What is an armillary sphere?
An armillary sphere is a miniature representation of celestial objects in the sky, depicted as a series of rings centered around a globe. Armillary spheres have a long history.
What is a sphere in math?
A sphere (from Greek σφαῖρα — sphaira, "globe, ball") is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance r from a given point in three-dimensional space.
What is the difference between circle and sphere?
A sphere is a three-dimensional object that is round in shape. The sphere is defined in three axes, i.e., x-axis, y-axis and z-axis. This is the main difference between circle and sphere.
What are some things that take the shape of a sphere?
Bubbles such as soap bubbles take a spherical shape in equilibrium. The Earth is often approximated as a sphere in geography, and the celestial sphere is an important concept in astronomy. Manufactured items including pressure vessels and most curved mirrors and lenses are based on spheres.
What does a sphere with an arrow mean?
An old astronomical instrument representing the ensemble of the celestial sphere and the movement of the celestial bodies. The central globe represents Earth, and the many concentric rings (armillae) the heavenly bodies. The arrow is directed towards the pole.
What is an armillary sphere with an arrow mean?
The contemporary sundial usually has three rings that form the sphere. These are supposed to represent, the Celestial Equator, the Meridian Circle, and the Horizontal Plane. The rod passing through the center, frequently depicted as an arrow, acts as the gnomon and casts the shadow over the hours on the lower band.
What is a globe with an arrow through it called?
Armillary spheres (sometimes referred to as armillary sundials) are a common decorative ornament in many gardens but can most often be spotted in the traditional English garden.
Is the armillary sphere still used today?
You can still purchase armillary spheres today, although some of them are extremely expensive, especially if they are antiques.
Which way should an armillary face?
Find true north with your compass. Aim the axis (or gnomon) arrow of the armillary north. In the northern hemisphere, at night this arrow should point towards Polaris, the North Star.
How do you read an armillary?
How to read the armillary sphere. Read the marks of the azimuth where it intersects the band of the horizon at 0 degrees (north) to determine for which degree of latitude the model is set. This information helps currents astronomers determine where one of the historical armillary spheres may have been made or used.
How do you use a celestial globe?
6:4515:00Celestial Globe Review - YouTubeYouTubeStart of suggested clipEnd of suggested clipSo if I were to set the celestial sphere up for a location of 60 degrees. Beginning at the NorthMoreSo if I were to set the celestial sphere up for a location of 60 degrees. Beginning at the North celestial pole I will count down 60 degrees using the declination circles. So this would be 15.
Where is armillary sphere new world?
Found on the east side of the Shattered Obelisk beneath the statue with four arms.
What are armillary spheres made of?
In the 18th century, armillary spheres were also made from wood and pasteboard. They were used through the 19th century, primarily as educational tools to teach the difference between the Ptolemaic and Copernican models of the universe.
Who invented the armillary sphere?
John Samuel SlaterArmillary sphere / InventorJohn Samuel Slater was a British professor of Civil Engineering at the Presidency College, Calcutta, and later principal of the Engineering College in Sibpur. Wikipedia
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Product Description
Iron Armillary Sphere Beautiful, eye-catching armillary sphere for your garden Made of iron Finished in a brown color Measures 19"H x 24"L x 14"W The base measures 8"L x 8"W Weighs approximately 10 pounds Some minor assembly required. Sphere is assembled. Just attach to base.
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What is the name of the pair of points on a sphere that lie on a straight line through the center
Any pair of points on a sphere that lie on a straight line through the sphere's center (i.e. the diameter) are called antipodal points —on the sphere, the distance between them is exactly half the length of the circumference. Any other (i.e. not antipodal) pair of distinct points on a sphere
What is the intersection of a sphere with a quadratic cone?
as the intersection of a sphere with a quadratic cone whose vertex is the sphere center; as the intersection of a sphere with an elliptic or hyperbolic cylinder whose axis passes through the sphere center; as the locus of points whose sum or difference of great-circle distances from a pair of foci is a constant.
