Columbus was looking for a SEA route to India and China because 40 years earlier Muslim Turks conquered Constantinople in 1453 cutting off the LAND routes.
A biography of Columbus was written by Washington Irving in 1828, A History of the Life and Voyages of Christopher Columbus, was filled imaginative dialogue, such as Europeans arguing that the Earth was flat.
Washington Irving was known for imaginative stories such as "Rip Van Winkle," "The Legend of Sleepy Hallow," Dutch tales of visits from St. Nick, and coining New York City's nickname "Gotham."
Europeans knew the Earth was round.
Pythagoras had speculated that the earth was a sphere in the 6th century BC, and Aristotle validated it in the 4th century BC.
In the 3rd century BC, Eratosthenes computed the circumference of the earth with amazing accuracy.
He had heard that at Aswan, Egpyt, the sun cast no shadow at noon on the summer solstice (June 21), yet at the exact same moment in Alexandria, Egypt, a stick in the ground cast a shadow with a 7.2 degree angle.
7.2 degrees is 1/50th of a 360 degree circle.
As the distance between Alexandria and Aswan was 5,000 stadia or 800 kilometers, all he had to do was multiply 800 times 50, which equals 40,000 kilometers, just 30 kilometers less than the actual.
Eratosthenes also calculated distance to the sun and moon, the tilt of the earth, and created the first world map with parallel latitude and meridian longitude lines.
In the 1st century BC, Posidonius used stellar observations at Alexandria and Rhodes to confirm Eratosthenese's measurements.
In the 2nd century AD, astronomer Ptolemy had written a Guide to Geography, in which he described a spherical earth with one ocean connecting Europe and Asia.
St. Isidore of Seville, Spain, wrote in the 7th century that the earth was round.
Around the year 723 AD, Saint Bede the Venerable wrote in his work "Reckoning of Time" that the Earth was spherical.
The Book of Isaiah 40:22 states: "It is He that sitteth upon the globe of the earth." (Douay-Rheims Bible)
Columbus knew the Earth was round, but the question was, how far around.
The confusion was over the length of a mile.
Columbus read Cardinal Pierre d'Ailly's "Imago Mundi," which gave Alfraganus' estimate that a degree of latitude (at the equator) was around 56.7 miles.
What Columbus did not realize was that this was expressed in longer Arabic miles rather than in shorter Roman miles.
Therefore Columbus incorrectly estimated the Earth to be smaller in circumference, about 19,000 miles, rather than the actual nearly 25,000 miles.
Columbus knew there was land to the west, as he had heard stories of Irish monk St. Brendan sailing in 530 AD to "The Land of the Promised Saints which God will give us on the last day."
He knew of the Christian Viking Leif Erickson's voyage in the year 1000 to Vinland.
Columbus read of Marco Polo's travels to China and India in 1271.
He studied Pliny's "Natural History," Sir John Mandeville, and Pope Pius II's "Historia Rerum Ubique Gestarum."
Columbus may have possibly seen maps, rumored to have been in Portugal's royal archives, from China's treasure fleets which were sent out in 1421 by Ming Emperor Zhu Di, led by Admiral Zheng He.
Columbus corresponded with Florentine physician Paolo dal Pozzo Toscanelli, who suggested China was just 5,000 miles west of Portugal.
Based on this, Columbus estimated that Japan, or as Marco Polo called it "Cipangu," was only 3,000 Roman miles west of the Canary Islands, rather than the actual 12,200 miles.
Since no ship at that time could carry enough food and water for such a long voyage, Columbus would have never set sail if he had known the actual distance.
As a young man, Columbus began sailing on a trip to a Genoese colony in the Aegean Sea named Chios.
In 1476, he sailed on an armed convoy from Genoa to northern Europe, docking in Bristol, England, and Galway, Ireland, and even possibly Iceland in 1477.
When Muslim Turks conquered Constantinople in 1453 and hindered land trade routes from Europe to India and China, Portugal, which had been freed from Muslim domination for two centuries, began to search for alternative sea routes.
Portugal, under Prince Henry the Navigator, led the world in the science of navigation and cartography (map-making), and developed a light ship that could travel fast and far, the "caravel."
During Portugal's Golden Age of Discovery under King John II, Columbus sailed along the west coast of Africa between 1482-1485, reaching the Portuguese trading port of Elmina on the coast of Guinea.
In 1498, Portuguese sailor Vasco de Gama did make it around South Africa to India.
But six years before that, in 1492, the Catholic Monarchs Ferdinand and Isabella finished driving the Muslims out of Spain and wanted to join the quest for a sea trade route to the India.
They backed Columbus' plan.
Though Columbus was wrong about the miles and degrees of longitude, he did understand trade winds across the Atlantic.
On August 3, 1492, Columbus set sail on the longest voyage to that date out of the sight of land.
Trade winds called "easterlies" pushed Columbus' ships for five weeks to the Bahamas.
On OCTOBER 12, 1492, Columbus sighted what he thought was India.
He imagined Haiti was Japan and Cuba was the tip of China.
Naming the first island "San Salvador" for the Holy Savior, Columbus wrote of the inhabitants:
"So that they might be well-disposed towards us, for I knew that they were a people to be ... converted to our Holy Faith rather by love than by force, I gave to some red caps and to others glass beads ...
They became so entirely our friends that ... I believe that they would easily be made Christians."
Columbus, Christopher. Oct. 8, 10, 12, 16, 28, Nov. 6, 27, Dec. 12, 16, 22, 24, 1492, in his Journal of the First Voyage (El Libro de la Primera Navegacion), as recounted in Bartolome' de Las Casas' abstract, translated into English by Samuel Eliot Morison, Journals & Other Documents on the Life & Voyages of Christopher Columbus (NY: Heritage Press, 1963), pp. 65, 72. John Bartlett, Bartlett's Familiar Quotations (Boston: Little, Brown & Co., 1855, 1980), pp. 150-151. John Eidsmoe, Columbus & Cortez, Conquerors for Christ (Green Forest, AR: New Leaf Press, 1992), pp. 85-86. Bjorn Landstrom, Columbus (NY: The Macmillan Co., 1966), pp. 66-75. Peter Marshall & David Manual, The Light & the Glory (Old Tappan, NJ: Fleming H. Revell Co., 1977), p. 42.