

The Orbit of the Moon around the Sun is Convex - jyrzyk
http://www.math.nus.edu.sg/aslaksen/teaching/convex.html

======
kqr2
The author also seems to have an interesting course on astronomy and culture:

 _We will look at questions like: How is the date of Chinese New Year
determined? Why do the Muslim and Chinese months start on different days? Will
the Moon ever look like it does on the Singapore flag? What date of the year
is the earliest sunrise in Singapore? How did ancient sailors navigate?_

<http://www.math.nus.edu.sg/aslaksen/teaching/heavenly.html>

------
andrewf
The key to really getting this for me was:

 _You may also want to remember that it is the barycenter of the Earth-Moon
system that moves in an ellipse around the Sun, and that the orbits of both
the Earth and the Moon are perturbations of this ellipse._

------
est
what about other planets & satellites in our solar system??

------
dexter
this is something i need a video to understand properly

~~~
kqr2
Not a video, but a helpful image:

[http://upload.wikimedia.org/wikipedia/commons/1/1d/Moon_traj...](http://upload.wikimedia.org/wikipedia/commons/1/1d/Moon_trajectory1.svg)

~~~
mapleoin
mm... nope. that didn't help

~~~
Chocobean
between the quote below from the article and the excellent picture above, you
should be able to see it....Try again, cuz it's really interesting.

"Imagine you're driving on a circular race track. You overtake a car on the
right, and immediately slow down and go into the left lane. When the other car
passes you, you speed up and overtake on the right again. You will then be
making circles around the other car, but when seen from above, both of you are
driving forward all the time and your path will be convex."

~~~
nebula
When I first saw the article on reddit, I tried to see if I could figure it
out myself, by trying to imagine motion of moon and Earth. But I couldn't.

Then I went to the article and was skimming through it. Just gave up when I
hit this imagine "race track" thing. Was too lazy at that point in time.

However the wikipedia picture did it in seconds. I didn't even have to read
the above quote :) Just proves that "a picture is worth a thousand words"

