This Week in the Universe you, the reader, we will learn about galaxies and you will have a homework assignment. Don’t worry. You can accomplish this work very easily with an Internet connection. Lets consider "nearby" galaxies in our universe.

Please go to and look at the first 24 images. All of these images, except the one of my son and I and the one of my telescope, are of galaxies.

The first thing you might notice is that the colors are different. The next thing you may note is that the galaxies are different sizes and shapes. This week you will learn why galaxies in our universe appear different.

The galaxies in the photos all lay at different angles and orientations to us (the Milky Way Galaxy) in their distribution throughout the universe. Now go back to the Web site above and look on the fourth and fifth rows.

The first image on each row is a galaxy we are seeing from the side. We call this an "edge-on" perspective. The other images on these rows are "face-on" views. We are seeing the edge-on galaxies from the side, while looking down or up at the face-on galaxies. Why is this?

Although the answer to "why" galaxies are oriented differently throughout the universe is very simple, it has profound implications with roots in the earliest moments of our universe. Here’s the answer to why galaxies lay at all different angles and orientations throughout the Universe.

About 13.7 billion years ago, the Big Bang exploded and spread matter in every direction. Matter was spread unevenly and got "clumpy". The areas where we find more matter are called "walls". These walls of matter appear to run randomly throughout the universe with some interesting "voids" where there is nearly nothing. Ready for the answer? OK.

Galaxies have formed along these walls and their rotational axes lie along the plane of the walls. It’s that simple. The galaxies have lined up where there is matter. If you don’t believe me, go ahead and check out the work of Trujillo, Carretero, and Patiri in the April 1st edition of the Astrophysical Journal Letters.

Even if we could see all the galaxies from the same perspective, we would see that many are shaped differently, but somehow similar. Why is this? There is also a very good answer to that question. You see, just like life itself, the galaxies are undergoing an evolutionary process.

Think of the shape of a tuning fork with one handle and two prongs. In your hand, you are holding the oldest of the galaxies with the central prong. On one of the prongs, are the Spiral Galaxies. There are four phases of Spiral Galaxies, classified as a-d, based on how tightly they are wound.

On the other prong of the tuning fork are Barred Spiral galaxies. These are similar to the spiral galaxies, except they have a straight bar in the middle. Like the normal Spiral Galaxies, there are four (a-d) classifications of Barred Spirals based on how tightly wound they are.

All these galaxies share the common characteristic of starting off as loose associations that wind-up more tightly as time goes on. Eventually, they wind up so tightly that we call them Elliptical galaxies.

The Ellipticals are basically enormous balls of stars. Unfortunately, these are mostly dead galaxies with no more star forming or other activity. There is one other "type" of galaxy called Irregular.

These galaxies are usually the result of some collision or other catastrophic event and they all look different and don’t fit into any one category. Now go back and look at the galaxy photos on that Web site and you will find every type of galaxy except one. Which type of galaxy is not in the gallery? Hey, I said it was a homework assignment so there has to be a question.