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Lighthouse

The presentation discusses the historical significance and engineering advancements in lighthouse design, starting with the Pharos of Alexandria as a foundational archetype. It highlights the introduction of the Fresnel lens in 1822, which dramatically improved light efficiency and visibility range. The document concludes with the modern era's shift towards automation and the cultural transformation of lighthouses from navigational aids to symbols of maritime heritage.

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6 views2 pages

Lighthouse

The presentation discusses the historical significance and engineering advancements in lighthouse design, starting with the Pharos of Alexandria as a foundational archetype. It highlights the introduction of the Fresnel lens in 1822, which dramatically improved light efficiency and visibility range. The document concludes with the modern era's shift towards automation and the cultural transformation of lighthouses from navigational aids to symbols of maritime heritage.

Uploaded by

thekemalrizky
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Title: Engineering and Symbolism in Lighthouse Design: A Historical

Review
Format: Academic Presentation Deck (Slide Deck)
Presenter: Dr. Arthur Shaw, Maritime History Institute
Conference: International Conference on Maritime Heritage (ICMH
2023)
Total Slides: 18 | Excerpt: Slides 5-7

(Slide 5 of 18)

The Classical Archetype: The Pharos of Alexandria


c. 280 BCE | Architect: Sostratus of Cnidus

 Historical Significance: One of the Seven Wonders of the


Ancient World; established the paradigm for all subsequent
lighthouse architecture.

 Engineering Speculation:

o Estimated Height: 100-130m (contested); among the


tallest man-made structures for centuries.

o Structure: Believed to be a three-tiered design: a square


base, an octagonal midsection, and a cylindrical top.

o Light Source & Optics: An open flame, likely amplified


during night hours by a sophisticated system of polished
bronze mirrors. This represents the first known use of
directed light in navigation.

 Legacy: More than a navigational aid; a symbol of Hellenistic


technological achievement and a beacon of civilization.

(Visual: Artist's rendering of the Pharos based on historical


descriptions and archaeological evidence.)

(Slide 6 of 18)

The Optical Revolution: The Fresnel Lens (1822)


Inventor: Augustin-Jean Fresnel

 The Problem: Previous lighthouse optics (parabolic reflectors)


were inefficient, losing over 80% of light output.
 The Innovation: A compound lens design comprising a
central bull's-eye lens surrounded by a series of concentric
prismatic rings.

 The Physics: The design works through refraction. The prisms


bend (refract) light rays that would otherwise be lost, directing
them into a single, powerful horizontal plane.

 The Impact:

o Efficiency: Captured over 83% of the light source.

o Range: Extended visibility from ~2-3 nautical miles


to over 20 nautical miles.

o Identification: Allowed for unique light


characteristics (e.g., flashing, occulting) by using rotating
lens assemblies.

(Visual: Diagram illustrating the path of light through the concentric


rings of a Fresnel lens.)

(Slide 7 of 18)

The Modern Era: Automation and Cultural Metamorphosis


20th Century - Present

 Technological Shift: Adoption of electric lamps, automated bulb


changers, and remote monitoring via telemetry. The role of the
lighthouse keeper became obsolete.

 Modern Function: While remains a official Aid to Navigation


(ATON) and a critical backup system, its primary navigational
role has been supplanted by GPS.

 New Status: Today, the lighthouse is primarily a cultural


symbol and a node of maritime heritage. Preservation efforts
focus on their architectural and historical value.

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