Notes: Stars and Planets

So far we have made some basic observations, and come to a conclusion about our place in the universe that, as far as we're concerned, is flawless, and frankly kind of gratifying. Centre of the universe huh? Who'd have guessed it. Enough back patting for now though, we have more looking at stuff to do.

For example, the fathomless depths of my eyes.

You may have noticed that while the moon is floating about, it's joined by a bunch of other tiny points of light. To save you the trouble of counting I will tell you now that there are roughly 4000 stars visible to the naked eye. Almost all of these move across the sky in a fixed pattern that, if you were of a type, you might want to sort into patterns and what not.

I am momentarily amused that iTunes, in an act of solidarity has just shuffled in Metallica's 'Orion'. Simple things. Excellent track though.

Alas, things are not as perfect as you might have liked. There are 5 points that don't seem to want to stay in place with the rest. And because you're an ancient Greek, you go ahead and call them astēr planētēs which sounds lovely until you realise it literally means 'Wandering star'. You decide to stick with 'planets' because you're English now and frankly we seem to have a properly hard time not nicking other cultures' words. They are named:

• Mercury
• Venus
• Mars
• Jupiter
• Saturn

Now I'd like to point a little something out. It's not quite so obvious in English where our days of the week are fairly Germanic in origin (There is something quite enjoyable about going to lectures on 'Thor's Day') but some of you may know the more Latin based, French  Check out their names for the days of the week starting on Monday:

• Lundi
• Mardi
• Mercidi
• Jeudi
• Vendredi

Now switch back to English for the weekend and we have:

• Saturday
• Sunday

It all has the same kind of root which is why I'm being fairly inconsistent with language. Point is that our 7 day week is based on the 7 key objects observable in the sky with the naked eye. Some languages name them with their Germanic roots, some Latin, some Gaelic, but on the whole they're all from the same thing, showing just how far back this astronomy business goes.

Right, enough linguistics¹. Back to the observational SCIENCE! So, these wanderers pique your curiosity, and you devote some time to observing them. What you notice is odd. They really do wander, sometimes completely randomly.

A composite view of Mars from Earth

It looped. Mars bloody looped around in the sky. This is nuts. This completely goes against your world view. Everything is meant to be nicely orbiting us and there is Mars pissing off doing it's own thing. What a wanker.  But nonetheless, you have new data to be interpreted. If it's not circling around us neatly it can only mean one thing.

Epicycles.

[1] If I wasn't a physicist I would absolutely go into studying linguistics and etymologies and what not, and not just so I could make hi-LAR-ious oral sex jokes.