# Chapter 1 - Think and Explain: 28

Assuming that the sun's rays are "practically parallel", and referring to Figure 1.1 on page 4, one may form two similar triangles. $$\frac{Pillar \,shadow}{Pillar \,height} = \frac{Distance \,from \,Alexandria \,to \,Syene}{Earth's \,radius}$$ The two 1-to-8 ratios are equal.

#### Work Step by Step

See figure 1.1 on page 4, and the discussion on that page.

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