Fundamental physics
Introduction
Fundamental physics is the branch of science that seeks to understand the basic principles governing the universe. It encompasses the study of matter, energy, space, and time, and aims to uncover the fundamental laws that dictate the behavior of the natural world. This field is foundational to all other branches of physics and provides the theoretical framework for understanding phenomena ranging from the subatomic to the cosmological scale.
Classical Mechanics
Classical mechanics, often regarded as the first branch of physics to be developed, deals with the motion of macroscopic objects. It is based on the laws of motion formulated by Sir Isaac Newton in the 17th century. These laws describe the relationship between a body and the forces acting upon it, and the body's motion in response to those forces.
Newton's Laws of Motion
Newton's first law, also known as the law of inertia, states that an object will remain at rest or in uniform motion unless acted upon by an external force. The second law quantifies the effect of force on an object's motion, establishing the equation \( F = ma \), where \( F \) is the force applied, \( m \) is the mass of the object, and \( a \) is the acceleration produced. The third law asserts that for every action, there is an equal and opposite reaction.
Conservation Laws
Classical mechanics also introduces the concept of conservation laws, which are pivotal in understanding physical interactions. The conservation of energy principle states that energy cannot be created or destroyed, only transformed from one form to another. Similarly, the conservation of momentum and angular momentum are fundamental principles that govern the dynamics of systems.
Electromagnetism
Electromagnetism is the study of electric and magnetic fields and their interactions with matter. It is described by Maxwell's equations, a set of four partial differential equations that form the foundation of classical electrodynamics, optics, and electric circuits.
Maxwell's Equations
Maxwell's equations unify the previously separate laws of electricity and magnetism. They describe how electric charges produce electric fields (Gauss's law), how magnetic poles produce magnetic fields (Gauss's law for magnetism), how a changing magnetic field induces an electric field (Faraday's law of induction), and how electric currents and changes in electric fields produce magnetic fields (Ampère's law with Maxwell's addition).
Electromagnetic Waves
One of the most significant predictions of Maxwell's equations is the existence of electromagnetic waves, which include visible light, radio waves, X-rays, and more. These waves propagate through space at the speed of light and are responsible for a wide range of phenomena, from the transmission of information via radio and television to the heating effect of microwaves.
Thermodynamics
Thermodynamics is the branch of physics that deals with heat, work, and the forms of energy involved in physical and chemical processes. It is governed by four fundamental laws that describe how energy is transferred and transformed.
The Laws of Thermodynamics
The zeroth law of thermodynamics establishes the concept of temperature and thermal equilibrium. The first law, also known as the law of energy conservation, states that the total energy of an isolated system is constant. The second law introduces the concept of entropy, a measure of the disorder or randomness of a system, and states that the total entropy of an isolated system can never decrease over time. The third law states that as the temperature of a system approaches absolute zero, the entropy approaches a minimum value.
Applications of Thermodynamics
Thermodynamics has wide-ranging applications, from designing engines and refrigerators to understanding biological processes and the behavior of black holes. It provides critical insights into the efficiency of energy conversion processes and the direction of spontaneous processes.
Quantum Mechanics
Quantum mechanics is the branch of physics that deals with the behavior of matter and energy at the atomic and subatomic levels. It challenges classical mechanics by introducing the concept of wave-particle duality and the uncertainty principle.
Wave-Particle Duality
Wave-particle duality is the concept that every particle or quantum entity exhibits both wave and particle properties. This duality is exemplified by the photoelectric effect, where light behaves as a particle, and the double-slit experiment, where particles such as electrons exhibit interference patterns characteristic of waves.
The Uncertainty Principle
The Heisenberg uncertainty principle states that it is impossible to simultaneously know both the position and momentum of a particle with absolute certainty. This principle has profound implications for the behavior of quantum systems and challenges the deterministic nature of classical mechanics.
Quantum Entanglement
Quantum entanglement is a phenomenon where two or more particles become interconnected in such a way that the state of one particle cannot be described independently of the state of the others. This leads to correlations between the particles that persist regardless of the distance separating them, a concept famously referred to by Einstein as "spooky action at a distance."
Relativity
Relativity is the branch of physics that deals with the structure of space-time and the effects of gravity on the motion of objects. It is divided into two theories: special relativity and general relativity.
Special Relativity
Special relativity, formulated by Albert Einstein in 1905, addresses the behavior of objects moving at constant speeds, particularly those approaching the speed of light. It introduces the concepts of time dilation and length contraction, which describe how time and space are perceived differently by observers in relative motion.
General Relativity
General relativity, published by Einstein in 1915, extends the principles of special relativity to include acceleration and gravity. It describes gravity as the curvature of space-time caused by the presence of mass, leading to the prediction of phenomena such as gravitational waves and black holes.
Particle Physics
Particle physics is the branch of physics that studies the fundamental constituents of matter and the forces that govern their interactions. It seeks to understand the universe at the smallest scales through the Standard Model of particle physics.
The Standard Model
The Standard Model is a theoretical framework that describes the electromagnetic, weak, and strong nuclear forces, as well as the fundamental particles that make up all matter. It includes quarks, leptons, and gauge bosons, and successfully predicts a wide range of phenomena, including the existence of the Higgs boson.
Beyond the Standard Model
Despite its successes, the Standard Model is incomplete, as it does not incorporate gravity or explain the nature of dark matter and dark energy. The search for a more comprehensive theory, such as string theory or loop quantum gravity, continues to be a major focus of research in fundamental physics.
Cosmology
Cosmology is the study of the origin, evolution, and eventual fate of the universe. It combines elements of astronomy and physics to understand the large-scale structure of the cosmos.
The Big Bang Theory
The Big Bang theory is the prevailing cosmological model that describes the early development of the universe. It posits that the universe began as a singularity approximately 13.8 billion years ago and has been expanding ever since. This expansion is evidenced by the cosmic microwave background radiation and the observed redshift of distant galaxies.
Dark Matter and Dark Energy
Dark matter and dark energy are two of the most significant mysteries in cosmology. Dark matter is a form of matter that does not emit or interact with electromagnetic radiation, making it invisible and detectable only through its gravitational effects. Dark energy is a mysterious force driving the accelerated expansion of the universe, accounting for approximately 68% of the total energy density of the cosmos.