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Thursday, May 5, 2022

Environmental policy in China

From Wikipedia, the free encyclopedia

Environmental policy in China is set by the National People's Congress and managed by the Ministry of Environmental Protection of the People's Republic of China. The Center for American Progress has described China's environmental policy as similar to that of the United States before 1970. That is, the central government issues fairly strict regulations, but the actual monitoring and enforcement are largely undertaken by local governments that have a greater interest in economic growth. The environmental work of non-governmental forces, such as lawyers, journalists, and non-governmental organizations, is limited by government regulations. Under the Ministry of Environmental Protection of the People's Republic of China, the Department of Policies, Laws, and Regulations is in charge of establishing and strengthening basic laws and policies such as environmental laws, administrative policies and economical regulations. It is also responsible for the development of national environmental protection policy and macro strategy.

China's rapid economic expansion combined with the country's relaxed environmental oversight has caused a number of ecological problems. In response to public pressure, the national government has undertaken a number of measures to curb pollution in China and improve the country's environmental situation. However, the government's response has been criticized as inadequate. Encouraged by national policy that judges regions solely by their economic development, corrupt and unwilling local authorities have hampered enforcement. Nonetheless, in April 2014, the government amended its environmental law to better fight pollution.

Since the 2010s, the government has given greater attention to environmental protection through policy actions such as the signing of the Paris climate accord, the 13th Five-Year Plan and the 2015 Environmental Protection Law reform  From 2006 to 2017, sulphur dioxide levels in China were reduced by 70 percent, and air pollution has decreased from 2013 to 2018 In 2017, investments in renewable energy amounted to US$279.8 billion worldwide, with China accounting for US$126.6 billion or 45% of the global investments. China has since become the world's largest investor, producer and consumer of renewable energy worldwide, manufacturing state-of-the-art solar panels, wind turbines and hydroelectric energy facilities as well as becoming the world’s largest producer of electric cars and buses.

Policy jurisdiction

The Ministry of Environmental Protection (MEP), formerly the State Environmental Protection Administration (SEPA), is a cabinet-level ministry in the executive branch of the Chinese Government that is responsible for implementing environmental policies, as well as the enforcement of environmental laws and regulations. The Ministry is tasked with protecting China's air, water, and land from pollution and contamination. Directly under the State Council, it is empowered and required by law to implement environmental policies and enforce environmental laws and regulations. Complementing its regulatory role, it funds and organizes research and development. There are 20 offices and departments under MEP including General Office, Department of Planning and Finance, Department of Policies, Laws and Regulations, Department of Human Resources Management and Institutional Arrangement, Department of Science, Technology and Standards Department of Environmental Impact Assessment, Department of Environmental Monitoring, Department of Water Environment Management, Department of Air Environment Management, Department of Soil Environment Management, Department of Nature and Ecology Conservation, Department of Nuclear Facility Safety Regulation, Department of Nuclear Power Safety Regulation, Department of Radiation Source Safety Regulation Bureau of Environmental Supervision and Inspection, Department of International Cooperation, Department of Education and Communications, The MEP Committee of Communist Party of China, Office of the CPC Central Commission for Discipline Inspection at MEP.[13] All 20 offices are at the judicial level in the government ranking system. They carry out regulatory tasks in different areas and make sure that the agency is functioning accordingly. Since 2006, there have been five regional centers to help with local inspections and enforcement.

History

In 1972, Chinese representatives attended the first United Nations Conference on the Human Environment. The next year, the Environmental Protection Leadership Group was established. In 1983, the Chinese government announced that environmental protection would become a state policy. In 1998, China went through a disastrous year of serious flooding, and the Chinese government upgraded the Leading Group to a ministry-level agency, which then became the State Environmental Protection Administration.

According to the Chinese government website, the Central Government invested more than 40 billion yuan between 1998 and 2001 on protection of vegetation, farm subsidies, and conversion of farm to forests. Between 1999 and 2002, China converted 7.7 million hectares of farmland into forest.

From 2001 to 2005, Chinese environmental authorities received more than 2.53 million letters and 430,000 visits by 597,000 petitioners seeking environmental redress. Meanwhile, the number of mass protests caused by concerns over environmental issues grew steadily from 2001 to 2007. The increased attention on environmental matters caused the Chinese government to display an increased level of concern towards environmental issues. For example, in his 2007 annual address Wen Jiabao, the Premier of the People's Republic of China, made 48 references to "environment," "pollution," and "environmental protection", and stricter environmental regulations were subsequently implemented. Subsidies for some polluting industries were cancelled, while other polluting industries were shut down. However, many internal environmental targets were missed.

After the 2007 address, the influence of corruption was a hindrance to effective enforcement, as local authorities ignored orders and hampered the effectiveness of central decisions. In response, CPC General Secretary Hu Jintao implemented the "Green G.D.P." project, where China's gross domestic product was adjusted to compensate for negative environmental effects; however, the program quickly lost official influence due to unfavorable data. The project's lead researcher claimed that provincial leaders "do not like to be lined up and told how they are not meeting the leadership’s goals ... They found it difficult to accept this." The government attempted to hold national "No Car Days" where cars were banned from central roads, but the action was largely ignored. In 2008, the State Environmental Protection Administration was official replaced by the Ministry of Environmental Protection during the March National People's Congress sessions in Beijing.

Citizen activism regarding government decisions that are perceived as environmentally damaging increased in the 2010s. In April 2012, protests occurred in the southern town of Yinggehai following the announcement of a power plant project. The protesters initially succeeded in halting the project, worth 3.9 billion renminbi (£387m). Another town was selected for the location of the plant, but when the residents in the second location also resisted the authorities returned to Yinggehai. A second round of protests occurred in October 2012 and police clashed with protester, leading to 50 arrests and almost 100 injuries. In response to a waste pipeline for a paper factory in the city of Qidong, several thousand demonstrators protested in July 2012. Sixteen of the protesters were sentenced to between twelve and eighteen months in prison; however, thirteen were granted a reprieve on the grounds that they had confessed and repented. In total, more than 50,000 environmental protests occurred in China during 2012.

In response to an increasing air pollution problem, the Chinese government announced a five-year, US$277 billion plan to address the issue in 2013. Northern China will receive particular attention, as the government aims to reduce air emissions by 25 percent by 2017, compared with 2012 levels.

