Introduction to Physics: Matter, Motion, and Energy

• Physics is the study of matter, its constituents, motion, and behavior through space and time, along with energy and force.
• Physicists specialize in physics, a fundamental scientific discipline and one of the oldest academic fields

Historical Context

• Physics, chemistry, biology, and some mathematics were part of natural philosophy for millennia.
• The Scientific Revolution in the 17th century led to these natural sciences branching off into separate research areas.
• Physics intersects with interdisciplinary areas like biophysics and quantum chemistry.
• New physics ideas explain fundamental mechanisms for other sciences, suggesting new research avenues.
• Advances in physics often lead to new technologies.
• Electromagnetism, solid-state physics, and nuclear physics advances led to television, computers, appliances, and nuclear weapons.
• Thermodynamics advancements spurred industrialization, mechanics advancements inspired calculus.

Early Astronomy

• Early civilizations like the Sumerians, Egyptians, and Indus Valley Civilization had predictive knowledge of the Sun, Moon, and stars before 3000 BCE.
• Stars and planets were often worshipped as gods.
• Early observations of stars traversing great circles laid the groundwork for later astronomy.
• Western astronomy's origins are in Mesopotamia, with all Western exact sciences stemming from late Babylonian astronomy, according to Asger Aaboe.
• Egyptian astronomers created monuments showing knowledge of constellations and celestial body motions.
• Greek astronomers later provided names for most constellations visible from the Northern Hemisphere.

Natural Philosophy's Origins

• Natural philosophy originated in Greece during the Archaic period (650 BCE – 480 BCE).
• Pre-Socratic philosophers like Thales rejected non-naturalistic explanations for natural phenomena and sought natural causes for all events.
• They proposed ideas verified by reason and observation.
• Atomism, proposed by Leucippus and Democritus, was confirmed about 2000 years later.

Classical Greece

• During the classical period (6th-4th centuries BCE) and Hellenistic times, natural philosophy developed along many lines of inquiry.
• Aristotle (384–322 BCE) wrote on many subjects.
• Aristotle wrote a treatise on "Physics" in the 4th century BC.
• Aristotelian physics was influential for about two millennia.
• Aristotle's approach mixed limited observation with logical deductive arguments, without much experimental verification.
• His approach is entirely superseded today.
• Aristotle explained motion and gravity with the theory of four elements: air, fire, water, and earth, each with its natural place based on density.
• His laws of motion stated heavier objects fall faster, with speed proportional to weight and inversely proportional to the density of the medium.
• Violent motion depends on the force applied.
• The philosophical concept of a "prime mover" was suggested as the source of all motion.

Middle Ages

• The Western Roman Empire's fall in the 5th century led to a decline in intellectual pursuits in Western Europe.
• The Eastern Roman (Byzantine) Empire continued to advance learning, including physics.
• In the 6th century, John Philoponus challenged Aristotelian science.
• In the sixth century, Isidore of Miletus created an important compilation of Archimedes' works that are copied in the Archimedes Palimpsest.
• Islamic scholars inherited and advanced Aristotelian physics, emphasizing observation and a priori reasoning, developing early forms of the scientific method.
• Notable innovations occurred in optics and vision, from scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna.
• Ibn al-Haytham's Book of Optics presented an alternative to the ancient Greek idea about vision.
• His discussed his experiments with camera obscura, showing that light moved in a straight line.
• He encouraged readers to reproduce his experiments making him one of the originators of the scientific method

Early Modern Europe

• Physics became a separate science as Europeans used experimental and quantitative methods to discover laws of physics.
• The geocentric model was replaced with the heliocentric Copernican model.
• Kepler determined the laws governing planetary motion between 1609 and 1619.
• Galileo pioneered work on telescopes and observational astronomy in the 16th and 17th centuries.
• Isaac Newton discovered and unified the laws of motion and universal gravitation.
• Newton and Gottfried Wilhelm Leibniz developed calculus, which Newton applied to physical problems.
• Laws in thermodynamics, chemistry, and electromagnetics resulted from Industrial Revolution research.

