#### heyuhua

**Registered Senior Member**

Where is the value of $$q_0$$ coming from? It's being set without justification, which pretty much looks like it was set after the fact in order to fit the data.

Except not really. That equation is derived for a static universe, where all forces cancel. So a sign-flip wouldn't show up in a equation of motion, because there literally is no motion.

q_0 is obtaind from calculation according to observational cosmic density and Hubble parameter value of today. And (1.15) is geodesic equation which is the dynamical equation of particle in gravitational field and equivalent to the standard geodesic equation, don't means to be applied to static universe only, about its derivation you may see the following Yang's article page 142,or arbitrary standard textbook of post Newton's mechanics

Yang's crticle:

http://www.journalrepository.org/media/journals/BJMCS_6/2011/May/1306478...

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