In March 2014, CPC General Secretary Xi Jinping "declared war" on pollution during the opening of the National People's Congress. After extensive debate lasting nearly two years, the parliament approved a new environmental law in April. The new law empowers environmental enforcement agencies with great punitive power, defines areas which require extra protection, and gives independent environmental groups more ability to operate in the country. The new articles of the law specifically address air pollution, and call for additional government oversight. Lawmaker Xin Chunying called the law "a heavy blow [in the fight against] our country's harsh environmental realities, and an important systemic construct". Three previous versions of the bill were voted down. The bill is the first revision to the environmental protection law since 1989.

In 2019, China launched the Belt and Road Initiative International Green Development Coalition.

In 2020, Chinese Communist Party general secretary Xi Jinping announced that China aims to peak emissions before 2030 and go carbon-neutral by 2060 in accordance with the Paris climate accord. According to Climate Action Tracker, if accomplished it would lower the expected rise in global temperature by 0.2 - 0.3 degrees - "the biggest single reduction ever estimated by the Climate Action Tracker".

In 2020, a sweeping law was passed by the Chinese government to protect the ecology of the Yangtze River. The new laws include strengthening ecological protection rules for hydropower projects along the river, banning chemical plants within 1 kilometer of the river, relocating polluting industries, severely restricting sand mining as well as a complete fishing ban on all the natural waterways of the river, including all its major tributaries and lakes.

Current law

When the new environmental protection provisions go into effect in January 2015, the government's environmental agencies will be allowed to enforce strict penalties and seize property of illegal polluters. Companies that break the law will be "named and shamed", with company executives subject to prison sentences of 15 days. There will be no upper limit on fines; previously, it was often cheaper for companies to pay the meager fines provisioned by the law than install anti-pollution measures. In all, the new law has 70 provisions, compared to the 47 of the existing law. More than 300 different groups will be able to sue on the behalf of people harmed by pollution. It remains to be seen whether these changes to the law will overcome some of the traditional problems with environmental litigation in China, such as difficulty getting cases accepted by the court, trouble gathering evidence and interference from local government.

Under the new law, local governments will be subject to discipline for failing to enforce environmental laws. Regions will no longer be judged solely on their economic progress, but instead must balance progress with environmental protection. Additionally, local governments will be required to disclose environmental information to the public. Individuals are encouraged to "adopt a low-carbon and frugal lifestyle and perform environmental protection duties" such as recycling their garbage under the law.

In June 2017, the Chinese government made a second amendment to the Water Pollution Prevention Act. Based on the first regulation of Water Pollution Prevention Act in 1996, the amendment will increase the punishment for water pollution and the penalty ceiling may be raised to 1 million yuan. According to the statement of the Minister of Environmental Protection, the second revised version further strengthened the responsibilities of local governments, and refined and improved the drinking water safety protection system. Since the legislation in 1984, this law has made a significant and positive contribution to improving the water environment in China. However, the quality of water environment in China is still not promising.

Protected areas

A number of different classes of protected areas are recognized under Chinese law. National, provincial, and local governments all have the power to designate areas as protected. Regardless of designation, most enforcement is made at the local level.

On January 1, 2019 the Chinese government promulgated the "Soil Pollution Prevention and Control Law". 1. The new law has guidelines for performing mergers and acquisitions environmental due diligence Phase II and III and HHRA (Human Health Risk Assessments) 2. Chinese government will not accept ASTM E1903 - 11 Standard Practice for Environmental Site Assessments: Phase II Environmental Site Assessment Process 3. Following the new Chinese law Phase II sampling guidance will cost 30-40% more than the ASTM methodology a. In part due to the requirements in the Chinese guidance that requires up-gradient and down gradient ground water testing and other technical guidance. b. Phase II due diligence sampling under the new Chinese regulation will become “Public Record” – accessible to any company or Chinese citizen. This transparency could damage global companies' reputation if a site under their control is publicly declared "polluted" c. The Chinese Technical guideline will necessarily add significant time to the process of due diligence – M&A (sale-deals need to factor this into transaction timelines - expect up to a year longer time line in cases where property in on a watch list or deemed by the government to be a PSPF (Priority Soil contamination Prevention and control Facility.) 4. Starting immediately ALL ACQUISITIONS NEED TO BE PREDICATED UPON A CHINESE POLLUTION LAW GUIDELINE COMPLIANT BASELINE – this requirement will add to the acquisition execution time line significantly. 5. Acquisitions need to establish contractual warranty and environmental escrow following the principles of the Chinese Regulation (Investor company legal counsel needs to change their acquisition agreement template to align with Chinese law guidance.) 6. If a target site has recently been found to be polluted under the regulation – M&A should cease until expert panel rules on remediation plans/proposals… buyers should not enter agreement to purchase until scope and cost to remediate have been approved by the expert panel and an escrow can be established along with warrantee language in the purchase agreement. 7. It is highly recommended that companies with property having historical recognized environmental conditions (HRECS) perform routine sampling that follows the Chinese guidelines a. If a company has facilities that fall into certain “High Risk Sectors” they are entered automatically in to the Watch List – including: i. Chemical ii. Pharma iii. Manufacturing iv. Oil & Gas v. Non Ferrous Metals b. Also a company can be listed on the Watch List if certain triggers are met: i. Store, Handle manager hazardous material ii. Generate >100 tonnes of Hazardous Waste per year iii. Located near sensitive areas (residential, water bodies) c. Sale or closure of any property on the “Watch List” must be accompanied by Phase II Assessments that follow the guideline d. Contaminated property discovery must be reported to the government – added to the “Watch List” which will be updated and released annually. 8. Where divestiture/purchase contracts include “indemnification” language protecting the seller or buyer – the new law provides these contractual provisions can be overridden by the Chinese Government. 9. Watch List site closure or sale (divestiture) requires Phase II report per the Chinese Pollution Law guideline – becomes public record – CAN HAVE NEGATIVE IMPACT TO COMPANY REPUTATION 10. Even though the new Chinese Law follows the principle of “polluter pays” - ERM sited client case studies where the “buyer” did not contribute to contamination – and yet ended up sharing the remediation cost with the seller. 11. Whenever a site has been found to be contaminated under the guidelines of the law – the owner must seek guidance from an “Expert Panel” who will make judgements/decisions about HHRA as well as remediation.

Current issues

Air pollution caused by industrial plants

China has many environmental issues, severely affecting its biophysical environment as well as human health.

