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156-644: Pelindaba ("Pelile Ndaba", Zulu for "end of story" or "the conclusion") is South Africa 's main nuclear research centre, run by the South African Nuclear Energy Corporation . It is situated south-east of the Hartbeespoort Dam , approximately 33 km (22 miles) west of Pretoria , on the farm that once belonged to Gustav Preller . During the apartheid era, it was the location where South Africa's atomic bombs were partially developed and constructed. The research reactor SAFARI-1

312-583: A nuclear reactor , where a metres-thick water layer is used as effective shielding. There are two sources of high energy particles entering the Earth's atmosphere from outer space: the sun and deep space. The sun continuously emits particles, primarily free protons, in the solar wind, and occasionally augments the flow hugely with coronal mass ejections (CME). The particles from deep space (inter- and extra-galactic) are much less frequent, but of much higher energies. These particles are also mostly protons, with much of

468-517: A body to a point high enough to ionize small fractions of atoms or molecules by the process of thermal-ionization (this, however, requires relatively extreme radiation intensities). As noted above, the lower part of the spectrum of ultraviolet, called soft UV, from 3 eV to about 10 eV, is non-ionizing. However, the effects of non-ionizing ultraviolet on chemistry and the damage to biological systems exposed to it (including oxidation, mutation, and cancer) are such that even this part of ultraviolet

624-442: A control room in the eastern block. According to the South African Nuclear Energy Corporation (NECSA), the state-owned entity that runs the facility, the four "technically sophisticated criminals" deactivated several layers of security, including a 10,000-volt electrical fence, suggesting insider knowledge of the system. An off-duty emergency services officer, who was shot by the men after a brief struggle, triggered an alarm, alerting

780-613: A fluorescence on a nearby plate of coated glass. Within a month, he discovered the main properties of X-rays that we understand to this day. In 1896, Henri Becquerel found that rays emanating from certain minerals penetrated black paper and caused fogging of an unexposed photographic plate. His doctoral student Marie Curie discovered that only certain chemical elements gave off these rays of energy. She named this behavior radioactivity . Alpha rays (alpha particles) and beta rays ( beta particles ) were differentiated by Ernest Rutherford through simple experimentation in 1899. Rutherford used

936-475: A framework, the nationalist government classified all peoples into three races ( Whites , Blacks , Indians and Coloured people (people of mixed race) ) and developed rights and limitations for each. The white minority (less than 20%) controlled the vastly larger black majority. The legally institutionalised segregation became known as apartheid . While whites enjoyed the highest standard of living in all of Africa, comparable to First World Western nations,

1092-456: A generally temperate climate because it is surrounded by the Atlantic and Indian Oceans on three sides, because it is located in the climatically milder Southern Hemisphere , and because its average elevation rises steadily toward the north (toward the equator) and further inland. This varied topography and oceanic influence result in a great variety of climatic zones. The climatic zones range from

1248-402: A generic pitchblende radioactive source and determined that the rays produced by the source had differing penetrations in materials. One type had short penetration (it was stopped by paper) and a positive charge, which Rutherford named alpha rays . The other was more penetrating (able to expose film through paper but not metal) and had a negative charge, and this type Rutherford named beta . This

1404-681: A half after the discovery of the cape sea route, Jan van Riebeeck established a victualling station at the Cape of Good Hope, at what would become Cape Town , on behalf of the Dutch East India Company. In time, the cape became home to a large population of vrijlieden , also known as vrijburgers ( lit.   ' free citizens ' ), former company employees who stayed in Dutch territories overseas after serving their contracts. Dutch traders also brought thousands of enslaved people to

1560-465: A health hazard if used improperly. Exposure to radiation causes damage to living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair loss, internal organ failure, and death, while any dose may result in an increased chance of cancer and genetic damage ; a particular form of cancer, thyroid cancer , often occurs when nuclear weapons and reactors are the radiation source because of

1716-409: A high point of 62 years in 1992 to a low of 53 in 2005, and the failure of the government to take steps to address the pandemic in its early years. In May 2008, riots left over 60 people dead. The Centre on Housing Rights and Evictions estimated that over 100,000 people were driven from their homes. The targets were mainly legal and illegal migrants , and refugees seeking asylum, but a third of

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1872-410: A higher orbital level, or if the photon is extremely energetic, it may knock an electron from the atom altogether, causing the atom to ionize. Generally, larger atoms are more likely to absorb an X-ray photon since they have greater energy differences between orbital electrons. The soft tissue in the human body is composed of smaller atoms than the calcium atoms that make up bone, so there is a contrast in

2028-436: A material medium. This includes: Radiation is often categorized as either ionizing or non-ionizing depending on the energy of the radiated particles. Ionizing radiation carries more than 10 electron volts (eV) , which is enough to ionize atoms and molecules and break chemical bonds . This is an important distinction due to the large difference in harmfulness to living organisms. A common source of ionizing radiation

2184-413: A nearby police station. The four attackers escaped the facility by the same way they had entered after 45 minutes alone in the compound. Though their images were captured on closed-circuit television, they were not detected by security officers because nobody was monitoring the cameras at the time. On 16 November, three suspects, between the ages of 17 and 28, were arrested by local police in connection with

2340-522: A period of intense political and economic crisis since 2020 with growing numbers of international institutions, businesses and political figures warning that the country risks collapsing into a failed state due to high unemployment, low economic growth, low business investment, rising levels of violent crime, disorder, political corruption, and state capture . The country has been undergoing an energy crisis since 2007, resulting in routine rolling electricity blackouts due to loadshedding . According to

2496-470: A period of significant upheaval, led to the formation of various African kingdoms, including the Zulu Kingdom . The region was further colonised, and diamonds and gold were discovered , bringing a shift towards industrialisation and urbanisation. The Union of South Africa was created in 1910 out of the former Cape , Natal , Transvaal , and Orange River colonies, becoming a republic in 1961 . Though

2652-643: A second term in office by the National Assembly against the leader of the Economic Freedom Fighters , Julius Malema . South Africa is in southernmost Africa, with a coastline that stretches more than 2,500 km (1,553 mi) and along two oceans (the South Atlantic and the Indian). At 1,219,912 km (471,011 sq mi), South Africa is the 24th-largest country in the world. Excluding

2808-460: A significant degree, and is sometimes referred to as vacuum ultraviolet . Although present in space, this part of the UV spectrum is not of biological importance, because it does not reach living organisms on Earth. There is a zone of the atmosphere in which ozone absorbs some 98% of non-ionizing but dangerous UV-C and UV-B. This ozone layer starts at about 20 miles (32 km) and extends upward. Some of

2964-469: A system of non-racial franchise had existed in the Cape, it was gradually eroded, and the vast majority of Black South Africans were not enfranchised until 1994. The National Party imposed apartheid in 1948, institutionalising previous racial segregation . After a largely non-violent struggle by the African National Congress and other anti-apartheid activists both inside and outside

3120-414: A temperature at or below room temperature would thus appear absolutely black, as it would not reflect any incident light nor would it emit enough radiation at visible wavelengths for our eyes to detect. Theoretically, a black-body emits electromagnetic radiation over the entire spectrum from very low frequency radio waves to x-rays, creating a continuum of radiation. The color of a radiating black-body tells

3276-617: A transition of policies and government. In 1990, the National Party government took the first step towards dismantling discrimination when it lifted the ban on the ANC and other political organisations. It released Nelson Mandela from prison after 27 years of serving a sentence for sabotage. A negotiation process followed. With approval from the white electorate in a 1992 referendum , the government continued negotiations to end apartheid. South Africa held its first universal elections in 1994 , which

