A total

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...

occurred at the Moon's descending node of orbit on Thursday, May 29, 1919, with a magnitude of 1.0719. A

occurs when the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

passes between

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring only 19 hours after perigee (on May 28, 1919, at 18:09 UTC), the Moon's apparent diameter was larger. This specific total solar eclipse was significant because it helped prove Einstein's theory of relativity. The eclipse was the subject of the Eddington experiment: two groups of British astronomers went to

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

and the west coast of

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

to take pictures of the

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s in the sky once the Moon covered the Sun and darkness was revealed. Those photos helped prove that the Sun interferes with the bend of starlight. The totality of this eclipse was visible from southeastern

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, northern

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

, much of

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

and central

, southern

Liberia Liberia, officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to Guinea–Liberia border, its north, Ivory Coast to Ivory Coast–Lib ...

, the southern

Ivory Coast Ivory Coast, also known as Côte d'Ivoire and officially the Republic of Côte d'Ivoire, is a country on the southern coast of West Africa. Its capital city of Yamoussoukro is located in the centre of the country, while its largest List of ci ...

Príncipe Príncipe (; ) is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa in the Gulf of Guinea. It has an area of (including offshore islets) and a population of 7,324 at the 2012 Cens ...

, Río Muni (now

Equatorial Guinea Equatorial Guinea, officially the Republic of Equatorial Guinea, is a country on the west coast of Central Africa. It has an area of . Formerly the colony of Spanish Guinea, its post-independence name refers to its location both near the Equ ...

), parts of central French Equatorial Africa (now

Gabon Gabon ( ; ), officially the Gabonese Republic (), is a country on the Atlantic coast of Central Africa, on the equator, bordered by Equatorial Guinea to the northwest, Cameroon to the north, the Republic of the Congo to the east and south, and ...

and the

Republic of the Congo The Republic of the Congo, also known as Congo-Brazzaville, the Congo Republic or simply the Congo (the last ambiguously also referring to the neighbouring Democratic Republic of the Congo), is a country located on the western coast of Central ...

Belgian Congo The Belgian Congo (, ; ) was a Belgian colonial empire, Belgian colony in Central Africa from 1908 until independence in 1960 and became the Republic of the Congo (Léopoldville). The former colony adopted its present name, the Democratic Repu ...

(now the

Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...

), northern

Rhodesia Rhodesia ( , ; ), officially the Republic of Rhodesia from 1970, was an unrecognised state, unrecognised state in Southern Africa that existed from 1965 to 1979. Rhodesia served as the ''de facto'' Succession of states, successor state to the ...

(now northern

Zambia Zambia, officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa. It is typically referred to being in South-Central Africa or Southern Africa. It is bor ...

), German East Africa (now

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

), northern

Nyasaland Nyasaland () was a British protectorate in Africa that was established in 1907 when the former British Central Africa Protectorate changed its name. Between 1953 and 1963, Nyasaland was part of the Federation of Rhodesia and Nyasaland. After ...

(now

Malawi Malawi, officially the Republic of Malawi, is a landlocked country in Southeastern Africa. It is bordered by Zambia to the west, Tanzania to the north and northeast, and Mozambique to the east, south, and southwest. Malawi spans over and ...

), northern

Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...

, and the western

Comoros The Comoros, officially the Union of the Comoros, is an archipelagic country made up of three islands in Southeastern Africa, located at the northern end of the Mozambique Channel in the Indian Ocean. Its capital and largest city is Moroni, ...

. A partial eclipse was visible for most of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

and

Observations and locations

A total solar eclipse occurred on Thursday, May 29, 1919. With the duration of totality at maximum eclipse of 6 minutes 50.75 seconds, it was the longest solar eclipse that occurred since May 27, 1416. A longer total solar eclipse would later occur on June 8, 1937. It was visible throughout most of

and

as a partial eclipse. Totality occurred through a narrow path across southeastern

, northern

, central

and

after sunrise, across the Atlantic Ocean and into south central Africa, covering southern

, southern

French West Africa French West Africa (, ) was a federation of eight French colonial empires#Second French colonial empire, French colonial territories in West Africa: Colonial Mauritania, Mauritania, French Senegal, Senegal, French Sudan (now Mali), French Guin ...

(the part now belonging to

), the extreme southwestern tip of the British Gold Coast (now

Ghana Ghana, officially the Republic of Ghana, is a country in West Africa. It is situated along the Gulf of Guinea and the Atlantic Ocean to the south, and shares borders with Côte d’Ivoire to the west, Burkina Faso to the north, and Togo to t ...

Island in Portuguese São Tomé and Príncipe, southern

Spanish Guinea Spanish Guinea () was a set of Insular Region (Equatorial Guinea), insular and Río Muni, continental territories controlled by Spain from 1778 in the Gulf of Guinea and on the Bight of Bonny, in Central Africa. It gained independence in 1968 a ...

