 17th century, society often relied on superstitions, belief in witches, and religious doctrines to explain natural phenomena they found frightening or mysterious. Newtons achievements seem even more impressive considering the intellectual climate of his time, where science was frequently overshadowed by unfounded beliefs. 

Despite this, Newton challenged theses beliefs and laid the foundation for modern physics. He wrote much about light, optics and mathematics (including the invention of calculus), but this article focuses on his revolutionary insights into gravity and motion.

At the age of 23, in 1666, Newton formulated his three laws of motion, which he later published in the „Principia Mathematica Pilosophiae Naturalis “.

His laws still describe most of our world, from the motion of the moon, to why planes fly.

Lex Prima (Newton's first law of motion)

Objects either stay at rest or move with constant velocity unless acted on by a force.

This law stated that an objects motion does not change unless an unbalanced force is applied. In other words, an object moving at constant velocity experiences either no forces or balanced forces, resulting in zero net force.

The motion of an object is quantified by its momentum p, defined as p=mv, where m is the mass and v is the velocity. If the derivation of the momentum dp/dt is zero, the objects state of motion remains constant.

Lex Secunda (Newton's second law of motion)

The force acting on an object is equal to the rate of change of its momentum: F=dp/dt.

In other words, a force F causes a change of momentum: F=dp/dt. This derivation of the momentum simplifies to F=ma (if dm/dt=0 and the mass does not change which is not always the case), where a is the acceleration of the object.

Newton’s second law establishes the relationship between the acceleration of an object and the force acting on it. Force and acceleration are directly proportional via the formula F=ma.

Lex Tertia (Newton's third law of motion)

For every action, there is an equal and opposite reaction.

In other words, if object A exerts a force on object B, B simultaneously exerts a force of equal magnitude and opposite direction on A.

This law not only explains interactions between objects but also leads to the conversation of momentum. For example, during the collision of two objects moving at constant velocity, the momentum is conserved.