The Sizes of Everything

The goal of this exercise is to identify objects spanning a full range of physical sizes. A secondary goal is to reacquaint you with power-of-ten notation. Get help quickly if you need it.

The exercise is much harder than it looks. You may work with a partner, but everyone must turn in their own version.


Sizes will be measured in light-seconds, light-hours, light-years, etc. A light-unit is the distance travelled by light in the indicated time. For example, since light travels at a speed of 300,000 km/sec, a light-second is 300,000 km. A light year (l-y) is the distance travelled by light in one year, or:

300,000 km/sec x 60 sec/min x 60min/hr x 24hr/day x 365.26 days/yr = 1013 km.

Your job is to fill the empty parts of the table below with examples of objects or distances of the appropriate size. You may not be able to fill all of the entries (feel free to leave any two boxes empty). Your entries in the table should follow the examples shown below. The words "distance" or "size" should appear in each entry along with a corresponding number rounded to the nearest power of 10.

Be as complete as you can. You may need to browse through the entire text to find the answers. Even better is the videotape "Powers of 10" available at the media center of the Oedegaard undergraduate library (mezzanine level). For faster service mention Astronomy 101 when requesting the tape.

There is no value in being highly precise in your answers. That's why the range of powers of ten is shown in each box. We're just looking for scale sizes. Its like saying that people are larger than rain drops (a few millimeters) and smaller than cars (a few meters).

Approx Size Example of object size or distance from Earth
10-18 - 10-15 l-s size of atom = about 10-19 light-sec
10-15 - 10-12 l-s  
10-12 - 10-9 l-s  
10-9 - 10-6 l-s size of person = few x 10-9 light-sec
10-6 - 10-3 l-s  
10-3 - 100 l-s  
100 - 103 l-s distance to Moon = about 1 light-sec
103 -106 l-s  
106 - 109 l-s
note: 107.5 l-s = 1 l-y
distance to nearest stars = a few light years
(Switch to the more reasonable units of light years hereafter...)
103 - 106 l-y  
106 - 109 l-y  
109 - 1012 l-y  
1012 - 1015 l-y