Water Shortage

China is facing three major water resources problems: water pollution, shortage of water resources and waste of water resources. The problem with water resources will be China's obstacles to achieve sustainable development in the 21st century. The government has begun to deal with water resources problems since the 1970s, establishing water pollution control and environmental protection agencies.

China ranks 5th globally in terms of water resources but the water resource per capita is less than 1/3 the world average. The Chinese government implemented two policies to alleviate the water shortage issues;supporting the South-North Water Diversion Project and improving water use efficiency. The government has provided funding for the South-North Water Diversion Project, which aims to bring 44.8 billion cubic meters of water to Beijing and other northern parts of China. The project will cause disruption to local inhabitants forcing the migration of nearly one million people. The total cost of this project is estimated at $62 billion. In 2010, the Communist Party of China and the State Council set policies to change ways of using water and improve water use efficiency. The central government had invested 1.8 trillion yuan to enable efficient water use by upgrading both agriculture irrigation systems and clean water systems in rural areas.

Water pollution is also an issue in China.

Besides the water shortage, the water quality is also an issue which has influenced public health and led to political disputes. Only less than half of all water resources meets the safe drinking water standards in China. Besides political oppositions between regions, the current government structure is also a barrier for water pollution control.

The Ministry of Ecology and Environment of the People's Republic of China is a relatively young ministry. It is assigned relatively less power and fewer employees than other existing ministries, which results in its heavy dependence on local environmental protection bureaus (EPB). The problem is that local EPBs do not only get controlled by higher EPB but also by local governments whose performance is assessed mainly by economic development. Therefore, the local governments have loose policies on companies that producing water pollution. Additionally, the financial support of EPBs comes from pollution fines instead of the Ministry of Ecology and Environment, which makes it difficult for the ministry to manage local EPBs.

Air pollution

Various forms of pollution have increased as China has industrialized, causing widespread environmental and health problems. In January 2013, fine airborne particulates rose as high as 993 micrograms per cubic meter in Beijing, compared with World Health Organization guidelines of no more than 25. Heavy industry, dominated by state-owned enterprises, has been promoted since the beginning of central planning and still has many special privileges such as access to cheap energy and loans. The industry possesses considerable power to resist environmental regulation.

At the end of October 2018, the Chinese government has issued the Atmospheric Pollution Prevention and Control Law (2018 Amendment), which will be implemented starting immediately. Experts believe that although the law is inevitably flawed in some aspects, if 80% of the law can be implemented, it is going to significantly improve the air quality. This law has been scrutinized three times. The new amendment has clearly stated out that enterprises of iron and steel, building materials, non-ferrous metals, petroleum, and chemical industry that discharge dust, sulfide, and nitrogen oxides in the course of production shall adopt cleaner production processes, construct dust-removing, desulfurization, and denitrification equipment in a complete set, or adopt technological transformation and other measures to control the discharge of air pollutants. Compared to the revised Air Pollution Control Law in 2000, the new version doubled the entries. Almost all the laws in the current version have been amended and revised to fit the current situation.

Based on 2015's China Environmental Bulletin published by the Chinese government, in 2015 the national urban air quality is getting better. The first implementation of the new air quality standards has made the PM 2.5 average concentration decreased by 14.1% compared to the year of 2014. The Ministry of Finance established a fund of 10.6 billion Yuan to improve the air quality and to control the air pollution around the Beijing-Tianjin-Hebei and the surrounding areas, Yangtze River, and other key areas. The government is also actively promoting renewable energy vehicles with an annual production of 390,000, four times more than the production in 2014.

Soil pollution

Soil pollution satellite image

Soil pollution problems, which is the land surface degradation caused by the abuse of resources and land caused by human activities, together with corresponding protection measures in China have occurred in recent decades. In total, nearly 16.1% of China's soil was polluted. These pollutions have caused a serious impact on the growth of crops and the health of the people. In terms of related policies, the Chinese government decided to draw on the successful examples of other countries and integrate China's national conditions to maintain long-term governance of soil pollution problems. From the 1980s to the 1990s, China began to work on soil environmental research by starting the Modern conservation tillage research with the support of Australia. From 2000 to now, the problem of soil pollution in China has become increasingly serious. The government has gradually put the prevention and control of soil pollution issues and other environmental protection issues in the first place by charging fines for polluted factories.

China conducted a large-scale soil quality sampling analysis nationwide from 2005 to 2013, and according to the National Soil Pollution Survey Bulletin promulgated by the Ministry of Environmental Protection of China in 2014, the total national soil exceedance rate (the percentage that exceeds the upper limit value) was 16.1%, of which slight, slight, moderate and heavy degree of pollution spot is 11.2%, 2.3%, 1.5% and 1.1%, respectively. From the point of view of pollution distribution, soil pollution in the south is heavier than in the north. The soil pollution problems in some regions such as the Yangtze River Delta, the Pearl River Delta, and the old industrial base in Northeast China are more severe. The soil in the southwest and south-central regions has exceeded the upper limit of heavy metals tolerance. The contents of the four inorganic pollutants such as cadmium, mercury, arsenic, and lead have gradually increased from northwest China to southeast China and from northeast China to southwest China. As far as the current state of legislation is concerned, China already has air pollution prevention and control law and water pollution control law, but it still lacks a soil pollution control law. In June 2017, the Ministry of Environmental Protection pointed out that China will establish a more refined working mechanism, continue to carry out investigation of soil pollution, promote the improvement of the legislative system, and fully cooperate with the National People's Congress in the legislation on soil pollution control law.

Desertification

Land desertification is another pressing environmental issue. A land survey conducted by the State Forestry Administration of China from 2013 to 2016 shows that 2.61 × 106 km2 of the national land, accounting for more than a quarter of China’s overall territory, is desertified. Arid, semi-arid, and sub-humid lands located in Northern and North-Western China make up for the majority of the affected territory. Desertification has long reaching consequences, resulting in ecological degradation, halting local economic development, as well as damaging the health of residents in the affected area. Desertified land facilitates the creation of sandstorms which threaten the health of residents in the nearby rural and urban areas alike. As the desert expands, it turns more and more land non-arable and unsuitable for development, creating poverty and food shortage. The current issue is a result of the combination of various anthropogenic and ecological factors. Devegetation brought about by unfavourable hydrologic conditions, climate change induced droughts, as well as unsustainable human activities such as overgrazing, agriculture, and deforestation, exposes the soil to frequent water and wind erosion, creating desert.

