Tag Archive for: doppler
![expandinguniverse](https://www.physicsforums.com/insights/wp-content/uploads/2018/01/expandinguniverse.png)
Explore Coordinate Dependent Statements in an Expanding Universe
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In this Insight we will discuss the general Robertson--Walker (RW) universe, in which a set of co-moving observers with proper time ##t## observe the universe…
![RelativityVariables](https://www.physicsforums.com/insights/wp-content/uploads/2017/03/RelativityVariables.png)
Relativity Variables: Velocity, Doppler-Bondi k, and Rapidity
Traditional presentations of special relativity place emphasis on "velocity", which of course has an important physical interpretation... carried over…