Reminders
Upcoming Deadlines
Announcements
IntroAstro Returns for a Second Session
Hey IntroAstro students,
It's been over nine months since our class ended. I hope you have had a good time continuing to learn about our amazing universe. I have partly recovered from the physical effort of developing the course and am missing the fun parts so much that I am teaching it again. Our second session launches December 2nd. The new course will be essentially the same as the first session. We are making a few changes based on what we learned but have not had the time to produce a substantially new course.
As with everything else here, this will be the first rerun of the course for me, so how the two sessions coexist is something we will find out as we go. As far as we can tell, there is no need to close the first session in order to open another, so for now we plan only one change to your experience with the first session of IntroAstro as we open the new course: the Wiki pages that are shared between sessions. To give new students the opportunity to fully enjoy the course, we will be removing some material from these pages, specifically the "Approaches to Solving Homework" pages. As we promised, we will give you a chance to preserve the contents of that page before making the change. This material will be removed on November 29. All other course materials, including the lecture videos, discussion forums, homework assignments, etc. will remain accessible to you by logging into the first session. Those still using the first session to communicate with classmates or to look back at the material are welcome to continue doing so.
Which brings me to one last aspect of a second session. Some of you may decide to follow the new class to see what is new or to revisit favorite parts - or particularly confusing ones. You are more than welcome to join us, and we invite you to share your experience and knowledge with the new students. In fact we hope some of you will choose to do so, up to a point. We may be reusing some of the homework assignments, for which you already have access to my solutions. I am sorry if this detracts from your experience retaking the course, but I must ask that you allow the new students to struggle with the assignments as you did. If you know the solution to a problem because you saw it solved last year, sharing that knowledge on the forums of the new session would be highly inappropriate. Such posts will be deleted, and repeat offenders will be banned from the forums. I doubt this will be needed - we have not banned anyone from our forums yet - but we prefer to be clear about the policy in advance. If you have any doubts about whether or not providing a particular bit of information is inappropriate, please don't post it. You can post questions in a thread on the forums for session 1. We will try to monitor these questions and respond there.
Thanks again for the great experience last year that was my induction into online teaching. Keep looking up!
ronen
It's been over nine months since our class ended. I hope you have had a good time continuing to learn about our amazing universe. I have partly recovered from the physical effort of developing the course and am missing the fun parts so much that I am teaching it again. Our second session launches December 2nd. The new course will be essentially the same as the first session. We are making a few changes based on what we learned but have not had the time to produce a substantially new course.
As with everything else here, this will be the first rerun of the course for me, so how the two sessions coexist is something we will find out as we go. As far as we can tell, there is no need to close the first session in order to open another, so for now we plan only one change to your experience with the first session of IntroAstro as we open the new course: the Wiki pages that are shared between sessions. To give new students the opportunity to fully enjoy the course, we will be removing some material from these pages, specifically the "Approaches to Solving Homework" pages. As we promised, we will give you a chance to preserve the contents of that page before making the change. This material will be removed on November 29. All other course materials, including the lecture videos, discussion forums, homework assignments, etc. will remain accessible to you by logging into the first session. Those still using the first session to communicate with classmates or to look back at the material are welcome to continue doing so.
Which brings me to one last aspect of a second session. Some of you may decide to follow the new class to see what is new or to revisit favorite parts - or particularly confusing ones. You are more than welcome to join us, and we invite you to share your experience and knowledge with the new students. In fact we hope some of you will choose to do so, up to a point. We may be reusing some of the homework assignments, for which you already have access to my solutions. I am sorry if this detracts from your experience retaking the course, but I must ask that you allow the new students to struggle with the assignments as you did. If you know the solution to a problem because you saw it solved last year, sharing that knowledge on the forums of the new session would be highly inappropriate. Such posts will be deleted, and repeat offenders will be banned from the forums. I doubt this will be needed - we have not banned anyone from our forums yet - but we prefer to be clear about the policy in advance. If you have any doubts about whether or not providing a particular bit of information is inappropriate, please don't post it. You can post questions in a thread on the forums for session 1. We will try to monitor these questions and respond there.
Thanks again for the great experience last year that was my induction into online teaching. Keep looking up!
ronen
Mon 18 Nov 2013 5:51 PM CET
Certificates Available
Students who completed the Introduction to Astronomy course can view their results and any earned certificates by checking their Course Records page.
If there are any questions regarding the Statement of Accomplishment certificate, please post them in the thread entitled "Certificate Now Available" and we'll try to address them.
If there are any questions regarding the Statement of Accomplishment certificate, please post them in the thread entitled "Certificate Now Available" and we'll try to address them.
Sun 24 Feb 2013 1:54 AM CET
Farewell to IntroAstro
Dear IntroAstro friends,
With Statements of Accomplishment issued, our journey is officially
over. I am writing primarily to thank you for joining Justin and I on
this remarkable ride, and to congratulate you for seeing it through.
I find I have quite a few words to say and hope you will forgive the
lengthy message. To motivate you to keep reading, I have put at the
end the answers to some questions that have come up recently.
Before I go any further, I would like to ask you to help us make
future classes better by answering a few questions about your
IntroAstro experience in this survey.
Over 2100 students qualified by completing 70% of the assignments
successfully. If you are among these, you have, in the past 11 weeks,
completed a class that is fully as rigorous and extensive as the one I
offer my students at Duke. I am sure you realize that despite all the
work we all put in this was, indeed, merely an introduction to the
amazing riches the universe offers, and I hope you will be inspired to
follow this class up by delving deeper into those topics. But what
you have achieved is definitely deserving of congratulations.
If you are among the 3000 or so students who watched all the video
lectures but for one reason or another did not complete the
assignments, I hope that you have still come away with an
understanding of what we know about the universe an an appreciation
for the remarkable combination of hard work and brilliant insights
that has gone into finding it all out. This too is worthy of
congratulations.
You are also deserving of my deepest thanks for sticking with me through
what has been a challenging course. I set some high expectations for
all of us when designing the class, in terms of the level at which I
wanted to present material and ask you to - as someone put it on the
forums - "think around" with the concepts. To the extent that this
has succeeded it is largely a result of the effort you put into it,
individually as well as collectively.
This was my first experience with online education, and I have to
admit I was quite surprised by the effectiveness of the discussion
forums. A great deal of teaching and learning happened on these, the
great majority of it involving students and not staff. All of you
who contributed to this by asking great questions, sharing your
insights, adding extra bits of information, or participating in the
common struggle to master tough material have played a huge part in
making this class a pleasure to teach and, I hope, a positive
experience for students. For this, too, I thank you.
As you probably gathered, the lecture videos were produced
more-or-less "live" during the class. This flies in the face of
accepted wisdom on best practices in the medium, which suggests that
all class materials be prepared well before launch. This had a cost
to all of us - the occasional (or more than occasional) errata, the
mis-statements or errors on slides or in autograder settings, even
the omission of entire segments either because I forgot them or
because I ran out of time. But in hindsight I think it was a wise
decision. As the course developed, I found myself, somewhat to my
surprise, developing an attachment to the class and the students
despite never having met any of you. I think this is largely due to a
real class spirit that developed through the discussion forums. This
meant that while technically I was lecturing to a laptop, in my mind I
could envision actual people, my class, listening. To me, this makes
a huge difference. In suffering the imperfections, you allowed me to
learn how to use the medium more effectively while giving me the sense
of a human connection that is, I think, so vital to teaching. I had
not expected this to happen in an online class, but it made it
possible for me to teach with the kind of focus that only such a
connection can sustain. If you compare the first weeks of the class
to the last ones, I think you will see this happening.
Which brings me to another thank you. This one goes to all of you who
have volunteered ideas on how the class could be improved. Some of
these we were able to use immediately, to the benefit of all of us.
Some will be used to make a future iteration of the class better in
many ways than this one. We will not be able to implement all of
them. Clearly, this class did not deliver what all of the students
who registered were looking for. I think this is true of any class in
any format, on any topic. There is not a universal formula for
education. The emphases in this class reflect both my personal taste
in science and my particular abilities; there are many other ways to
teach an introductory class in astronomy, and over time I am sure some
of these will be offered through this exciting new medium. When I
teach the course again it will largely be similar, but many things
will hopefully be improved, thanks largely to the comments,
suggestions, and complaints (yes!) of those who braved the first
draft. So future students owe you thanks, but surely I do. Thank you.
Finally, some answers to questions that have been asked by many:
- Enrollment in the class has been closed. When you find our class
on the Coursera page, "go to class" option will not show up. - The entire class structure - lecture videos, resources, forums,
etc. will remain open to all of us for the forseeable future. To
access the class you will need to click the "go to class archive"
link. Despite the new name, the content or access will not change at
all. - Justin and I will follow the discussion forums at some level, but
probably not with the same regularity with which we did this while
class was in session. We encourage you to continue to use these to
discuss class-related topics or to remain in touch with your
classmates and the staff. When interest in the forums wanes they
will be closed to new posts. It is possible that at some future time it will become
necessary to prevent further access to site content. If this happens we will be
sure to give everyone plenty of advance notice so they can download any material
they wish to preserve. - As I wrote above, we definitely intend to offer this class again.
There is some work to do implementing all those suggestions before we
do this, and it is not yet clear when we will have time for this.
We will let you know as plans firm up. - Teaching another class on another topic is tempting, because I had
such a great time here. But also daunting, because this class
literally took over my entire life for a few months. It will
probably be a while before I consider undertaking such a commitment
again.
We have all been part of a grand experiment in education. It is very
difficult to tell, at this point in time, how the capabilities of this
new technology will shape the way knowledge is shared and produced,
but I think it is clear that some profound changes are coming. For
now, I am grateful that we have had the opportunity to share this
remarkable experience. It's been awesome.
Sincerely yours
ronen
Tue 12 Feb 2013 11:27 PM CET
Last Google Hangout, Monday February 4th, 11:00 am
The Google Hangout with Dr. Plesser will take place Monday, February 4th at 11:00 am EST, and will be broadcast live on the IntroAstro2012 Google+ page as well as on YouTube (the YouTube link will be provided in the discussion thread when the broadcast starts). We still have lots of room for additional students to participate, so if you are interested, please post in this thread!
Sat 2 Feb 2013 9:08 PM CET
Optional Self-assessments Available During This Week!
