Loose Leaf For Explorations:  Introduction To Astronomy
Loose Leaf For Explorations: Introduction To Astronomy
9th Edition
ISBN: 9781260432145
Author: Thomas T Arny, Stephen E Schneider Professor
Publisher: McGraw-Hill Education
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Chapter 17, Problem 10TY
To determine

The ratio of dark matter to visible matter in a typical elliptical or spiral galaxy is.

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What happens when galaxies collide? A. Star collisions will be rare but the shapes of the galaxies will be largely distorted. B. The shapes of the galaxies will be largely distorted and many of the stars of one galaxy will collide with stars of the other galaxy. C. The shapes of the galaxies will be distorted and many stars will collide with stars of the other galaxy, as well as with other stars in the same galaxy. D. Star collisions will be rare and the two galaxies will just pass through each other without any changes. Is the answer A? Thank you!
1. The current (critical) density of our universe is pe = 10-26kg/m³. Assume the universe is filled with cubes with equal size that each contain one person of m = 100kg. What would the length of the side of such a cube have to be in order to give the correct critical density? How many hydrogen atoms would you need in a box of 1 m³ to reach the critical density? The matter we know, which consists mostly of hydrogen, constitutes only 4.8% of the current critical energy density of our universe. So how many hydrogen atoms are actually in a box of 1 m3 in our universe? Deep space is very empty and a much better vacuum than we can obtain on earth in a laboratory.
where did the 50 x 10^-3 come from and how did you get the math of -7.5
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