Editing Shadow (section)

== Daytime variation ==
The sun casts shadows that change dramatically through the day. The length of a shadow cast on the ground is proportional to the [[cotangent]] of the sun's [[Altitude (astronomy)#Elevation angle|elevation angle]]—its angle ''θ'' relative to the horizon. Near sunrise and sunset, when ''θ'' = 0° and ''cot(θ)'' = ∞, shadows can be extremely long. If the sun passes directly overhead (only possible in locations between the Tropics of Cancer and Capricorn), then ''θ'' = 90°, ''cot(θ)'' = 0, and shadows are cast directly underneath objects.{{Cn|date=March 2025}}

Such variations have long aided travellers during their travels, especially in barren regions such as the [[Arabian Desert]].<ref>{{cite book|title=The Edinburgh monthly review|date=1820|page=372}}</ref>