Richard Feynman Explains What a State Is

This long-form physics lecture is an original explanation, focused on one of the most fundamental but often misunderstood concepts in physics: the idea of a physical state.

In physics, a state is not a vague condition or a casual description. It is the complete physical information required to determine how a system can change. This video explores what physicists mean by a state, why states are central to all physical laws, and how this concept connects classical mechanics, thermodynamics, chaos, and quantum mechanics into a single coherent framework.


Topics covered include:

What a physical state is in classical physics

Why physics ignores history and focuses on present conditions

How states determine what can and cannot happen next

Why different systems can share the same state

States in thermodynamics and large systems

Sensitivity to states in chaotic systems

What a quantum state represents

Why measurement is a physical interaction

The limits of prediction versus the limits of physical law

What physics can explain about states — and what it cannot

This video emphasizes an important distinction: physics does not describe reality by telling stories about the past. It describes reality by identifying what information must be carried forward to determine future behavior. That information is the state.

The explanation is suitable for beginners, students, and anyone interested in modern physics, theoretical physics, and physics education. No advanced background is required, but the discussion remains accurate and faithful to how physicists actually use the concept.


By the end of the video, viewers should be able to clearly explain:

What a state is in physics

Why states are central to all physical laws

How states connect different areas of physics

Why prediction has limits even in a lawful universe

If you enjoy physics lectures, modern physics explanations, and the teaching philosophy associated with Richard Feynman, this video is designed to give you a deep and usable grasp of one of physics’ most important ideas.

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