Strangely, the phrase “orders of magnitude” featured in a visitor’s search efforts while browsing the sciencebase site. Unfortunately, other than using the phrase myself in the context of, for instance: “the amount of greenhouse gases emitted by human activities is several orders of magnitude smaller than those emitted by natural processes”. I did not actually have a definition of orders of magnitude on the site. Until now. So here goes:
The order of magnitude is the scale of any given amount where each class contains values of a fixed ratio to the class preceding it. The ratio most commonly used is 10. For example, a kilogram is three orders of magnitude bigger than a gram.
In the greenhouse gas instance cited above, the phrase “orders of magnitude” is simply being used colloquially and can apply in many situations, such as the volume of water in the Pacific Ocean is many orders of magnitude greater than that contained in Lake Michigan. To give a more solid example, one might say “An order of magnitude difference between two values is a factor of 10. For example, the mass of the planet Saturn is almost 100 times that of Earth, so Saturn is two orders of magnitude more massive than Earth.
Orders of magnitude are not always on the decimal scale. For instance, the difference in size between a megabyte and a gigabyte is three orders of magnitude, but the multiplier is 1024 rather than 1000. Please correct me if I’m wrong on that, I guess you could define a single order of magnitude her as being based on 1024 rather than “10″.
More on order of magnitude here.