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/m3thought necessary to halt the expansion of the universe.
_____ m3
(b) Find the radius of a sphere of this volume in light years.
_____ ly
(c) What would this radius be if the density were that of luminous matter, which is approximately 5% that of the critical density?
_____ly
(d) Compare the radius found in part (c) with the 4 ly average separation of stars in the arms of the Milky Way.