Several optional self-assessments will be provided this week by the instructor and staff for this course. They are NOT part of the final course grade! Instead, they give students an opportunity to assess their own retention of the material.
Each assessment contains 6 questions. One hour (60 minutes) will be allotted for each of the optional self-assessments. The timer for the self-assessment cannot be paused for any reason, so be sure to set aside a full hour without distractions before starting the assessment. Students can attempt the optional self-assessments up to 2 times, with a mandatory wait period of 2 hours between attempts. There is no deadline to complete the optional self-assessments.
Note that the questions are randomized, so your second attempt may not have the same questions! Read carefully!
Each assessment contains 6 questions. One hour (60 minutes) will be allotted for each of the optional self-assessments. The timer for the self-assessment cannot be paused for any reason, so be sure to set aside a full hour without distractions before starting the assessment. Students can attempt the optional self-assessments up to 2 times, with a mandatory wait period of 2 hours between attempts. There is no deadline to complete the optional self-assessments.
Note that the questions are randomized, so your second attempt may not have the same questions! Read carefully!
Mon 28 Jan 2013 6:00 PM CET
HW8 Corrections
Several errors have been discovered - primarily by students - in the HW8 autograder setup. Let's be fair here, not one of these has anything to do with the autograder, they all reflect errors I made in solving the problems and/or in typing in the accepted ranges. So human error all the way this time.
There have been corrections to:
I think this makes the HW settings correct. If there are any errors left I am sure they will be found soon. I want to apologize to everyone who wasted time trying to get a correct answer past an autograder I had set wrong, and to bots everywhere for the bad feelings this may have engendered towards their kind. Not the way I wanted to end this, but perhaps a sign that I am just about spent and this is a good time to stop.
There have been corrections to:
- Part A Question 5: Accepted range was initially wrong, I dropped the "k" in kpc....
- Part B Question 3: My answer to third part here was incorrect due to a typo, I entered CMB temperature with two digits permuted.
- Part B Question 3: In addition, I computed my answers for second and third part using the expression I gave in Clip 4 for the energy density of a relativistic gas. This was itself wrong: the correct answer is a factor of eight larger (see Course Corrections). Since this is a multipart question the grader cannot handle multiple accepted ranges for one part. Thus the accepted ranges for second and third parts are now set to one big range that includes the answers one would obtain using either the incorrect value given in the video or the correct value.
- Part B Question 5: The accepted range here was wrong because I computed it wrong.
I think this makes the HW settings correct. If there are any errors left I am sure they will be found soon. I want to apologize to everyone who wasted time trying to get a correct answer past an autograder I had set wrong, and to bots everywhere for the bad feelings this may have engendered towards their kind. Not the way I wanted to end this, but perhaps a sign that I am just about spent and this is a good time to stop.
Thu 24 Jan 2013 11:57 PM CET
Week 8
Hey there IntroAstro,
The last week of lectures is processing, hopefully the videos will be available soon. This week we will be discussing cosmology, the science of the universe at the largest scales. As we have often seen in the past, looking at the largest scales will send us back to understanding nature at the smallest scales better, so particle physics will creep into the story at a few places. Some of the material this week is quite technical, the presentation borders on calculus at some points when I could find no better way to say things. I hope I will not lose you in the equations, the results are quite remarkable.
Homework 8 will be delayed by a day, I need some time to finish writing it. Thanks for your patience with this and all the other delays we have experienced.
It feels strange that this amazing experience is ending. I will write more about that, and about ways we can perhaps continue the conversations we've been having, later. For the next few weeks the course materials will remain available and the forums open. I expect that at some point they will be taken down, but see no reason that should be soon; we will discuss this with the folks at Coursera in the coming weeks.
ronen
The last week of lectures is processing, hopefully the videos will be available soon. This week we will be discussing cosmology, the science of the universe at the largest scales. As we have often seen in the past, looking at the largest scales will send us back to understanding nature at the smallest scales better, so particle physics will creep into the story at a few places. Some of the material this week is quite technical, the presentation borders on calculus at some points when I could find no better way to say things. I hope I will not lose you in the equations, the results are quite remarkable.
Homework 8 will be delayed by a day, I need some time to finish writing it. Thanks for your patience with this and all the other delays we have experienced.
It feels strange that this amazing experience is ending. I will write more about that, and about ways we can perhaps continue the conversations we've been having, later. For the next few weeks the course materials will remain available and the forums open. I expect that at some point they will be taken down, but see no reason that should be soon; we will discuss this with the folks at Coursera in the coming weeks.
ronen
Mon 21 Jan 2013 6:42 PM CET
Week 8 Nuts and Bolts
This week we will be discussing large-scale cosmology of the universe.
Homework: This week the eighth and final homework set opens. The two parts should be completed at least once before the Monday, Feb. 11th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 13 new lecture segments that should be viewed. These can be found in the Week 8 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Homework: This week the eighth and final homework set opens. The two parts should be completed at least once before the Monday, Feb. 11th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 13 new lecture segments that should be viewed. These can be found in the Week 8 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Mon 21 Jan 2013 6:00 PM CET
Google Hangout on Tuesday, January 22nd: Planned for 12:00 pm EST
Thanks to all of you who have expressed interest in joining the Google Hangout this coming Tuesday, and for voting in the poll. We have decided to host this Hangout at 12:00 pm EST on January 22nd, this coming Tuesday. If you are interested in joining us, please do continue to post to the thread, and we will try to get as many people involved as possible.
Remember that this Hangout will NOT be broadcast, so if you are not participating directly, be aware that it will not be possible to view the discussion.
Remember that this Hangout will NOT be broadcast, so if you are not participating directly, be aware that it will not be possible to view the discussion.
Sun 20 Jan 2013 4:00 AM CET
Google Hangout on Tuesday, January 22nd
The Google Hangout with Dr. Plesser will take place on Tuesday, January 22nd, and will not be broadcast live. We still have lots of room for additional students to participate, so if you are interested, please post in this thread!
Thu 17 Jan 2013 3:48 PM CET
Week 7 Nuts and Bolts
This week we will be discussing the structure and classification of galaxies as well as discussing dark matter.
Homework: This week the seventh homework set opens. The two parts should be completed at least once before the Monday, Feb. 4th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 13 new lecture segments that should be viewed. These can be found in the Week 7 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Homework: This week the seventh homework set opens. The two parts should be completed at least once before the Monday, Feb. 4th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 13 new lecture segments that should be viewed. These can be found in the Week 7 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Mon 14 Jan 2013 6:00 PM CET
Google Hangout on Friday, Jan. 11th: 8:00 pm EST
The Google Hangout with Dr. Plesser will take place tonight at 8:00 pm EST, and will be broadcast live on the IntroAstro2012 Google+ page as well as on YouTube (the YouTube link will be provided in the discussion thread when the broadcast starts). We still have lots of room for additional students to participate, so if you are interested, please post in this thread!
Fri 11 Jan 2013 2:44 PM CET
Adjustment to ranges on HW 6.
After evaluating the ranges accepted by the auto-grader for Homework 6, we've decided to make a few adjustments. After making the adjustments, we will issue a regrade of all quizzes, which may change the score you received. We ask that all students re-check their previous quizzes for Week 6 tomorrow and make sure that there are no serious errors. If you find such an error, please create a thread in the Technical Forum that starts with "HW6 Regrade Error - " and after the hyphen has the problem described in a short handful of words, with elaboration in the post itself.
Tue 8 Jan 2013 5:00 PM CET
Week 6 Nuts and Bolts
This week we will be discussing relativity.
Homework: This week the sixth homework set opens. The two parts should be completed at least once before the Monday, Jan. 28th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Note on Homework Discussion Threads: This week, we ask that students create discussion threads according to their need. These threads should have a title with the following format:
- Details threads: "Week 6, Part ?, Question ? - Details", where the ? are filled in with the appropriate values (A/B for part, 1-10 for question number). These threads are free to discuss every detail of the question, although we ask students to refrain from stating the final answer and from confirming whether they were graded correct or incorrect by the auto-grader. Students who view these threads should be prepared to see every aspect of the solution; because of this, we ask that students attempt a question themselves before looking at the associated details thread.
- Clarification threads: "Week 6, Part ?, Question ? - Clarification" These threads should not discuss any calculation involved in the problem, but instead be focused on identifying confusing words or phrases in the question, or clarifying concepts that seemed vague or undefined. Students should feel comfortable viewing these threads at any time without finding spoilers for the solution of the problem. Addition of calculation details to a Clarification thread may result in that detail post being deleted by the staff.
Lectures: There are 14 new lecture segments that should be viewed, and 1 optional lecture segment on paradoxes in special relativity. These can be found in the Week 6 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Homework: This week the sixth homework set opens. The two parts should be completed at least once before the Monday, Jan. 28th, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Note on Homework Discussion Threads: This week, we ask that students create discussion threads according to their need. These threads should have a title with the following format:
- Details threads: "Week 6, Part ?, Question ? - Details", where the ? are filled in with the appropriate values (A/B for part, 1-10 for question number). These threads are free to discuss every detail of the question, although we ask students to refrain from stating the final answer and from confirming whether they were graded correct or incorrect by the auto-grader. Students who view these threads should be prepared to see every aspect of the solution; because of this, we ask that students attempt a question themselves before looking at the associated details thread.
- Clarification threads: "Week 6, Part ?, Question ? - Clarification" These threads should not discuss any calculation involved in the problem, but instead be focused on identifying confusing words or phrases in the question, or clarifying concepts that seemed vague or undefined. Students should feel comfortable viewing these threads at any time without finding spoilers for the solution of the problem. Addition of calculation details to a Clarification thread may result in that detail post being deleted by the staff.
Lectures: There are 14 new lecture segments that should be viewed, and 1 optional lecture segment on paradoxes in special relativity. These can be found in the Week 6 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Mon 7 Jan 2013 6:00 PM CET
Google Hangout Time
This Hangout will take place at 11:30 AM EST on Saturday, January 5th.
We will send invitations to join the Hangout at that time. If you are planning to participate, make sure you have a Gmail account and have set up your Google+ account as well. Also check that your microphone and video all work properly.
We will send invitations to join the Hangout at that time. If you are planning to participate, make sure you have a Gmail account and have set up your Google+ account as well. Also check that your microphone and video all work properly.
