Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 25, Problem 33Q
To determine
(a)
The value of
To determine
(b)
Whether it is accurate to describe the universe as matter-oriented or radiation-oriented if the average density of matter is unchanged.
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I asked the following question and was given the attached solution:
Suppose that the universe were full of spherical objects, each of mass m and radius r . If the objects were distributed uniformly throughout the universe, what number density (#/m3) of spherical objects would be required to make the density equal to the critical density of our Universe?
Values:
m = 4 kg
r = 0.0407 m
Answer must be in scientific notation and include zero decimal places (1 sig fig --- e.g., 1234 should be written as 1*10^3)
I don't follow the work and I got the wrong answer, so please help and show your work as I do not follow along easily
thanks
Suppose that the universe were full of spherical objects, each of mass m and radius r . If the objects were distributed uniformly throughout the universe, what number density (#/m3) of spherical objects would be required to make the density equal to the critical density of our Universe?
Values:
m = 4 kg
r = 0.0407 m
Answer must be in scientific notation and include zero decimal places (1 sig fig --- e.g., 1234 should be written as 1*10^3)
To get an idea of how empty deep space is on the average, perform the following calculations:
(a) Find the volume our Sun would occupy if it had an average density equal to the critical density of 10-26 kg / m3 thought necessary to halt the expansion of the universe.
(b) Find the radius of a sphere of this volume in light years.
(c) What would this radius be if the density were that of luminous matter, which is approximately 5% that of the critical density?
(d) Compare the radius found in part (c) with the 4-ly average separation of stars in the arms of the Milky Way.
Chapter 25 Solutions
Universe: Stars And Galaxies
Ch. 25 - Prob. 1QCh. 25 - Prob. 2QCh. 25 - Prob. 3QCh. 25 - Prob. 4QCh. 25 - Prob. 5QCh. 25 - Prob. 6QCh. 25 - Prob. 7QCh. 25 - Prob. 8QCh. 25 - Prob. 9QCh. 25 - Prob. 10Q
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