ELI5: Explain Like I'm 5

Timeline of classical mechanics

Hey there little one, today we'll talk about the timeline of classical mechanics! Classical mechanics is basically the study of how things move and why they move that way.

Long, long ago, even before there were any books, theories or scientific methods, people were trying to understand why things move. They observed things around them and tried to make sense of it. This was the age of prehistoric times.

As time passed, people slowly started to understand more about motion. One of the first people to make significant contributions to the study of motion was a guy named Aristotle. Aristotle believed that the natural state of objects was to be at rest and that objects would only move if they were forced to do so. He also believed that heavier objects would fall faster than lighter objects. Many people believed in his ideas for a long time!

Then, in the 17th century, along came a famous mathematician and physicist named Isaac Newton. He revolutionized classical mechanics by introducing three laws of motion which still remain as the foundation of the field. His first law states that an object at rest will remain at rest and an object in motion will continue to move in a straight line with a constant velocity, unless acted upon by an external force. That means, if you're moving something and you stop, it'll stay stopped unless you apply a force. His second law is all about force and acceleration (how fast something is speeding up or slowing down). He explained that the acceleration of an object is proportional to the force applied to it and inversely proportional to its mass. This means, if you apply a small force to a heavy object, it won't accelerate as fast as if you applied the same force to a lighter object. Finally, his third law states that for every action, there is an equal and opposite reaction.

Newton's laws really helped the study of classical mechanics to take off. So many people got interested in it and started studying it more, which led to some important further discoveries. For example, in the mid-18th century, a man named Leonhard Euler came up with the concept of angular momentum. Angular momentum has to do with things moving in circles, like a spinning top. He observed that the angular momentum of an object remains constant unless an external force is applied, like friction or gravity.

Later on, in the 19th century, other important figures like Jean-Baptiste Joseph Fourier and Joseph-Louis Lagrange made more advancements to classical mechanics. Fourier introduced the study of heat transfer, while Lagrange developed the idea of the "Lagrangian" which helps understand the motion of particles and how they move in certain situations.

Today, we still use classical mechanics to study motion and its causes. It's been about 400 years since Newton first developed his laws, but they are still relevant and useful to many of us in the scientific community!