Thu 3 Jan 2013 11:05 PM CET
Google Hangout for our Younger Students
We are planning to have a Hangout this Saturday that can include our students who are under 18 years of age. This Hangout will not be broadcast (Google requires that broadcast Hangouts have all participants above 18 years old). If any students want to participate (of any age) please follow this link, https://class.coursera.org/introastro-2012-001/forum/thread?thread_id=1656 , to a discussion forum and post your name and if you are over or under 18 years old (you need not write a specific age). We will attempt to include as many young students as possible, so they will have first priority in selection.
Thu 3 Jan 2013 5:38 PM CET
Week 5 Nuts and Bolts
This week we will be discussing stellar evolution, before and after the Main Sequence period in their lifetimes.
Homework: This week the fifth homework set opens. The two parts should be completed at least once before the Monday, Jan. 21st, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 15 new lecture segments that should be viewed. These can be found in the Week 5 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Homework: This week the fifth homework set opens. The two parts should be completed at least once before the Monday, Jan. 21st, 12:00 pm EST deadline. Please read the Grading Policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Please do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 15 new lecture segments that should be viewed. These can be found in the Week 5 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Tue 1 Jan 2013 6:26 PM CET
Happy New Year!
Happy new year to all. I know this is late for some of you, but it's still 2012 here. And welcome back from our holiday break to the second half of IntroAstro.
This week we will be working on stellar evolution. Stellar astrophysics is a highly developed field and involves many different fields of physics. Theoretical insights and experimental data are combined as input to detailed simulations of complicated dynamics. Stars, when you think about them, are amazingly complex systems. We will not really do justice to this rich field. I am not enough of an expert, for one thing, but also we would need far more time and more fundamental physics. We will try as best we can to discuss some of the general features. In some cases I will just quote simulation results; whenever possible I will try to motivate the important features. As always, the best we can do is to clarify general features and encourage you to follow the details up on your own. We will make heavy use of dimensional analysis, the kind of reasoning we used to find the acceleration in uniform circular motion, to understand the dependence of stellar properties on the relevant physical parameters to within "geometric" factors of order one.
Reading the forums is a lot of fun, there is a lot to learn from some of the thoughtful posts you are producing. I know I am learning much both about ways to think about the material I am trying to teach and about many things we are not covering at all. It seems you are also doing a wonderful job teaching each other. This new model of education has some amazing power. I am thankful to all for the time and effort you are putting into making this a better class.
Wishing you all a happy, gratifying 2013 full of new thoughts and ideas,
ronen
This week we will be working on stellar evolution. Stellar astrophysics is a highly developed field and involves many different fields of physics. Theoretical insights and experimental data are combined as input to detailed simulations of complicated dynamics. Stars, when you think about them, are amazingly complex systems. We will not really do justice to this rich field. I am not enough of an expert, for one thing, but also we would need far more time and more fundamental physics. We will try as best we can to discuss some of the general features. In some cases I will just quote simulation results; whenever possible I will try to motivate the important features. As always, the best we can do is to clarify general features and encourage you to follow the details up on your own. We will make heavy use of dimensional analysis, the kind of reasoning we used to find the acceleration in uniform circular motion, to understand the dependence of stellar properties on the relevant physical parameters to within "geometric" factors of order one.
Reading the forums is a lot of fun, there is a lot to learn from some of the thoughtful posts you are producing. I know I am learning much both about ways to think about the material I am trying to teach and about many things we are not covering at all. It seems you are also doing a wonderful job teaching each other. This new model of education has some amazing power. I am thankful to all for the time and effort you are putting into making this a better class.
Wishing you all a happy, gratifying 2013 full of new thoughts and ideas,
ronen
Tue 1 Jan 2013 2:26 AM CET
HW4 as PDF
In response to requests, we have produced a PDF version of HW4 (parts A and B together). You can get this here.
Wed 19 Dec 2012 10:23 PM CET
Google Hangout in a few minutes!
We are going live with our second Google Hangout in a few minutes. You can follow on the Coursera thread here: https://class.coursera.org/introastro-2012-001/forum/thread?thread_id=1344
Feel free to post questions; we will be monitoring and hopefully get everyone more involved, even if you cannot be in the Hangout!
- Justin
Feel free to post questions; we will be monitoring and hopefully get everyone more involved, even if you cannot be in the Hangout!
- Justin
Wed 19 Dec 2012 3:54 PM CET
Hangout 2: Wednesday, December 19, 10:00am EST (15:00 GMT)
Hanging out with some of you Friday was so much fun we will do it again on Wednesday December 19 at 10:00am EST (15:00GMT). Note time change from what was previously announced. We have changed a few of the procedures
from last time in an attempt to improve the experience, below is a description of how it will work.
We look forward to seeing (some of) you Wednesday.
Justin and Ronen
Things to do if you want to participate in the hangout:
1) Please make sure you have a computer with a working video camera and microphone. You cannot participate without these.
2) Please make sure you have an active GMail account. You cannot participate without this.
3) Please make sure you are OK with being recorded and having the recording deposited into YouTube. Also, sadly, because we are broadcasting this you may only participate if you are over 18. Apologies to our younger students. We will have a separate hangout, not broadcast, for these students later.
4) Create a Google+ account using your Gmail account. Navigate to http://plus.google.com/ and choose "Sign Up."
5) In Google+, search for the user Justin Ronen (introastro2012@gmail.com) and add him to one of your cicles. We will add you back before the hangout starts, but please be patient.
6) In Google+, open your Chat list in the bottom right corner of the screen. Click the arrow next to your name. Select Chat settings from the menu. Click “Verify your settings.“ You may need to install the voice and video chat plug-in by following this link: https://www.google.com/chat/video. If you are still having problems with verifying your settings, follow this link: http://support.google.com/chat/bin/answer.py?hl=en&answer=162174.
When the Hangout starts we may not have time to help troubleshoot video and audio problems, so please make sure to verify your video settings beforehand.
7) Your sound: Make sure you are in a quiet, controlled environment. Hangouts will pick up on background noise, so make sure there are no noise distractions around you. We recommend that you wear headphones to avoid audio feedback problems. If audio problems from your computer or background noise do distract from the conversation, we may need to mute your video or ask that you exit the Hangout early so that others can participate.
8) Your video: Hangouts work best in a well-lit environment. If you can’t flood the room with light, make sure you set up a light source facing you (behind the webcam, but directing light towards you). Also, it's best to have your webcam at eye-level, so that you are not looking down or up at the camera.
9) If you are invited to join the initial group, please be ready to join us 15min before the hangout starts to sort out technical issues and get started on time.
10) If you are not invited to the initial group, be on Google+ at 10am (EST). Your Google+ stream will inform you of the hangout starting. Post your responses to the conversation there, and you may be invited to join the hangout later on.
11) If you click the link and the Hangout is full, you can watch the live webcast and try joining when there is room. Please note:close the live stream before joining the Hangout, or you may cause sound echo problems.
12) Inside the Hangout, each participant will add and activate the Hangouts Toolkit app to display their name for others to see. You can turn this on by clicking the Hangouts Toolkit button on the left side of your screen. A window will appear on the right side of your screen. Click the "Lower Third" button. Ensure that your name is correctly written, and optionally type in your location or other info you’d like people to know. You can even use the dropdown menu to select your country and a flag will be displayed next to your name. Select the switch that says "Off" to turn on your Lower Third.
You will now see your name displayed on your video! You will notice that your video is mirrored, however this is normal, and others in the hangout will see and read your video just fine.
13) Please show respect for everyone involved in the Hangout, and try not to disrupt or distract from the conversation.
14) Have fun!
from last time in an attempt to improve the experience, below is a description of how it will work.
- We will be inviting a number of students to be the initial group on-camera, based on contributions to the class so far. We will restrict attention to those students who have added introastro2012 to a circle on Google+ so if you are interested in taking part and have not done this yet please do it.
- At any given time we will limit the number of participants in the hangout to 7 (5 students).
- As the conversation proceeds we will ask some people to leave to make room for others, and add new participants, so we hope to have a chance to hear from more of you this time.
- During the hangout, we will be monitoring both the Google+ comment stream and a thread we will open on the Discussion Forums. If you are not on air, you can post your suggestions for discussion topics and responses to what is said, and we will incorporate these into the discussion. Posts on the Google+ comment stream might lead to an invitation to join the hangout as people rotate out.
We look forward to seeing (some of) you Wednesday.
Justin and Ronen
Things to do if you want to participate in the hangout:
1) Please make sure you have a computer with a working video camera and microphone. You cannot participate without these.
2) Please make sure you have an active GMail account. You cannot participate without this.
3) Please make sure you are OK with being recorded and having the recording deposited into YouTube. Also, sadly, because we are broadcasting this you may only participate if you are over 18. Apologies to our younger students. We will have a separate hangout, not broadcast, for these students later.
4) Create a Google+ account using your Gmail account. Navigate to http://plus.google.com/ and choose "Sign Up."
5) In Google+, search for the user Justin Ronen (introastro2012@gmail.com) and add him to one of your cicles. We will add you back before the hangout starts, but please be patient.
6) In Google+, open your Chat list in the bottom right corner of the screen. Click the arrow next to your name. Select Chat settings from the menu. Click “Verify your settings.“ You may need to install the voice and video chat plug-in by following this link: https://www.google.com/chat/video. If you are still having problems with verifying your settings, follow this link: http://support.google.com/chat/bin/answer.py?hl=en&answer=162174.
When the Hangout starts we may not have time to help troubleshoot video and audio problems, so please make sure to verify your video settings beforehand.
7) Your sound: Make sure you are in a quiet, controlled environment. Hangouts will pick up on background noise, so make sure there are no noise distractions around you. We recommend that you wear headphones to avoid audio feedback problems. If audio problems from your computer or background noise do distract from the conversation, we may need to mute your video or ask that you exit the Hangout early so that others can participate.
8) Your video: Hangouts work best in a well-lit environment. If you can’t flood the room with light, make sure you set up a light source facing you (behind the webcam, but directing light towards you). Also, it's best to have your webcam at eye-level, so that you are not looking down or up at the camera.
9) If you are invited to join the initial group, please be ready to join us 15min before the hangout starts to sort out technical issues and get started on time.