To combat land desertification, China has implemented a range of legislative policies as well as restorative programs. Laws are passed to prevent logging, agriculture, and animal grazing in locations of high desertification risk, establishing these areas as ecological function reserves. In areas surrounding desertified land, a large scale of protective forests and shelterbelts are created by programs such as the Three-Norths Shelter Forest Construction Program to reduce the effect of wind erosion. Since 1999, The Ministry of Forestry has been providing monetary rewards for farmers who plant trees instead of crops, as well as auctioning away national land to individuals to rehabilitate for economic gains. In 2002, The Sand Prevention and Control Law was introduced to encourage sustainable development in desertified areas, encouraging afforestation and establishment of green industries such as water efficient pasture and natural pharmaceutical production. This policy is met with wide support from the residents in these areas as it also stimulates local economic growth. Residents in the Kubuqi Desert, for example, have had their annual income increased from $56 to $2000 in less than 30 years.

Impact

China's lax environmental oversight had contributed to its environmental problems. Sixteen of the world's twenty most polluted cities were found in China in 2013, but has since reduced to just one at 19th place Government response has been criticized as inadequate. An official report released in 2014, found that 20% of the country's farmland, and 16% of its soil overall, is polluted. An estimated 60% of the groundwater is polluted.

According to the U.S. Environmental Protection Agency, China has shown great determination to "develop, implement, and enforce a solid environmental law framework" However, the impact of such efforts is not yet clear. The harmonization of Chinese society and the natural environment is billed as one of the country's top national priorities.

International groups called the law revision passed in April 2014 a positive development, but cautioned seeing the laws through to implementation would be a challenge.

Because China does not have a fully established legal system, enterprise executives base their environmental practices largely on perceptions about regulators rather than concerns for legal issues, according to a 2014 study published in Journal of Public Administration Research and Theory. One executive interviewed said that China's environmental regulations were “comprehensive” but yet “vague,” leaving local officials with large discretion in terms of enforcement. If executives think local officials may arbitrarily target their enterprises for enforcement, they are likely to adopt proactive practices, such as “developing certifiable environmental management systems,” but not basic ones, such as waste recycling.

Solar eclipse

From Wikipedia, the free encyclopedia

Total solar eclipse
A total solar eclipse occurs when the Moon completely covers the Sun's disk, as seen in this 1999 solar eclipse. Solar prominences can be seen along the limb (in red) as well as extensive coronal filaments.
 
Annular solar eclipsePartial solar eclipse
An annular solar eclipse (left) occurs when the Moon is too far away to completely cover the Sun's disk (May 20, 2012). During a partial solar eclipse (right), the Moon blocks only part of the Sun's disk (October 23, 2014).

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring Earth's view of the Sun, totally or partially. Such an alignment coincides with a new moon, indicating the Moon is closest to the plane of the Earth's orbit. In a total eclipse, the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses, only part of the Sun is obscured.

If the Moon were in a perfectly circular orbit and in the same orbital plane as Earth, there would be total solar eclipses every new moon. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during eclipse seasons, resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Total eclipses are more rare because they require a more precise alignment between the centers of the Sun and Moon, and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun. Total solar eclipses occur rarely at a given place on Earth, on average about every 360 to 410 years.

An eclipse is a natural phenomenon. In some ancient and modern cultures, solar eclipses were attributed to supernatural causes or regarded as bad omens. Astronomers' predictions of eclipses began in China as early as the 4th century BC; eclipses hundreds of years into the future may now be predicted with high accuracy.

Looking directly at the Sun can lead to permanent eye damage, so special eye protection or indirect viewing techniques are used when viewing a solar eclipse. Only the total phase of a total solar eclipse is safe to view without protection. Enthusiasts known as eclipse chasers or umbraphiles travel to remote locations to see solar eclipses.

Types

Partial and annular phases of solar eclipse on May 20, 2012

There are four types of solar eclipses:

  • A total eclipse occurs when the dark silhouette of the Moon completely obscures the intensely bright light of the Sun, allowing the much fainter solar corona to be visible. During any one eclipse, totality occurs at best only in a narrow track on the surface of Earth. This narrow track is called the path of totality.
  • An annular eclipse occurs when the Sun and Moon are exactly in line with the Earth, but the apparent size of the Moon is smaller than that of the Sun. Hence the Sun appears as a very bright ring, or annulus, surrounding the dark disk of the Moon.
  • A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare.
  • A partial eclipse occurs when the Sun and Moon are not exactly in line with the Earth and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of the Earth outside of the track of an annular or total eclipse. However, some eclipses can be seen only as a partial eclipse, because the umbra passes above the Earth's polar regions and never intersects the Earth's surface. Partial eclipses are virtually unnoticeable in terms of the Sun's brightness, as it takes well over 90% coverage to notice any darkening at all. Even at 99%, it would be no darker than civil twilight. Of course, partial eclipses (and partial stages of other eclipses) can be observed if one is viewing the Sun through a darkening filter (which should always be used for safety).
Comparison of minimum and maximum apparent sizes of the Sun and Moon (and planets). An annular eclipse can occur when the Sun has a larger apparent size than the Moon, whereas a total eclipse can occur when the Moon has a larger apparent size.

The Sun's distance from Earth is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure.

A separate category of solar eclipses is that of the Sun being occluded by a body other than the Earth's Moon, as can be observed at points in space away from the Earth's surface. Two examples are when the crew of Apollo 12 observed the Earth eclipse the Sun in 1969 and when the Cassini probe observed Saturn eclipsing the Sun in 2006.

The Moon's orbit around the Earth is slightly elliptical, as is the Earth's orbit around the Sun. The apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse that occurs when the Moon is near its closest distance to Earth (i.e., near its perigee) can be a total eclipse because the Moon will appear to be large enough to completely cover the Sun's bright disk or photosphere; a total eclipse has a magnitude greater than or equal to 1.000. Conversely, an eclipse that occurs when the Moon is near its farthest distance from Earth (i.e., near its apogee) can be only an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1.

A hybrid eclipse occurs when the magnitude of an eclipse changes during the event from less to greater than one, so the eclipse appears to be total at locations nearer the midpoint, and annular at other locations nearer the beginning and end, since the sides of the Earth are slightly further away from the Moon. These eclipses are extremely narrow in their path width and relatively short in their duration at any point compared with fully total eclipses; the 2023 April 20 hybrid eclipse's totality is over a minute in duration at various points along the path of totality. Like a focal point, the width and duration of totality and annularity are near zero at the points where the changes between the two occur.

