PBS
Pbs Learning Media: How Big Is the Universe?
In this media-rich essay from the NOVA Web site, astronomer Brent Tully of the University of Hawaii walks you through the latest scientific theories about the size of the universe.
Khan Academy
Khan Academy: Activity: Powers of 10
Together with the video, Powers of Ten, this activity provides a quick lesson on using scientific notation as a tool to simplify some of the massive and minuscule numbers you'll encounter when looking at things on the extreme ends of a...