Shadows look blurry because the sun is not just a tiny dot of light but a big ball. Imagine standing between a pointed flashlight and a wall; your shadow has a sharp dark center and a fuzzy edge. This happens because the light comes from many directions across the surface of the sun. The penumbra is that fuzzy area where some light gets in while other light is blocked. When you move closer to the wall, your shadow becomes sharper because less of the big sun's face can peek around you.
Why It Happens A [point source](/search?q=point%20source) like a tiny LED makes sharp shadows because all [light rays](/search?q=light%20rays) travel straight from one spot. An [extended source](/search?q=extended%20source) like the sun casts shadows with fuzzy edges. The bigger the light, the fuzzier the shadow. This is called penumbral blur. You can see it clearly during an eclipse when the moon blocks different parts of the sun differently.
Examples
- A flashlight far away makes a sharp shadow.
- Holding your hand close to a wall gives a clear outline.
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