Outline of physics facts for kids

This outline helps you explore the exciting world of physics!

Physics is a natural science that studies matter and how it moves through spacetime. It also looks at related ideas like energy and force. Simply put, physics tries to understand how the universe works.

What is Physics All About?

Physics is a big and important subject. Here's what makes it special:

• It's an academic discipline. This means it has its own school subjects, degrees, and groups for scientists.
• It's a scientific field. Physics is a main part of science with its own special words and research.
  • It's a natural science. Physics uses experiments and the scientific method to find out how the natural world works.
    • It's a physical science. This part of physics studies things that are not alive.
    • It's also a biological science. This looks at how physics helps us understand living things. For more, see Outline of biophysics.

Main Areas of Physics

Physics has many different branches, each focusing on a specific part of the universe.

Exploring Space: Astronomy

Astronomy studies everything beyond Earth. This includes how the universe began, how galaxies and planets form, and how they move.

• Astrodynamics is about how rockets and spacecraft move in space.
• Astrometry measures the exact positions and movements of stars.
• Astrophysics looks at the physical side of space objects.
• Celestial mechanics calculates how planets and other space objects move.
• Extragalactic astronomy studies objects outside our own Milky Way Galaxy.
• Galactic astronomy focuses on our Milky Way galaxy and everything inside it.
• Physical cosmology studies the biggest structures and changes in the universe. It asks big questions about how the universe started and grew.
• Planetary science is the study of planets (including Earth), moons, and other planetary systems.
• Stellar astronomy studies stars, planets, comets, and galaxies. It also looks at things like cosmic background radiation from space.

Earth and Atmosphere

• Atmospheric physics studies how physics applies to Earth's atmosphere.
• Geophysics is the physics of Earth and its space environment. It uses physics to study our planet.

Tiny Particles and Light

• Atomic, molecular, and optical physics studies how tiny bits of matter and light interact.
  • Optics is the study of light. It looks at how light behaves, how it interacts with matter, and how instruments like telescopes work.
• Particle physics studies the smallest parts of matter and energy.
• Nuclear physics looks at the tiny building blocks and forces inside atomic nuclei.
• Plasma physics studies plasma, which is a state of matter like a gas but with charged particles.

Life and Materials

• Biophysics uses physics methods to study living systems.
  • Neurophysics focuses on the nervous system using physics.
  • Polymer physics studies polymers, which are large molecules, and how they behave.
  • Quantum biology applies quantum mechanics to living things.
• Chemical physics studies chemical processes from a physics point of view.
• Condensed matter physics studies the physical properties of solid and liquid materials.
• Materials physics uses physics to describe materials in many ways, like how they react to force, heat, or light.

Forces and Motion

• Electricity is the study of electrical events.
• Electromagnetism studies the forces between electrically charged particles.
• Magnetism studies physical events caused by magnetic fields.
• Mechanics is about how physical objects behave when forces push or pull them.
  • Aerodynamics studies how air moves.
  • Biomechanics uses mechanics to study how biological systems like humans or animals work.
  • Classical mechanics describes how objects move under different forces.
    • Kinematics describes motion without looking at what causes it.
  • Continuum mechanics studies materials as a continuous mass, not separate particles.
  • Dynamics studies what causes motion and changes in motion.
  • Fluid mechanics studies fluids (liquids and gases) and the forces on them.
    • Fluid statics studies fluids that are not moving.
    • Fluid kinematics studies fluids that are moving.
    • Fluid dynamics studies how forces affect fluid motion.
  • Statics studies forces on systems that are not moving or are moving at a constant speed.

Energy and Heat

• Statistical mechanics studies physical systems with many parts.
• Thermodynamics is about heat and how it relates to other forms of energy and work.
• Cryogenics studies very low temperatures (below -150°C) and how materials act at these temperatures.

Advanced Concepts

• Computational physics uses computer programs to solve physics problems.
• Mathematical physics uses math to solve physics problems and create new theories.
• Medical Physics applies physics to medicine, like in imaging (such as NMR and PET scans) and radiotherapy.
• Psychophysics measures the link between physical things we sense and how we perceive them.
• Quantum physics studies physical events at a very tiny scale, where the action is related to Planck's constant.
  • Quantum field theory applies quantum ideas to fields.
  • Quantum information theory studies how quantum mechanics can process information.
  • Quantum foundations tries to understand the strange parts of quantum theory.
• Quantum gravity tries to combine gravity with quantum theory.
• Relativity describes how space and time are connected.
  • General Relativity is a theory of gravity that doesn't use quantum ideas.
  • Special Relativity describes how matter and light behave at very high speeds.

Other Interesting Areas

• Agrophysics applies physics to farming and ecosystems.
  • Soil physics studies the physical properties of soil.
• Econophysics uses physics ideas to solve problems in economics.
• Vehicle dynamics studies how ground vehicles move.
• Philosophy of physics looks at the big ideas and meanings behind modern physics.

History of Physics

The History of physics tells us how our understanding of matter, motion, energy, and force has grown over time.

