Physics is the science of how the universe works at its most basic level. It studies matter (the stuff everything is made of) and energy (the ability to do work), and the forces that connect them. Physics explains why a ball falls when you drop it, why a magnet attracts iron, how light travels, how a battery powers your phone and how stars shine. From the very tiny (atoms, quarks, electrons) to the very big (galaxies, black holes, the whole universe), physics tries to find the simple rules that explain everything.
- What it studiesMatter, energy, forcesPlus space, time and the universe
- Speed of light299,792,458 m/sThe cosmic speed limit
- Speed of soundAbout 343 m/s in airMuch slower than light
- Newtons three lawsInertia, F=ma, action-reactionFoundation of motion
- Earths gravity9.8 m/s2Speeds up falling objects
- Atoms in a personAround 7 x 10^27Mostly hydrogen, oxygen and carbon
The main branches of physics
- Classical mechanics: how objects move and what makes them move. The physics of footballs, planets, cars and bridges.
- Electromagnetism: electricity, magnetism and how they connect. Powers nearly every modern device.
- Optics: the study of light: how it travels, reflects, refracts and behaves.
- Thermodynamics: heat, temperature, and how energy moves around.
- Quantum physics: the strange behaviour of very small things (atoms, electrons, photons).
- Relativity: how space, time and gravity work, especially near very fast speeds or very heavy objects.
- Astrophysics and cosmology: the physics of stars, galaxies and the whole universe.
What physicists do
Physicists ask "why" and "how" about the world and try to answer with experiments, theories and equations. They:
- Design experiments to test how things behave.
- Build mathematical models to predict outcomes.
- Invent new technologies based on what they discover (computers, MRI scanners, lasers, the internet, GPS).
- Try to find the simplest rules that explain everything (a "theory of everything" is still being searched for).
Why physics matters
Almost every modern invention you use depends on physics. Smartphones, satellites, MRI scanners, electric cars, lasers, solar panels, the internet, microwave ovens and nuclear power all came from physics research. Even older inventions like the steam engine, the light bulb and the radio rely on physical laws first worked out by scientists like Newton, Faraday and Maxwell. Studying physics is one of the best ways to understand how the world works and to help build the technology of the future.
Explore physics
Start with one of the sub-sections below, each covering a major topic in physics:
- Forces and motion: pushes, pulls, gravity and Newtons laws.
- Energy: what energy is and how it moves between forms.
- Electricity and magnetism: how electricity flows and how magnets work.
- Light and optics: how light behaves and what makes rainbows.
- Sound and waves: how sound travels and the science of music.
- Gravity: the force that holds the universe together.
- Simple machines: the six basic devices that make work easier.