10) If you are not invited to the initial group, be on Google+ at 10am (EST). Your Google+ stream will inform you of the hangout starting. Post your responses to the conversation there, and you may be invited to join the hangout later on.
11) If you click the link and the Hangout is full, you can watch the live webcast and try joining when there is room. Please note:close the live stream before joining the Hangout, or you may cause sound echo problems.
12) Inside the Hangout, each participant will add and activate the Hangouts Toolkit app to display their name for others to see. You can turn this on by clicking the Hangouts Toolkit button on the left side of your screen. A window will appear on the right side of your screen. Click the "Lower Third" button. Ensure that your name is correctly written, and optionally type in your location or other info you’d like people to know. You can even use the dropdown menu to select your country and a flag will be displayed next to your name. Select the switch that says "Off" to turn on your Lower Third.
You will now see your name displayed on your video! You will notice that your video is mirrored, however this is normal, and others in the hangout will see and read your video just fine.
13) Please show respect for everyone involved in the Hangout, and try not to disrupt or distract from the conversation.
14) Have fun!
Tue 18 Dec 2012 5:23 AM CET
Week 4 Nuts and Bolts
This week we will be discussing stellar structure, physical characteristics and classification this week.
Homework: This week is the fourth homework set. The two parts should be completed at least once before the Monday, Jan. 7th, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 15 new lecture segments that should be viewed this week (Dec 15 - 24). These can be found in the Week 4 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Homework: This week is the fourth homework set. The two parts should be completed at least once before the Monday, Jan. 7th, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
Instant feedback will continue to be available for the homework. There is no extension version of the homework. Do not discuss the instant feedback you received from submitting your homework with your fellow students!
Lectures: There are 15 new lecture segments that should be viewed this week (Dec 15 - 24). These can be found in the Week 4 collapsible menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
“See” you out there!
Ronen and Justin
Mon 17 Dec 2012 6:00 PM CET
Welcome to Week 4
Hi there IntroAstro!
The Solar System is fun, and we left many stones unturned, but there is a whole huge Universe waiting out there. This week we start our journey into more distant realms by learning what we can about main sequence stars.
Understanding how stars shine, in the sense in which we use this term here, has to be one of the most gratifying intellectual achievements of the twentieth century, and we will try to get in on as much of that thrill as we can. This will involve adding yet more physics to our arsenal, because the energy source underlying starlight is the strong nuclear force, and the fusion reactions in a star require the action of the weak interaction as well, so that we will by now have listed all four fundamental forces of nature. We know of no others. We will spend some time learning how it is that we know what we do about stars.
An important ingredient will be measuring the distances to stars, plucking them from the “celestial sphere” and adding them to our growing three-dimensional universe. This will be the first of several steps we will take on what is called the “cosmic distance ladder,” the name given to the collection of interdependent techniques we use to measure distances to remote objects.
This week, we come back to astronomy, armed with all the tools we have collected, and I hope you will find that the effort last week pays off as we begin to apply them. We will spend this week in our local neighborhood, the Solar system, and see what we can learn about how it works and where it came from. At the end, we will look at other planetary systems - a privilege of our timing, these have only been known for some 15 years - and see how they compare to ours.
The video clips this week are numerous but short and focused, I hope you will find this format easier to digest and welcome your feedback on this. You will also find that some videos use a novel editing “gimmick.” You will know it when you see it, if you have an opinion on it let us know, perhaps in this thread.
Our first hangout was fun, and I hope we learned some valuable lessons on conducting these events. We hope to hold another hangout this Wednesday, December 19, at 9:00am EST (December 19 14:00 GMT). Details will be announced as we have them.
It has been fun to see so many of you take advantage of the modified deadlines to keep working on the week 2 assignments. I hope you are finding them helpful in understanding how to apply the abstract concepts to reality. This is the big step we want to take here. It has also been fun to see the discussion forums used to extend the class both in depth and breadth way beyond what I can do in the lectures. Clearly a lot of learning and teaching is going on here for which I can take no credit. Keep up the good work there, and keep the mostly positive, supportive atmosphere of these discussions going.
Some have raised the question of too many detailed solutions to homework being discussed in the forums. I think the level of detail in which one chooses to collaborate with others is a matter of taste. The main purpose of these assignments is to give you an opportunity to think hard and help you learn. If you find working out every detail at a virtual blackboard with others is your preferred mode of collaborative work (I do) then by all means do so. If you prefer to discuss only broad principles and feel that too much detail spoils your fun, there should be a place for this. We will try this week to create two threads for each question on the assignment. One, called “Details,” will be for the first type of collaborative work. You can discuss your work at any level of detail, so long as you do not mention the feedback you received (some have been narrowly skirting this line). The second, called “Ideas,” is for discussing principles without providing detailed solutions. We will see if this allows both types of collaboration to coexist. As always, your feedback is welcomed.
After this week, we will take a one-week break as many of us turn to celebrate various solstice-related holidays. Week 5 will start Monday, December 31 (videos will be available Friday, December 28).
ronen
The Solar System is fun, and we left many stones unturned, but there is a whole huge Universe waiting out there. This week we start our journey into more distant realms by learning what we can about main sequence stars.
Understanding how stars shine, in the sense in which we use this term here, has to be one of the most gratifying intellectual achievements of the twentieth century, and we will try to get in on as much of that thrill as we can. This will involve adding yet more physics to our arsenal, because the energy source underlying starlight is the strong nuclear force, and the fusion reactions in a star require the action of the weak interaction as well, so that we will by now have listed all four fundamental forces of nature. We know of no others. We will spend some time learning how it is that we know what we do about stars.
An important ingredient will be measuring the distances to stars, plucking them from the “celestial sphere” and adding them to our growing three-dimensional universe. This will be the first of several steps we will take on what is called the “cosmic distance ladder,” the name given to the collection of interdependent techniques we use to measure distances to remote objects.
This week, we come back to astronomy, armed with all the tools we have collected, and I hope you will find that the effort last week pays off as we begin to apply them. We will spend this week in our local neighborhood, the Solar system, and see what we can learn about how it works and where it came from. At the end, we will look at other planetary systems - a privilege of our timing, these have only been known for some 15 years - and see how they compare to ours.
The video clips this week are numerous but short and focused, I hope you will find this format easier to digest and welcome your feedback on this. You will also find that some videos use a novel editing “gimmick.” You will know it when you see it, if you have an opinion on it let us know, perhaps in this thread.
Our first hangout was fun, and I hope we learned some valuable lessons on conducting these events. We hope to hold another hangout this Wednesday, December 19, at 9:00am EST (December 19 14:00 GMT). Details will be announced as we have them.
It has been fun to see so many of you take advantage of the modified deadlines to keep working on the week 2 assignments. I hope you are finding them helpful in understanding how to apply the abstract concepts to reality. This is the big step we want to take here. It has also been fun to see the discussion forums used to extend the class both in depth and breadth way beyond what I can do in the lectures. Clearly a lot of learning and teaching is going on here for which I can take no credit. Keep up the good work there, and keep the mostly positive, supportive atmosphere of these discussions going.
Some have raised the question of too many detailed solutions to homework being discussed in the forums. I think the level of detail in which one chooses to collaborate with others is a matter of taste. The main purpose of these assignments is to give you an opportunity to think hard and help you learn. If you find working out every detail at a virtual blackboard with others is your preferred mode of collaborative work (I do) then by all means do so. If you prefer to discuss only broad principles and feel that too much detail spoils your fun, there should be a place for this. We will try this week to create two threads for each question on the assignment. One, called “Details,” will be for the first type of collaborative work. You can discuss your work at any level of detail, so long as you do not mention the feedback you received (some have been narrowly skirting this line). The second, called “Ideas,” is for discussing principles without providing detailed solutions. We will see if this allows both types of collaboration to coexist. As always, your feedback is welcomed.
After this week, we will take a one-week break as many of us turn to celebrate various solstice-related holidays. Week 5 will start Monday, December 31 (videos will be available Friday, December 28).
ronen
Mon 17 Dec 2012 6:00 PM CET
Google+ Hangout at 4:00pm Today
Fri 14 Dec 2012 4:14 PM CET
Google+ Hangout Today!!!
Justin and I would like to chat with a few of you briefly, both to get to know a few of you and to get a feel for how the class is going so far. As such, we're planning a "Google Hangout" on Friday, December 14, at 4:00pm eastern USA time. (Note time zone: this would be Friday, December 14, 2012 at 21:00:00 GMT.)
If you'd like to WATCH this discussion (either live or later), a link will be posted when it begins so you can do so.
If you'd like to participate yourself, below are directions for doing this.
Google Hangouts is, unfortunately, limited to 10 simultaneous users, so we may not be able to get everyone interested. We'll aim for 10 participants and several alternates in case some people don't show up online at the right time (or have to leave). You'll receive more information at your GMail address on how to proceed.
Thanks, we look forward to meeting a handful of you, and we hope others of you might enjoy watching the meetup!
Justin and ronen
1) Please make sure you have a computer with a working video camera and microphone. You cannot participate without these.
2) Please make sure you have an active GMail account. You cannot participate without this.
3) Please make sure you are OK with being recorded and having the recording deposited into YouTube. Also, sadly, because we are broadcasting this you may only participate if you are over 18. Apologies to our younger students.
4) Please make sure you are available today.
5) Create a Google+ account using your Gmail account. Navigate to http://plus.google.com/ and choose "Sign Up."
6) In Google+, search for the user Justin Ronen (introastro2012@gmail.com) and add him to one of your cicles. We will add you back before the hangout starts, but please be patient.
7) In Google+, open your Chat list in the bottom right corner of the screen. Click the arrow next to your name. Select Chat settings from the menu. Click “Verify your settings.“ You may need to install the voice and video chat plug-in by following this link: https://www.google.com/chat/video. If you are still having problems with verifying your settings, follow this link: http://support.google.com/chat/bin/answer.py?hl=en&answer=162174.
When the Hangout starts we may not have time to help troubleshoot video and audio problems, so please make sure to verify your video settings beforehand.
8) Your sound: Make sure you are in a quiet, controlled environment. Hangouts will pick up on background noise, so make sure there are no noise distractions around you. We recommend that you wear headphones to avoid audio feedback problems. If audio problems from your computer do distract from the conversation, we may need to mute your video or ask that you exit the Hangout early so that others can participate.