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3432-629: A violent part of the universe's early history. The kinetic energy of particles of non-ionizing radiation is too small to produce charged ions when passing through matter. For non-ionizing electromagnetic radiation (see types below), the associated particles (photons) have only sufficient energy to change the rotational, vibrational or electronic valence configurations of molecules and atoms. The effect of non-ionizing forms of radiation on living tissue has only recently been studied. Nevertheless, different biological effects are observed for different types of non-ionizing radiation. Even "non-ionizing" radiation

3588-450: A wavelength less than about 10  m (greater than 3 × 10  Hz and 1240 eV ). A smaller wavelength corresponds to a higher energy according to the equation E = h c / λ . ( E is Energy; h is the Planck constant; c is the speed of light; λ is wavelength.) When an X-ray photon collides with an atom, the atom may absorb the energy of the photon and boost an electron to

3744-434: Is radioactive materials that emit α, β, or γ radiation , consisting of helium nuclei , electrons or positrons , and photons , respectively. Other sources include X-rays from medical radiography examinations and muons , mesons , positrons, neutrons and other particles that constitute the secondary cosmic rays that are produced after primary cosmic rays interact with Earth's atmosphere . Gamma rays, X-rays, and

3900-403: Is a common synonym for infrared radiation emitted by objects at temperatures often encountered on Earth. Thermal radiation refers not only to the radiation itself, but also the process by which the surface of an object radiates its thermal energy in the form of black-body radiation. Infrared or red radiation from a common household radiator or electric heater is an example of thermal radiation, as

4056-486: Is also ionizing. Neutrons are categorized according to their speed/energy. Neutron radiation consists of free neutrons . These neutrons may be emitted during either spontaneous or induced nuclear fission. Neutrons are rare radiation particles; they are produced in large numbers only where chain reaction fission or fusion reactions are active; this happens for about 10 microseconds in a thermonuclear explosion, or continuously inside an operating nuclear reactor; production of

4212-610: Is aware of uncertainties and lack of precision of the models and parameter values", "Collective effective dose is not intended as a tool for epidemiological risk assessment, and it is inappropriate to use it in risk projections" and "in particular, the calculation of the number of cancer deaths based on collective effective doses from trivial individual doses should be avoided". Ultraviolet, of wavelengths from 10 nm to 200 nm, ionizes air molecules, causing it to be strongly absorbed by air and by ozone (O 3 ) in particular. Ionizing UV therefore does not penetrate Earth's atmosphere to

4368-841: Is broken. This leads to production of chemical free radicals . In addition, very high energy neutrons can cause ionizing radiation by "neutron spallation" or knockout, wherein neutrons cause emission of high-energy protons from atomic nuclei (especially hydrogen nuclei) on impact. The last process imparts most of the neutron's energy to the proton, much like one billiard ball striking another. The charged protons and other products from such reactions are directly ionizing. High-energy neutrons are very penetrating and can travel great distances in air (hundreds or even thousands of metres) and moderate distances (several metres) in common solids. They typically require hydrogen rich shielding, such as concrete or water, to block them within distances of less than 1 m. A common source of neutron radiation occurs inside

4524-480: Is capable of causing thermal-ionization if it deposits enough heat to raise temperatures to ionization energies. These reactions occur at far higher total energies than with ionization radiation, which requires only single particles to cause ionization. A familiar example of thermal ionization is the flame-ionization of a common fire, and the browning reactions in common food items induced by infrared radiation, during broiling-type cooking. The electromagnetic spectrum

4680-404: Is composed of photons, which have neither mass nor electric charge and, as a result, penetrates much further through matter than either alpha or beta radiation. Gamma rays can be stopped by a sufficiently thick or dense layer of material, where the stopping power of the material per given area depends mostly (but not entirely) on the total mass along the path of the radiation, regardless of whether

4836-580: Is considered one of the most unequal countries in the world, if not the most unequal. The name "South Africa" is derived from the country's geographic location at the southern tip of Africa. Upon formation, the country was named the Union of South Africa in English and Unie van Zuid-Afrika in Dutch , reflecting its origin from the unification of four British colonies. Since 1961, the long formal name in English has been

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4992-534: Is electromagnetic radiation with a wavelength between 0.7 and 300 μm, which corresponds to a frequency range between 430 and 1 THz respectively. IR wavelengths are longer than that of visible light, but shorter than that of microwaves. Infrared may be detected at a distance from the radiating objects by "feel". Infrared sensing snakes can detect and focus infrared by use of a pinhole lens in their heads, called "pits". Bright sunlight provides an irradiance of just over 1 kW/m at sea level. Of this energy, 53%

5148-411: Is infrared radiation, 44% is visible light, and 3% is ultraviolet radiation. Microwaves are electromagnetic waves with wavelengths ranging from as short as 1 mm to as long as 1 m, which equates to a frequency range of 300 MHz to 300 GHz. This broad definition includes both UHF and EHF (millimetre waves), but various sources use different other limits. In all cases, microwaves include

5304-651: Is known as Namaqualand , which becomes more arid near the Orange River. The little rain that falls tends to fall in winter, which results in one of the world's most spectacular displays of flowers carpeting huge stretches of veld in spring (August–September). South Africa also has one offshore possession, the small sub-Antarctic archipelago of the Prince Edward Islands, consisting of Marion Island (290 km or 110 sq mi) and Prince Edward Island (45 km or 17 sq mi) South Africa has

5460-408: Is made of trillions of atoms, only a small fraction of those will be ionized at low to moderate radiation powers. The probability of ionizing radiation causing cancer is dependent upon the absorbed dose of the radiation and is a function of the damaging tendency of the type of radiation ( equivalent dose ) and the sensitivity of the irradiated organism or tissue ( effective dose ). If the source of

5616-403: Is more penetrating than alpha radiation but less than gamma. Beta radiation from radioactive decay can be stopped with a few centimetres of plastic or a few millimetres of metal. It occurs when a neutron decays into a proton in a nucleus, releasing the beta particle and an antineutrino . Beta radiation from linac accelerators is far more energetic and penetrating than natural beta radiation. It

5772-543: Is naturally present in the environment, since most rocks and soil have small concentrations of radioactive materials. Since this radiation is invisible and not directly detectable by human senses, instruments such as Geiger counters are usually required to detect its presence. In some cases, it may lead to secondary emission of visible light upon its interaction with matter, as in the case of Cherenkov radiation and radio-luminescence. Ionizing radiation has many practical uses in medicine, research, and construction, but presents

5928-409: Is often compared with ionizing radiation. Light, or visible light, is a very narrow range of electromagnetic radiation of a wavelength that is visible to the human eye, or 380–750 nm which equates to a frequency range of 790 to 400 THz respectively. More broadly, physicists use the term "light" to mean electromagnetic radiation of all wavelengths, whether visible or not. Infrared (IR) light

6084-602: Is often referred to as the " rainbow nation " to describe the country's multicultural diversity, especially in the wake of apartheid. As a middle power in international affairs, South Africa maintains a significant regional influence . In addition to that, the country is a member of BRICS+ , the African Union , SADC , SACU , the Commonwealth of Nations , and the G20 . A developing , newly industrialised country , South Africa has

6240-721: Is radiation frequencies from 3 to 30 Hz (10 to 10  m respectively). In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU Radio Bands. A massive military ELF antenna in Michigan radiates very slow messages to otherwise unreachable receivers, such as submerged submarines. Thermal radiation

