Question

how can we say that earth is round​

Answer 1

Answer:

The earliest documented mention of the spherical Earth concept dates from around the 5th century BC, when it was mentioned by ancient Greek philosophers. It remained a matter of speculation until the 3rd century BC, when Hellenistic astronomy established the spherical shape of the Earth as a physical fact and calculated the Earth's circumference. The paradigm was gradually adopted throughout the Old World during Late Antiquity and the Middle Ages. A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan and Juan Sebastián Elcano's circumnavigation (1519–1522).

The concept of a spherical Earth displaced earlier beliefs in a flat Earth: In early Mesopotamian mythology, the world was portrayed as a flat disk floating in the ocean with a hemispherical sky-dome above, and this forms the premise for early world maps like those of Anaximander and Hecataeus of Miletus. Other speculations on the shape of Earth include a seven-layered ziggurat or cosmic mountain, alluded to in the Avesta and ancient Persian writings (see seven climes).

The realization that the figure of the Earth is more accurately described as an ellipsoid dates to the 17th century, as described by Isaac Newton in Principia. In the early 19th century, the flattening of the earth ellipsoid was determined to be of the order of 1/300 (Delambre, Everest). The modern value as determined by the US DoD World Geodetic System since the 1960s is close to 1/298.25.

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Answer 2

Answer:

There are few pieces of evidence which prove that the earth is round. There is an ambiguity related to the exact shape of the earth as few Greek Philosophers also claimed that earth is spherical in shape.  

Few points which highlight that the earth is round or spherical are:

• Ships while sailing on the wide ocean seems to be sinking from the   origin point it’s because of the shape of the earth.

• During Lunar Eclipse the earth’s shadow falls on the Moon. Thus, it confirms the shape of the moon.

• In the clear night sky, bright lights are visible from faraway places in the city.

• The curvature of the earth is visible at an elevation of 50,000 feet.

Explanation:

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