Lighthouse


A lighthouse.

An aid for navigation at sea, a lighthouse is a tower building or framework sending out light from a system of lamps and lenses or, in older times, from a burning fire. More primitive navigational aids were once used such as a fire on top of a hill or cliff, (see beacon). Because of modern navigational aids, the number of active lighthouses has declined to fewer than 1,500 worldwide. Lighthouses are used to mark dangerous coastlines, hazardous shoals away from the coast and safe entries to harbors.

The light is used efficiently:

  • vertically the light is bundled into horizontal directions
  • horizontally the light is bundled into one or a few directions at a time, but sweeping around, so that it can be observed from every horizontal direction

Thus an observer, rather than seeing a continuous weak light, sees a brighter light during short time intervals. These instants of bright light form a pattern specific for the particular lighthouse, e.g. for that of Scheveningen the time intervals between these instants are alternately 2.5 and 7.5 seconds.

Lighthouses have become popular tourist destinations.

In the United States, lighthouses are maintained by the United States Coast Guard. In the United Kingdom, they are looked after by Trinity House.

Perhaps the most famous lighthouse in history is the Lighthouse of Alexandria, built on the island of Pharos in ancient Egypt. The name of the island is still used as the noun for "lighthouse" in some languages, for example French (phare), Italian (faro), Spanish (faro) and Portuguese (farol).

In the beginning of the 20th century Swedish inventor Gustav Dahlén invented the AGA Lighthouse which made manned lighthouses obsolote. Today there are no manned lighthouses left in existence.

See also: List of lighthouses and lightvessels, lightvessel, Robert Louis Stevenson, Grace Darling, Jean Guichard

External link

Light patterns for lighthouses in the Netherlands



In the News

Lack Of Deep Sleep May Increase Risk Of Type 2 Diabetes
Suppression of slow-wave sleep in healthy young adults significantly decreases their ability to regulate blood-sugar levels and increases the risk of type 2 diabetes. This study found that after only three nights of selective slow-wave sleep suppression, young healthy subjects became less sensitive to insulin.

Relationship Between Androgen Deficiency And Cardiovascular Disease Pr
Researchers believe that androgen deficiency might be the underlying cause for a variety of common clinical conditions, including diabetes, erectile dysfunction, metabolic syndrome and cardiovascular disease.

Designer's One-Legged Table: What's the Secret of Its Stability?
Alexandre Boucher's "Levitation Table" is a glass-topped surface with just one leg. So far, the designer has not revealed what keeps his monopod creation from tipping over.

Live Operators Crucial Factor For Public Health Department Disease-rep
Public health departments that staff disease-reporting hotlines with live operators at all times are more likely to meet federal guidelines designed to help stop the spread of infectious diseases, according to a RAND Corp. study issued today.

Cracking Open The Black Box Of Autoimmune Disease
Autoimmune diseases such as type 1 diabetes, lupus and rheumatoid arthritis occur when the immune system fails to regulate itself. But researchers have not known precisely where the molecular breakdowns responsible for such failures occur. Now, a team of scientists from the Whitehead Institute and the Dana-Farber Cancer Institute have identified a key set of genes that lie at the core of autoimmune disease, findings that may help scientists develop new methods for manipulating immune system activity.

San Andreas Earthquake Observatory Achieves Milestone As Drillers Pene
The San Andreas Fault Observatory at Depth (SAFOD) reached a significant goal on Aug. 2 when scientists drilled into a seismically active section of the fault approximately two miles below the surface of the Earth.

Ceramic Tubes Could Cut Greenhouse Gas Emissions From Power Stations
Greenhouse gas emissions from electricity generating stations could be cut to almost zero by controlling the combustion process with an advanced ceramic material, claim engineers.

Computer Network Prepared To Handle Massive Data Flow From World's Lar
Massive quantities of data will soon begin flowing from the largest scientific instrument ever built into an international network of computer centers, including one operated jointly by the University of Chicago and Indiana University. The first phase of the Chicago-Indiana center, formally known as the MidWest Tier 2 Center, is now up and running, crunching test data in preparation for the real thing.

Jewish in Seattle: The Official Website of the Jewish Federation of Gr
Find news, a calendar of events, listing of volunteer opportunities, list of holidays and candle lighting times, and many links, including sites for seniors and teens.

Quick Identification Needed To Save Florida's Citrus Industry From Dev
The recent discovery of citrus greening (huanglongbing) in samples collected from trees in South Florida poses a definite threat to Florida's $9 billion commercial citrus industry. Proper identification and eradication methods are needed to reduce the amount of crop loss caused by this disease, say plant pathologists with the American Phytopathological Society (APS).




MP3 Music Downloads

Preview songs, Download Free Music,Burn CDs at ITunes.com
iTunes_RGB_9mm

 

Google




InformationQuickFind.com - Find Information Fast

Links | Privacy Policy | News |