Overheard: floating rocks

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Submerged crustal rocks
http://www.flickr.com/photos/waiferx/536539070/
Originally uploaded by Waifer X

(Overheard in introductory astronomy lab.)

(Students dropping rocks into a water-filled graduated cylinder, in order to determine their displacement volume.)

(Beat.)

Student: "Wait! Why aren't the rocks floating?"