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A positively curved universe is described by elliptic geometry, and can be thought of as a three-dimensional hypersphere, or some other spherical 3-manifold (such as the Poincaré dodecahedral space), all of which are quotients of the 3-sphere.
16 mar 2020 · Cosmological evidence suggests that the part of the universe we can see is smooth and homogeneous, at least approximately. The local fabric of space looks much the same at every point and in every direction. Only three geometries fit this description: flat, spherical and hyperbolic.
Elliptical galaxies are characterized by several properties that make them distinct from other classes of galaxy. They are spherical or ovoid masses of stars, starved of star-making gases.
The disk model for elliptic geometry, \((\mathbb{P}^2,{\cal S})\text{,}\) is the geometry whose space is \(\mathbb{P}^2\) and whose group of transformations \(\cal{S}\) consists of all Möbius transformations that preserve antipodal points.
The orbit of a planet is an ellipse with the Sun at one of the two foci. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. The square of a planet's orbital period is proportional to the cube of the length of the semi-major axis of its orbit.
30 gru 2020 · Visualizing the orbit of the spaceship going to Mars, and remembering it is an ellipse with the sun at one focus, the smallest ellipse we can manage has the point furthest from the sun at Mars, and the point nearest to the sun at earth.
9 lut 2018 · An ellipse with zero eccentricity is a circle; the greater the eccentricity, the more elongated the ellipse. In a highly eccentric orbit a planet will pass very close to the sun and then...
