Maybe I shouldn't have started this blog now, not with everything that's been going on.

Last Friday when one of the students made up for the missed experiment on Composition of Concurrent Forces, one of the methods to be used to verify the measurement from the force table was the trigonometric method. It was the part where the student got the largest percentage difference between the experimental and the theoretical value.

It was only then that my team teaching partner in the lab, David, told me that the formula given in the manual for computing the angle was incorrect. That is, it should not be the Law of Sines used but the Law of Cosines. This is because the angle derived using the Law of Sines is not the same one as the angle measured by the students in the experiment, and still has to be derived from the angle that IS computed.

Maybe my former teacher and co-faculty who wrote the latest edition of the manual (now teaching in Texas) did foresee that, which is why she also required a partial graphical representation for the trigonometric method like the purely graphical derivations of the parallelogram and polygon methods. The purely computational component method, for comparison, does not have space provided for drawing graphs. But it was unclear how the angle could be calculated from the Law of Sines.

I have yet to derive it myself for use in future terms.

Last Saturday morning, I had another meeting with the students doing their thesis on astronomy software. They showed me the 3D simulations that they had had made, which included retrograde motion of the superior planets*, transitions of the inferior planets**, lunar and solar eclipses, all as seen from outside of the Earth, and as seen from the Earth.

* planets whose orbits are outside the orbit of the Earth
** planets whose orbits are inside the orbit of the Earth

The graphics were great, especially when the Moon revolved around the Earth, passed through the Earth’s shadow and in turn also cast its shadow on the surface of the Earth. I had the minor recommendations of the labels on the planets being placed, which in retrospect I realize would be redundant, because the animation would only show up when the user clicks “Comparison of motion of Jupiter and the Earth”, and thus would already know what planets are involved.

The only major change I told them was with the transitions. As seen from the Earth, the inferior planet in their graphics was as large as the Moon. I told them that as evidenced by the transition of Mercury in front of the Sun during the daytime in May of last year, that the planet is not large enough to eclipse the entire Sun, so that graphic had to be changed.

I also gave them the instructions on how to use the star maps when standing and when lying down, for which the orientation of the star map is different, as well as the portion of the sky that is visible. This is for use not only in printouts but also for their PDA component.

When standing, the direction one is facing should be placed at the bottom of the star map, because one can only see the bottom quarter pie-slice of the map. When lying down, one should place the direction the head is pointing at the top of the star map, and the whole map is visible.

I’ll elaborate on this some more next time. I have to have lunch now before my 1120am class.