Congratulations! You have reached the last week of our class. While many students will be using the next four days (from Tuesday, May 12 through Friday, May 15) to take final exams, in this course we will use this time to apply the finishing touch. We will do that by:
- Complete the course evaluation with the Blackboard course link.
- Review your scores for all assignments in the Blackboard gradebook.
- Verify that those scores match your understanding and any agreements we may have formed.
- Email the instructor if you notice any discrepancies.
- Turn in any missing assignments. (Note: Discussion assignments are time-sensitive and are not generally allowed as late work.)
- Revise and resubmit assignments per instructor feedback.
- If you have any partially completed assignments and cannot complete them, go ahead and turn them in for partial credit.
Now is your chance to tie up any loose ends and increase your scores. It is also your chance to offer constructive criticism of the class that will help future astronomy students.
Talk about mind-expanding! How about blowing up your brain to the size of the Universe? Maybe you would prefer winding the clock back to the barest instant after the Universe began. Cosmologists do that. For a long time, there was no way to test their ideas, but lately cosmology must answer to hard data. The results are spectacular: through direct observation of the early Universe astronomers have verified to a high degree the standard model, and have even nailed down the relative amounts of atomic matter, dark matter, and dark energy. Not only that, they can guess with some certainty the overall geometry of the Universe, whether it is flat or curved.
Those are some pretty impressive accomplishments, not just for physicists, but for everyone who wants to know more about the world in which they live. Big ideas like these change how people perceive the world, and changing perceptions can change the way people act. But wait -- not everything fits a tidy explanation. There are still mysteries and debates about critical components of our theory. What better way to end our course but to open our minds to some of the unsolved questions that tantalize astronomers today? As we come to the end of our textbook, we realize that astronomy is not a closed book.
Expand your vision beyond galaxies to include all of space and time.
Explain a mysterious aspect or theory of the Universe to your peers.
Simulate the angular spectrum of the cosmic microwave background by adjusting the relative amounts of atomic matter, dark matter, and dark energy in a mathematical model.
A long, long time ago, in a galaxy far, far away ....
Tada! Just imagine the adventures that are going on right now in all those other "Island Universes" out there. Although we will never know of those struggles and triumphs, we can wonder and marvel at the beauty and majesty of those galaxies and the billions of stars that they contain.
This is the point where the Universe becomes overwhelming. It is hard to comprehend the number of stars in our galaxy: over 100 billion. Now try to fit the possibility of 100 billion galaxies into your head, each one with many millions or billions of stars. It all seems too grand for our tiny minds to contain.
Yet we attempt to contain them by classification. We can distinguish them by their shapes, sizes, distances, brightness, type of radiation emitted, proximity to other galaxies, interactions, etc. Grouping galaxies helps us compare them, and even contains the keys to their formation and evolution. Such is the power of science.
There is some pretty scary stuff out there. There are burned-out cores of stars, white-hot glowing balls of super-dense carbon the size of the Earth, but with the mass of a star. There are even more massive and more compact objects, too, pulsars that have crushed the entire magnetic field of a star into the size of Manhattan Island. The resulting field is so strong that it rips electrons from their orbits in the atom and hurls them out into space in highly energetic beams of radiation. And then there is the black hole, something so dense that no force can resist the crushing power of gravity. Not even light can escape from its grasp inside the event horizon.