Wednesday, 9 March 2011

Question 15 from Heinamenn's Physics Textbook

Question 15 from Heinamenn's Physics Textbook


a) Explain the significant of the critical density of matter in the universe with respect to the possible fate of the universe
Since the critical density is the theoretical value of the density that creates a flat universe, if the the mass density were greater then the critical density then a closed universe would occur. However, if the critical density were greater than the mass density then an open universe would occur.


b) calculate the value of the critical density
\rho_c = \frac{3 H^2}{8 \pi G}.
P = 3 x ((2.7 x 10^-18) ^2) / (8 x π x 6.67 x 10^-11)
=1.3 x 10^-26

ii) Determine the equivalent number of nucleons per unit volume at this critical density





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