FULL COLOR. 36 pages. Extract on Earth's Rotation from book Relatively Simple, 2nd Edition. This extract from Relatively Simple gives a taste of the book's scope. The chapter on Earth's rotation in and with the Universe introduces an appendix evaluating Sagnac Ring-Laser principles. Detail study is made of rectangular 'rings' in which contra-circulating beams of light are used to generate a 'beat' frequency from their interference as the ring rotates with Earth's movement. Actual examples are evaluated. For Relatively Simple and other works search Lulu.com for Geoff Robinson or direct via tinyurl.com/relativelysimple or bit.ly/relativelysimple