19th Century

• By the end of the 19th century, theories of thermodynamics, mechanics, and electromagnetics matched many observations.
• These theories formed the basis for classical physics.
• Some experimental results remained inexplicable.
• Classical electromagnetism presumed a luminiferous aether for wave propagation, which could not be detected.
• The intensity of light from blackbody objects and electron emission from illuminated metals didn't match predictions.

Modern Physics

• Modern physics began in the early 20th century with Max Planck's quantum theory and Albert Einstein's theory of relativity.
• These theories arose from inaccuracies in classical mechanics.
• Classical mechanics predicted light speed depends on the observer's motion, conflicting with Maxwell's equations.
• Einstein's special relativity corrected this, replacing classical mechanics for fast-moving bodies and allowing a constant speed of light.
• Planck proposed that material oscillator excitation occurs in discrete steps proportional to frequency, solving the black-body radiation problem.
• Quantum mechanics, pioneered by Werner Heisenberg, Erwin Schrödinger, and Paul Dirac, improved on classical physics at small scales.
• The Standard Model of particle physics was derived, and following the discovery of a Higgs boson-consistent particle at CERN in 2012, predicted fundamental particles appear to exist; research continues beyond the Standard Model.

Core Theories

• Experimental testing has validated various theories as approximations of nature.
• Central theories include classical mechanics, quantum mechanics, thermodynamics and statistical mechanics, electromagnetism, and special relativity.
• Proficiency in these theories is expected of all physicists.

Classical vs Modern Physics

• Discoveries in quantum mechanics and relativity revolutionized physics in the early 20th century.
• These new concepts became the foundation of "modern physics", with other topics becoming "classical physics".
• The majority of physics applications are classical.
• Classical physics accurately describes systems with length scales greater than atomic and motions much slower than light speed.
• Classical physics includes mechanics, thermodynamics, and electromagnetism.
• Classical mechanics deals with forces and motion, divided into statics, kinematics, and dynamics, and solid and fluid mechanics.
• Acoustics studies sound production, control, transmission, and reception.
• Optics studies light, including infrared and ultraviolet radiation and associated phenomena.
• Heat is a form of energy; thermodynamics studies the relationships between heat and other forms of energy.
• Electricity and magnetism are a single branch since the connection was discovered in the early 19th century.

Modern vs Classical Physics

• Modern physics transformed the conceptual basis of physics without diminishing the practical value of earlier theories.
• Topics are divided into "classical physics" and "modern physics," with the latter including quantum mechanics and relativity.
• Classical physics is concerned with matter and energy at normal scales, while modern physics deals with extreme conditions or very large or small scales.
• Atomic and nuclear physics study matter on the smallest scale.
• Elementary particle physics, also known as high-energy physics, examines the most basic units of matter.
• Ordinary notions of space, time, matter, and energy are no longer valid at this scale.
• Modern physics' two chief theories present a different view of space, time, and matter compared to classical physics.
• Classical mechanics approximates nature as continuous.
• Quantum theory deals with the discrete nature of phenomena at the atomic and subatomic level.
• The theory of relativity describes phenomena in a frame of reference in motion.
• Both quantum theory and relativity are applied in modern physics.

Scientific Method

• Physicists use the scientific method to test the validity of physical theories.
• Experiments and observations validate or invalidate theories, thus the necessity for repeatable experiments.
• Theorists develop mathematical models that agree with past experiments and predict future results.
• Experimentalists devise and perform experiments to test theoretical predictions and explore new phenomena.
• Theory and experiment are developed separately but depend on each other.
• Progress occurs when experimental results defy existing theories, prompting new modelling, and when new theories generate experimentally testable predictions.
• Phenomenologists study complex phenomena observed in experiment and relate them to fundamental theories.
• Theoretical physics has historically taken inspiration from philosophy.
• Theoretical physics deals with hypothetical issues like parallel universes, multiverses, and higher dimensions.
• These ideas aim to solve problems with existing theories and make testable predictions.
• Experimental physics expands and is expanded by engineering and technology.
• Experimental physicists in basic research design and perform experiments with equipment like particle accelerators and lasers.
• Applied research physicists often work in industry, developing technologies like MRI and transistors.
• Experimentalists may seek areas unexplored by theorists