9) Your video: We’ve all seen it before. A webcam, a dark room, the glow of the monitor casting unflattering light across someone’s face. Don’t be that person. Hangouts work best in a well-lit environment. If you can’t flood the room with light, make sure you set up a light source facing you (behind the webcam, but directing light towards you). Also, it's best to have your webcam at eye-level, so that you are not looking down or up at the camera.
10) At the indicated time, you will receive an email in your Gmail account (and your Chat window) inviting you to the Hangout. Click this link to join the Hangout.
11) If you click the link and the Hangout is full, you can watch the live webcast and try joining when there is room. Please note: close the live stream before joining the Hangout, or you may cause sound echo problems.
12) Inside the Hangout, each participant will add and activate the Hangouts Toolkit app to display their name for others to see. You can turn this on by clicking the Hangouts Toolkit button on the left side of your screen.
A window will appear on the right side of your screen. Click the "Lower Third" button.
Ensure that your name is correctly written, and optionally type in your location or other info you’d like people to know. You can even use the dropdown menu to select your country and a flag will be displayed next to your name. Select the switch that says "Off" to turn on your Lower Third.
You will now see your name displayed on your video! You will notice that your video is mirrored, however this is normal, and others in the hangout will see and read your video just fine.
13) Please show respect for everyone involved in the Hangout, and try not to disrupt or distract from the conversation.
14) Have fun!
If you'd like to WATCH this discussion (either live or later), a link will be posted when it begins so you can do so.
If you'd like to participate yourself, below are directions for doing this.
Google Hangouts is, unfortunately, limited to 10 simultaneous users, so we may not be able to get everyone interested. We'll aim for 10 participants and several alternates in case some people don't show up online at the right time (or have to leave). You'll receive more information at your GMail address on how to proceed.
Thanks, we look forward to meeting a handful of you, and we hope others of you might enjoy watching the meetup!
Justin and ronen
1) Please make sure you have a computer with a working video camera and microphone. You cannot participate without these.
2) Please make sure you have an active GMail account. You cannot participate without this.
3) Please make sure you are OK with being recorded and having the recording deposited into YouTube. Also, sadly, because we are broadcasting this you may only participate if you are over 18. Apologies to our younger students.
4) Please make sure you are available today.
5) Create a Google+ account using your Gmail account. Navigate to http://plus.google.com/ and choose "Sign Up."
6) In Google+, search for the user Justin Ronen (introastro2012@gmail.com) and add him to one of your cicles. We will add you back before the hangout starts, but please be patient.
7) In Google+, open your Chat list in the bottom right corner of the screen. Click the arrow next to your name. Select Chat settings from the menu. Click “Verify your settings.“ You may need to install the voice and video chat plug-in by following this link: https://www.google.com/chat/video. If you are still having problems with verifying your settings, follow this link: http://support.google.com/chat/bin/answer.py?hl=en&answer=162174.
When the Hangout starts we may not have time to help troubleshoot video and audio problems, so please make sure to verify your video settings beforehand.
8) Your sound: Make sure you are in a quiet, controlled environment. Hangouts will pick up on background noise, so make sure there are no noise distractions around you. We recommend that you wear headphones to avoid audio feedback problems. If audio problems from your computer do distract from the conversation, we may need to mute your video or ask that you exit the Hangout early so that others can participate.
9) Your video: We’ve all seen it before. A webcam, a dark room, the glow of the monitor casting unflattering light across someone’s face. Don’t be that person. Hangouts work best in a well-lit environment. If you can’t flood the room with light, make sure you set up a light source facing you (behind the webcam, but directing light towards you). Also, it's best to have your webcam at eye-level, so that you are not looking down or up at the camera.
10) At the indicated time, you will receive an email in your Gmail account (and your Chat window) inviting you to the Hangout. Click this link to join the Hangout.
11) If you click the link and the Hangout is full, you can watch the live webcast and try joining when there is room. Please note: close the live stream before joining the Hangout, or you may cause sound echo problems.
12) Inside the Hangout, each participant will add and activate the Hangouts Toolkit app to display their name for others to see. You can turn this on by clicking the Hangouts Toolkit button on the left side of your screen.
A window will appear on the right side of your screen. Click the "Lower Third" button.
Ensure that your name is correctly written, and optionally type in your location or other info you’d like people to know. You can even use the dropdown menu to select your country and a flag will be displayed next to your name. Select the switch that says "Off" to turn on your Lower Third.
You will now see your name displayed on your video! You will notice that your video is mirrored, however this is normal, and others in the hangout will see and read your video just fine.
13) Please show respect for everyone involved in the Hangout, and try not to disrupt or distract from the conversation.
14) Have fun!
Fri 14 Dec 2012 3:15 PM CET
Week 2 Instant Feedback
Instant feedback should now be available for students on the Week 2 homework. Please post in the Technical Issues forum if you notice any errors in function, that is, if there are any technical glitches. If you feel there is an error in the writing of a problem, that should be posted in either the Homework subforum or the Errata subforum for the appropriate week.
Wed 12 Dec 2012 3:07 PM CET
Week 3 Nuts and Bolts
This week we will be discussing the origins and characteristics of the diverse bodies in the solar system.
Homework: This week is the third homework set. The two parts should be completed at least once before the Monday, Dec. 31st, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
DUE TO OUR GRADING POLICY CHANGE FOR WEEK 3, CORRECT/INCORRECT FEEDBACK WILL BE IMMEDIATELY AVAILABLE UPON SUBMISSION OF A HOMEWORK ATTEMPT. Please read Dr. Plesser’s announcement email for further details. There will no longer be an extension version of the homework. Do not discuss the instant feedback you received from submitting your homework with your fellow students! By this, we mean that comments similar to, "You should use my answer because it was graded as correct" will be removed from forums as inappropriate discussion.
There will also be a solution set to the week 2 Homework provided by Dr. Plesser after the deadline has passed. In addition, we will be highlighting exemplary solutions by the students in the forums at the same time, in the “How Did You Successfully Solve...” series of threads.
Lectures: There are eight new core lecture segments (Clips 1-7 and clip 11) that should be viewed this week (Dec 8 - 19). These can be found in the Week 3 collapsable menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed. There are also three new lecture segments that are labelled OPTIONAL! in their title (Clips 8-10), and the subject matter in these videos is not required for completing the homework for this week, or for understanding any future lectures.
-------------------------------------------------------------------------------------
Note on accepted numerical format for homework questions
Many students continue to express confusion and difficulty with the required format for entering their answers on the homework. The machine grader is not able to cope with commas or punctuation other than the decimal point (apologies to the international students!), words (including units), or the 10^ format for scientific notation.
If a problem were asking for a radius in kilometers rounded to 2 significant digits, and the answer calculated turned out to be 1512.3424 km:
Examples of good answer entries: 1.5e3 or 1500
Examples of ‘error-prone’ answer entries: 1,500 or 1500 km or 1.5 * 10^3 or 1,5e3 or R = 1500
All of the ‘error-prone’ examples above exhibit some feature that may throw off the machine grader. Please make careful note of how your answers are formatted!
Note on rounding and numerical ranges of answers
Many students are also concerned with the correct approach to rounding their values. While this is addressed in the Homework Tips, here are some additional points to consider.
The method of rounding the number will not affect the grading of the answer. Whether you truncate the number at the desired digit, or round ‘5’ up all the time, or round ‘5’ up only with even preceding digits, etc..., all of these results should be including in the range of the accepted numerical answers, provided the proper calculation was performed.
Example: A result gives 14520 years as an exact answer. The machine grader might be given a range of acceptable answers between 14000 and 15000 years.
Rounding to two significant digits: 15000 or 14000 would be accepted as correct. Rounding to three significant digits: 14500 would be accepted as correct. Indeed, submitting the entire result exactly as calculated (14520) in this case would also be accepted as correct. HOWEVER, an answer of 13999 would be graded as incorrect in this example, if not rounded up to 14000. What this means is that rounded answers are NOT REQUIRED in your answer submission, but rounding your answer will essentially make it more likely that your answer falls into the accepted range.
If there are additional questions beyond those topics covered here, don’t hesitate to ask! However, future questions specifically answered by this post may be referred here.
“See” you out there!
Ronen and Justin
Homework: This week is the third homework set. The two parts should be completed at least once before the Monday, Dec. 31st, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course.
DUE TO OUR GRADING POLICY CHANGE FOR WEEK 3, CORRECT/INCORRECT FEEDBACK WILL BE IMMEDIATELY AVAILABLE UPON SUBMISSION OF A HOMEWORK ATTEMPT. Please read Dr. Plesser’s announcement email for further details. There will no longer be an extension version of the homework. Do not discuss the instant feedback you received from submitting your homework with your fellow students! By this, we mean that comments similar to, "You should use my answer because it was graded as correct" will be removed from forums as inappropriate discussion.
There will also be a solution set to the week 2 Homework provided by Dr. Plesser after the deadline has passed. In addition, we will be highlighting exemplary solutions by the students in the forums at the same time, in the “How Did You Successfully Solve...” series of threads.
Lectures: There are eight new core lecture segments (Clips 1-7 and clip 11) that should be viewed this week (Dec 8 - 19). These can be found in the Week 3 collapsable menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed. There are also three new lecture segments that are labelled OPTIONAL! in their title (Clips 8-10), and the subject matter in these videos is not required for completing the homework for this week, or for understanding any future lectures.
-------------------------------------------------------------------------------------
Note on accepted numerical format for homework questions
Many students continue to express confusion and difficulty with the required format for entering their answers on the homework. The machine grader is not able to cope with commas or punctuation other than the decimal point (apologies to the international students!), words (including units), or the 10^ format for scientific notation.
If a problem were asking for a radius in kilometers rounded to 2 significant digits, and the answer calculated turned out to be 1512.3424 km:
Examples of good answer entries: 1.5e3 or 1500
Examples of ‘error-prone’ answer entries: 1,500 or 1500 km or 1.5 * 10^3 or 1,5e3 or R = 1500
All of the ‘error-prone’ examples above exhibit some feature that may throw off the machine grader. Please make careful note of how your answers are formatted!
