Metric System and Distances
Scietific notations
Astronomical Units
Vastness emptiness of space
Light year
Gas clouds
Filaments and voids

"The longest journey begins with a single (first) step". Confucius

"Little drops of water, little grains of sand makes the mighty ocean and land".

Our planet earth is a spaceship, orbiting around a star called Sun that drifts through the universe, of which future time and distance are unknown.
No matter how big the universe is, it obeys a set of rules, called the laws of physics.
How big is a star? To grasp the answer to this question in a reasonable way, we need to understand scales of things or objects.
We shall take a number of Steps to reach the size of the known Universe. Each scale or size is 100 times greater than before.

Think of a girl sitting on a campus bench studying Astronomy. We begin with this picture of a scene 50 feet in diameter (size of a basketball field).

If we increase the field of view by 100 times we will see an area 1 mile in diameter, (half the size of Potsdam Village from this Campus to the Hospital). Keeping the size of the picture card same, the individual people, trees and sidewalks have vanished. In such a situation, we expect only to see Potsdam College campus, parts of Racquette river and some of the Church buildings.

This 2nd picture has a field of view one mile is actually 1.6 km. JUST CROSS THE BORDER, INTO CANADA, THEY USE METRIC SYSTEM LIKE MOST PEOPLE IN THE WORLD, Americans and British people are exceptions. For now on, we will use kilometers in this course in solidarity with the rest of the world.

3rd picture card of same length, includes distances 100 times greater than the second card (that is, 100 miles wide). In such a picture card, we will see most of the Adirondack Mountain Forests with Lake placid in the middle, the St Lawrence river, Lake Champlain and parts of Lake Ontario.

4th picture card will be 10,000 miles wide and we will see the entire earth.
5th picture will cover three times the earth-moon distance (3 x 240,000 miles).
6th picture will accommodate the earth-sun distance, called One Astronomical Unit (AU) equal to 1.6x108 km
7th will have all of our solar system in the card,
8th will have a tiny dot for the entire solar system in a vast empty space,
9th will bring about a dozen of nearby stars in the field of view, distance has new unit called One light year (ly) equal to 63,000 AU
Nearest star Proxima Centauri is 4.2 ly away.
10th card will see "thousands of stars" in a distance of 1700 ly in diameter.
11th card will accommodate the "Milky way" our own spiral galaxy.
12th card will see about two dozens nearby galaxies in a cluster, called "Local Group."
13th the last card will accommodate a "Super Cluster", a tiny dot of which is our cluster, the Local Group.

These are the 12 steps to the size of our known Universe. If we go further to look at the heavens, Super clusters are joined in filament like long structures, separated by what seemed like immense empty space (voids).

In the universe, each of the billions of galaxies contain billions of stars, and our sun is a single average star. Universe may span vast amount of space, but the laws governing its administration seem to be "only a handful", the natural laws of physics.

The laws have tremendous power to simplify the vastness of space, motion and energy. For example, Newton's law of gravity is at the heart of all kinds of heavenly motion, everything from the phases of the moon, seasons of the year and drifting of the stars and galaxies. The nice thing about Astronomy, that it explains the subject in simple terms about the vast universe.


Sun is one of 100 billion stars in our galaxy called the Milky way.

The Milky way is one of the billions of galaxies in the universe. 
Galaxies appear to be grouped as Clusters which form Super clusters. Super clusters have filament like long structures in the background of possibly vast empty space.
One Astronomical Unit (AU) equal to 1.6x108 km
One light year (ly) equal to 63,000 AU
NOW WE MUST THINK, HOW TINY WE ARE in the vast expanse of the entire universe!

Updated 02/28/99