• History of acoustics looks at the study of sound and vibrations.
• History of agrophysics explores how physics was first applied to farming.
• History of astrophysics traces the study of the physical side of space objects.
• History of astronomy covers the study of the universe beyond Earth.
  • History of astrodynamics looks at how we learned to move rockets in space.
  • History of astrometry shows how we started measuring star positions.
  • History of cosmology explores how our ideas about the universe as a whole developed.
  • History of the Big Bang theory explains the origin of the universe.
• History of atomic, molecular, and optical physics covers how we learned about matter and light interacting.
• History of biophysics looks at how physics began to be used to study living things.
• History of condensed matter physics traces the study of solid and liquid materials.
• History of electromagnetism tells the story of electricity, magnets, and light.
  • History of Maxwell's equations shows how these key equations of electromagnetism were developed.
• History of geophysics covers the physics of Earth.
• History of gravitational theory explores the earliest physics theory about gravity.
• History of mechanics looks at how we understood the movement of objects.
  • History of biomechanics shows how mechanics was applied to biological systems.
  • History of classical mechanics traces the laws of motion.
  • History of fluid mechanics covers the study of fluids.
• History of nuclear physics explores the study of atomic nuclei.
• History of nuclear fusion looks at the process that powers stars.
• History of materials science shows how we learned to understand and change materials.
• History of optics covers the history of light and optical instruments.
• History of quantum mechanics explores the development of quantum theory.
• History of relativity covers the theories of special and general relativity.
• History of thermodynamics traces the study of heat and energy.
• History of superconductivity looks at the discovery of ultra-cold states of matter.

Key Ideas in Physics

Basic Principles

Physics is a "fundamental science" because other natural sciences, like biology, follow its laws. Physics says that the laws of matter, energy, and basic forces control how particles and objects interact. Some main goals of physics include:

• Describing and measuring objects and their motion.
  • Newton's laws of motion explain how forces affect motion.
  • Understanding Mass, force, and weight (and the difference between mass and weight).
  • Learning about Momentum and the conservation of energy.
  • Studying Gravity and different theories about it.
  • Understanding Energy, work, and how they are related.
  • How motion, position, and energy are connected.
  • Different forms of Energy, how they change into each other, and how some energy is always lost as heat (Thermodynamics).
  • Energy conservation, conversion, and transfer.
  • Energy sources and how energy moves from one place to another to do work.
• Kinetic molecular theory explains how gases behave.
  • Phases of matter (like solid, liquid, gas) and how they change.
  • Temperature and how thermometers measure it.
  • The connection between Energy and heat.
  • Heat flow: conduction, convection, and radiation.
  • The four laws of thermodynamics.
• The rules of waves and sound.
• The rules of electricity, magnetism, and electromagnetism.
• The rules, sources, and features of light.
• Basic measurements:
  • Acceleration (how quickly speed changes)
  • Electric charge
  • Energy
  • Entropy (a measure of disorder)
  • Force (a push or pull)
  • Length
  • Mass (how much "stuff" is in an object)
  • Matter (anything that has mass and takes up space)
  • Momentum (mass in motion)
  • Potential energy (stored energy)
  • Space
  • Temperature
  • Time
  • Velocity (speed with direction)

Other important ideas: Gravity, light, physical system, physical observation, physical quantity, physical state, physical unit, physical theory, physical experiment.

Theoretical ideas: Mass–energy equivalence, elementary particle, physical law, fundamental force, physical constant.

Core Concepts

• Causality: Cause and effect.
• Symmetry: When something looks the same after a change.
• Action: A key idea in how systems change over time.
• Covariance: How physical laws look the same in different viewpoints.
• Space: The three dimensions we live in.
• Time: The fourth dimension, moving forward.
• Oscillations and Waves: Repeating movements and disturbances that carry energy.
• Physical field: A region where a force can be felt.
• Physical interaction: How objects affect each other.
• Statistical ensemble: A collection of many possible states of a system.
• Quantum: The smallest possible unit of energy or matter.
• Particle: A tiny piece of matter.

How We Measure Things

• Measurement: Finding the size or amount of something.
• SI units: The standard system of units used worldwide (like meters, kilograms, seconds).
• Conversion of units: Changing from one unit to another.
• Length: How long something is.
• Time: How long an event lasts.
• Mass: How much matter is in an object.
• Density: How much mass is in a certain space.

Understanding Motion

• Motion: The act of changing position.
• Velocity: How fast something is moving and in what direction.
• Speed: How fast something is moving.
• Acceleration: How quickly velocity changes.
• Constant acceleration: When velocity changes at a steady rate.
• Newton's laws of motion: Rules that describe how objects move and interact with forces.

Main Theories in Physics

Here are the main theories in physics, their major topics, and key ideas.

Ideas by Physics Field

More About Physics

Here are some lists that can help you learn more about physics:

• Index of physics articles
• List of common physics notations
• Lists of physics equations
• List of important publications in physics
• List of laws in science
• List of letters used in mathematics and science
• List of physicists
• List of physics journals
• List of scientific units named after people
• Variables commonly used in physics
• List of physics awards

See Also

• Category:Concepts in physics
• Category:Physics-related lists
• Elementary physics formulae
• Glossary of classical physics
• List of physics concepts in primary and secondary education curricula