6396-475: Is rare. The coldest place on mainland South Africa is Buffelsfontein in the Eastern Cape , where a temperature of −20.1 °C (−4.2 °F) was recorded in 2013. The Prince Edward Islands have colder average annual temperatures, but Buffelsfontein has colder extremes. The deep interior of mainland South Africa has the hottest temperatures: a temperature of 51.7 °C (125.06 °F) was recorded in 1948 in

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6552-532: Is sometimes used therapeutically in radiotherapy to treat superficial tumors. Beta-plus (β ) radiation is the emission of positrons , which are the antimatter form of electrons. When a positron slows to speeds similar to those of electrons in the material, the positron will annihilate an electron, releasing two gamma photons of 511 keV in the process. Those two gamma photons will be traveling in (approximately) opposite directions. The gamma radiation from positron annihilation consists of high energy photons, and

6708-527: Is stripped (or "knocked out") from an electron shell of the atom, which leaves the atom with a net positive charge. Because living cells and, more importantly, the DNA in those cells can be damaged by this ionization, exposure to ionizing radiation increases the risk of cancer . Thus "ionizing radiation" is somewhat artificially separated from particle radiation and electromagnetic radiation, simply due to its great potential for biological damage. While an individual cell

6864-694: Is surrounded by the Great Escarpment whose eastern, and highest, stretch is known as the Drakensberg . Mafadi in the Drakensberg at 3,450 m (11,320 ft) is the highest peak. The KwaZulu-Natal–Lesotho international border is formed by the highest portion of the Great Escarpment which reaches an altitude of over 3,000 m (9,800 ft). The south and south-western parts of the plateau (at approximately 1,100–1,800   m above sea level) and

7020-414: Is technically not ionizing. The highest frequencies of ultraviolet light, as well as all X-rays and gamma-rays are ionizing. The occurrence of ionization depends on the energy of the individual particles or waves, and not on their number. An intense flood of particles or waves will not cause ionization if these particles or waves do not carry enough energy to be ionizing, unless they raise the temperature of

7176-407: Is the heat emitted by an operating incandescent light bulb. Thermal radiation is generated when energy from the movement of charged particles within atoms is converted to electromagnetic radiation. As noted above, even low-frequency thermal radiation may cause temperature-ionization whenever it deposits sufficient thermal energy to raise temperatures to a high enough level. Common examples of this are

7332-696: Is the range of all possible electromagnetic radiation frequencies. The electromagnetic spectrum (usually just spectrum) of an object is the characteristic distribution of electromagnetic radiation emitted by, or absorbed by, that particular object. The non-ionizing portion of electromagnetic radiation consists of electromagnetic waves that (as individual quanta or particles, see photon ) are not energetic enough to detach electrons from atoms or molecules and hence cause their ionization. These include radio waves, microwaves, infrared, and (sometimes) visible light. The lower frequencies of ultraviolet light may cause chemical changes and molecular damage similar to ionization, but

7488-469: The Dutch East India Company were shipwrecked at the cape for several months. The sailors were able to survive by obtaining fresh water and meat from the natives. They also sowed vegetables in the fertile soil. Upon their return to Holland, they reported favourably on the cape's potential as a "warehouse and garden" for provisions to stock passing ships for long voyages. In 1652, a century and

7644-596: The Highveld . This relatively well-watered area is home to a great proportion of the country's commercial farmlands and contains its largest conurbation (Gauteng). To the north of Highveld, from about the 25°   30'   S line of latitude, the plateau slopes downwards into the Bushveld , which ultimately gives way to the Limpopo River lowlands or Lowveld . The coastal belt, below the Great Escarpment, moving clockwise from

7800-682: The Indian Ocean trade . The events around Mapungubwe's collapse circa 1300 are unknown, however trade routes shifted north from the Limpopo to the Zambezi , precipitating the rise of Great Zimbabwe . The hill was abandoned and Mapungubwe's population scattered. In 1487, the Portuguese explorer Bartolomeu Dias led the first European voyage to land in southern Africa. On 4 December, he landed at Walfisch Bay (now known as Walvis Bay in present-day Namibia). This

7956-828: The International Court of Justice regarding Israel 's conduct in the Gaza Strip as part of the Israel–Hamas war , alleging that Israel had committed and was committing genocide against Palestinians in the Gaza Strip. South Africa has repeatedly hosted senior leaders of Hamas , the group responsible for the October 7th massacre in Israel. Following the 2024 general elections , the African National Congress saw its share of

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8112-484: The International Monetary Fund , South Africa is suffering from "massive corruption" and state capture. The Zondo Commission , established in 2018 in order to investigate allegations of corruption and state capture released its findings in 2022. It found rampant corruption at every level of government, including Transnet , Eskom , and Denel , as well as law enforcement , intelligence agencies , and

8268-713: The Native Location Act of 1879 and the system of pass laws . Eight years after the end of the Second Boer War and after four years of negotiation, the South Africa Act 1909 granted nominal independence while creating the Union of South Africa on 31 May 1910. The union was a dominion that included the former territories of the Cape, Transvaal and Natal colonies, as well as the Orange Free State republic. The Natives' Land Act of 1913 severely restricted

8424-719: The New York Times reported that the SAFARI-1 reactor at Pelindaba was regularly inspected by the IAEA. In 1992, it was revealed that the Valindaba facility had enriched uranium for the manufacture of nuclear weapons. The plant was operational from 1975 until 1990. In 1996, the Associated Press described Pelindaba as the place "once at the heart of South Africa's (nuclear) weapons program". The South African Nuclear Energy Corporation (NECSA)

8580-729: The Outeniqua and Langeberg ranges to the south and the Swartberg range to the north is known as the Little Karoo , which consists of semi-desert shrubland similar to that of the Great Karoo, except that its northern strip along the foothills of the Swartberg Mountains has a somewhat higher rainfall and is, therefore, more cultivated than the Great Karoo. The Little Karoo is famous for its ostrich farming around Oudtshoorn . The lowland area to

8736-923: The Pedi people . King Sekhukhune managed to defeat the army on 1 August 1876. Another attack by the Lydenburg Volunteer Corps was also repulsed. On 16 February 1877, the two parties signed a peace treaty at Botshabelo . The Boers' inability to subdue the Pedi led to the departure of Burgers in favour of Paul Kruger and the British annexation of the South African Republic. In 1878 and 1879 three British attacks were successfully repelled until Garnet Wolseley defeated Sekhukhune in November 1879 with an army of 2,000 British soldiers, Boers and 10,000 Swazis. The Anglo-Zulu War

8892-489: The Prince Edward Islands , the country lies between latitudes 22° and 35°S , and longitudes 16° and 33°E . The interior of South Africa consists of a large, in most places almost flat plateau with an altitude of between 1,000 m (3,300 ft) and 2,100 m (6,900 ft), highest in the east and sloping gently downwards towards the west and north, and slightly so to the south and south-west. This plateau

9048-639: The Republic of South Africa ( RSA ), is the southernmost country in Africa . Its nine provinces are bounded to the south by 2,798 kilometres (1,739 miles) of coastline that stretches along the South Atlantic and Indian Ocean ; to the north by the neighbouring countries of Namibia , Botswana , and Zimbabwe ; to the east and northeast by Mozambique and Eswatini ; and it encloses Lesotho . Covering an area of 1,221,037 square kilometres (471,445 square miles),