Scope of Physics

• Physics covers a wide range of phenomena, from elementary particles to superclusters of galaxies.
• Because it includes the most basic objects composing all other things, physics is called the "fundamental science".
• Physics describes phenomena in terms of simpler phenomena.
• Physics connects observable things to root causes and then connects these causes together.
• Ancient observations of magnetism and electricity were later understood as electromagnetism.
• Electromagnetism and the weak nuclear force are now considered aspects of the electroweak interaction.
• Physics seeks to find an ultimate theory of everything.
• Research in physics is continually progressing on many fronts.
• An important unsolved theoretical problem in condensed matter physics is high-temperature superconductivity.
• Many condensed matter experiments aim to fabricate workable spintronics and quantum computers.
• In particle physics, evidence for physics beyond the Standard Model has begun to appear.
• Indications that neutrinos have non-zero mass have solved the solar neutrino problem.
• The Large Hadron Collider has found the Higgs boson, but future research aims to prove or disprove supersymmetry.
• Research is ongoing on the nature of dark matter and dark energy.
• Many everyday phenomena involving complexity, chaos, or turbulence are poorly understood.
• These complex phenomena have received growing attention since the 1970s due to modern methods and computers.
• Complex physics has become part of interdisciplinary research, such as turbulence in aerodynamics and pattern formation in biological systems.

Branches of Physics

• Branches include classical mechanics, thermodynamics and statistical mechanics, electromagnetism and photonics, relativity, quantum mechanics, atomic physics, molecular physics, optics and acoustics, condensed matter physics, high-energy particle physics and nuclear physics, cosmology, and interdisciplinary fields.
• Since the 20th century, individual fields have become increasingly specialised.

Particle Physics

• Particle physics studies matter and energy's elementary constituents and their interactions.
• Particle physicists design and develop the accelerators, detectors, and computer programs necessary for this research.
• The field is also called "high-energy physics" because many elementary particles are created during high-energy collisions.
• Currently, the interactions of elementary particles and fields are described by the Standard Model.
• The model accounts for the 12 known particles of matter (quarks and leptons) interacting via fundamental forces.
• Dynamics are described in terms of matter particles exchanging gauge bosons.The Standard Model also predicts the Higgs boson.
• In July 2012, CERN announced the detection of a particle consistent with the Higgs boson

Nuclear Physics

• Nuclear physics studies the constituents and interactions of atomic nuclei.
• Applications include nuclear power and weapons, nuclear medicine, MRI, ion implantation, and radiocarbon dating.

Atomic, Molecular, and Optical Physics (AMO)

• AMO studies matter—matter and light—matter interactions on the scale of single atoms and molecules.
• The areas are grouped together due to interrelationships, similar methods, and common energy scales.
• All three areas include classical, semi-classical and quantum treatments and treat their subject microscopically.
• Atomic physics studies the electron shells of atoms, focusing on quantum control, cooling and trapping of atoms and ions, low-temperature collision dynamics, and electron correlation effects.
• Molecular physics focuses on multi-atomic structures and their internal and external interactions with matter and light.
• Optical physics focuses on the fundamental properties of optical fields and their interactions with matter in the microscopic realm.

Condensed Matter Physics

• Condensed matter physics deals with the macroscopic physical properties of matter.
• It is concerned with the "condensed" phases when the number of particles is extremely large and the interactions between them are strong.
• The most familiar examples of condensed phases are solids and liquids.
• More exotic phases include superfluid, Bose–Einstein condensate, superconducting, ferromagnetic and antiferromagnetic phases.
• Condensed matter physics is the largest field of contemporary physics.
• The term was coined by Philip Anderson in 1967.
• Condensed matter overlaps with chemistry, materials science, nanotechnology, and engineering.

