The discussion focuses on calculating the kinetic energy of rotating planets, exploring the necessary assumptions and methods for determining mass momentum and rotational characteristics. It includes considerations of theoretical models and practical applications.
Participants express differing views on the assumptions necessary for calculating kinetic energy, particularly regarding the uniform density model and its applicability to various planets. The discussion remains unresolved with multiple competing perspectives on the topic.
Participants highlight limitations related to the assumptions made about the uniformity of planetary density and the implications for moment of inertia calculations. There are also unresolved mathematical steps in the kinetic energy calculations presented.
Alternatively, do a google search for the Earth's moment of inertia. The simplistic assumption of a uniform sphere yields a value that is off by more than 20%. In other words, while it is in the right ball park, it is not very good.mgb_phys said:You probably have to make some assumptions that the planet is a uniform solid sphere (a bit of an overestimate for a real planet)
Nobody said anything about Earth !D H said:Alternatively, do a google search for the Earth's moment of inertia..
Fine. Look up the moment of inertia for any planet. The uniform density assumption overstates the moment of inertia for the Sun by almost an order of magnitude, the gas giants by 60% to 100%, and the terrestrial planets by 10% (Mars) to 20% (Earth).mgb_phys said:Nobody said anything about Earth !