9204-462: The Second Boer War (1899–1902) and, although suffering heavy casualties due to Boer attrition warfare , they were ultimately successful due in part to scorched earth tactics such as concentration camps , in which 27,000 Boer civilians died due to a combination of disease and neglect. South Africa's urban population grew rapidly from the end of the 19th century onward. After the devastation of

9360-646: The South African Party and National Party merged to form the United Party , seeking reconciliation between Afrikaners and English-speaking whites. In 1939, the party split over the entry of the union into World War II, as an ally of the United Kingdom, a move which National Party followers opposed. In 1948, the National Party was elected to power. It strengthened the racial segregation begun under Dutch and British colonial rule. Taking Canada's Indian Act as

9516-798: The South African Republic , the Natalia Republic , and the Orange Free State . In the interior, the Cape Colony expanded at the expense of the Batswana and Griqua , and Boer expansion caused great instability in the Middle Orange River region. The Matabele kingdom came to dominate the eastern interior, and raided the Venda kingdom. The discovery of diamonds in 1867 and gold in 1884 in

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9672-534: The Sun and detected the infrared (beyond the red part of the spectrum), through an increase in the temperature recorded by a thermometer . In 1801, the German physicist Johann Wilhelm Ritter made the discovery of ultraviolet by noting that the rays from a prism darkened silver chloride preparations more quickly than violet light. Ritter's experiments were an early precursor to what would become photography. Ritter noted that

9828-512: The Vaal River valley. Settlements of Bantu-speaking peoples , who were iron-using agriculturists and herdsmen , were present south of the Limpopo River (now the northern border with Botswana and Zimbabwe ) by the 4th or 5th century CE. The Bantu slowly moved south. The earliest ironworks in modern-day KwaZulu-Natal Province are believed to date from around 1050. The southernmost group

9984-788: The Xhosa Wars , as both sides competed for the pastureland near the Great Fish River, which the colonists desired for grazing cattle. Vrijburgers who became independent farmers on the frontier were known as Boers , with some adopting semi-nomadic lifestyles being denoted as trekboers . The Boers formed loose militias , which they termed commandos , and forged alliances with Khoisan peoples to repel Xhosa raids. Both sides launched bloody but inconclusive offensives, and sporadic violence, often accompanied by livestock theft, remained common for several decades. Great Britain occupied Cape Town between 1795 and 1803 to prevent it from falling under

10140-519: The civil service . It documented evidence of systemic corruption , fraud , racketeering , bribery , money laundering , and state capture. It investigated the African National Congress party and Jacob Zuma, whom it concluded were complicit in state capture through their direct assistance to the Gupta family . "The Commission estimated the total amount of money spent by the state which was 'tainted' by state capture to be around R57 billion. More than 97% of

10296-490: The largest economy in Africa by nominal GDP. It is tied with Ethiopia for the most UNESCO World Heritage Sites in Africa, and is a biodiversity hotspot with unique biomes , plant, and animal life. Since the end of apartheid, government accountability and quality of life have substantially improved. However, crime , poverty , and inequality remain widespread. Having the highest Gini coefficient of 0.63, South Africa

10452-522: The "Republic of South Africa" and Republiek van Suid-Afrika in Afrikaans . The country has an official name in 12 official languages . Mzansi , derived from the Xhosa noun uMzantsi meaning "south", is a colloquial name for South Africa, while some Pan-Africanist political parties prefer the term " Azania ". South Africa contains some of the oldest archaeological and human-fossil sites in

10608-513: The 14th largest emitter of carbon dioxide, primarily from its heavy reliance on coal and oil for energy production . As part of its international commitments, South Africa has pledged to peak emissions between 2020 and 2025. South Africa signed the Rio Convention on Biological Diversity on 4 June 1994 and became a party to the convention on 2 November 1995. It has subsequently produced a National Biodiversity Strategy and Action Plan , which

10764-594: The ANC won by an overwhelming majority. It has been in power ever since. The country rejoined the Commonwealth of Nations and became a member of the Southern African Development Community . In post-apartheid South Africa, unemployment remained high. While many black people have risen to middle or upper classes, the overall unemployment rate of black people worsened between 1994 and 2003 by official metrics but declined significantly using expanded definitions. Poverty among white South Africans, which

10920-674: The Bushveld exists in the north-east including Kruger National Park and the Sabi Sand Game Reserve , as well as in the far north in the Waterberg Biosphere . South Africa houses many endemic species , among them the critically endangered riverine rabbit ( Bunolagus monticullaris ) in the Karoo. Radiation In physics , radiation is the emission or transmission of energy in the form of waves or particles through space or

11076-463: The Congo , Rwanda , Eritrea , Ethiopia and Somalia . Competition over jobs, business opportunities, public services and housing has led to tension between refugees and host communities. While xenophobia in South Africa is still a problem, the United Nations High Commissioner for Refugees in 2011 reported that recent violence had not been as widespread as initially feared. Nevertheless, as South Africa continues to grapple with racial issues, one of

11232-644: The Earth from outer space were finally definitively recognized and proven to exist in 1912, as the scientist Victor Hess carried an electrometer to various altitudes in a free balloon flight. The nature of these radiations was only gradually understood in later years. The Neutron and neutron radiation were discovered by James Chadwick in 1932. A number of other high energy particulate radiations such as positrons , muons , and pions were discovered by cloud chamber examination of cosmic ray reactions shortly thereafter, and others types of particle radiation were produced artificially in particle accelerators , through

11388-501: The Lowveld covering 19,633 square kilometres (7,580 sq mi) The coastal belt below the south and south-western stretches of the Great Escarpment contains several ranges of Cape Fold Mountains which run parallel to the coast, separating the Great Escarpment from the ocean. (These parallel ranges of fold mountains are shown on the map, above left. Note the course of the Great Escarpment to the north of these mountain ranges.) The land between

11544-506: The Ndwandwe, however were repelled by Gaza. During the early 19th century, many Dutch settlers departed from the Cape Colony , where they had been subjected to British control, in a series of migrant groups who came to be known as Voortrekkers , meaning "pathfinders" or "pioneers". They migrated to the future Natal , Free State, and Transvaal regions. The Boers founded the Boer republics :

11700-624: The Northern Cape Kalahari near Upington , but this temperature is unofficial and was not recorded with standard equipment; the official highest temperature is 48.8 °C (119.84 °F) at Vioolsdrif in January 1993. Climate change in South Africa is leading to increased temperatures and rainfall variability. Extreme weather events are becoming more prominent. This is a critical concern for South Africans as climate change will affect

11856-452: The Pacific. In 1970, it was officially revealed that the development of a pilot plant for the enrichment of uranium was under way. Prime Minister John Vorster said of the development that "our sole objective in the development and application of the process is to promote the peaceful application of nuclear energy. Only then can it be to our benefit and to the benefit of mankind." Details of

12012-554: The R57 billion came from Transnet and Eskom. Out of these funds, the Gupta enterprise received at least R15 billion. The total loss to the state is difficult to quantify, but would far exceed that R15 billion." South Africa has maintained a position of neutrality in regards to the Russia invasion of Ukraine in 2022 and the ongoing war . On 29 December 2023, South Africa formally submitted its case to

12168-805: The South African National Biodiversity Institute, parts of southern Africa will see an increase in temperature by about 1 °C (1.8 °F) along the coast to more than 4 °C (7.2 °F) in the already hot hinterland such as the Northern Cape in late spring and summertime by 2050. The Cape Floral Region is predicted to be hit very hard by climate change. Drought, increased intensity and frequency of fire, and climbing temperatures are expected to push many rare species towards extinction. South Africa has published two national climate change reports in 2011 and 2016. South Africa contributes considerable carbon dioxide emissions , being

