Homework #5 Solutions
Chapter 14, p. 314 Problems 7-11
For each of the stars in problems 7-11, decide whether you think it is possible that it could harbor an advanced civilization, and explain your reasoning in one or two paragraphs.
For each of 7-11, consider what is necessary for an advanced civilization to develop. Assuming that this civilization is similar to us, an environment at a moderate temperature with an atmosphere to protect against harmful ultraviolet rays is needed. Liquid water is a necessity, as well as relatively stable temperatures. These things are needed for a long period of time in order for the civilization to advance technologically.
If one is considering an advanced civilization very different from our own understanding of life on this planet, all bets are off.
For each star, some main points are listed:
Chapter 15, p. 329 Review 10
What is the event horizon of a black hole? How does it get its name? How is it related to the Schwarzschild radius?
The event horizon is the location at which nothing can escape the gravitational pull of the black hole, not even radiation (light). “The event horizon gets its name because information can never reach us from events that occur within it.” (p. 324) The Schwarzschild radius is the distance from the center of the Black Hole (singularity), given in Cartesian coordinates, where the event horizon is located. It depends only on the mass of the black hole, and is tricky to compute since space-time becomes more warped as one approaches the event horizon.
Chapter 16, p. 350 Review 1
Draw simple sketches of our galaxy as it would appear face-on and edge-on, identifying the disk, bulge, halo and spiral arms.
Chapter 17, p. 381 Review 1
Distinguish between spiral galaxies and elliptical galaxies in terms of their shapes and colors. What are irregular galaxies?
“Spiral galaxies look like flat, white disks with yellowish bulges at their centers. The disks are filled with cool gas and dust, interspersed with hotter ionized gas… and usually display beautiful spiral arms. Elliptical galaxies are redder, more rounded, and often longer in one direction than in the other, like a football. Compared with spiral galaxies, elliptical galaxies contain very little cool gas and dust, though they often contain very hot, ionized gas. Galaxies that appear neither disklike nor rounded are classified as irregular galaxies. The sizes of all three types of galaxies span a wide range…”