ASTRON 1F03 Lecture Notes - Lecture 26: Cosmological Principle, Parsec, Cosmological Constant
18 Dec 2015
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Chapter 17: modern cosmology and the origin of structure. A rocket launched from the moon can escape or fall back again due to the gravity of. A massive expanding ball of gas or dust can collapse again due to its own gravity if it. The cosmological principle enshrines the idea that we are not at a special place and there are no special directions. The cosmological principle states that on large enough scales, the universe appears homogeneous and isotropic: homogeneous: we are not at a special place. The universe is similar everywhere: isotropic: there are no special directions. The cosmological principle indicates the universe on large scales is like a homologous ball of matter. The gravity of any patch of space slows down the expansion of that patch of space. The universe is like a big ball of material (radiation, gas and dark matter) that feels its own gravity.
