Discussion Overview
The discussion revolves around calculating the total energy of a system formed by the merger of two elliptical galaxies with the same mass, size, and velocity dispersion. Participants explore concepts related to energy definitions, the virial theorem, and the implications of galaxy dynamics during the merging process.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- One participant questions how to define the "energy of a galaxy," suggesting that clarity is needed on kinetic and potential energy in this context.
- Another participant states the relationship K.E = -1/2 P.E as per the virial theorem, assuming stability in the galaxies.
- There is a reiteration of the kinetic energy formula K.E = 1/2 Mv^2, with a focus on the definition of "velocity" for a galaxy, which is noted to be complex due to varying velocities of individual stars.
- Some participants propose using average velocity as a potential solution to the velocity definition issue.
- A participant reflects on the complexity of the topic and suggests that they may not be the best person to contribute further to the discussion.
- Another participant suggests that the total energy of the merged system could be viewed as the sum of the energies of the two separate galaxies, with considerations for energy changes during the merger process, including potential energy loss due to ejected material.
Areas of Agreement / Disagreement
Participants express differing views on how to define and calculate the energy of galaxies, with no consensus reached on the best approach or the implications of energy changes during the merger.
Contextual Notes
There are limitations in the definitions of kinetic and potential energy specific to galaxies, as well as assumptions regarding stability and the reference point for measuring energy. The discussion also highlights the complexity of velocities within galaxies.