Theoretical physics

Theoretical physics is a part of science that uses math and ideas to explain how nature works. Scientists in theoretical physics use models and theories instead of doing experiments in a lab. These models help us understand things we see and can even predict things we have not discovered yet.

Science grows when experiments and theories work together. Sometimes, theorists focus on math and ideas and do not worry much about real-world experiments. For example, when Albert Einstein developed his theory of special relativity, he was more interested in solving math problems than in experiments.

Theories are also important for explaining experiments. Einstein won a Nobel Prize for explaining something called the photoelectric effect, which experiments had observed but no one could explain before. This shows how both experiments and theories help us learn new things.

Overview

A physical theory is a way to explain how nature works, using ideas and math. It is judged by how well its predictions match what we actually see and measure. Unlike math ideas, physical theories must agree with real-world experiments.

Theoretical physics uses many different methods. Some scientists use simple formulas that match experiments, while others create new ideas to explain things we don’t fully understand yet. Some focus on making theories easier to use, even if they aren’t perfect. Others try to connect existing theories or create brand-new ones. Sometimes, math ideas can inspire new ways to think about physics. For example, the idea that space might be curved helped shape our understanding of gravity.

History

Further information: History of physics

Theoretical physics began more than 2,300 years ago with thinkers like Plato and Aristotle. For a long time, people studied subjects such as grammar, logic, arithmetic, geometry, music, and astronomy.

Later, during the Scientific Revolution, scientists like Galileo Galilei, Johannes Kepler, and Isaac Newton used experiments and theories to learn about nature.

In the 1800s and 1900s, new ideas changed physics. Scientists learned about energy, heat, and electricity. Then, Albert Einstein created relativity theory, and others started quantum mechanics. These ideas helped us understand light, atoms, and the Universe. Today, theoretical physicists use math and models to explain more about our world.

Mainstream theories

Mainstream theories are ideas in science that many experts agree on. These theories help us understand how nature works and can be tested through experiments.

Some important mainstream theories include:

• Big Bang
• Chaos theory
• Classical mechanics
• Classical field theory
• Dynamo theory
• Field theory
• Ginzburg–Landau theory
• Kinetic theory of gases
• Classical electromagnetism
• Perturbation theory (quantum mechanics)
• Physical cosmology
• Quantum chromodynamics
• Quantum complexity theory
• Quantum electrodynamics
• Quantum field theory
• Quantum field theory in curved spacetime
• Quantum information theory
• Quantum mechanics
• Quantum thermodynamics
• Relativistic quantum mechanics
• Scattering theory
• Standard Model
• Statistical physics
• Theory of relativity
• Wave–particle duality

Proposed theories

Proposed theories in physics are new ideas that help scientists understand how nature works. These theories have not been tested yet, but they give scientists new ways to think about and explain things.

Some famous proposed theories include AdS/CFT correspondence, Chern–Simons theory, graviton, magnetic monopole, string theory, and theory of everything. Scientists also study different ways to understand quantum mechanics, which is the study of very tiny parts of matter.

Fringe theories

Fringe theories are new ideas in science that are still being tested. They might become widely accepted in the future. Some of these theories turn out to be correct and join mainstream science, while others are proven wrong.

These theories can sometimes be called protoscience or pseudoscience, depending on how well they match with existing evidence.

Some examples of fringe theories in physics include Aether (classical element), Digital physics, Electrogravitics, Stochastic electrodynamics, and Tesla's dynamic theory of gravity.

Thought experiments vs real experiments

Main article: Thought experiment

Thought experiments are ideas we imagine in our minds to explore questions that are hard to test directly. They help us understand things we cannot easily see or experience every day. For example, famous thought experiments include Schrödinger's cat, the EPR thought experiment, and simple ideas about time passing slowly for fast-moving objects simple illustrations of time dilation. These imaginative exercises often inspire real experiments to check if the ideas are correct. The EPR thought experiment led to the Bell inequalities, which were tested in many ways. These tests helped scientists accept our current understanding of quantum mechanics and how we use chances to predict what will happen probabilism as a way to explain nature working hypothesis.