show that the lowest two non-vanishing multipole components of the gravitational field of a cubical planet are the monopole and the octupole. what's the next-lowest non-vanishing multipole?
(a solution without a multipole expansion and the added bonus question on the shape of the surface of a lake on such a planet is discussed in http://arxiv.org/pdf/1206.3857v1.pdf)
with that, we wish all readers of CQW a nice summer vacation and hope to see you again in october. if you came across an interesting question that would fit our blog, you're invited to appear as a guest author: please contact us for that purpose under cosmologyquestionoftheweek"[AT]"gmail"[DOT]"com.
Wednesday, July 29, 2015
Wednesday, July 22, 2015
imagine a device which is able to measure the thermal radiation power $S(\nu)$ at a given frequency $\nu$. would it be possible to determine unambiguously the temperature of a blackbody by carrying out measurements at two frequencies $\nu_1$ and $\nu_2$?
Eingestellt von spirou um 7/22/2015 12:00:00 AM
Wednesday, July 15, 2015
Wednesday, July 8, 2015
imagine to extend Maxwell electrodynamics with a magnetic charge density $\rho_m$. would the resulting set of equations still obey energy-momentum conservation? what changes would this yield in the Poynting-law?
Eingestellt von spirou um 7/08/2015 12:00:00 AM