Expert: Jesse Martinez - 1/18/2010

Question
I am a science fiction fan, but not too well informed on the science part. I am starting to notice the inconsistency with which some terms, like galaxy and system and universe are referred to in sci-fi films and series. I have read explanations of the terms, but the way they are used in the TV shows and movies confuses me. In one series, which has been around a long time with the spin offs from the original 60's Star Trek as well as every other sci-fi space program, the terms galaxy, system and quadrant among others are confusing. Within the same series, galaxies are too big to be travelled in a lifetime and also accessible in a few hours. What is the deal here?

Answer
Hello John. I see you have noticed the great inconsistency we knowledgeable science fiction fans have to put up with in the TV and film explanations and usages of these terms. Let me start by defining the hierarchy of terms. A system usually refers to the system of planets and other objects around a star or multiple star system (like the dual suns of Tatooine in Star Wars). Our sun and the planets around it along with the asteroids is called the Solar System, after our sun, Sol. So something like the “Dagobah System” (also Star Wars) refers to a star, Dagobah, that has planets around it.

Then there are galaxies that have billions of stars that could have systems around them. The sci-fi subdivision of a Galaxy is a Quadrant. To use a famous quote from space travel history, “Houston, we have a problem” (that is, we have a failure in nomenclature). There has been an attempt here to divide a three dimensional space into four equal areas. It can be done, but I think the sci-fi writers were trying to translate a 2D concept onto a 3D space (for simplicity or because of ignorance). The best way to subdivide a three dimensional space into the smallest equal 3D subdivisions defined by 90 degree angles is into octants. So there should be an Alpha, Beta, Gamma and Delta, both North and South subdivisions, a total of eight Octants (or with whatever nomenclature desired). I wish I could draw a picture, but I don’t have the software or the manual dexterity to do this at this time. Just think of dividing a cube into eight equal sections with three cuts. This is best represented by a graph with x,y and z axes.

In  reality, the distance between most of the stars in our octant of the galaxy is about 4 to 30,000 light years. The distance between us and the nearest galaxy, Andromeda is 2,900,000 light years. Our galaxy, the Milky Way, is about 100,000 light years wide and an average of 1000 light years thick. So if it takes 75 years to go from one side of our galaxy to another (at faster than light, FTL, speed of course) the trip to Andromeda would take 2175 years. On the other hand, if we could travel to Andromeda in one month, we could traverse our galaxy in less than a day.

It is “science fiction” after all. The greatest inconsistencies and inaccuracies I see in sci-fi happen all the time. They involve sound in a vacuum, where there should be none, and motion and momentum stop when the engines stop, where the ship should keep going at the last speed before the engines were cut.

Ignore the inconsistencies and enjoy the story.