12324-609: The South African government because of its racial policies. The boycotts and restrictions were later extended to international sanctions and the divestment of holdings by foreign investors. The Mahlabatini Declaration of Faith , signed by Mangosuthu Buthelezi and Harry Schwarz in 1974, enshrined the principles of peaceful transition of power and equality for all, the first of such agreements by black and white political leaders in South Africa. Ultimately, F.W. de Klerk opened bilateral discussions with Nelson Mandela in 1993 for

12480-551: The U.S. 27 months later, no shipments had been received. In 1975, Prime Minister John Vorster said that he expected South Africa to have new uranium enrichment capacity by 1983. He stated that while South Africa was seeking international partners in its enrichment program, it would "go it alone" if necessary. The enrichment process developed at Pelindaba promised to provide major efficiency gains over prior centrifugal processes. In 1977, Finance Minister Owen Horwood stated that his party stood by its assurance that its nuclear program

12636-531: The UV rays were capable of causing chemical reactions. The first radio waves detected were not from a natural source, but were produced deliberately and artificially by the German scientist Heinrich Hertz in 1887, using electrical circuits calculated to produce oscillations in the radio frequency range, following formulas suggested by the equations of James Clerk Maxwell . Wilhelm Röntgen discovered and named X-rays . While experimenting with high voltages applied to an evacuated tube on 8 November 1895, he noticed

12792-422: The absolute temperature of that body. The radiation emitted covers the entire electromagnetic spectrum and the intensity of the radiation (power/unit-area) at a given frequency is described by Planck's law of radiation. For a given temperature of a black-body there is a particular frequency at which the radiation emitted is at its maximum intensity. That maximum radiation frequency moves toward higher frequencies as

12948-466: The absorption of X-rays. X-ray machines are specifically designed to take advantage of the absorption difference between bone and soft tissue, allowing physicians to examine structure in the human body. X-rays are also totally absorbed by the thickness of the earth's atmosphere, resulting in the prevention of the X-ray output of the sun, smaller in quantity than that of UV but nonetheless powerful, from reaching

13104-516: The adjoining plain below (at approximately 700–800   m above sea level – see map on the right) is known as the Great Karoo , which consists of sparsely populated shrubland . To the north, the Great Karoo fades into the more arid Bushmanland, which eventually becomes the Kalahari Desert in the north-west of the country. The mid-eastern and highest part of the plateau is known as

13260-657: The arrival of the 1820 Settlers . The new colonists were induced to settle for a variety of reasons, namely to increase the size of the European workforce and to bolster frontier regions against Xhosa incursions. In the early 1800s, the Mfecane (lit. 'crushing') saw a heightened period of conflict, migration, and state formation among native groups, caused by the complex interplay of international trade, environmental instability, and European colonisation. Chiefdoms grew wealthier and competed over trade routes and grazing land, leading to

13416-555: The biological proclivities of the radioactive iodine fission product, iodine-131 . However, calculating the exact risk and chance of cancer forming in cells caused by ionizing radiation is still not well understood, and currently estimates are loosely determined by population-based data from the atomic bombings of Hiroshima and Nagasaki and from follow-up of reactor accidents, such as the Chernobyl disaster . The International Commission on Radiological Protection states that "The Commission

13572-563: The black majority remained disadvantaged by almost every standard, including income, education, housing, and life expectancy. The Freedom Charter , adopted in 1955 by the Congress Alliance , demanded a non-racial society and an end to discrimination. On 31 May 1961, the country became a republic following a referendum (only open to white voters) which narrowly passed; the British-dominated Natal province largely voted against

13728-491: The coast, which is subtropical . The Free State is particularly flat because it lies centrally on the high plateau. North of the Vaal River , the Highveld becomes better watered and does not experience subtropical extremes of heat. Johannesburg, in the centre of the Highveld, is at 1,740 m (5,709 ft) above sea level and receives an annual rainfall of 760 mm (29.9 in). Winters in this region are cold, although snow

13884-722: The control of the French First Republic , which had invaded the Low Countries . After briefly returning to Dutch rule under the Batavian Republic in 1803, the cape was occupied again by the British in 1806. Following the end of the Napoleonic Wars , it was formally ceded to Great Britain and became an integral part of the British Empire . British emigration to South Africa began around 1818, subsequently culminating in

14040-520: The country has over 62 million people . Pretoria is the administrative capital, while Cape Town , as the seat of Parliament , is the legislative capital. Bloemfontein has traditionally been regarded as the judicial capital. The largest and most populous city is Johannesburg , followed by Cape Town and the busiest port city in sub-Saharan Africa, Durban . Archaeological findings suggest that various hominid species existed in South Africa about 2.5 million years ago, and modern humans inhabited

14196-404: The country, the repeal of discriminatory laws began in the mid-1980s. Universal elections took place in 1994 , following which all racial groups have held political representation in the country's liberal democracy , which comprises a parliamentary republic and nine provinces. South Africa is a multi-ethnic society encompassing a wide variety of cultures , languages , and religions ; it

14352-416: The energies; there is some overlap in the effects of specific frequencies . The word "radiation" arises from the phenomenon of waves radiating (i.e., traveling outward in all directions) from a source. This aspect leads to a system of measurements and physical units that apply to all types of radiation. Because such radiation expands as it passes through space, and as its energy is conserved (in vacuum),

14508-457: The energy away as radio waves; these are mostly termed interference. Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves may bend at the rate of the curvature of the Earth and may cover a part of the Earth very consistently, shorter waves travel around the world by multiple reflections off the ionosphere and the Earth. Much shorter wavelengths bend or reflect very little and travel along

14664-545: The energy of such waves by passing through, on the average, 500 ft (150 m). Alpha particles are helium-4 nuclei (two protons and two neutrons). They interact with matter strongly due to their charges and combined mass, and at their usual velocities only penetrate a few centimetres of air, or a few millimetres of low density material (such as the thin mica material which is specially placed in some Geiger counter tubes to allow alpha particles in). This means that alpha particles from ordinary alpha decay do not penetrate

14820-399: The entire super high frequency band (3 to 30 GHz, or 10 to 1 cm) at minimum, with RF engineering often putting the lower boundary at 1 GHz (30 cm), and the upper around 100 GHz (3 mm). Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Like all other electromagnetic waves, they travel at

14976-537: The extreme desert of the southern Namib in the farthest northwest to the lush subtropical climate in the east along the border with Mozambique and the Indian Ocean. Winters in South Africa occur between June and August. The extreme southwest has a climate similar to that of the Mediterranean with wet winters and hot, dry summers, hosting the famous fynbos biome of shrubland and thicket . This area produces much of

15132-1235: The first hominin fossil discovered in Africa, the Taung Child (found near Taung ) in 1924. Other hominin remains have come from the sites of Makapansgat in Limpopo Province; Cornelia and Florisbad in Free State Province ; Border Cave in KwaZulu-Natal Province; Klasies River Caves in Eastern Cape Province; and Pinnacle Point , Elandsfontein and Die Kelders Cave in Western Cape Province. These finds suggest that various hominid species existed in South Africa from about three million years ago, starting with Australopithecus africanus , followed by Australopithecus sediba , Homo ergaster , Homo erectus , Homo rhodesiensis , Homo helmei , Homo naledi and modern humans ( Homo sapiens ). Modern humans have inhabited Southern Africa for at least 170,000 years. Various researchers have located pebble tools within