(now

), French Equatorial Africa (the parts now belonging to

and R. Congo, including Libreville),

(now

DR Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...

), northeastern

Northern Rhodesia Northern Rhodesia was a British protectorate in Southern Africa, now the independent country of Zambia. It was formed in 1911 by Amalgamation (politics), amalgamating the two earlier protectorates of Barotziland-North-Western Rhodesia and North ...

(now

), the northern tip of

(now

), German East Africa (now belonging to

) and northeastern Portuguese Mozambique (now

), ending near sunset in eastern Africa.

Planets and stars visible during totality

The Sun was at about its nearest to Aldebaran, so that star was potentially visible throughout the eclipse path.

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

had its conjunction with the Sun twenty days earlier and shone at 2nd magnitude a few degrees to the west. Much brighter Mercury was several degrees farther west of the Sun than Mars. Those were the only two bright planets visible in Bolivia, where the eclipsed Sun was very low in the east. Deneb, Altair, Fomalhaut and Achernar were the only 1st-magnitude stars well clear of the horizon; Vega, Aldebaran, Rigel and

Canopus Canopus is the brightest star in the southern constellation of Carina (constellation), Carina and the list of brightest stars, second-brightest star in the night sky. It is also Bayer designation, designated α Carinae, which is Rom ...

were very low. Observers in western

had a much more impressive eclipse sky with the Winter Hexagon well up, along with

Venus Venus is the second planet from the Sun. It is often called Earth's "twin" or "sister" planet for having almost the same size and mass, and the closest orbit to Earth's. While both are rocky planets, Venus has an atmosphere much thicker ...

and

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

were brilliant near Pollux and

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

was close to the west of

Regulus Regulus is the brightest object in the constellation Leo (constellation), Leo and one of the List of brightest stars, brightest stars in the night sky. It has the Bayer designation designated α Leonis, which is Latinisation of names, ...

Connection to the general theory of relativity

Newton's laws of physics ran on the belief of absolute time and three dimensions of space. This idea meant that time had only one dimension, and that it was universal. Einstein had the idea of combining space and time to make a four-dimensional world that worked together. Einstein's idea meant that extremely small matter particles could produce massive amounts of energy. If Einstein's theory was correct, matter and radiation would be connected to energy and momentum, meaning that when light was passing a large mass there would be an observable bend to the light. Einstein's prediction of the bending of light by the gravity of the Sun, one of the components of his general theory of relativity, can be tested during a solar eclipse, when stars with apparent position near the Sun become visible. The stars cannot be seen without a solar eclipse because stars passing the sun are drowned by solar glares. Following an unsuccessful attempt to validate this prediction during the Solar eclipse of June 8, 1918, two expeditions were made to measure positions of stars during this eclipse (see Eddington experiment). They were organized under the direction of Sir Frank Watson Dyson. One expedition was led by Sir Arthur Eddington to the island of

(off the west coast of Africa), the other by Andrew Claude de la Cherois Crommelin and Charles Rundle Davidson to Sobral in Brazil. The stars that both expeditions observed, the Hyades, were in the constellation Taurus. The solar eclipse of May 29, 1919 allowed Einstein to finalize his theory of relativity. However, the May eclipse was almost missed, due to unexpected storms. The astronomers were almost unable to get photos of this eclipse due to a cloud. A thunderstorm happened during the morning of the eclipse, and it had been overcast that day and many of the days beforehand. Only thirty minutes before the eclipse did the clouds begin to dissipate, and even then they were taking many photos through gaps in the clouds. The photographs taken during the eclipse of May 29, 1919, proved Einstein correct and changed ideas of physics. They also provided evidence that the Sun's mass did shift the way a star's light will bend. From the findings from these expeditions Dyson is quoted saying, "After a careful study of the plates, I am prepared to say that they confirm Einstein's prediction." He continued to explain that it left little doubt about light deflection in the area around the Sun and it was the amount Einstein demanded in his generalized theory of relativity.

Eclipse details

Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.

Eclipse season

This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.

Related eclipses

Earlier eclipses related to the Theory of Relativity

Before 1919 there were two eclipses in 1912 where this idea was almost proven, but there were outside factors against astronomers. The first eclipse in 1912 was on April 17, but superstition, underfunding, and time overwhelmed the astronomers on this date. The April 17 eclipse was nicknamed "The Titanic Eclipse", because it occurred two days after the sinking of the ''Titanic''. There is a history of people connecting eclipses to "divine events", and due to the continued search and rescue of victims, people started to believe that the eclipse and wreck were connected. The surrounding superstition of the eclipse led to it being less a study on physics and more of a party. However, a lack of funding, preparation, and time of total coverage of the sun would have also caused issues for the astronomers. The second eclipse they wanted to photograph was on October 10, 1912, and it was unable to be photographed due to rain.