Expert: Philip Stahl - 3/1/2006

Question
Hi, my name is Tom Moorby and I am currently studying at Canterbury University in the South Island of New Zealand. At the moment I am doing my first assignment for the year. The objective of the assignment is to use e-mail as a tool for research, by trawling the internet for email addresses of people to ask the question to. To be successful we need to receive email replies from the people we send the emails to, and compose a report on our findings. I have been interested in astronomy and anything space related since very young, and this question has been on my mind for some time. In space, is there a North, South, East and West? And why?

Thank you for any information and thank you for your time.

Tom


Answer
Hello.


Compass directions such as North, South, East and West only serve a viable purpose when there is a coordinate system that can be devised - and in which such directions can be used. Thus the Earth system of latitude and longitude allows for such - since two distinct poles (North, South) can be defined, as well as an equator midway between.

A similar convention of directions can be implemented for galaxies. For example, if you check out a 'Norton's Star Atlas' you will find a "Galactic Chart" at the back (my particular edition registers this as 'Map 18') which sets out coordinates for our galaxy, the Milky way. A Galactic Equator is found at zero degrees, and the Galactic latitudes are divided into 'North' and 'South' (e.g. north and south of the galactic equator).

Again, this is useful as a convention, to help in identifying positions of objects in the galaxy with reference to its own particular inertial system. Similar coordinate maps could be set up for Andromeda, or theoretically any other galaxy.

In the case of the universe at large, outside any planets, galaxies, or localized inertial systems, things aren't quite so easy or straightforward. The main problem is that there is no 'center' of the system that can be identified. Hence, there is no 'equator' that can be isolated- and certainly no 'poles' either.

Celestial navigation will, in this case, depend on establishing any convenient reference system - usually based on visible objects, stars. In deep space. Or it may require setting up - using advanced computers- some kind of imaginary reference frame for the ship and its direction.

The bottom line is that the cardinal compass directions, much like latitude and longitude lines, do not actually exist in reality - but purely as imaginary referents for humans to reckon their bearings, and pinpoint object locations.

So, to answer your question - there is NO intrinsic north, south, east or west in space apart from how we define it in terms of a particular coordinate system (e.g. galactic, equatorial, ecliptic etc.)  that we superimpose via a subjective choice.