The Case for Supermassive Black Holes

Online Discussion assignments for this course will consist of multiple questions/topics presented via a forum created for each module. You must create a post of at least 200-words in answer to ONE of the week’s Discussion questions/topics.
 
Be sure to identify the title of the question when posting.
Our Fate: Scientists, philosophers, and poets alike have speculated on the fate of the universe. How would you prefer the universe as we know it to end, in a “Big Crunch” or through eternal expansion? Explain the reasons behind your preference.
Dark Matter or Revised Gravity: One possible explanation for the evidence we find for dark matter is that we are currently using the wrong law of gravity to measure the masses of very large objects. If we really do misunderstand gravity, then many fundamental theories of physics, including Einstein’s theory of general relativity, will need to be revised. Which explanation for our observations do you find more appealing: dark matter or revised gravity? Explain why. Why do you suppose most astronomers find dark matter more appealing?
The Case for Supermassive Black Holes: The evidence for supermassive black holes at the center of galaxies is strong. however, it is very difficult to prove absolutely that they exist because the black holes themselves emit no light. We can only infer their existence from their powerful gravitational influences on surrounding matter. How compelling is the evidence? Do you think astronomers have proved the case for black holes beyond a reasonable doubt? Defend your opinion.
Cosmology and Philosophy: One hundred years ago, many scientists believed that the universe was infinite and eternal, with no beginning and no end. When Einstein first developed his general theory of relativity, he found that it predicted that the universe should be either expanding or contacting. He believed so strongly in an eternal and unchanging universe that he modified his theory, a modification he would call his “greatest blunder.” Why do you think Einstein and others assumed that the universe had no beginning? Do you think that a universe with a definite beginning in time, some 14 billion or so years ago, has any important philosophical implications? Explain.