Theoretical physics

Theoretical physics is a fascinating part of science that uses math and ideas to explain how nature works. Instead of doing experiments in a lab, scientists in theoretical physics create models and theories to understand the world around us. These models help explain things we see and even predict things we haven’t discovered yet.

Science grows when experiments and theories work together. Sometimes, theorists focus mainly on math and ideas, paying less attention to real-world experiments. For example, when Albert Einstein developed his theory of special relativity, he was more interested in solving math problems than in the experiments being done at the time.

On the other hand, 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 with theory before. This shows how both experiments and theories are important in advancing our knowledge.

Overview

A physical theory is a way to explain how things in nature work, 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 has a long history, starting more than 2,300 years ago with early thinkers like Plato and Aristotle. For many years, learning focused only on subjects like grammar, logic, arithmetic, geometry, music, and astronomy. Later, during a time called the Scientific Revolution, great scientists such as Galileo Galilei, Johannes Kepler, and Isaac Newton began to mix careful experiments with smart theories to explain how nature works.

In the 1800s and 1900s, amazing new ideas changed physics forever. Scientists discovered important rules about energy, heat, and electricity. Then, Albert Einstein created relativity theory, and others built the foundation of quantum mechanics. These ideas helped us understand things like light, the structure of atoms, and even the whole Universe. Today, theoretical physicists keep working to explain more about our world using math and models, even when experiments are not possible.

Mainstream theories

Mainstream theories are well-supported 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 scientists use to understand how nature works. These theories often haven't been tested yet, but they help scientists think about new ways to explain things. Some of these ideas have been around for a long time but are still being studied.

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

Fringe theories

Fringe theories are new scientific ideas that are still being tested and might become widely accepted in the future. Some of these theories turn out to be correct and are later included in 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 and predictions.

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 that 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, for instance, 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.