Earth Shadow Tapering: Why Does It Happen?

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Discussion Overview

The discussion revolves around the phenomenon of the Earth's shadow tapering and seeks to understand the underlying reasons for this effect. Participants explore concepts related to light sources and shadow formation, with references to both Earth and Venus.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant questions why the Earth's shadow tapers, prompting exploration of the nature of light sources.
  • Another participant notes that Venus also casts a shadow, which is observed as a small spot during transits, suggesting a comparison between planetary shadows.
  • Some participants propose that the tapering occurs because the Sun is an extended object rather than a point source of light, although there is a question about the implications of this distinction.
  • There is a suggestion that if the Sun were a point source, the shadow would not taper, leading to further inquiry about the characteristics of the shadow in that scenario.
  • Links to Wikipedia articles on umbra, penumbra, and antumbra are shared for additional context.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the tapering of shadows, with some agreeing on the role of the Sun as an extended light source, while others seek clarification on specific terms and concepts. The discussion remains unresolved regarding the implications of these ideas.

Contextual Notes

Some assumptions about the definitions of tapering and the nature of light sources are not fully explored, and there are unresolved questions about the characteristics of shadows cast by point versus extended sources.

oreo
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The Earth casts a shadow. Why does this shadow taper?
 
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Venus also casts a shadow. On Earth we just see a small spot when Venus transits the Sun.
 
Because the Sun is not a point source of light but an extended object. Does that answer your question or have I misunderstood what taper means here?
 
Drakkith said:
Because the Sun is not a point source of light but an extended object. Does that answer your question or have I misunderstood what taper means here?
You mean if it were a point source, the shadow would not tapper (thinned) . So would it get thicker?
 

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