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- As countless photos from space can attest, Earth is round—the "Blue Marble," as astronauts have affectionately dubbed it. Appearances, however, can be deceiving. Planet Earth is not, in fact, perfectly round. This is not to say Earth is flat.
www.scientificamerican.com/article/earth-is-not-round/
Apr 12, 2007 · Planet Earth is not, in fact, perfectly round. Isaac Newton first proposed that Earth was not perfectly round. Instead, he suggested it was an oblate spheroid—a sphere that is squashed at...
- Satellite Data Reveal a Plumper Planet Earth
The earth is more like a pumpkin than a perfect sphere: it's...
- Satellite Data Reveal a Plumper Planet Earth
Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth to a sphere. The concept of a spherical Earth gradually displaced earlier beliefs in a flat Earth during classical antiquity and the Middle Ages.
Dec 21, 2020 · The ancient Greeks believed the Earth was round and calculated its circumference with remarkable accuracy, while observers inferred our planet’s spherical shape as it cast a curved shadow on the Moon during lunar eclipses.
- Overview
- Historical evidence
- Evidence from modern instrumentation
spherical Earth, refers to any figure of Earth as represented by a sphere. Although other models, including the geoid model (which is based on approximations of Earth’s gravitational field) and the ellipsoid model (which is based on mathematical approximations of Earth’s shape), are more accurate for many purposes, spherical models are useful as a ...
Human beings have long known that Earth is curved; however, the knowledge of Earth’s shape was not always widely known to people who had no formal education. Over the millennia, some people believed the world is flat by relying on their own observations as they stood on its surface and looked toward the horizon. In contrast, arguments for Earth having a curved surface were first posited during the 6th century bce, by the ancient Greek philosopher Pythagoras, who observed the spherical nature of other planets and posited that Earth also possesses a spherical shape. In the 5th century bce Anaxagoras noted that during lunar eclipses the curved shadow of Earth moves across the face of the Moon, leading him to infer that Earth is round. During the 4th century bce Aristotle attempted to use Earth’s circumference to calculate the size of Earth, and by about 240 bce Eratosthenes used geometry to estimate Earth’s circumference, based on the evidence of shadows and their angles relative to the Sun.
Other evidence of Earth’s curved shape was gathered by sailors and navigators. They observed that the stars appeared to move from their familiar locations in the sky to different locations as ships and their crews traveled to different parts of the world, and sailors traveling from one hemisphere to the other reported the existence of constellations they had never seen before. In addition, sailors looking toward the horizon observed that ships in the distance appeared to their view in stages, with the tops of ships’ masts, sails, and other rigging revealing themselves first before the decks and hulls appeared. Similarly, a seated person can observe the Sun appearing to sink completely below the horizon. However, if the individual stands up, the Sun’s edge will again become visible, allowing the viewer to watch it again slip below the horizon.
Modern satellite imagery and measurements of Earth’s gravitational field support the notion that Earth is not a perfect sphere but rather an oblate spheroid (that is, a sphere which is flattened at the poles). This shape derives from the way Earth spins on its axis, generating centrifugal force that causes the planet to bulge at the Equator. The pr...
Jun 3, 2016 · Animated short video in which Adam Rutherford & Hannah Fry explain why the Earth isn't rou. So what is the true shape of our planet?
- Adam Proctor
The length of twilight would be very different on a flat Earth. On a round Earth, the atmosphere above the ground is lit for a while before sunrise and after sunset are observed at ground level, because the Sun is still visible from higher altitudes.
While the Earth appears to be round when viewed from the vantage point of space, it is actually closer to an ellipsoid. However, even an ellipsoid does not adequately describe the Earth's unique and ever-changing shape.