Note on rounding and numerical ranges of answers
Many students are also concerned with the correct approach to rounding their values. While this is addressed in the Homework Tips, here are some additional points to consider.
The method of rounding the number will not affect the grading of the answer. Whether you truncate the number at the desired digit, or round ‘5’ up all the time, or round ‘5’ up only with even preceding digits, etc..., all of these results should be including in the range of the accepted numerical answers, provided the proper calculation was performed.
Example: A result gives 14520 years as an exact answer. The machine grader might be given a range of acceptable answers between 14000 and 15000 years.
Rounding to two significant digits: 15000 or 14000 would be accepted as correct. Rounding to three significant digits: 14500 would be accepted as correct. Indeed, submitting the entire result exactly as calculated (14520) in this case would also be accepted as correct. HOWEVER, an answer of 13999 would be graded as incorrect in this example, if not rounded up to 14000. What this means is that rounded answers are NOT REQUIRED in your answer submission, but rounding your answer will essentially make it more likely that your answer falls into the accepted range.
If there are additional questions beyond those topics covered here, don’t hesitate to ask! However, future questions specifically answered by this post may be referred here.
“See” you out there!
Ronen and Justin
Mon 10 Dec 2012 6:00 PM CET
Week 3
Hi there IntroAstro!
Week 2 was, as promised, busy. We took a whirlwind tour through a few centuries of physics, and I am sure we are all still a little dizzy.
This week, we come back to astronomy, armed with all the tools we have collected, and I hope you will find that the effort last week pays off as we begin to apply them. We will spend this week in our local neighborhood, the Solar system, and see what we can learn about how it works and where it came from. At the end, we will look at other planetary systems - a privilege of our timing, these have only been known for some 15 years - and see how they compare to ours.
I hope you are beginning to gain an understanding of what this class is trying to achieve and how we hope to get there. Knowing how to apply fundamental principles to understand the workings of the cosmos is a very gratifying experience. It takes work to get there, but we hope you will find the effort worthwhile. That said, we also understand that the amount of time and effort each of us can afford to invest in this class is limited, and it is important to make efficient use of that time. We also realize that learning to think about science this way needs time. Not just work time but also days to digest and think about it and sleep on it. We are impressed by the effort you have been making and want to make taking the class, and qualifying for the certificate, as accessible as we can without changing our goals or compromising on the level at which we want you to engage the material.
A lot of time is spent working the problems. This is a good thing, in our opinion, because figuring out how to apply the concepts to real phenomena is the best way to gain insight as well as command. This is the real purpose of the assignments; the fact that they are used to produce grades is secondary. We want your time to be spent thinking about the science, not the numbers. We also want as many people as possible to work the problems, because we consider that the best way to learn the science, and realize that once submission deadlines pass and solutions are posted, motivation to work the problems drops. To that end, here are some changes to grading policy and one (hopefully) helpful clarification.
The policy changes concern homework, due dates, and feedback. When we designed the class we intended the feedback policy to be the one we used in week 2. An error caused week 1 homework assignments to provide immediate feedback on performance. The error was corrected in week 2, but it got us thinking about the issue, and in the interest of maximizing time spent on science, we will change the feedback settings so that students will know upon submission which problems they got wrong and so can work more efficiently on these. In addition, to allow more of you to complete the homework before the due date, we will be changing the due dates for homework, so that you have three weeks to submit a homework assignment for full credit, starting with the week 2 homework which is now due December 24.
We realize that making these changes mid-course is not ideal. Some of you, having worked very hard to get HW2 in on time, now discover you could have waited. Moreover, you will not receive feedback or solutions (we will try to see if we can arrange feedback for HW2 but it is not certain this will be possible) for two more weeks. Some of you have plans in early February that will not allow you to take advantage of the extra time. I guess we are all learning here, and pioneering this exciting new frontier of teaching is not without risks. We are trying hard to make the experience as rewarding for everyone as we can.
Please remember that we will post no new material the week of December 24-30. We resume with week 5 on Monday, December 31.
I also want to clarify one point about our calculations. We are not trying in this class to obtain truly precise results. In the interest of simplifying things we neglect many subtleties. The idea is to capture the essence of a phenomenon, not to actually launch a spacecraft to Mars. Thus, our calculations of known quantities will not always agree with published values, and computing from two different starting points can lead to slightly different answers. This is fine with me, and we set the intervals defining correct answers to homework in such a way that any reasonable calculation will lead to results accepted as correct. What is remarkable, to me, is not that our calculation of the density of Saturn is off by a few percent. We neglect such factors as the planet’s oblateness, the eccentricity and inclination of orbits, etc. What is remarkable to me is that we can get pretty close to the right answer with these simple calculations, and understand roughly what it takes to do better! So please do not be concerned with the precise values you find. If you think a correct answer has been rejected please let us know, and if there is a problem we will fix it or tell you how to proceed.
I hope you will have fun in the Solar System this week,
ronen
Week 2 was, as promised, busy. We took a whirlwind tour through a few centuries of physics, and I am sure we are all still a little dizzy.
This week, we come back to astronomy, armed with all the tools we have collected, and I hope you will find that the effort last week pays off as we begin to apply them. We will spend this week in our local neighborhood, the Solar system, and see what we can learn about how it works and where it came from. At the end, we will look at other planetary systems - a privilege of our timing, these have only been known for some 15 years - and see how they compare to ours.
I hope you are beginning to gain an understanding of what this class is trying to achieve and how we hope to get there. Knowing how to apply fundamental principles to understand the workings of the cosmos is a very gratifying experience. It takes work to get there, but we hope you will find the effort worthwhile. That said, we also understand that the amount of time and effort each of us can afford to invest in this class is limited, and it is important to make efficient use of that time. We also realize that learning to think about science this way needs time. Not just work time but also days to digest and think about it and sleep on it. We are impressed by the effort you have been making and want to make taking the class, and qualifying for the certificate, as accessible as we can without changing our goals or compromising on the level at which we want you to engage the material.
A lot of time is spent working the problems. This is a good thing, in our opinion, because figuring out how to apply the concepts to real phenomena is the best way to gain insight as well as command. This is the real purpose of the assignments; the fact that they are used to produce grades is secondary. We want your time to be spent thinking about the science, not the numbers. We also want as many people as possible to work the problems, because we consider that the best way to learn the science, and realize that once submission deadlines pass and solutions are posted, motivation to work the problems drops. To that end, here are some changes to grading policy and one (hopefully) helpful clarification.
The policy changes concern homework, due dates, and feedback. When we designed the class we intended the feedback policy to be the one we used in week 2. An error caused week 1 homework assignments to provide immediate feedback on performance. The error was corrected in week 2, but it got us thinking about the issue, and in the interest of maximizing time spent on science, we will change the feedback settings so that students will know upon submission which problems they got wrong and so can work more efficiently on these. In addition, to allow more of you to complete the homework before the due date, we will be changing the due dates for homework, so that you have three weeks to submit a homework assignment for full credit, starting with the week 2 homework which is now due December 24.
- Homework assignments will provide immediate feedback as they did in week 1.
- You can submit each assignment up to 20 times.
- Homework will be available at noon (Eastern time) Monday, and will be due by noon
(Eastern time) Monday three weeks later. This means you have three weeks to complete the assignments, except that a new assignment will be out every week. - The last assignment, for week 8, will be due at noon (Eastern time) on Monday, February 11.
- Your score on each assignment will be the score of the last submission before the deadline.
- After the deadline homework can be submitted for feedback but credit will not be assigned. There will no longer be an ‘Extension’ version of the homework.
- As before, you are encouraged to discuss your thoughts on the homework problems and your ideas for solving them on the Discussion Forums. We ask that if you submitted your work you do not include the feedback in your posts. You can argue why you think your solution is correct, but not invoke the fact that it was accepted. Readers of the post will have to decide what they think of your argument. Posts that specifically add or strongly imply that they were graded correct may be removed by the staff.
- Solutions to the problems will be posted immediately following the deadline.
We realize that making these changes mid-course is not ideal. Some of you, having worked very hard to get HW2 in on time, now discover you could have waited. Moreover, you will not receive feedback or solutions (we will try to see if we can arrange feedback for HW2 but it is not certain this will be possible) for two more weeks. Some of you have plans in early February that will not allow you to take advantage of the extra time. I guess we are all learning here, and pioneering this exciting new frontier of teaching is not without risks. We are trying hard to make the experience as rewarding for everyone as we can.
Please remember that we will post no new material the week of December 24-30. We resume with week 5 on Monday, December 31.
I also want to clarify one point about our calculations. We are not trying in this class to obtain truly precise results. In the interest of simplifying things we neglect many subtleties. The idea is to capture the essence of a phenomenon, not to actually launch a spacecraft to Mars. Thus, our calculations of known quantities will not always agree with published values, and computing from two different starting points can lead to slightly different answers. This is fine with me, and we set the intervals defining correct answers to homework in such a way that any reasonable calculation will lead to results accepted as correct. What is remarkable, to me, is not that our calculation of the density of Saturn is off by a few percent. We neglect such factors as the planet’s oblateness, the eccentricity and inclination of orbits, etc. What is remarkable to me is that we can get pretty close to the right answer with these simple calculations, and understand roughly what it takes to do better! So please do not be concerned with the precise values you find. If you think a correct answer has been rejected please let us know, and if there is a problem we will fix it or tell you how to proceed.
I hope you will have fun in the Solar System this week,
ronen
Mon 10 Dec 2012 6:00 PM CET
One Week In
Hi there IntroAstro!
We are starting our second week, thought I would share some thoughts about the class.
Our first week dealt with the way things move in the sky. The mental gymnastics involved in seeing things simultaneously in three mutually rotating coordinate systems are always challenging. The reward for sticking with this, though, is understanding what goes on around us. Thinking in this way is not something that comes naturally to most of us, and becoming comfortable with it takes time - both work time and chronological time. If you still find some of the material confusing you are in good company. The good news is that, with time, it should become clearer. Also, while we will start off the second week from where we left off the first, most of the rest of the class can be done quite independently of the material from this week, although thinking in three dimensions (and in time) is a skill we will need - and continue to develop - because that is where (and when?) we live.
If nothing else, you should have developed a healthy respect for the early workers in the field who worked out all of this without simulations, or calculators, or even slide rules!