15288-523: The fledgling colony from Indonesia , Madagascar , and parts of eastern Africa. Some of the earliest mixed race communities in the country were formed between vrijburgers , enslaved people, and indigenous peoples. This led to the development of a new ethnic group, the Cape Coloureds , most of whom adopted the Dutch language and Christian faith. The Khoisan people, comprising the Khoikhoi and San, were

15444-470: The formation of the Ndwandwe and Mthethwa Paramountcies in the east. Ndwandwe defeated Mthethwa which split into different groups, one of which was led by Shaka of the amaZulu . The 1810s saw the fourth and fifth Xhosa Wars as British colonisation expanded. Ndwandwe splintered amid costly raids and Shaka's Zulu Kingdom rose to fill the power vacuum. The Gaza kingdom formed. The Zulu totally defeated

15600-417: The higher energy range of ultraviolet light constitute the ionizing part of the electromagnetic spectrum . The word "ionize" refers to the breaking of one or more electrons away from an atom, an action that requires the relatively high energies that these electromagnetic waves supply. Further down the spectrum, the non-ionizing lower energies of the lower ultraviolet spectrum cannot ionize atoms, but can disrupt

15756-639: The incident but were later released. In response to the attack, NECSA suspended six Pelindaba security personnel, including the general manager of security and promised an "internal investigation which will cover culpability, negligence and improvements of security systems." China has been speculated to be behind the attacks. On 16 March 2009, a leak of radioactive gases from Pelindaba was reported by NECSA. Abnormal levels of gamma radiation associated with xenon and krypton gases were detected, causing an emergency to be declared. Members of staff were evacuated. South Africa South Africa , officially

15912-445: The indigenous inhabitants of South Africa. Conflicts with Dutch settlers began in the 17th century and continued for centuries. Initial encounters between Dutch coloniers and Khoikhoi were peaceful, but tensions arose over land and resources. The Khoikhoi resisted Dutch expansion, leading to skirmishes and battles. The eastward expansion of Dutch colonists ushered in a series of wars with the southwesterly migrating Xhosa tribe, known as

16068-450: The intensity of all types of radiation from a point source follows an inverse-square law in relation to the distance from its source. Like any ideal law, the inverse-square law approximates a measured radiation intensity to the extent that the source approximates a geometric point. Radiation with sufficiently high energy can ionize atoms; that is to say it can knock electrons off atoms, creating ions. Ionization occurs when an electron

16224-478: The inter-atomic bonds that form molecules, thereby breaking down molecules rather than atoms; a good example of this is sunburn caused by long- wavelength solar ultraviolet. The waves of longer wavelength than UV in visible light, infrared, and microwave frequencies cannot break bonds but can cause vibrations in the bonds which are sensed as heat . Radio wavelengths and below generally are not regarded as harmful to biological systems. These are not sharp delineations of

16380-546: The interior started the Mineral Revolution and increased economic growth and immigration. This intensified British subjugation of the indigenous people. The struggle to control these important economic resources was a factor in relations between Europeans and the indigenous population and also between the Boers and the British. On 16 May 1876, President Thomas François Burgers of the South African Republic declared war against

16536-409: The ionization (plasma) seen in common flames, and the molecular changes caused by the " browning " during food-cooking, which is a chemical process that begins with a large component of ionization. Black-body radiation is an idealized spectrum of radiation emitted by a body that is at a uniform temperature. The shape of the spectrum and the total amount of energy emitted by the body is a function of

16692-406: The ionizing radiation is a radioactive material or a nuclear process such as fission or fusion , there is particle radiation to consider. Particle radiation is subatomic particles accelerated to relativistic speeds by nuclear reactions. Because of their momenta , they are quite capable of knocking out electrons and ionizing materials, but since most have an electrical charge, they do not have

16848-522: The line of sight. Very low frequency (VLF) refers to a frequency range of 30 Hz to 3 kHz which corresponds to wavelengths of 100 000 to 10 000  m respectively. Since there is not much bandwidth in this range of the radio spectrum, only the very simplest signals can be transmitted, such as for radio navigation. Also known as the myriametre band or myriametre wave as the wavelengths range from 100 km to 10 km (an obsolete metric unit equal to 10 km). Extremely low frequency (ELF)

17004-425: The material is of high or low density. However, as is the case with X-rays, materials with a high atomic number such as lead or depleted uranium add a modest (typically 20% to 30%) amount of stopping power over an equal mass of less dense and lower atomic weight materials (such as water or concrete). The atmosphere absorbs all gamma rays approaching Earth from space. Even air is capable of absorbing gamma rays, halving

17160-574: The method of uranium enrichment were withheld as official state secrets. In 1971, the Chairman of the South African Atomic Energy Board, Abraham J. A. Roux, stated that long hair would not be tolerated in the workplace at Pelindaba. In 1975, Pelindaba ordered shipments of weapons grade uranium from the U.S., specified for "peaceful uses only". It was to be supplied on condition that any plutonium produced from its fission be returned to

17316-404: The most common isotopes of both types atoms present (hydrogen and oxygen) capture neutrons and become heavier but remain stable forms of those atoms. Only the absorption of more than one neutron, a statistically rare occurrence, can activate a hydrogen atom, while oxygen requires two additional absorptions. Thus water is only very weakly capable of activation. The sodium in salt (as in sea water), on

17472-586: The national vote fall below 50% for the first time since the end of Apartheid, though it remained the single largest party in the South African Parliament. President Ramaphosa announced a national unity government , the first since the Cabinet of Nelson Mandela , and entered a deal with the Democratic Alliance , the previous main opposition party, and other minor parties. Ramaphosa was reelected for

17628-448: The neutrons stops almost immediately in the reactor when it goes non-critical. Neutrons can make other objects, or material, radioactive. This process, called neutron activation , is the primary method used to produce radioactive sources for use in medical, academic, and industrial applications. Even comparatively low speed thermal neutrons cause neutron activation (in fact, they cause it more efficiently). Neutrons do not ionize atoms in

17784-645: The north of the Cape Peninsula is bounded on the west by the Atlantic Ocean and the first row of north–south running Cape Fold Mountains to the east. The Cape Fold Mountains peter out at about the 32°   S line of latitude, after which the Great Escarpment bounds the coastal plain. The most southerly portion of this coastal belt is known as the Swartland and Malmesbury Plain, which is an important wheat growing region, relying on winter rains. The region further north

17940-635: The north of the Swartberg range up to the Great Escarpment is the lowland part of the Great Karoo, which is climatically and botanically almost indistinguishable from the Karoo above the Great Escarpment. The narrow coastal strip between the Outeniqua and Langeberg ranges and the ocean has a moderately high year-round rainfall, which is known as the Garden Route . It is famous for the most extensive areas of forests in South Africa (a generally forest-poor country). In

18096-644: The northeast, consists of the Limpopo Lowveld, which merges into the Mpumalanga Lowveld, below the Mpumalanga Drakensberg (the eastern portion of the Great Escarpment). This is hotter, drier and less intensely cultivated than the Highveld above the escarpment. The Kruger National Park , located in the provinces of Limpopo and Mpumalanga in north-eastern South Africa, occupies a large portion of

18252-727: The obstacles were the presence of the independent states of the Boers, and the Zululand army. The Zulu nation defeated the British at the Battle of Isandlwana . Eventually Zululand lost the war, resulting in the termination of the Zulu nation's independence. The Boer republics successfully resisted British encroachments during the First Boer War (1880–1881) using guerrilla warfare tactics, which were well-suited to local conditions. The British returned with greater numbers, more experience, and new strategy in

