Stellar and galactic crowding: The comparison of objects' sizes to the distance between them gives a sense of their relative density, i.e., how "crowded" they are. A typical human is about 1 meter across the shoulders. Compare the relative density of people in the case where they are standing on average 1 meter apart compared to a situation where they are on average 10 meters apart (hint: describe the separation in units of person- size). Now, compare the "crowding" of stars to that of galaxies. A typical star has a diameter of about 1 million km, while the average space between stars is about 5 light- years. A typical spiral galaxy in a cluster (such as the Milky Way)is 100,000 light- years across, and has another spiral galaxy within about 10 million light years.

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The Answer of Stellar and galactic crowding: The comparison of objects' sizes to the distance between them gives a sense of their relative density, i.e., how "crowded" they are. A typical human is about 1 meter across the shoulders. Compare the relative density of people in the case where they are standing on average 1 meter apart compared to a situation where they are on average 10 meters apart (hint: describe the separation in units of person- size). Now, compare the "crowding" of stars to that of galaxies. A typical star has a diameter of about 1 million km, while the average space between stars is about 5 light- years. A typical spiral galaxy in a cluster (such as the Milky Way)is 100,000 light- years across, and has another spiral galaxy within about 10 million light years.

Stellar and Galactic Crowding: the Comparison of Objects' Sizes to the Distance