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Teaching an Introductory Course on Astrophysics

Recently I had an opportunity to teach basic astrophysics to a group of young students in 8th, 9th, and 10th standards. It was a set of 5 lectures, each lecture lasting for 2 hours.

Before the workshop began, I had requested the students to send me questions they may have on astrophysics based on their prior reading of books or watching of YouTube videos. I received questions on a wide variety of topics, from planetary science to black holes. There were also a few questions on stars and the universe.

I had designed the workshop “an introduction to astrophysics” keeping the stars in sharp focus, plus a bit of cosmology, about the beginning of the universe and evolution of the universe. Astrophysics happens to be a rather complex part of physics, in that it requires knowledge of diverse topics such as classical mechanics, thermal physics, statistical physics, quantum physics, general relativity, hydrodynamics and so on. Now the mathematics of these topics was beyond the reach of the students attending my course and the concepts were also new to them. Therefore I had to make a choice: either give them a lot of jargon filled information without any detailed understanding, OR to focus on specific things in which I could introduce them to not just facts but to conceptual frameworks as well. I also wanted the students to be able to do simple quantitative calculations because in my view a significant part of the beauty of science is in its ability to make quantitative measurable statements.

Apart from that, it was important to me that students get a real feel for how a scientist works. I wanted to give them classwork and homework problems which were slightly open ended and which would challenge them to think. For example while discussing Newton’s law of gravitation, the key force responsible for star formation, I asked them to imagine that they were Newton, and to figure out how Newton could determine the value of the universal gravitational constant G. Another example was to ask them to calculate how fast a proton would be moving at the core of a star. This example gave them a compelling context to understand the nature of heat and temperature.

“I am currently solving the homework questions and will be mailing them to you soon enough. The answers in them are based on what I think is the method to do them, so I am not sure.The way the value of G was found out was so beautiful. I can't believe that an equation that I have been studying for years had so much beauty and simplicity to it.”

Note from a girl while working on her homework assignment

I can go on and give more examples but it suffices to say these questions were very challenging to them and it was certainly very different from the style of learning they were used to (and bored with) in school. I discovered an interesting problem related to science teaching at this level. On the one hand the students nowadays are bored with science in school and are thrilled with lots of information and buzzwords related to science; on the other hand they are not very comfortable with open ended and fuzzy questions either. In a small way, I wanted to get them comfortable with handling “ill posed questions.” If such questions ignite the minds of a few students in each course, like the girl who wrote to me about her ‘new insight into an old equation’, that shall be reward enough for me.

Over five days I could take them rather deep inside the physics of formation of a star, the connection between its surface temperature and spectrum, and what happens to a star at the end of its life cycle. I wanted to take them through a bit more detail about the beginning of the universe, Big Bang Theory, but at the end I ran out of time and could just give them a sketch of this fascinating topic.

So what happened to the questions that they had submitted to me? Some of them I covered in the class; some I didn’t know the answer to, but got my astrophysicist friends to answer them and forwarded the answers to the students. On some of the questions, like the one on black holes, Quark stars, multiverse universe, wormholes etc, I told them they needed to learn Einstein's equation and its implications before they could understand these.. But I did show them the mathematical expression for a solution to Einstein’s equation and tried to explain that the universe does not expand “into some other space” but the distances get stretched !

I hope reading about this experience motivates some of the young students to join the next edition of the course. I am planning to stick to the same topics in the next edition too. But I will go slower and probably break down my classwork and homework assignments into more concrete and solvable parts.

I look forward to interacting with more young minds in the next workshop.

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