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For simplicity, let's pick a standard star, of radius $R_\odot$ (you can easily generalize this for stars of any radius by picking $R_\odot$ to be the lower bound of star radius). Let's split the universe into cubes. It would be much easier to use concentric shells, but later on it will be practical to have everything split into components of standard ...


The scale factor of the universe depends on the matter and energy density in a way that depends on which component is dominant. This is discussed in the question How does the Hubble parameter change with the age of the universe? on the Physics Stack Exchange, and from that I have taken this graph showing how the scale factor changes with time for our ...


EdS universe represents a matter-dominated universe. Since the universe evolving towards lambda dominated and recently it was matter dominated, its a good approximation to use the EdS model to calculate the age of the universe.

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