Wednesday, March 26, 2014

fundamentals of cosmology

can you give an intuitive explanation why one needs general relativity for describing the dynamics of the Universe?

Wednesday, March 19, 2014

fat Hubble sphere

the Hubble sphere is a spherical surface around an observer in a FLRW-universe at which the recession velocity becomes larger than the speed of light. at what scale factor are the recession velocities stationary?


Wednesday, March 12, 2014

astronomy units in cosmology

can you express the flux density of the cosmic microwave background in Jansky per squared arcminute?

Wednesday, March 5, 2014

axioms of Lagrangian mechanics

imagine you'd want to formulate mechanics based on an extremal principle. what would you need to require such that all three Newton-axioms are fulfilled?