Because the Earth's orbit around the Sun is also elliptical, the Earth's distance from the Sun similarly varies throughout the year. This affects the apparent size of the Sun in the same way, but not as much as does the Moon's varying distance from Earth. When Earth approaches its farthest distance from the Sun in early July, a total eclipse is somewhat more likely, whereas conditions favour an annular eclipse when Earth approaches its closest distance to the Sun in early January.

Terminology for central eclipse

Each icon shows the view from the centre of its black spot, representing the Moon (not to scale)
 
Diamond ring effect at third contact—the end of totality—with visible prominences

Central eclipse is often used as a generic term for a total, annular, or hybrid eclipse. This is, however, not completely correct: the definition of a central eclipse is an eclipse during which the central line of the umbra touches the Earth's surface. It is possible, though extremely rare, that part of the umbra intersects with the Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse. Gamma is a measure of how centrally the shadow strikes. The last (umbral yet) non-central solar eclipse was on April 29, 2014. This was an annular eclipse. The next non-central total solar eclipse will be on April 9, 2043.

The visual phases observed during a total eclipse are called:

  • First contact—when the Moon's limb (edge) is exactly tangential to the Sun's limb.
  • Second contact—starting with Baily's Beads (caused by light shining through valleys on the Moon's surface) and the diamond ring effect. Almost the entire disk is covered.
  • Totality—the Moon obscures the entire disk of the Sun and only the solar corona is visible.
  • Third contact—when the first bright light becomes visible and the Moon's shadow is moving away from the observer. Again a diamond ring may be observed.
  • Fourth contact—when the trailing edge of the Moon ceases to overlap with the solar disk and the eclipse ends.

Predictions

Geometry

Geometry of a total solar eclipse (not to scale)

The diagrams to the right show the alignment of the Sun, Moon, and Earth during a solar eclipse. The dark gray region between the Moon and Earth is the umbra, where the Sun is completely obscured by the Moon. The small area where the umbra touches Earth's surface is where a total eclipse can be seen. The larger light gray area is the penumbra, in which a partial eclipse can be seen. An observer in the antumbra, the area of shadow beyond the umbra, will see an annular eclipse.

The Moon's orbit around the Earth is inclined at an angle of just over 5 degrees to the plane of the Earth's orbit around the Sun (the ecliptic). Because of this, at the time of a new moon, the Moon will usually pass to the north or south of the Sun. A solar eclipse can occur only when a new moon occurs close to one of the points (known as nodes) where the Moon's orbit crosses the ecliptic.

As noted above, the Moon's orbit is also elliptical. The Moon's distance from the Earth can vary by about 6% from its average value. Therefore, the Moon's apparent size varies with its distance from the Earth, and it is this effect that leads to the difference between total and annular eclipses. The distance of the Earth from the Sun also varies during the year, but this is a smaller effect. On average, the Moon appears to be slightly smaller than the Sun as seen from the Earth, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to the Earth than average (near its perigee) that a total eclipse occurs.

  Moon Sun
At perigee
(nearest)
At apogee
(farthest)
At perihelion
(nearest)
At aphelion
(farthest)
Mean radius 1,737.10 km
(1,079.38 mi)
696,000 km
(432,000 mi)
Distance 363,104 km
(225,622 mi)
405,696 km
(252,088 mi)
147,098,070 km
(91,402,500 mi)
152,097,700 km
(94,509,100 mi)
Angular
diameter
33' 30"
(0.5583°)
29' 26"
(0.4905°)
32' 42"
(0.5450°)
31' 36"
(0.5267°)
Apparent size
to scale
-Phase of the moon NO.16.jpg -Phase of the moon NO.16.jpg The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100801.jpg The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100801.jpg
Order by
decreasing
apparent size
1st 4th 2nd 3rd

The Moon orbits the Earth in approximately 27.3 days, relative to a fixed frame of reference. This is known as the sidereal month. However, during one sidereal month, Earth has revolved part way around the Sun, making the average time between one new moon and the next longer than the sidereal month: it is approximately 29.5 days. This is known as the synodic month and corresponds to what is commonly called the lunar month.

The Moon crosses from south to north of the ecliptic at its ascending node, and vice versa at its descending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion, due to the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.6 years. This regression means that the time between each passage of the Moon through the ascending node is slightly shorter than the sidereal month. This period is called the nodical or draconic month.

Finally, the Moon's perigee is moving forwards or precessing in its orbit and makes a complete circuit in 8.85 years. The time between one perigee and the next is slightly longer than the sidereal month and known as the anomalistic month.

The Moon's orbit intersects with the ecliptic at the two nodes that are 180 degrees apart. Therefore, the new moon occurs close to the nodes at two periods of the year approximately six months (173.3 days) apart, known as eclipse seasons, and there will always be at least one solar eclipse during these periods. Sometimes the new moon occurs close enough to a node during two consecutive months to eclipse the Sun on both occasions in two partial eclipses. This means that, in any given year, there will always be at least two solar eclipses, and there can be as many as five.

Eclipses can occur only when the Sun is within about 15 to 18 degrees of a node, (10 to 12 degrees for central eclipses). This is referred to as an eclipse limit, and is given in ranges because the apparent sizes and speeds of the Sun and Moon vary throughout the year. In the time it takes for the Moon to return to a node (draconic month), the apparent position of the Sun has moved about 29 degrees, relative to the nodes. Since the eclipse limit creates a window of opportunity of up to 36 degrees (24 degrees for central eclipses), it is possible for partial eclipses (or rarely a partial and a central eclipse) to occur in consecutive months.

Fraction of the Sun's disc covered, f, when the same-sized discs are offset a fraction t of their diameter.

Path

During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across the Earth. The Earth is also rotating from west to east, at about 28 km/min at the Equator, but as the Moon is moving in the same direction as the Earth's rotation at about 61 km/min, the umbra almost always appears to move in a roughly west–east direction across a map of the Earth at the speed of the Moon's orbital velocity minus the Earth's rotational velocity. Rare exceptions can occur in polar regions where the path may go over or near the pole, as in 2021 on June 10 and December 4.

