Lighthouse in the context of "Reef"

Cape Emine (Bulgarian: Нос Емине [ˈnɔs ˈɛminɛ]) is a headland located at the Bulgarian Black Sea Coast. It is located 79 kilometres (49 mi) south of Varna, 55 km (34 mi) north of Burgas and 14 km (9 mi) south of Obzor. It forms the tip of Stara Planina. Cape Emine is said to be Bulgaria's stormiest cape.

In the Middle Ages, there was a fortress called Emona on Cape Emine. Its name was derived from Aemon, the ancient name for Stara Planina. Nowadays, only some ruins of the fortress are left. There are also remnants of a monastery and a lighthouse. The village of Emona is located nearby.

The Lighthouse of Alexandria, sometimes called the Pharos of Alexandria, was a lighthouse built by the Ptolemaic Kingdom of Ancient Egypt, during the reign of Ptolemy II Philadelphus (280–247 BC). It has been estimated to have been at least 100 metres (330 ft) in overall height. One of the Seven Wonders of the Ancient World, for many centuries it was one of the tallest man-made structures in the world.

The lighthouse was severely damaged by three earthquakes between 956 and 1303 AD and became an abandoned ruin. It was the third-longest surviving ancient wonder, after the Mausoleum at Halicarnassus and the extant Great Pyramid of Giza, surviving in part until 1480, when the last of its remnant stones were used to build the Citadel of Qaitbay on the site.

A pulsar (pulsating star, on the model of quasar) is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Earth (similar to the way a lighthouse can be seen only when the light is pointed in the direction of an observer), and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays (see also centrifugal mechanism of acceleration).

Pulsars’ highly regular pulses make them very useful tools for astronomers. For example, observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered in 1992 around a pulsar, specifically PSR B1257+12. In 1983, certain types of pulsars were detected that, at that time, exceeded the accuracy of atomic clocks in keeping time.

Maritime history is the study of human interaction with and activity at sea. It covers a broad thematic element of history that often uses a global approach, although national and regional histories remain predominant. As an academic subject, it often crosses the boundaries of standard disciplines, focusing on understanding humankind's various relationships to the oceans, seas, and major waterways of the globe. Nautical history records and interprets past events involving ships, shipping, navigation, and seafarers.

Maritime history is the broad overarching subject that includes fishing, whaling, international maritime law, naval history, the history of ships, ship design, shipbuilding, the history of navigation, the history of the various maritime-related sciences (oceanography, cartography, hydrography, etc.), sea exploration, maritime economics and trade, shipping, yachting, seaside resorts, the history of lighthouses and aids to navigation, maritime themes in literature, maritime themes in art, the social history of sailors and passengers and sea-related communities. There are a number of approaches to the field, sometimes divided into two broad categories: Traditionalists, who seek to engage a small audience of other academics, and Utilitarians, who seek to influence policy makers and a wider audience.

In economics, a public good (also referred to as a social good or collective good) is a commodity, product or service that is both non-excludable and non-rivalrous and which is typically provided by a government and paid for through taxation. Use by one person neither prevents access by other people, nor does it reduce availability to others, so the good can be used simultaneously by more than one person. This is in contrast to a common good, such as wild fish stocks in the ocean, which is non-excludable but rivalrous to a certain degree. If too many fish were harvested, the stocks would deplete, limiting the access of fish for others. A public good must be valuable to more than one user, otherwise, its simultaneous availability to more than one person would be economically irrelevant.

Capital goods may be used to produce public goods or services that are "...typically provided on a large scale to many consumers." Similarly, using capital goods to produce public goods may result in the creation of new capital goods. In some cases, public goods or services are considered "...insufficiently profitable to be provided by the private sector.... (and), in the absence of government provision, these goods or services would be produced in relatively small quantities or, perhaps, not at all."

A radioisotope thermoelectric generator (RTG, RITEG), or radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts and is ideal for deployment in remote and harsh environments for extended periods with no risk of parts wearing out or malfunctioning.

RTGs are usually the most desirable power source for unmaintained situations that need a few hundred watts (or less) of power for durations too long for fuel cells, batteries, or generators to provide economically, and in places where solar cells are not practical. RTGs have been used as power sources in satellites, space probes, and uncrewed remote facilities such as a series of lighthouses built by the Soviet Union inside the Arctic Circle.

Strongyli Megistis (Greek: Στρογγυλή Μεγίστης), also called simply Strongyli or Ypsili, is a Greek islet which lies in the eastern Mediterranean Sea, about four kilometers south-east of the island of Kastellorizo. The island is about 1.5 kilometres (0.9 miles) long, and up to 700 metres (2,300 ft) wide. It covers an area of about 0.9 square kilometres (0.3 sq mi). It is rather flat and covered with macchia.

Strongyli is the easternmost Greek territory. Administratively, it is part of the Municipality of Megisti. According to the 2021 census, the island has 1 inhabitant. It has a lighthouse, which has the characteristic of being the easternmost building in Greece. There is also a cargo aerial cableway which is used by the army to transport cargo from the area of disembarkation to the Surveillance Outpost of Stroghyli.

Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, fully supplanting Newton's corpuscular theory, from the late 1830s  until the end of the 19th century. He is perhaps better known for inventing the catadioptric (reflective/refractive) Fresnel lens and for pioneering the use of "stepped" lenses to extend the visibility of lighthouses, saving countless lives at sea. The simpler dioptric (purely refractive) stepped lens, first proposed by Count Buffon  and independently reinvented by Fresnel, is used in screen magnifiers and in condenser lenses for overhead projectors.

Fresnel gave the first satisfactory explanation of diffraction by straight edges, including the first satisfactory wave-based explanation of rectilinear propagation. By further supposing that light waves are purely transverse, Fresnel explained the nature of polarization. He then worked on double refraction.