Notes: The Moon

Back onto the astronomy thing. As mentioned last time, we are moving onto the second most obvious thing in the sky, The Moon.

To begin with, it's worth knowing a little about something called the ecliptic. This is basically the path the sun took during the day. Secondly, you need to know that everything has an angular position. There is a brilliant rule of thumb for this. I urge you to try it, it works for damn near everyone. Simply hold your arm out in front of you, with your hand up straight, like a traffic cop telling you to stop or something. Your finger is roughly 1°. With this in mind, know that the Moon can be found within 5° of the ecliptic.

Incidentally, both the Moon and the sun are roughly 0.5°, meaning you can more or less cover them with one finger, though if you want to test this one I'd recommend trying it on the Moon first. The Sun is very formal, and pointing is quite rude.

Alright, so you see the Moon, you observe it over some time, and you notice it changes shape with a certain regularity. These are called the phases of the moon and proceed like so:

Incidentally, in the same manner as with Dara O'Brien's slip up, I had my reservations about the accuracy of this particular advert that some of you may remember from our youth.

That clearly should be "Full moon, Waning crescent, No moon", but I guess marketing departments have no time for scientific accuracy.

Anyway, distraction aside, this cycle repeats itself more or less every 29 days.

Interpretation of the Data

Ok, so you're a blank sheet of potential human observation. Telescopes and what not have yet to be invented and all you have seen so far is the Sun and the Moon, going around and around in an eternal game of celestial kiss chase, one full of fiery passion, the other kinda turning invisible half the time. I don't know, I never played kiss chase.

Using this data you try to craft a model of the universe, and eventually settle on one that fits your Sun-Moon-Earth data perfectly. Thus came about the Ptolemiac system, from which arose much of Geocentric cosmology, a view that persisted for a good 1400 years, and one that has clouded much of western philosophy, religion and science.

This incidentally is fine. It's all very well to look back and scoff about how uneducated past folk are, but do remember that given the data they had, this view fit perfectly  They were using what we might now call a "non-inertial reference frame", which in this case is kind of a nice way of saying they didn't know the Earth was also moving.

I'm not strictly holding to the lecture by lecture notes thing at this point instead opting to separate them into similar sub-subjects. So, I'll cut these notes half way through and next time I'll say a little about stars and what not.

Now if you'll excuse me, I need to go buy some Jaffa Cakes.

Heaven.