The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. In the most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be up to 267 km (166 mi) wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse is seen over a much larger area of the Earth. Typically, the umbra is 100–160 km wide, while the penumbral diameter is in excess of 6400 km.

Besselian elements are used to predict whether an eclipse will be partial, annular, or total (or annular/total), and what the eclipse circumstances will be at any given location. Calculations with Besselian elements can determine the exact shape of the umbra's shadow on the Earth's surface. But at what longitudes on the Earth's surface the shadow will fall, is a function of the Earth's rotation, and on how much that rotation has slowed down over time. A number called ΔT is used in eclipse prediction to take this slowing into account. As the Earth slows, ΔT increases. ΔT for dates in the future can only be roughly estimated because the Earth's rotation is slowing irregularly. This means that, although it is possible to predict that there will be a total eclipse on a certain date in the far future, it is not possible to predict in the far future exactly at what longitudes that eclipse will be total. Historical records of eclipses allow estimates of past values of ΔT and so of the Earth's rotation.

Duration

The following factors determine the duration of a total solar eclipse (in order of decreasing importance):

  1. The Moon being almost exactly at perigee (making its angular diameter as large as possible).
  2. The Earth being very near aphelion (furthest away from the Sun in its elliptical orbit, making its angular diameter nearly as small as possible).
  3. The midpoint of the eclipse being very close to the Earth's equator, where the rotational velocity is greatest.
  4. The vector of the eclipse path at the midpoint of the eclipse aligning with the vector of the Earth's rotation (i.e. not diagonal but due east).
  5. The midpoint of the eclipse being near the subsolar point (the part of the Earth closest to the Sun).

The longest eclipse that has been calculated thus far is the eclipse of July 16, 2186 (with a maximum duration of 7 minutes 29 seconds over northern Guyana).

Occurrence and cycles

Total solar eclipse paths: 1001–2000, showing that total solar eclipses occur almost everywhere on Earth. This image was merged from 50 separate images from NASA.

Total solar eclipses are rare events. Although they occur somewhere on Earth every 18 months on average, it is estimated that they recur at any given place only once every 360 to 410 years, on average. The total eclipse lasts for only a maximum of a few minutes at any location, because the Moon's umbra moves eastward at over 1700 km/h. Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s. The last time an eclipse longer than 7 minutes occurred was June 30, 1973 (7 min 3 sec). Observers aboard a Concorde supersonic aircraft were able to stretch totality for this eclipse to about 74 minutes by flying along the path of the Moon's umbra. The next total eclipse exceeding seven minutes in duration will not occur until June 25, 2150. The longest total solar eclipse during the 11,000 year period from 3000 BC to at least 8000 AD will occur on July 16, 2186, when totality will last 7 min 29 s. For comparison, the longest total eclipse of the 20th century at 7 min 8 s occurred on June 20, 1955, and there are no total solar eclipses over 7 min in duration in the 21st century.

It is possible to predict other eclipses using eclipse cycles. The saros is probably the best known and one of the most accurate. A saros lasts 6,585.3 days (a little over 18 years), which means that, after this period, a practically identical eclipse will occur. The most notable difference will be a westward shift of about 120° in longitude (due to the 0.3 days) and a little in latitude (north-south for odd-numbered cycles, the reverse for even-numbered ones). A saros series always starts with a partial eclipse near one of Earth's polar regions, then shifts over the globe through a series of annular or total eclipses, and ends with a partial eclipse at the opposite polar region. A saros series lasts 1226 to 1550 years and 69 to 87 eclipses, with about 40 to 60 of them being central.

Frequency per year

Between two and five solar eclipses occur every year, with at least one per eclipse season. Since the Gregorian calendar was instituted in 1582, years that have had five solar eclipses were 1693, 1758, 1805, 1823, 1870, and 1935. The next occurrence will be 2206. On average, there are about 240 solar eclipses each century.

The 5 solar eclipses of 1935
January 5 February 3 June 30 July 30 December 25
Partial
(south)
Partial
(north)
Partial
(north)
Partial
(south)
Annular
(south)
SE1935Jan05P.png
Saros 111
SE1935Feb03P.png
Saros 149
SE1935Jun30P.png
Saros 116
SE1935Jul30P.png
Saros 154
SE1935Dec25A.png
Saros 121

Final totality

Total solar eclipses are seen on Earth because of a fortuitous combination of circumstances. Even on Earth, the diversity of eclipses familiar to people today is a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was closer to the Earth and therefore apparently larger, so every solar eclipse was total or partial, and there were no annular eclipses. Due to tidal acceleration, the orbit of the Moon around the Earth becomes approximately 3.8 cm more distant each year. Millions of years in the future, the Moon will be too far away to fully occlude the Sun, and no total eclipses will occur. In the same timeframe, the Sun may become brighter, making it appear larger in size. Estimates of the time when the Moon will be unable to occlude the entire Sun when viewed from the Earth range between 650 million and 1.4 billion years in the future.

Historical eclipses

Astronomers Studying an Eclipse painted by Antoine Caron in 1571

Historical eclipses are a very valuable resource for historians, in that they allow a few historical events to be dated precisely, from which other dates and ancient calendars may be deduced.[46] A solar eclipse of June 15, 763 BC mentioned in an Assyrian text is important for the chronology of the ancient Near East. There have been other claims to date earlier eclipses. The Book of Joshua 10:13 describes the sun staying still for an entire day in the sky; a group of University of Cambridge scholars concluded this to be the annular solar eclipse that occurred on 30 October 1207 BC. The Chinese king Zhong Kang supposedly beheaded two astronomers, Hsi and Ho, who failed to predict an eclipse 4,000 years ago. Perhaps the earliest still-unproven claim is that of archaeologist Bruce Masse, who putatively links an eclipse that occurred on May 10, 2807, BC with a possible meteor impact in the Indian Ocean on the basis of several ancient flood myths that mention a total solar eclipse.

Records of the solar eclipses of 993 and 1004 as well as the lunar eclipses of 1001 and 1002 by Ibn Yunus of Cairo (c. 1005).