18408-821: The organisation in 1961 and rejoined it in 1994. Despite opposition to apartheid both within and outside the country, the government legislated for a continuation of apartheid. The security forces cracked down on internal dissent, and violence became widespread, with anti-apartheid organisations such as the African National Congress (ANC), the Azanian People's Organisation , and the Pan-Africanist Congress carrying out guerrilla warfare and urban sabotage. The three rival resistance movements also engaged in occasional inter-factional clashes as they jockeyed for domestic influence. Apartheid became increasingly controversial, and several countries began to boycott business with

18564-415: The other hand, need only absorb a single neutron to become Na-24, a very intense source of beta decay, with a half-life of 15 hours. In addition, high-energy (high-speed) neutrons have the ability to directly ionize atoms. One mechanism by which high energy neutrons ionize atoms is to strike the nucleus of an atom and knock the atom out of a molecule, leaving one or more electrons behind as the chemical bond

18720-497: The outer layers of dead skin cells and cause no damage to the live tissues below. Some very high energy alpha particles compose about 10% of cosmic rays , and these are capable of penetrating the body and even thin metal plates. However, they are of danger only to astronauts, since they are deflected by the Earth's magnetic field and then stopped by its atmosphere. Alpha radiation is dangerous when alpha-emitting radioisotopes are inhaled or ingested (breathed or swallowed). This brings

18876-404: The overall status and wellbeing of the country, for example with regards to water resources . Speedy environmental changes are resulting in clear effects on the community and environmental level in different ways and aspects, starting with air quality, to temperature and weather patterns, reaching out to food security and disease burden. According to computer-generated climate modelling produced by

19032-607: The ownership of land by blacks; at that stage they controlled only 7% of the country. The amount of land reserved for indigenous peoples was later marginally increased. In 1931, the union became fully sovereign from the United Kingdom with the passage of the Statute of Westminster , which abolished the last powers of the Parliament of the United Kingdom to legislate in the country. Only three other African countries—Liberia, Ethiopia, and Egypt—had been independent prior to that point. In 1934,

19188-614: The penetrating power of ionizing radiation. The exception is neutron particles; see below. There are several different kinds of these particles, but the majority are alpha particles , beta particles , neutrons , and protons . Roughly speaking, photons and particles with energies above about 10 electron volts (eV) are ionizing (some authorities use 33 eV, the ionization energy for water). Particle radiation from radioactive material or cosmic rays almost invariably carries enough energy to be ionizing. Most ionizing radiation originates from radioactive materials and space (cosmic rays), and as such

19344-560: The present-day Groot River , in May 1488. On his return he saw the cape, which he named Cabo das Tormentas ('Cape of Storms'). King John II renamed the point Cabo da Boa Esperança , or Cape of Good Hope , as it led to the riches of the East Indies . Dias' feat of navigation was immortalised in Luís de Camões ' 1572 epic poem Os Lusíadas . By the early 17th century, Portugal's maritime power

19500-686: The presidency, National Director of Public Prosecutions Shaun Abrahams announced that Zuma would again face prosecution on 16 criminal charges – 12 charges of fraud, two of corruption, and one each of racketeering and money laundering, just as in the 2006 indictment. A warrant was issued for his arrest in February 2020 after he failed to appear in court. In 2021 he was found guilty of contempt of court and sentenced to 15 months' imprisonment. In response, supporters of Zuma engaged in protests which led to riots, looting, vandalism and widespread violence, leaving 354 people dead. South Africa has been undergoing

19656-587: The proposal. Elizabeth II lost the title Queen of South Africa , and the last Governor-General , Charles Robberts Swart , became state president . As a concession to the Westminster system , the appointment of the president remained by parliament and was virtually powerless until P. W. Botha 's Constitution Act of 1983 , which eliminated the office of prime minister and instated a unique "strong presidency" responsible to parliament . Pressured by other Commonwealth of Nations countries, South Africa withdrew from

19812-404: The proposed solutions has been to pass legislation, such as the pending Hate Crimes and Hate Speech Bill , to uphold South Africa's ban on racism and commitment to equality. On 14 February 2018, Jacob Zuma resigned the presidency. Since 15 February, ANC president Cyril Ramaphosa has been President of South Africa. On 16 March 2018, just over a month after President Jacob Zuma resigned from

19968-516: The radioisotope close enough to sensitive live tissue for the alpha radiation to damage cells. Per unit of energy, alpha particles are at least 20 times more effective at cell-damage than gamma rays and X-rays. See relative biological effectiveness for a discussion of this. Examples of highly poisonous alpha-emitters are all isotopes of radium , radon , and polonium , due to the amount of decay that occur in these short half-life materials. Beta-minus (β ) radiation consists of an energetic electron. It

20124-479: The region over 100,000 years ago. The first known people were the indigenous Khoisan , and Bantu-speaking peoples who expanded from West and Central Africa later settled in the region 2,000 to 1,000 years ago. In the north, the Kingdom of Mapungubwe formed in the 13th century. In 1652, the Dutch established the first European settlement at Table Bay , and in 1795 and 1806 , the British occupied it. The Mfecane ,

20280-521: The remainder consisting of helions (alpha particles). A few completely ionized nuclei of heavier elements are present. The origin of these galactic cosmic rays is not yet well understood, but they seem to be remnants of supernovae and especially gamma-ray bursts (GRB), which feature magnetic fields capable of the huge accelerations measured from these particles. They may also be generated by quasars , which are galaxy-wide jet phenomena similar to GRBs but known for their much larger size, and which seem to be

20436-531: The ruins are thought to be created by the Bakone , a Northern Sotho people. Around 1220, in the Limpopo - Shashe Basin, the elite of K2 moved to settle the flat-topped summit of Mapungubwe Hill, with the population settling below. Rainmaking was crucial to the development of sacral kingship . By 1250, the capital had a population of 5000 and the state covered 30,000 km² (11,500 square miles), growing wealthy through

20592-482: The same way that charged particles such as protons and electrons do (by the excitation of an electron), because neutrons have no charge. It is through their absorption by nuclei which then become unstable that they cause ionization. Hence, neutrons are said to be "indirectly ionizing". Even neutrons without significant kinetic energy are indirectly ionizing, and are thus a significant radiation hazard. Not all materials are capable of neutron activation; in water, for example,

20748-533: The south-west corner of the country, the Cape Peninsula forms the southernmost tip of the coastal strip which borders the Atlantic Ocean and ultimately terminates at the country's border with Namibia at the Orange River . The Cape Peninsula has a Mediterranean climate , making it and its immediate surrounds the only portion of Sub-Saharan Africa which receives most of its rainfall in winter. The coastal belt to

20904-404: The speed of light. Naturally occurring radio waves are made by lightning, or by certain astronomical objects. Artificially generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, satellite communication, computer networks and innumerable other applications. In addition, almost any wire carrying alternating current will radiate some of

21060-440: The surface. Gamma (γ) radiation consists of photons with a wavelength less than 3 × 10  m (greater than 10  Hz and 41.4 keV). Gamma radiation emission is a nuclear process that occurs to rid an unstable nucleus of excess energy after most nuclear reactions. Both alpha and beta particles have an electric charge and mass, and thus are quite likely to interact with other atoms in their path. Gamma radiation, however,

21216-406: The temperature of its radiating surface. It is responsible for the color of stars , which vary from infrared through red ( 2500 K ), to yellow ( 5800 K ), to white and to blue-white ( 15 000  K ) as the peak radiance passes through those points in the visible spectrum. When the peak is below the visible spectrum the body is black, while when it is above the body is blue-white, since all

