History of Heat in Timeline

In thermodynamics, heat is defined as the transfer of thermal energy between systems having different temperatures. While in casual conversation, heat is often used interchangeably with thermal energy. Thermal energy itself represents the kinetic energy associated with the random movements of atoms and molecules within a substance.

1907: Publication of G.H. Bryan's Investigation of Thermodynamics

In 1907, G.H. Bryan published his work, 'Thermodynamics: an Introductory Treatise dealing mainly with First Principles and their Direct Applications,' exploring the foundations of thermodynamics.

1909: Carathéodory's Approach to Thermodynamics without Unverified Hypotheses

Carathéodory, in 1909, aimed to establish thermodynamics without relying on unverified hypotheses, a significant departure from the traditional view that treated heat, temperature, and thermal equilibrium as primitive notions. He emphasized the importance of experimental verification in thermodynamic theory.

1909: Carathéodory's Definition of Heat in Closed Systems

Carathéodory, in 1909, put forth a well-known definition of heat in thermodynamics, focusing on processes within closed systems. His work was a response to Max Born's suggestion to examine the logical structure of thermodynamics.

1909: Carathéodory's Concepts of Adiabatic and Diathermal Walls

In 1909, Carathéodory defined adiabatic walls, which allow energy transfer as work but not as heat or matter. He contrasted these with diathermal walls, which are postulated to be permeable only to heat, outlining his concepts of adiabatic and diathermal walls.

1909: Carathéodory's Work on the Logical Structure of Thermodynamics

In 1909, Carathéodory, a mathematician, delved into the logical structure of thermodynamics, following a suggestion by Max Born. This period saw significant interest in defining the logical underpinnings of thermodynamics, which had been empirically established.

1926: Planck's Advocacy for Defining Heat through Friction

In 1926, Planck strongly advocated for defining heat through the generation of heat by rubbing, considering it the most specific definition. He criticized Carathéodory for overlooking this aspect. Planck's emphasis on friction as a fundamental aspect of heat contrasted with Carathéodory's focus on adiabatic processes.