Though I am sure that most of you would prefer that you did not need to see a number during the entire course, I am afraid that there is no way to avoid it entirely. We will restrict ourselves to simple manipulations, except possibly in the lab portion of the course (if that applies to you). I do want to expose you to numerical notations you will encounter during your course work. We will also briefly discuss units common in astronomy and why we use them.

Astronomy is a unique science in that it works with the largest numbers in the sciences as well as the smallest fractions. To that end we must become somewhat comfortable with scientific notation. Instead of explaining it here, you can find the information in your text or go to the Institute for Energy and Environmental Research web site on scientific notation. They also have an accompanying worksheet to see if you are following the concept. The IEER has graciously allowed me to reproduce their web pages on this local site.

You may be somewhat familiar with scientific notation even though you are not aware of it. Most of the prefixes used when talking about computer speed or memory are really simplified scientific notation. For example, hard drive space is measure in gigabytes. Giga means billion, or 10⁹. So a gigabyte means 10⁹ bytes. Hard drive access times are measured in milliseconds, some around 8 ms or 8 milliseconds. The prefix milli means 1/1000th, so 8 ms is 8/1000th's of a second, or 0.008 seconds. That's pretty fast. Other scientific notation and prefixes you may encounter are in the table below. Notice that all the exponents of 10 are divisible by 3 except the centi, which is only used in centimeters.

You will undoubtedly come across several of these numbers and prefixes before the semester is over, so it is advised that you try to become familiar with them as time goes on. You may even see a few on quizzes and exams.

This page was last updated on 06/06/01.