21372-421: The temperature of the body increases. The frequency at which the black-body radiation is at maximum is given by Wien's displacement law and is a function of the body's absolute temperature. A black-body is one that emits at any temperature the maximum possible amount of radiation at any given wavelength. A black-body will also absorb the maximum possible incident radiation at any given wavelength. A black-body with

21528-437: The ultraviolet spectrum some of the dangers of ionizing radiation in biological systems without actual ionization occurring. In contrast, visible light and longer-wavelength electromagnetic radiation, such as infrared, microwaves, and radio waves, consists of photons with too little energy to cause damaging molecular excitation, and thus this radiation is far less hazardous per unit of energy. X-rays are electromagnetic waves with

21684-444: The ultraviolet spectrum that does reach the ground is non-ionizing, but is still biologically hazardous due to the ability of single photons of this energy to cause electronic excitation in biological molecules, and thus damage them by means of unwanted reactions. An example is the formation of pyrimidine dimers in DNA, which begins at wavelengths below 365 nm (3.4 eV), which is well below ionization energy. This property gives

21840-534: The victims were South African citizens. In a 2006 survey, the South African Migration Project concluded that South Africans are more opposed to immigration than any other national group. The UN High Commissioner for Refugees in 2008 reported that over 200,000 refugees applied for asylum in South Africa, almost four times as many as the year before. These people were mainly from Zimbabwe , though many also come from Burundi , Democratic Republic of

21996-457: The visible colors are represented from blue decreasing to red. Electromagnetic radiation of wavelengths other than visible light were discovered in the early 19th century. The discovery of infrared radiation is ascribed to William Herschel , the astronomer . Herschel published his results in 1800 before the Royal Society of London . Herschel, like Ritter, used a prism to refract light from

22152-438: The wars, Dutch-descendant Boer farmers fled into cities from the devastated Transvaal and Orange Free State territories to become the class of the white urban poor. Anti-British policies among white South Africans focused on independence. During the Dutch and British colonial years, racial segregation was mostly informal, though some legislation was enacted to control the settlement and movement of indigenous people, including

22308-413: The wine in South Africa and is known for its wind, which blows intermittently almost all year. The severity of this wind made passing around the Cape of Good Hope particularly treacherous for sailors, causing many shipwrecks. Further east on the south coast, rainfall is distributed more evenly throughout the year, producing a green landscape. The annual rainfall increases south of the Lowveld, especially near

22464-563: The world. Archaeologists have recovered extensive fossil remains from a series of caves in Gauteng Province. The area, a UNESCO World Heritage Site , has been branded "the Cradle of Humankind ". The sites include Sterkfontein , one of the richest sites for hominin fossils in the world, as well as Swartkrans , Gondolin Cave , Kromdraai , Cooper's Cave and Malapa . Raymond Dart identified

22620-581: Was anticipated. That relationship ultimately lead to the establishment of the Koeberg Nuclear Power Station . While the official purpose of the Pelindaba facility was "to harness the versatile power of the atom and apply it to maximum peaceful advantage" it was also speculated that South Africa could produce its own atomic weapons by 1966. In 1966, Pelindaba reported detecting elevated levels of radiation following French nuclear weapons tests in

22776-422: Was detected on 16 August. The contents of 30 barrels were discovered dumped near Pelindaba and as of 4 September, 100 barrels remained missing. An accident at the Pelindaba research facility exposed workers to radiation . Harold Daniels and several others died from radiation burns and cancers related to the exposure. Shortly after midnight on 8 November 2007, four armed men entered the facility and headed towards

22932-461: Was established as a public company by the new government of South Africa in 1999. A 4 MV Van de Graaff particle accelerator operates at Pelindaba for various purposes in nuclear scientific research . In 1986, a fire at Pelindaba killed two cleaning staff and injured two other personnel. No radioactive releases occurred during the incident. In August 1994, barrels containing "enriched uranium residue" were stolen from Pelindaba. The theft

23088-546: Was for peaceful purposes, but also that it reserved the right to use its potential for other-than-peaceful purposes. The same year, the London Telegraph reported that South Africa had the capability to make nuclear weapons "any time it wishes." In 1984, the Associated Press reported that South Africa had refused international inspections of facilities at Pelindaba and associated enrichment works at Valindaba . In 1988,

23244-606: Was fought in 1879 between the British and the Zulu Kingdom . Following Lord Carnarvon 's successful introduction of federation in Canada , it was thought that similar political effort, coupled with military campaigns, might succeed with the African kingdoms, tribal areas and Boer republics in South Africa. In 1874, Henry Bartle Frere was sent to South Africa as the British High Commissioner to bring such plans into being. Among

23400-508: Was previously rare, increased. The government struggled to achieve the monetary and fiscal discipline to ensure both redistribution of wealth and economic growth. The United Nations Human Development Index rose steadily until the mid-1990s then fell from 1995 to 2005 before recovering its 1995 peak in 2013. The fall is in large part attributable to the South African HIV/AIDS pandemic which saw South African life expectancy fall from

23556-519: Was received by the convention on 7 June 2006. The country is ranked sixth out of the world's seventeen megadiverse countries . Ecotourism in South Africa has become more prevalent in recent years, as a possible method of maintaining and improving biodiversity. Numerous mammals are found in the Bushveld including lions, African leopards , South African cheetahs , southern white rhinos , blue wildebeest , kudus , impalas , hyenas , hippopotamuses and South African giraffes . A significant extent of

23712-462: Was received from the United States , constructed and inaugurated in 1965. Since then, it has operated with an output of up to 20 MW. The reactor cost $ 10.5 million. Enriched uranium for use in the reactor was initially supplied by the U.S. and has been subject to IAEA safeguards. At the time of Pelindaba's inauguration, future cooperation between France and South Africa on nuclear technology

23868-464: Was south of the furthest point reached in 1485 by his predecessor, the Portuguese navigator Diogo Cão ( Cape Cross , north of the bay). Dias continued down the western coast of southern Africa. After 8 January 1488, prevented by storms from proceeding along the coast, he sailed out of sight of land and passed the southernmost point of Africa without seeing it. He reached as far up the eastern coast of Africa as, what he called, Rio do Infante , probably

24024-484: Was starting to decline, and English and Dutch merchants competed to oust Portugal from its lucrative monopoly on the spice trade . Representatives of the British East India Company sporadically called at the cape in search of provisions as early as 1601 but later came to favour Ascension Island and Saint Helena as alternative ports of refuge. Dutch interest was aroused after 1647, when two employees of

24180-478: Was the Xhosa people , whose language incorporates certain linguistic traits from the earlier Khoisan people. The Xhosa reached the Great Fish River , in today's Eastern Cape Province. As they migrated, these larger Iron Age populations displaced or assimilated earlier peoples. In Mpumalanga Province, several stone circles have been found along with a stone arrangement that has been named Adam's Calendar , and

24336-705: Was the radiation that had been first detected by Becquerel from uranium salts. In 1900, the French scientist Paul Villard discovered a third neutrally charged and especially penetrating type of radiation from radium, and after he described it, Rutherford realized it must be yet a third type of radiation, which in 1903 Rutherford named gamma rays . Henri Becquerel himself proved that beta rays are fast electrons, while Rutherford and Thomas Royds proved in 1909 that alpha particles are ionized helium. Rutherford and Edward Andrade proved in 1914 that gamma rays are like X-rays, but with shorter wavelengths. Cosmic ray radiations striking

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