Why are shadows never sharp?
In: Physics
No light is emitted from a single pin-point source. The sun is a disc, and at the edges of shadows only a part of the sun will be obscured (meaning that it’s less illuminated). This is a matter of angles and the sun itself takes up about half a degree (which is scattered a bit by the atmosphere) so this will contribute to half a degree of blurry shadow. This becomes more visible the further away a shadow is from the object that created it.
So if you’re out in the sun, and you cast a shadow on an object that’s 5 meters away, then about 4.5cm of the edge of the shadow will be blurry due to the sun being a big ball of superhot gas and not a pin-point source of light.
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