# Frank Morgan's Math Chat - From Galaxies to Electrons

December 3, 1998

OLD CHALLENGE. What are the largest and smallest objects anyone has ever seen with the naked eye? heard? felt? (For the first part, the whole object must be seen, though not necessarily in full detail or from every side.)

ANSWER. The largest object visible to the naked eye is the Andromeda Galaxy, with a diameter of over 100,000 light years (about one quintillion miles). It is so big that even though it is over two million light years away, its apparent size (to a sensitive instrument) is about an inch at two feet. The smallest visible object is perhaps a speck of dust. (Tinier photons of light can activate the eye, but I'd consider light the means rather than the object of sight.) You can hear the giant plates of the earth's crust as they slide against each other during an earthquake. At the other extreme, you can hear atoms of materials under stress "sliding against each other." You can reach down and touch the earth. At the other extreme, you can feel electrons in an electric shock.

NEW CHALLENGE. Math Chat invites each reader to send in a number. The most commonly submitted number, with the best explanation of why, will win the challenge. No collaboration!

Copyright 1998 Frank Morgan

Send answers, comments, and new questions by email to Frank.Morgan@williams.edu, to be eligible for Flatland and other book awards. Winning answers will appear in the next Math Chat. Math Chat appears on the first and third Thursdays of each month. Prof. Morgan's homepage is at www.williams.edu/Mathematics/fmorgan. Ã?1998, Frank Morgan.

on sabbatical 1998-99
Frank.Morgan@williams.edu
http://www.williams.edu/Mathematics/fmorgan
Math Chat column (appearing the first and third Thursday of each month) and TV show are both available at /news/columns.html