Eclipses have been interpreted as omens, or portents. The ancient Greek historian Herodotus wrote that Thales of Miletus predicted an eclipse that occurred during a battle between the Medes and the Lydians. Both sides put down their weapons and declared peace as a result of the eclipse. The exact eclipse involved remains uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BC, probably near the Halys river in Asia Minor. An eclipse recorded by Herodotus before Xerxes departed for his expedition against Greece,[54] which is traditionally dated to 480 BC, was matched by John Russell Hind to an annular eclipse of the Sun at Sardis on February 17, 478 BC. Alternatively, a partial eclipse was visible from Persia on October 2, 480 BC. Herodotus also reports a solar eclipse at Sparta during the Second Persian invasion of Greece. The date of the eclipse (August 1, 477 BC) does not match exactly the conventional dates for the invasion accepted by historians.

Chinese records of eclipses begin at around 720 BC.[59] The 4th century BC astronomer Shi Shen described the prediction of eclipses by using the relative positions of the Moon and Sun.

Attempts have been made to establish the exact date of Good Friday by assuming that the darkness described at Jesus's crucifixion was a solar eclipse. This research has not yielded conclusive results, and Good Friday is recorded as being at Passover, which is held at the time of a full moon. Further, the darkness lasted from the sixth hour to the ninth, or three hours, which is much, much longer than the eight-minute upper limit for any solar eclipse's totality. Contemporary chronicles wrote about an eclipse at the beginning of May 664 that coincided with the beginning of the plague of 664 in the British isles. In the Western hemisphere, there are few reliable records of eclipses before AD 800, until the advent of Arab and monastic observations in the early medieval period. The Cairo astronomer Ibn Yunus wrote that the calculation of eclipses was one of the many things that connect astronomy with the Islamic law, because it allowed knowing when a special prayer can be made. The first recorded observation of the corona was made in Constantinople in AD 968.

The first known telescopic observation of a total solar eclipse was made in France in 1706. Nine years later, English astronomer Edmund Halley accurately predicted and observed the solar eclipse of May 3, 1715. By the mid-19th century, scientific understanding of the Sun was improving through observations of the Sun's corona during solar eclipses. The corona was identified as part of the Sun's atmosphere in 1842, and the first photograph (or daguerreotype) of a total eclipse was taken of the solar eclipse of July 28, 1851. Spectroscope observations were made of the solar eclipse of August 18, 1868, which helped to determine the chemical composition of the Sun.

Erhard Weigel, predicted course of moon shadow on 12 August 1654 (O.S. 2 August)
 
Illustration from De magna eclipsi solari, quae continget anno 1764 published in Acta Eruditorum, 1762

John Fiske summed up myths about the solar eclipse like this in his 1872 book Myth and Myth-Makers,

the myth of Hercules and Cacus, the fundamental idea is the victory of the solar god over the robber who steals the light. Now whether the robber carries off the light in the evening when Indra has gone to sleep, or boldly rears his black form against the sky during the daytime, causing darkness to spread over the earth, would make little difference to the framers of the myth. To a chicken a solar eclipse is the same thing as nightfall, and he goes to roost accordingly. Why, then, should the primitive thinker have made a distinction between the darkening of the sky caused by black clouds and that caused by the rotation of the earth? He had no more conception of the scientific explanation of these phenomena than the chicken has of the scientific explanation of an eclipse. For him it was enough to know that the solar radiance was stolen, in the one case as in the other, and to suspect that the same demon was to blame for both robberies.

Viewing

Looking directly at the photosphere of the Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including blindness. The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there is no warning that injury is occurring.

Under normal conditions, the Sun is so bright that it is difficult to stare at it directly. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during a total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage within a fraction of a second.

Partial and annular eclipses

Eclipse glasses filter out eye damaging radiation, allowing direct viewing of the Sun during all partial eclipse phases; they are not used during totality, when the Sun is completely eclipsed
 
Pinhole projection method of observing partial solar eclipse. Insert (upper left): partially eclipsed Sun photographed with a white solar filter. Main image: projections of the partially eclipsed Sun (bottom right)

Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods if eye damage is to be avoided. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Sunglasses do not make viewing the Sun safe. Only properly designed and certified solar filters should be used for direct viewing of the Sun's disk. Especially, self-made filters using common objects such as a floppy disk removed from its case, a Compact Disc, a black colour slide film, smoked glass, etc. must be avoided.

The safest way to view the Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. Care must be taken, however, to ensure that no one looks through the projector (telescope, pinhole, etc.) directly. Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe. Securely mounting #14 welder's glass in front of the lens and viewfinder protects the equipment and makes viewing possible. Professional workmanship is essential because of the dire consequences any gaps or detaching mountings will have. In the partial eclipse path, one will not be able to see the corona or nearly complete darkening of the sky. However, depending on how much of the Sun's disk is obscured, some darkening may be noticeable. If three-quarters or more of the Sun is obscured, then an effect can be observed by which the daylight appears to be dim, as if the sky were overcast, yet objects still cast sharp shadows.

Totality

Baily's beads, sunlight visible through lunar valleys
 
Composite image with corona, prominences, and diamond ring effect

When the shrinking visible part of the photosphere becomes very small, Baily's beads will occur. These are caused by the sunlight still being able to reach the Earth through lunar valleys. Totality then begins with the diamond ring effect, the last bright flash of sunlight.

It is safe to observe the total phase of a solar eclipse directly only when the Sun's photosphere is completely covered by the Moon, and not before or after totality. During this period, the Sun is too dim to be seen through filters. The Sun's faint corona will be visible, and the chromosphere, solar prominences, and possibly even a solar flare may be seen. At the end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon.

Eclipse chasing

A dedicated group of eclipse chasers have pursued the observation of solar eclipses when they occur around the Earth. A person who chases eclipses is known as an umbraphile, meaning shadow lover. Umbraphiles travel for eclipses and use various tools to help view the sun including solar viewing glasses, also known as eclipse glasses, as well as telescopes.

Photography

The progression of a solar eclipse on August 1, 2008 in Novosibirsk, Russia. All times UTC (local time was UTC+7). The time span between shots is three minutes.

Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the Sun/Moon to be easily visible, a fairly high magnification long focus lens is needed (at least 200 mm for a 35 mm camera), and for the disk to fill most of the frame, a longer lens is needed (over 500 mm). As with viewing the Sun directly, looking at it through the optical viewfinder of a camera can produce damage to the retina, so care is recommended. Solar filters are required for digital photography even if an optical viewfinder is not used. Using a camera's live view feature or an electronic viewfinder is safe for the human eye, but the Sun's rays could potentially irreparably damage digital image sensors unless the lens is covered by a properly designed solar filter.

