Physics encompasses diverse branches, each offering unique insights into the universe. Classical mechanics, often called Newtonian mechanics after Isaac Newton, describes the fundamental laws of motion and forces acting upon bodies, forming the basis for understanding everything from particle movement to fluid dynamics. Expanding on this, thermodynamics investigates how temperature, pressure, and volume affect macroscopic systems, focusing on energy transfer as heat and the concept of entropy, a field historically influenced by the desire for more efficient steam engines.
Bridging into modern physics, electromagnetism explores the intricate interactions of electrons, magnetic fields, and light. A revolutionary development came with Albert Einstein's theory of relativity: his special relativity (1905) unified space and time into spacetime and reconciled classical mechanics with electromagnetism, postulating a constant speed of light. Subsequently, general relativity (published 1915/16) redefined gravitation as the curvature of spacetime caused by mass and energy, profoundly changing our understanding of the universe.