En astronomía, una esfera armilar, conocida también con el nombre de astrolabio esférico, es un modelo de la esfera celeste utilizada para mostrar el movimiento aparente de las estrellas alrededor de la Tierra o el Sol. La esfera armilar fue inventada por Eratóstenes alrededor del 255 a. C. El nombre procede del latín armilla (círculo, brazalete), dado que el instrumento está construido sobre un esqueleto de círculos graduados mostrando el ecuador, la eclíptica y los meridianos y paralelos astronómicos. Es la figura central de la bandera de Portugal. \n* Astrolabio

Leer el artículo completo en Wikipedia · CC-BY-SA

An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (in the celestial sphere), consisting of a spherical framework of rings, centred on Earth or the Sun, that represent lines of celestial longitude and latitude and other astronomically important features such as the ecliptic. As such, it differs from a celestial globe, which is a smooth sphere whose principal purpose is to map the constellations. It was invented separately in ancient Greece and ancient China, with later use in the Islamic world and Medieval Europe. With the Earth as center, an armillary sphere is known as Ptolemaic. With the sun as center, it is known as Copernican. The flag of Portugal features an armillary sphere. The armillary sphere is also featured in Portuguese heraldry, associated with the Portuguese discoveries during the Age of Exploration.

Leer el artículo completo en Wikipedia · CC-BY-SA