The Cosmic Distance Scale
By Maggie Masetti, updated March 2008.

This feature will give an impression of how immense our Universe is by employing a method used many times in "Power of 10" films - that is, starting with an image of the Earth and then zooming out towards the furthest visible reaches of our Universe.

This is not, however, an exercise in "powers of 10" - on the contrary, our goal is to show you astronomical distances without scientific notation. We instead focus on the large number of zeros that are in astronomical distances when we measure them with a familiar unit like the kilometer. The number of zeros increase with each zoom, though not at a constant rate.

Why was this feature written? The Imagine the Universe! "Ask An Astrophysicist " service gets many questions asking why humans do not travel to the nearest star or galaxy - many people do not realize how spectacularly far away the "nearest" astronomical objects are.

A note to teachers: For information about Educational Standards that this feature meets, please visit the DLESE catalogue's entry for the Cosmic Distance Scale: http://www.dlese.org/library/catalog_DLESE-000-000-006-009.htm

How do I begin?

Simply click below on the button that says "Begin". A window will pop up with our starting point - Earth. From there, you may zoom out to the next stopping point on our voyage into the depths of outer space by clicking on the "zoom out" button. Every page will give you an opportunity to stop and learn about the objects that are located at that particular distance via a link at the bottom of each page. Each "Tell Me About _____!" page will have information about the image, about the object, how far away it is, what kind of units astronomers use when referring to distances of that magnitude (to avoid using large numbers of zeros!), how distances to that kind of object are determined, why these distances are important to astronomers, and how long it would take for us to travel from Earth to that object. Often external links are employed when they are deemed useful. Click on the word "Back" at the bottom of the page to go back to the Distance Scale. If you wish to zoom back to the Earth, just click on the "zoom in" buttons.

Enjoy your journey!