Theories of Everything with Curt Jaimungal What is “Energy,” Actually?
51 snips
Jun 6, 2025 Delve into the perplexing nature of energy, revealing that it may not even be a well-defined concept. The discussion highlights the complexities of energy within the framework of general relativity, questioning traditional definitions and interpretations. Gravitational energy poses unique challenges, particularly in the context of gravitational waves. Thought-provoking insights showcase the struggle to understand energy's role in dynamically curved space-time, igniting curiosity about its true essence.
AI Snips
Chapters
Transcript
Episode notes
Energy Not Well-Defined in GR
- Energy is not well-defined in general relativity and is not simply conserved as in classical physics.
- The energy of the gravitational field depends on coordinate choice, highlighting fundamental issues with defining gravitational energy.
Einstein's Pseudotensor Problem
- Einstein introduced a pseudotensor to represent gravitational energy to maintain energy conservation.
- However, this pseudotensor breaks general covariance and depends on coordinate choices, making it unphysical.
Energy Requires Spacetime Symmetry
- If spacetime has a timelike killing vector, energy can be defined in a coordinate-independent, conserved way.
- Most realistic spacetimes lack such symmetry, so this energy definition is limited and not universal.