What is the antipodal quotient of the sphere?
The antipodal quotient of the sphere is the surface called the real projective plane, which can also be thought of as the Northern Hemisphere with antipodal points of the equator identified.
What is a sphere in physics?
A sphere (from Greek σφαῖρα — sphaira, "globe, ball") is a geometrical object in three-dimensional space that is the surface of a ball (viz. , analogous to the circular objects in two dimensions , where a " circle " circumscribes its "disk" ).
What is the name of the plane sections of a sphere?
The plane sections of a sphere are called spheric sections — which are either great circles for planes through the sphere's center or small circles for all others.
What is geocentric geometry?
Terms borrowed directly from geography of the Earth, despite its spheroidal shape having greater or lesser departures from a perfect sphere (see geoid ), are widely well-understood. In geometry unrelated to astronomical bodies, geocentric terminology should be used only for illustration and noted as such, unless there is no chance of misunderstanding.
What is a sphere in Euclidean space?
For any natural number n, an " n -sphere," often written as Sn, is the set of points in ( n + 1 )-dimensional Euclidean space that are at a fixed distance r from a central point of that space, where r is, as before, a positive real number. In particular:
What is a sphere?
A sphere is a three dimensional solid that is round in shape, in geometry. The surface of a sphere is at equidistant (called radius) from the center. Learn its properties, formulas with examples in an easy way, at BYJU’S. Login.
What is the shape of a sphere?
In geometry, a sphereis a solid, that is absolutely round in shape defined in three-dimensional space (XYZ space). Mathematically, a sphere is defined as the set of points that is at equal distances from a common point in three dimensional space. This constant distance is called radius of sphereand the common point is the center of sphere.
What is the distance between a sphere and a common point?
The distance between surface and the common point is the radius and the common point is called center of sphere.
What is the surface area of a sphere?
Surface Area of a Sphere. The surface area of a sphere is the total area covered by the surface of a sphere in a three dimensional space. The formula of surface are is given by:
What are the dimensions of a sphere?
Unlike circle, which is a plane shape or flat shape, defined in XY plane, a sphere is defined in three dimensions, i.e. x-axis, y-axis and z-axis. Important Facts: A sphere is a symmetrical object. All the surface points of sphere are at equidistant from center.
Does a sphere have a vertex?
Theshape of a sphereis round and it does not have any faces. Sphere is a geometrical three dimensional solid having curved surface. Like other solids, such as cube, cuboid, cone and cylinder, a sphere does not have any flat surface or a vertex or an edge. The real-life examples of sphere is:
What is an armillary sphere?
Updated February 22, 2019. An armillary sphere is a miniature representation of celestial objects in the sky, depicted as a series of rings centered around a globe. Armillary spheres have a long history.
When did armillary spheres first appear?
Armillary spheres first appeared in China during the Han Dynasty (206 BCE-220 CE). One early Chinese armillary sphere can be traced to Zhang Heng, an astronomer in the Eastern Han Dynasty (25-220 CE). The exact origin of armillary spheres cannot be confirmed. However, during the Middle Ages, armillary spheres became widespread ...
Overview
An armillary sphere (variations are known as spherical astrolabe, armilla, or armil) is a model of objects in the sky (on the celestial sphere), consisting of a spherical framework of rings, centered 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 smoot…
Description and use
The exterior parts of this machine are a compages [or framework] of brass rings, which represent the principal circles of the heavens.
1. The equinoctial A, which is divided into 360 degrees (beginning at its intersection with the ecliptic in Aries) for showing the sun's right ascension in degrees; and also into 24 hours, for showing its right ascension in time.
History
Throughout Chinese history, astronomers have created celestial globes (Chinese: 渾象) to assist the observation of the stars. The Chinese also used the armillary sphere in aiding calendrical computations and calculations.