Other observations

A total solar eclipse provides a rare opportunity to observe the corona (the outer layer of the Sun's atmosphere). Normally this is not visible because the photosphere is much brighter than the corona. According to the point reached in the solar cycle, the corona may appear small and symmetric, or large and fuzzy. It is very hard to predict this in advance.

As the light filters through leaves of trees during a partial eclipse, the overlapping leaves create natural pinholes, displaying mini eclipses on the ground.

Phenomena associated with eclipses include shadow bands (also known as flying shadows), which are similar to shadows on the bottom of a swimming pool. They occur only just prior to and after totality, when a narrow solar crescent acts as an anisotropic light source.

1919 observations

Eddington's original photograph of the 1919 eclipse, which provided evidence for Einstein's theory of general relativity.

The observation of a total solar eclipse of May 29, 1919, helped to confirm Einstein's theory of general relativity. By comparing the apparent distance between stars in the constellation Taurus, with and without the Sun between them, Arthur Eddington stated that the theoretical predictions about gravitational lenses were confirmed. The observation with the Sun between the stars was possible only during totality since the stars are then visible. Though Eddington's observations were near the experimental limits of accuracy at the time, work in the later half of the 20th century confirmed his results.

Gravity anomalies

There is a long history of observations of gravity-related phenomena during solar eclipses, especially during the period of totality. In 1954, and again in 1959, Maurice Allais reported observations of strange and unexplained movement during solar eclipses. The reality of this phenomenon, named the Allais effect, has remained controversial. Similarly, in 1970, Saxl and Allen observed the sudden change in motion of a torsion pendulum; this phenomenon is called the Saxl effect.

Observation during the 1997 solar eclipse by Wang et al. suggested a possible gravitational shielding effect, which generated debate. In 2002, Wang and a collaborator published detailed data analysis, which suggested that the phenomenon still remains unexplained.

Eclipses and transits

In principle, the simultaneous occurrence of a solar eclipse and a transit of a planet is possible. But these events are extremely rare because of their short durations. The next anticipated simultaneous occurrence of a solar eclipse and a transit of Mercury will be on July 5, 6757, and a solar eclipse and a transit of Venus is expected on April 5, 15232.

More common, but still infrequent, is a conjunction of a planet (especially, but not only, Mercury or Venus) at the time of a total solar eclipse, in which event the planet will be visible very near the eclipsed Sun, when without the eclipse it would have been lost in the Sun's glare. At one time, some scientists hypothesized that there may be a planet (often given the name Vulcan) even closer to the Sun than Mercury; the only way to confirm its existence would have been to observe it in transit or during a total solar eclipse. No such planet was ever found, and general relativity has since explained the observations that led astronomers to suggest that Vulcan might exist.

Earthshine

From space, the Moon's shadow during a solar eclipse appears as a dark spot moving across the Earth.

During a total solar eclipse, the Moon's shadow covers only a small fraction of the Earth. The Earth continues to receive at least 92 percent of the amount of sunlight it receives without an eclipse – more if the penumbra of the Moon's shadow partly misses the Earth. Seen from the Moon, the Earth during a total solar eclipse is mostly brilliantly illuminated, with only a small dark patch showing the Moon's shadow. The brilliantly lit Earth reflects a lot of light to the Moon. If the corona of the eclipsed Sun were not present, the Moon, illuminated by earthlight, would be easily visible from Earth. This would be essentially the same as the earthshine which can frequently be seen when the Moon's phase is a narrow crescent. In reality, the corona, though much less brilliant than the Sun's photosphere, is much brighter than the Moon illuminated by earthlight. Therefore, by contrast, the Moon during a total solar eclipse appears to be black, with the corona surrounding it.

Artificial satellites

The Moon's shadow over Turkey and Cyprus, seen from the ISS during a 2006 total solar eclipse.
 
A composite image showing the ISS transit of the Sun while the 2017 solar eclipse was in progress.

Artificial satellites can also pass in front of the Sun as seen from the Earth, but none is large enough to cause an eclipse. At the altitude of the International Space Station, for example, an object would need to be about 3.35 km (2.08 mi) across to blot the Sun out entirely. These transits are difficult to watch because the zone of visibility is very small. The satellite passes over the face of the Sun in about a second, typically. As with a transit of a planet, it will not get dark.

Observations of eclipses from spacecraft or artificial satellites orbiting above the Earth's atmosphere are not subject to weather conditions. The crew of Gemini 12 observed a total solar eclipse from space in 1966. The partial phase of the 1999 total eclipse was visible from Mir.

During the Apollo–Soyuz Test Project conducted in July 1975, the Apollo spacecraft was positioned to create an artificial solar eclipse giving the Soyuz crew an opportunity to photograph the solar corona.

Impact

The solar eclipse of March 20, 2015, was the first occurrence of an eclipse estimated to potentially have a significant impact on the power system, with the electricity sector taking measures to mitigate any impact. The continental Europe and Great Britain synchronous areas were estimated to have about 90 gigawatts of solar power and it was estimated that production would temporarily decrease by up to 34 GW compared to a clear sky day.

Eclipses may cause the temperature to decrease by 3 °C, with wind power potentially decreasing as winds are reduced by 0.7 m/s.

In addition to the drop in light level and air temperature, animals change their behavior during totality. For example, birds and squirrels return to their nests and crickets chirp.

Recent and forthcoming solar eclipses

Eclipse path for total and hybrid eclipses from 2021 to 2040.

Eclipses occur only in the eclipse season, when the Sun is close to either the ascending or descending node of the Moon. Each eclipse is separated by one, five or six lunations (synodic months), and the midpoint of each season is separated by 173.3 days, which is the mean time for the Sun to travel from one node to the next. The period is a little less than half a calendar year because the lunar nodes slowly regress. Because 223 synodic months is roughly equal to 239 anomalistic months and 242 draconic months, eclipses with similar geometry recur 223 synodic months (about 6,585.3 days) apart. This period (18 years 11.3 days) is a saros. Because 223 synodic months is not identical to 239 anomalistic months or 242 draconic months, saros cycles do not endlessly repeat. Each cycle begins with the Moon's shadow crossing the Earth near the north or south pole, and subsequent events progress toward the other pole until the Moon's shadow misses the Earth and the series ends. Saros cycles are numbered; currently, cycles 117 to 156 are active.

Solar eclipses
1997–20002000–20032004–20072008–20112011–20142015–20182018–20212022–20252026–2029

Equality (mathematics)

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