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I've been thinking about the RW line element (c^2 d tau^2), and I understand that there is a term which describes the geometry of the Universe (d sigma^2) and then a term corresponding to the cosmic time (c^2 dt^2). The resulting (c^2 d tau^2 ) term would be the line measured by some fundamental observer.

I am confused as to how you may relate this line element to the density of the Universe, as I have read that there is an important relationship between the geometry of the Universe and its density.

I can see how the 'Friedmann equation' may give you a value for density, but I really cannot see the relationship between the Friedmann equation and the RW line element equation? :-S

Any help would be very much appreciated :-)

Thanks

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# Using the RW Line element

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