edX Courses in Astrophysics

[mikemarotta]

https://www.edx.org

I signed up for the Introduction to Astrophysics from the Ecole Polytechnique Federale Lausanne. It is a short 7-week class. When I complete that, I will take on the larger and deeper challenge from Australia National University.

 

What you'll learn

Influence of gravity on celestial bodies

Matter-radiation interactions

Star formation and evolution

Basics of cosmology

I found the first two sessions easy enough. Session three is on statistical mechanics of globular clusters. I had to google for Virial Mechanics. Now the learning begins.

I have worked through some other self-teaching guides from books. I paid for the certification for this course. 

 

 

 

 

Edited December 11, 2020 by mikemarotta

[JamesF]

Prerequisites

Physics and Maths (1st year of bachelor):

• Trigonometry
• Derivatives and Taylor expansions
• Integral calculus
• 1st order differential equations

Trig I can handle, probably derivatives, calculus and differential equations too.  I'll have to look up Taylor series stuff though.  I know I did that at school more than thirty-five years ago, but I can recall nothing about it now.  I have a vague idea that it's about approximation using infinite sums of values in a geometric progression, but I could be completely wrong there.

Looks like an interesting course though.  Do you know if the course runs in rotation if I don't have time to start it right now, or is it a one-off?

James

[mikemarotta]

On 11/12/2020 at 11:43, JamesF said:

Looks like an interesting course though.  Do you know if the course runs in rotation if I don't have time to start it right now, or is it a one-off? -- James

You can sign up any time. It is canned. You watch the videos and take the quizzes.  (See my follow-up below.)

[mikemarotta]

Review of an Online Class in Astrophysics
By Michael E. Marotta

I recently completed an online class offered by the École polytechnique fédérale de Lausanne through edX, a program created by Harvard and MIT and now involving many other institutions. I recommend this class with serious reservations. 

If you want a structured experience in learning astrophysics on your own, this can help. I found the content informative, challenging, and edifying. However, the presentation was often marred by careless transcription and poor translation of the lectures. I do grant that as listed, Physics 209, this is about what I would expect from an American university for a sophomore class in physics, though for non-majors. Calculus is at a minimum here.(You are not required to do any integration or differentiation, but you are expected to understand them when the instructor does them.) If you did well at “Conceptual Physics” and have a head for algebra, this is a solid survey of topics in astrophysics. 

Nominally, the course takes seven weeks to work through seven chapters which are presented as 27 lectures and quizzes. Each lecture is about 20 to 35 minutes. They say three to four hours a week, but that is an absolute minimum. For myself, I did about once each week spend about an hour on one problem, but as I say below, I am not talented at this. There is a thin textbook  that you can download as a PDF. I found it helpful. I printed some of it out and captured equations from other pages to include in my own notes.

I took the course for certification. So, I paid the registration fee of USD 139. Personally, I need that kind of motivation. If I had not been financially invested in the outcome, I would have walked away from it—which I also considered. More than once, I almost cut my losses and left the money on the table. Instead, I toughed it out and actually earned the certificate of completion a little more than halfway through the class because at that point, it was arithmetically impossible for me to fail. Nonetheless, my notebook is filled with answers copied “from the back of the book.” Even after the certification, I viewed all of the videos and worked through all the problem sets.

First, and foremost, I do not have the mindset of a physicist or I would have become one a long, long time ago. So, for some problems, I had to see how it was done, what approach was needed, which contexts were relevant, where the equations of solution had to come from. So, that was learning. I missed a couple of others just because I did not understand what was being asked. 

I also invested a lot of time into correcting the transcripts of the lectures. The English language speaker did not understand the material he was reading. Often, he spoke “v” for the Greek letter nu and “p” for rho, and so on. Sometimes he left symbols out entirely. Once, he spoke “proton” for “photon.” The course was replete with such problems. In one way, the careless transcription of text gave me the opportunity to read and review the lecture in detail. I formatted paragraphs and formatted equations. The fact remains that some lecture notes lacked any punctuation.

A more subtle difficulty was in the differences between sentence structure in French and English. The English speaker paused when the professor did, even though the thoughts presented as subordinate clauses, parenthetical comments, noted asides, or dependent clauses were strung differently in the two languages. 

Despite the fact that the course was supposedly monitored by a professor and three assistants, in point of fact, no one monitored the course. When I finally tried to send an email the EPFL coordinator, the message bounced as undeliverable. So, you are on your own here. 

Edited March 14, 2021 by mikemarotta

[mikemarotta]

 

Quote

 

The grading system is simple. Each video is followed by several quizz, either multiple choice questions or questions requesting a numerical answer. In most cases it is possible to try 2-3 answers before giving the final answer. You qualify for the certificate with at least 50% of correct answers for at least 19 out of the 22 quizz that we propose. 

When a numerical answer is required, usually, a 10% error bar is included in the calculation, more if it's an order of magnitude estimate.

Week 1: General introduction - Kepler's Laws - Virial theorem.
Week 2: Radiation processes - Line radiation - Black body - Measuring radiation.
Week 3: Doppler-Fizeau effect and astrophysical applications - Interstellar and intergalactic radiation - Strömgroen sphere - Absorption/emission - Color index - Tidal forces. 
Week 4: Roche limit - Comets - Planetary energy balance - Planetary atmospheres - 
Week 5: Stellar formation - Stellar classification - Stellar evolution. 
Week 6: The galaxies - Rotation of the Milky Way and Oort constants - Dark matter.
Week 7: Fundamentals of cosmology - Distance ladder - Gravitational lensing.

Length: 7 Weeks
Effort: 3–4 hours per week

 

 

They drop your three lowest scores. With that, I averaged 90%.

Through a YouTube channel created by a maths boffin named Tibees, I found online courseware from MIT. She misidentified it as a final exam in astrophysics. It is merely plain old astronomy, which, apparently, at MIT is astrophysics. 

https://ocw.mit.edu/courses/physics/8-282j-introduction-to-astronomy-spring-2006/exams/final_02_soln.pdf

Anyway, the course from EFPL covers this material. The EFPL course is only designed to be seven weeks, half a semester or so. And lectures are 30 minutes, not 50. So, it was not this much in depth. However, most of these topics were touched on by at least one quiz question.

 

Edited March 14, 2021 by mikemarotta

[mikemarotta]

On 11/12/2020 at 11:43, JamesF said:

Prerequisites

Physics and Maths (1st year of bachelor) ... Trig I can handle, probably derivatives, calculus and differential equations too.  I'll have to look up Taylor series stuff though.  James

Not that much mathematics was required all in all.  As long as you understand the concept, it is enough. You do not need to grind through differential equations or integrations to provide a numerical answer.  

I am now working through this book.

If I had not had the EPFL course, this would be even more opaque.