This second week we start where we left off - adding ingredients to our model of the Universe. Very soon we find that a two-dimensional planetarium show projected on a “very large” celestial sphere is not a good enough description. Tearing the planets - and, in two weeks, the stars as well, out of the celestial realm and into a three-dimensional, physical universe is one of the remarkable achievements of humans, and we will be able to follow much of the thought, if not the detailed computations, that go into this.
Understanding planetary motion will naturally lead us - both historically and intellectually - to Newton’s mechanics and his theory of gravity. We will not be thorough, but will hopefully work
enough examples to get what we need for our purposes. The rest of the week throws history aside and rushes us through a selection of the insights that followed - with a few centuries’ hard work by some very brilliant scientists - from Newton’s ideas. We will use examples from astronomy to demonstrate what we are talking about, but the topic will be physics. We are gearing up for our assault on the Universe, this will be time well spent.
If you have never taken a physics class, this will be a lot. If you have, some of it may be a repetition of things you know. We have an amazing diversity of backgrounds and interest in this class, and we try to strike some balance so everyone can get something from it. Some of the clips this week are long. Too long. This will not happen again - as you know I am learning how to do this as I go. I recommend using in-video quizzes as natural break points at which to stop, go do something else, and return after letting the material “settle” a bit. Few of us can focus on a one-hour video.
Some of the algebra will be more involved than last week, but typically students find the material less difficult. In general, in my experience the first week is often the toughest for many students. In part this is because of the geometric complexity. In part it has to do with becoming comfortable with thinking in the way physicists do. This too takes time, but I think it can be the most rewarding part of this class. What this involves is learning to look at a problem, a system, a situation, and discern what is going on. It is not (in this class) a matter of performing some incredibly complex calculation. It’s more a matter of struggling to figure out how the mathematical expressions relate to the problem at hand.
One of the most exciting things, for me, was to watch the forums and observe how students with such diverse backgrounds - in astronomy and beyond astronomy - interacted. There were a lot of good, substantive discussions of issues related to class at all levels, and there were a lot of great discussions of issues unrelated to class as well. The opportunity to share the learning experience with a large, diverse community and to profit from each other’s insights is a wonderful feature of this mode of teaching, and many of you seem to know how to use it.
This class is a pioneering experiment. I don’t know if anyone knows how to do it right, I know I am just learning, and I appreciate your patience. I also appreciate the many useful suggestions and ideas in your comments. I am still (gasp!) recording video for the class and will try to implement some of these. Please keep them coming!
ronen
We are starting our second week, thought I would share some thoughts about the class.
Our first week dealt with the way things move in the sky. The mental gymnastics involved in seeing things simultaneously in three mutually rotating coordinate systems are always challenging. The reward for sticking with this, though, is understanding what goes on around us. Thinking in this way is not something that comes naturally to most of us, and becoming comfortable with it takes time - both work time and chronological time. If you still find some of the material confusing you are in good company. The good news is that, with time, it should become clearer. Also, while we will start off the second week from where we left off the first, most of the rest of the class can be done quite independently of the material from this week, although thinking in three dimensions (and in time) is a skill we will need - and continue to develop - because that is where (and when?) we live.
If nothing else, you should have developed a healthy respect for the early workers in the field who worked out all of this without simulations, or calculators, or even slide rules!
This second week we start where we left off - adding ingredients to our model of the Universe. Very soon we find that a two-dimensional planetarium show projected on a “very large” celestial sphere is not a good enough description. Tearing the planets - and, in two weeks, the stars as well, out of the celestial realm and into a three-dimensional, physical universe is one of the remarkable achievements of humans, and we will be able to follow much of the thought, if not the detailed computations, that go into this.
Understanding planetary motion will naturally lead us - both historically and intellectually - to Newton’s mechanics and his theory of gravity. We will not be thorough, but will hopefully work
enough examples to get what we need for our purposes. The rest of the week throws history aside and rushes us through a selection of the insights that followed - with a few centuries’ hard work by some very brilliant scientists - from Newton’s ideas. We will use examples from astronomy to demonstrate what we are talking about, but the topic will be physics. We are gearing up for our assault on the Universe, this will be time well spent.
If you have never taken a physics class, this will be a lot. If you have, some of it may be a repetition of things you know. We have an amazing diversity of backgrounds and interest in this class, and we try to strike some balance so everyone can get something from it. Some of the clips this week are long. Too long. This will not happen again - as you know I am learning how to do this as I go. I recommend using in-video quizzes as natural break points at which to stop, go do something else, and return after letting the material “settle” a bit. Few of us can focus on a one-hour video.
Some of the algebra will be more involved than last week, but typically students find the material less difficult. In general, in my experience the first week is often the toughest for many students. In part this is because of the geometric complexity. In part it has to do with becoming comfortable with thinking in the way physicists do. This too takes time, but I think it can be the most rewarding part of this class. What this involves is learning to look at a problem, a system, a situation, and discern what is going on. It is not (in this class) a matter of performing some incredibly complex calculation. It’s more a matter of struggling to figure out how the mathematical expressions relate to the problem at hand.
One of the most exciting things, for me, was to watch the forums and observe how students with such diverse backgrounds - in astronomy and beyond astronomy - interacted. There were a lot of good, substantive discussions of issues related to class at all levels, and there were a lot of great discussions of issues unrelated to class as well. The opportunity to share the learning experience with a large, diverse community and to profit from each other’s insights is a wonderful feature of this mode of teaching, and many of you seem to know how to use it.
This class is a pioneering experiment. I don’t know if anyone knows how to do it right, I know I am just learning, and I appreciate your patience. I also appreciate the many useful suggestions and ideas in your comments. I am still (gasp!) recording video for the class and will try to implement some of these. Please keep them coming!
ronen
Tue 4 Dec 2012 2:49 AM CET
Week 2: Nuts and Bolts
This week we will be covering some of the historical advances in physics that contribute to our understanding of astronomy.
Homework: This week is the second homework set. The two parts should be completed at least once before the Monday, Dec. 10th, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course. Be aware that the ‘correct/incorrect’ labels will not appear immediately on homework submissions this week, but will instead appear after the primary deadline on Monday, Dec 10th.
There is a new thread in the Math Help forum titled ‘Worked Problems with the TA’ where Justin will be working through some example problems and discussing them with students. Look for this if you would like to see examples.
There will also be a solution set to the week 1 Homework provided by Dr. Plesser on Wed. Dec 5th, at 12:00 pm EST, after the extended deadline has passed. In addition, we will be highlighting exemplary solutions by the students in the forums at the same time.
Lectures: There are seven new lecture segments that should be viewed this week (Dec 3 - 10). These can be found in the Week 2 collapsable menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
In future weeks, we are planning to make the new set of video lectures available on Fridays, starting this Friday, Dec 7th, at 12:00 pm EST. These videos will be made visible to students if they are available; however, there may not always be subtitles completed for these early release versions.
“See” you out there!
Ronen and Justin
Homework: This week is the second homework set. The two parts should be completed at least once before the Monday, Dec. 10th, 12:00 pm EST deadline. Please read the grading policy and attempt the Sample Homework (if you haven’t already done so) before completing the homework, to better understand the requirements for the course. Be aware that the ‘correct/incorrect’ labels will not appear immediately on homework submissions this week, but will instead appear after the primary deadline on Monday, Dec 10th.
There is a new thread in the Math Help forum titled ‘Worked Problems with the TA’ where Justin will be working through some example problems and discussing them with students. Look for this if you would like to see examples.
There will also be a solution set to the week 1 Homework provided by Dr. Plesser on Wed. Dec 5th, at 12:00 pm EST, after the extended deadline has passed. In addition, we will be highlighting exemplary solutions by the students in the forums at the same time.
Lectures: There are seven new lecture segments that should be viewed this week (Dec 3 - 10). These can be found in the Week 2 collapsable menu on the Video Lectures page. Please also look at the Syllabus for a brief overview of the topics that will be discussed.
In future weeks, we are planning to make the new set of video lectures available on Fridays, starting this Friday, Dec 7th, at 12:00 pm EST. These videos will be made visible to students if they are available; however, there may not always be subtitles completed for these early release versions.
“See” you out there!
Ronen and Justin
Tue 4 Dec 2012 2:09 AM CET
Coursera Weekly Digest Email
This week Coursera is rolling out a new feature, the Weekly Digest. This is an automated email created to reflect your progress on the week's class material. Hopefully this will be a helpful new addition to your study!
As with most new features, however, there may be a window of refinement. As many students have noticed, the email refers to 6 assessments, which is not correct. We expect to learn more details on Monday about how the automated email service identifies assessments and will hopefully have this ironed out in the coming weeks. Thanks to all of you for your patience as we experiment with new ways to make this class and platform better!
As with most new features, however, there may be a window of refinement. As many students have noticed, the email refers to 6 assessments, which is not correct. We expect to learn more details on Monday about how the automated email service identifies assessments and will hopefully have this ironed out in the coming weeks. Thanks to all of you for your patience as we experiment with new ways to make this class and platform better!
Sat 1 Dec 2012 9:24 PM CET
Tokyo meet up of Duke Courserians Dec. 5th or 7th
Lynne O'Brien ( http://cit.duke.edu/about/staff/obrien/ ), who is coordinating Duke's Coursera projects, will be in Tokyo next week. She would love to meet with anyone taking a Duke Coursera course to get feedback on current courses and to hear ideas for future courses. If you are interested in attending a brief, informal discussion with her in the early evening of Dec. 5th or Dec 7th, please email her at lynne.obrien@duke.edu. The meeting will be either in the lobby of the Grand Hyatt Hotel, 6-10-3 Roppongi, Minato-Ku, Tokyo, Japan 106-0032 or in a nearby coffee shop.
Fri 30 Nov 2012 9:00 PM CET
Welcome to Intro to Astronomy!
Welcome to week 1 of IntroAstro!! Our journey through the cosmos begins this week on Tuesday, Nov 27th, 12:00 pm (noon) EST.
Auspiciously, if you look up this evening - almost anywhere - you will be treated to a pretty conjunction (what astronomers call an event in which two objects appear near each other in the sky) of the full Moon and Jupiter - the two brightest objects in the night sky. For those living at longitudes between Europe and Eastern Asia this will create a dimming of the Moon due to a deep penumbral lunar eclipse ar 14:33 GMT on November 28.
