Lighthouses and the reading of a coastline

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Lighthouses are structures associated with lights used to help identify coastal locations and hazards. Their visibility can make them prominent landmarks from both sea and land. They occur on headlands, islands, harbour entrances, and other sites where a recognisable signal is useful. The height and shape of a lighthouse reflect its surroundings as well as the practical requirements of providing and maintaining the light.

A lighthouse signal is more informative than a bright point alone. Distinctive patterns of light and darkness can help distinguish one station from another. The position and height of the light also affect how it is seen from a distance. Weather, visibility, and the observer’s location influence the result. A light that is clear on one occasion may be partly hidden or difficult to recognise under different conditions.

The building must respond to the character of its site. Exposed rocks and windy headlands present different conditions from a sheltered harbour. Access for construction and maintenance may be difficult, and the surrounding sea can shape the form of both the tower and its supporting facilities. The structure visible above the shore is therefore part of a wider arrangement that includes foundations, access routes, equipment, and the demands of the local environment.

The technologies used to produce and direct lighthouse light have changed over time. Different sources of illumination and optical systems have helped make signals visible while controlling how the light is distributed. Automation has also changed the way many stations are operated. These developments do not remove the importance of position, identification, and upkeep; they alter the means by which those functions are carried out.

Observing a lighthouse in the daytime reveals details that may not be visible from the water at night. Its colour, silhouette, and relationship with nearby landforms contribute to its identity. Seen within the broader coastline, it becomes more than an isolated tower. It is one element in a long history of finding routes, recognising places, and responding to the changing conditions where land meets the sea.

Whales: Giants of the Ocean

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Coronavirus disease 2019

COVID-19 is a contagious disease caused by the coronavirus SARS-CoV-2. In January 2020, the disease spread worldwide, resulting in the COVID-19 pandemic.

The symptoms of COVID‑19 can vary but often include fever,[7] fatigue, cough, breathing difficulties, loss of smell, and loss of taste.[8][9][10] Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms.[11][12] Of those who develop symptoms noticeable enough to be classified as patients, most (81%) develop mild to moderate symptoms (up to mild pneumonia), while 14% develop severe symptoms (dyspnea, hypoxia, or more than 50% lung involvement on imaging), and 5% develop critical symptoms (respiratory failure, shock, or multiorgan dysfunction).[13] Older people have a higher risk of developing severe symptoms. Some complications result in death. Some people continue to experience a range of effects (long COVID) for months or years after infection, and damage to organs has been observed.[14] Multi-year studies on the long-term effects are ongoing.[15]

COVID‑19 transmission occurs when infectious particles are breathed in or come into contact with the eyes, nose, or mouth. The risk is highest when people are in close proximity, but small airborne particles containing the virus can remain suspended in the air and travel over longer distances, particularly indoors. Transmission can also occur when people touch their eyes, nose, or mouth after touching surfaces or objects that have been contaminated by the virus. People remain contagious for up to 20 days and can spread the virus even if they do not develop symptoms.[16]

Testing methods for COVID-19 to detect the virus’s nucleic acid include real-time reverse transcription polymerase chain reaction (RT‑PCR),[17][18] transcription-mediated amplification,[17][18][19] and reverse transcription loop-mediated isothermal amplification (RT‑LAMP)[17][18] from a nasopharyngeal swab.[20]

Several COVID-19 vaccines have been approved and distributed in various countries, many of which have initiated mass vaccination campaigns. Other preventive measures include physical or social distancing, quarantining, ventilation of indoor spaces, use of face masks or coverings in public, covering coughs and sneezes, hand washing, and keeping unwashed hands away from the face. While drugs have been developed to inhibit the virus, the primary treatment is still symptomatic, managing the disease through supportive care, isolation, and experimental measures.