The five pillars that define the laws of our universe
In short: From the motion of planets to the flow of time, physics boils down to five core domains. By understanding how force, energy, and entropy interact, we can decode the fundamental rules governing everything from a moving car to the behavior of subatomic particles.
The foundation of our physical understanding begins with Classical Mechanics and Thermodynamics. Newton’s second law (F=ma) provides the basic framework for predicting motion by linking force, mass, and acceleration. This is expanded by the law of universal gravitation, which explains how celestial bodies move based on their masses and the square of the distance between them. While force is a vector, energy is a scalar—a simple number representing the capacity to do work. This energy is never created or destroyed; it only shifts between kinetic (motion) and potential forms, such as the chemical energy stored in gasoline or the gravitational potential of an object at height.
Thermodynamics introduces the concept of entropy, which measures the disorder or the information required to describe a system's microstates. The second law dictates that entropy in an isolated system can never decrease. This transition from low-entropy energy—which can perform work—to high-entropy states provides a potential explanation for the forward flow of time. Furthermore, temperature is revealed not as a mystical property, but as the average kinetic energy of atoms within a system, while thermal energy represents the total kinetic energy of those atoms.
Modern physics completes the picture with Electromagnetism and Relativity. Maxwell’s equations describe how moving charges and magnets interact, with the speed of light determined by the permeability and permittivity of free space. However, when objects move at high speeds, Classical Mechanics fails. Einstein’s Special Relativity resolved this by postulating that the laws of physics are constant for all observers. To maintain this consistency, he demonstrated that time cannot be fixed; it must be relative to the observer's frame of reference.
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Sources
- Summary by Intellect · source: All physics explained in 15 minutes (worth remembering)
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