This week we will begin our discussion by thinking about the apparent motions of objects in the sky, understanding what they tell us, and developing some mathematical machinery to describe them. At the end of the week, you will be able to follow the reasoning that led me, upon looking up a few days ago, to realize a conjunction was likely coming tomorrow night, and why a conjunction with Jupiter at full Moon suggests an eclipse is likely. We will not take the math all the way to making precise long-term predictions of sky events like eclipses. Modern software can take care of the details. However, we will know enough to explain what goes into the software and make rough estimates of our own.
We suggest you start by clicking the Start Here! button on the Navigation bar to the left hand side to learn some general things about the class.
This week’s material is covered in six video clips, with in-video quizzes to help you see how well you are following the discussion. There is a two-part homework assignment due Monday, Dec. 3 at 12:00 pm EST. Before tackling this, you should do the quick "Sample Homework" to help familiarize yourself with the types of questions you might encounter and the way the system handles your responses.
We are all excited to “meet” you finally, and we’d like to know a bit about you. If you have not yet filled out the survey please do so. In addition, we have a Forum thread asking you where you are from and why you are taking this class. Finally, if you like, you are invited to join an optional Facebook Community for our class.
“See” you tomorrow!
Ronen and Justin
Auspiciously, if you look up this evening - almost anywhere - you will be treated to a pretty conjunction (what astronomers call an event in which two objects appear near each other in the sky) of the full Moon and Jupiter - the two brightest objects in the night sky. For those living at longitudes between Europe and Eastern Asia this will create a dimming of the Moon due to a deep penumbral lunar eclipse ar 14:33 GMT on November 28.
This week we will begin our discussion by thinking about the apparent motions of objects in the sky, understanding what they tell us, and developing some mathematical machinery to describe them. At the end of the week, you will be able to follow the reasoning that led me, upon looking up a few days ago, to realize a conjunction was likely coming tomorrow night, and why a conjunction with Jupiter at full Moon suggests an eclipse is likely. We will not take the math all the way to making precise long-term predictions of sky events like eclipses. Modern software can take care of the details. However, we will know enough to explain what goes into the software and make rough estimates of our own.
We suggest you start by clicking the Start Here! button on the Navigation bar to the left hand side to learn some general things about the class.
This week’s material is covered in six video clips, with in-video quizzes to help you see how well you are following the discussion. There is a two-part homework assignment due Monday, Dec. 3 at 12:00 pm EST. Before tackling this, you should do the quick "Sample Homework" to help familiarize yourself with the types of questions you might encounter and the way the system handles your responses.
We are all excited to “meet” you finally, and we’d like to know a bit about you. If you have not yet filled out the survey please do so. In addition, we have a Forum thread asking you where you are from and why you are taking this class. Finally, if you like, you are invited to join an optional Facebook Community for our class.
“See” you tomorrow!
Ronen and Justin
Mon 26 Nov 2012 11:52 PM CET
Starry Night Software Offer
We will use a sky simulator called "Starry Night" to demonstrate motions of the sky in the class, especially in the first few weeks. Simulators like this are helpful in understanding the Night Sky and also a lot of fun. If you want to purchase Starry Night, a version called "Starry Night College" is available to students in this class at a special price of $14.95. To take advantage of this offer, go to the dedicated web page and follow these instructions:
- Go to www.starrynight.com/dukeastronomy
- Scroll to the bottom of the page
- Select 1 year license
- Enter the download code DUKE12
- Click "Checkout"
- Enter email address and billing information
- Click the "Continue to Next Step" button
- Enter your credit card number and details
- Click "Complete Purchase" button
- Students will receive two emails; First the receipt, then the download
links (Windows and Mac) - Click the appropriate link, follow screen prompts to register. Download
takes just 15 minutes with most connections
Support for this version is available here.
Please note, owning this software is helpful but not necessary for the class. A similar product is available
for free download here
Fri 23 Nov 2012 8:18 PM CET
Welcome!
Hello, and welcome to Introduction to Astronomy. Our class starts in only one more week, and we are all excited here at Duke. As we count down the days to our launch, I wanted to thank you for undertaking this journey with me and share a few things.
This class is intended for students with little or no prior knowledge of astronomy, and we assume only a familiarity with high school level algebra. If you are not comfortable with algebra or it has been a while since you last did any math, you may want to consult one of the math reviews listed below. We will try to introduce all of the physics concepts we use but these introductions will be brief. Some sources for a review of physics topics are listed separately. In general, the more you know the more you will get out of this class, but if you are able to put some work in you should be able to follow the lectures, and do the homework, without much prior experience.
We will not be following a particular textbook, nor will we produce detailed notes for the class. The PowerPoint slides are written to serve as skeleton notes - equations written by hand into the slide on the video will be reproduced in the next slide so you have a record, for example - and we encourage you to produce your own more expansive notes. There are many standard textbooks in many languages that cover roughly the same material we will cover, and you are encouraged to read any of these along with our class. The online Wikibook General Astronomy covers much of the material we cover although the treatment of gravitation, for example, is not as rigorous as what we will do.
In the early weeks of our class we will make heavy use of a simulation tool called “Starry Night.” You can purchase a version of this software that turns your computer into a planetarium at starrynight.com or you can find a similar, free simulation tool at stellarium.org. These simulations are fun and can help you understand the motions of the sky as well as identify what you see in the sky.
There will be weekly homework sets, designed to help you deepen your understanding of the concepts we are covering. Your grades on these will be the basis for the final course grade; there will not be any exams in this class. Even if you are not interested in a grade, we encourage you to work on the problems. At least half the fun of science is doing it, and this is your opportunity. Collaborating with others on these problems is encouraged: that is how science is done. The weekly forums provide a way to do this. If you simply copy down answers from the forums, however, you will not achieve the kind of understanding that comes from thinking through a problem on your own before and after discussing it with others.
The forums are your way to communicate with other students about the class. Having thousands of colleagues worldwide is one of the exciting aspects of taking this new kind of online class. They are also your way to communicate with course staff. Please do not try to contact us directly. Although the opportunity to hear from over 48,000 of you the world over is one of the exciting part of the class for us, the sheer number makes direct communication impractical.
We would like to know some things about our students, so we can better adapt this class, as well as further offerings, to the audience we attract. To this end we ask that you fill out the survey at https://duke.qualtrics.com/SE/?SID=SV_eRJeXDURv5as26F. This is not required, should not take more than 5 minutes, and the information you provide will be used only in aggregate ways that do not identify you personally. In particular, your answers will have no bearing on this or any other Coursera class you might take.
Thanks again, and I really hope you enjoy this class!
ronen
Some Algebra Reviews:
http://www.maths.lse.ac.uk/Refreshers/algebra_refresher.pdf
http://go.hrw.com/resources/go_mt/alg1/alg1refresher.pdf
or, for an astronomy-motivated approach, try Chapter 1 of
http://spacemath.gsfc.nasa.gov/algebra2.html
or
http://physics.bgsu.edu/~tiede/class/bmastronomy1.2.pdf
A listing of some relevant Physics formulas is at
http://astronomyonline.org/Science/Physics.asp?Cate=Science&SubCate=MP04
This class is intended for students with little or no prior knowledge of astronomy, and we assume only a familiarity with high school level algebra. If you are not comfortable with algebra or it has been a while since you last did any math, you may want to consult one of the math reviews listed below. We will try to introduce all of the physics concepts we use but these introductions will be brief. Some sources for a review of physics topics are listed separately. In general, the more you know the more you will get out of this class, but if you are able to put some work in you should be able to follow the lectures, and do the homework, without much prior experience.
We will not be following a particular textbook, nor will we produce detailed notes for the class. The PowerPoint slides are written to serve as skeleton notes - equations written by hand into the slide on the video will be reproduced in the next slide so you have a record, for example - and we encourage you to produce your own more expansive notes. There are many standard textbooks in many languages that cover roughly the same material we will cover, and you are encouraged to read any of these along with our class. The online Wikibook General Astronomy covers much of the material we cover although the treatment of gravitation, for example, is not as rigorous as what we will do.
In the early weeks of our class we will make heavy use of a simulation tool called “Starry Night.” You can purchase a version of this software that turns your computer into a planetarium at starrynight.com or you can find a similar, free simulation tool at stellarium.org. These simulations are fun and can help you understand the motions of the sky as well as identify what you see in the sky.
There will be weekly homework sets, designed to help you deepen your understanding of the concepts we are covering. Your grades on these will be the basis for the final course grade; there will not be any exams in this class. Even if you are not interested in a grade, we encourage you to work on the problems. At least half the fun of science is doing it, and this is your opportunity. Collaborating with others on these problems is encouraged: that is how science is done. The weekly forums provide a way to do this. If you simply copy down answers from the forums, however, you will not achieve the kind of understanding that comes from thinking through a problem on your own before and after discussing it with others.
The forums are your way to communicate with other students about the class. Having thousands of colleagues worldwide is one of the exciting aspects of taking this new kind of online class. They are also your way to communicate with course staff. Please do not try to contact us directly. Although the opportunity to hear from over 48,000 of you the world over is one of the exciting part of the class for us, the sheer number makes direct communication impractical.
We would like to know some things about our students, so we can better adapt this class, as well as further offerings, to the audience we attract. To this end we ask that you fill out the survey at https://duke.qualtrics.com/SE/?SID=SV_eRJeXDURv5as26F. This is not required, should not take more than 5 minutes, and the information you provide will be used only in aggregate ways that do not identify you personally. In particular, your answers will have no bearing on this or any other Coursera class you might take.
Thanks again, and I really hope you enjoy this class!
ronen
Some Algebra Reviews:
http://www.maths.lse.ac.uk/Refreshers/algebra_refresher.pdf
http://go.hrw.com/resources/go_mt/alg1/alg1refresher.pdf
or, for an astronomy-motivated approach, try Chapter 1 of
http://spacemath.gsfc.nasa.gov/algebra2.html
or
http://physics.bgsu.edu/~tiede/class/bmastronomy1.2.pdf
A listing of some relevant Physics formulas is at
http://astronomyonline.org/Science/Physics.asp?Cate=Science&SubCate=MP04
Mon 19 Nov 2012 11:00 PM CET