According to Needham, the earliest development of the armillary sphere in China goes back to the astronomers Shi Shen and Gan De in the 4th century BC, as the…
Paralympic Games
An artwork-based model of an Armillary sphere has been used since the March 1, 2014 to light the Paralympic heritage flame at Stoke Mandeville Stadium, United Kingdom. The sphere includes a wheelchair that the user can rotate to spark the flame as part of a ceremony to celebrate the past, present and future of the Paralympic Movement in the UK. The Armillary Sphere was created by artist Jon Bausor and will be used for future Heritage Flame events. The flame in the first-ever ce…
Heraldry and vexillology
The armillary sphere is commonly used in heraldry and vexillology, being mainly known as a symbol associated with Portugal, the Portuguese Empire and the Portuguese discoveries.
In the end of the 15th century, the armillary sphere became the personal heraldic badge of the future King Manuel I of Portugal, when he was still a Prince. The int…
See also
• Antikythera mechanism – Ancient analogue astronomical computer
• Chinese constellations – Groupings used in Chinese astrology
• De sphaera mundi – Book by Sacrobosco, describes the late medieval (Ptolemaic) cosmos
External links
• Starry Messenger (dead link)
• Armillary Spheres and Teaching Astronomy | Whipple Museum
• AstroMedia* Verlag in Germany offers a cardboard construction kit for an armillary sphere ("Das Kleine Tischplanetarium")
Overview
A sphere (from Ancient Greek σφαῖρα (sphaîra) 'globe, ball') is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance r from a given point in three-dimensional space. That given point is the centre of the sphere, and r is the sphere's radius. The earliest known mentions of spheres appear in the work of …
Basic terminology
As mentioned earlier r is the sphere's radius; any line from the center to a point on the sphere is also called a radius.
If a radius is extended through the center to the opposite side of the sphere, it creates a diameter. Like the radius, the length of a diameter is also called the diameter, and denoted d. Diameters are the longest line segments that can be …
Equations
In analytic geometry, a sphere with center (x0, y0, z0) and radius r is the locus of all points (x, y, z) such that
Since it can be expressed as a quadratic polynomial, a sphere is a quadric surface, a type of algebraic surface.
Let a, b, c, d, e be real numbers with a ≠ 0 and put
Properties
In three dimensions, the volume inside a sphere (that is, the volume of a ball, but classically referred to as the volume of a sphere) is
where r is the radius and d is the diameter of the sphere. Archimedes first derived this formula by showing that the volume inside a sphere is twice the volume between the sphere and the circumscribed cylinder of that sphere (having the h…
Treatment by area of mathematics
The basic elements of Euclidean plane geometry are points and lines. On the sphere, points are defined in the usual sense. The analogue of the "line" is the geodesic, which is a great circle; the defining characteristic of a great circle is that the plane containing all its points also passes through the center of the sphere. Measuring by arc length shows that the shortest path between two poi…
Curves on a sphere
Circles on the sphere are, like circles in the plane, made up of all points a certain distance from a fixed point on the sphere. The intersection of a sphere and a plane is a circle, a point, or empty. Great circles are the intersection of the sphere with a plane passing through the center of a sphere: others are called small circles.
Generalizations
An ellipsoid is a sphere that has been stretched or compressed in one or more directions. More exactly, it is the image of a sphere under an affine transformation. An ellipsoid bears the same relationship to the sphere that an ellipse does to a circle.
Spheres can be generalized to spaces of any number of dimensions. For any natural number n, an "n-sphere," often written as S , is the set of points in (n + 1)-dimensional Euclidean space that ar…
History
The geometry of the sphere was studied by the Greeks. Euclid's Elements defines the sphere in book XI, discusses various properties of the sphere in book XII, and shows how to inscribe the five regular polyhedra within a sphere in book XIII. Euclid does not include the area and volume of a sphere, only a theorem that the volume of a sphere varies as the third power of its diameter, probably due to Eudoxus of Cnidus. The volume and area formulas were first determined in Archi…