Astrophysics and Astronomy

• Astrophysics and astronomy apply physics theories and methods to study stellar structure, stellar evolution, and the origin of the Solar System.
• Astrophysicists apply disciplines including mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum mechanics, relativity, nuclear and particle physics, and atomic and molecular physics.
• Karl Jansky's discovery in 1931 initiated radio astronomy.
• Space exploration has expanded astronomy's frontiers.
• Space-based observations are necessary for infrared, ultraviolet, gamma-ray, and X-ray astronomy due to atmospheric interference.

Physical Cosmology

• Physical cosmology studies the formation and evolution of the universe on its largest scales.
• Einstein's theory of relativity plays a central role in modern cosmological theories.
• Hubble's discovery of the expanding universe prompted the steady state and Big Bang theories.
• The Big Bang was confirmed by Big Bang nucleosynthesis and the discovery of the cosmic microwave background in 1964.
• The Big Bang model rests on general relativity and the cosmological principle.
• Cosmologists have established the ΛCDM model of the universe's evolution, including cosmic inflation, dark energy, and dark matter.

Physicist

• A physicist specializes in the interactions of matter and energy at all scales.
• Physicists are interested in the root causes of phenomena and frame their understanding mathematically.
• They work across a wide range of research fields, from sub-atomic and particle physics, through biological physics, to cosmological length scales.
• The field includes experimental physicists who specialize in observation and experiment analysis, and theoretical physicists who specialize in mathematical modeling.
• Physics relies on the philosophy of science and the "scientific method".
• The scientific method employs a priori and a posteriori reasoning and Bayesian inference.
• The philosophy of physics involves issues such as space and time, determinism, and metaphysical outlooks.
• Many physicists have written about the philosophical implications of their work.

Mathematics in Physics

• Mathematics provides a compact and exact language to describe nature.
• Some theorists hold that logical truths and mathematical reasoning depend on the empirical world.
• Physics uses mathematics to organise and formulate experimental results.
• Results give solutions or quantitative results, from which new predictions can be made and confirmed or negated.
• Results from physics experiments include numerical data with units of measure and error estimates.
• Technologies based on mathematics have made computational physics an active area of research.
• Ontology is a prerequisite for physics, but not for mathematics, meaning physics describes the real world, while mathematics is concerned with abstract patterns.
• Physics statements are synthetic, while mathematical statements are analytic.
• Mathematics contains hypotheses, while physics contains theories.
• Mathematical statements have to be only logically true, while predictions of physics statements must match observed and experimental data.

Applied Physics

• Physics is a branch of fundamental science; its laws constrain all branches of natural science.
• Chemistry studies properties, structures, and reactions of matter, distinguished from physics by its focus on the molecular and atomic scale.
• Fundamental physics explains phenomena in all spheres, without a specific practical application.
• Applied physics is physics research and development that is intended for a particular use.
• Applied physicists may not be designing something in particular, but rather using physics to develop new technologies or solve a problem.
• Applied physicists use physics in scientific research. One application could be better particle detectors.

Application of Physics

• Physics is used heavily in engineering.
• Statics is a field of Mechanics, and is used in the building of bridges and other static structures.
• The understanding and use of acoustics results in sound control and better concert halls.
• Optics creates better optical devices.
• An understanding of physics makes for more realistic flight simulators, video games, and forensic investigations.
• With the laws of physics being universal and unchanging, models of Earth's mass, temperature, and rate of rotation can be used to estimate those figures at a given moment in the past.
• Simulations in engineering can speed up the development of new technology.
• There is considerable interdisciplinarity, so many other important fields are influenced by physics.

Physics studies matter, motion, energy, and force. It's a fundamental science that has shaped technological advancements. From early natural philosophy to modern interdisciplinary applications, physics provides essential mechanisms and insights for various scientific fields.