Sphere

A sphere (from <a href="/facts/Ancient_Greek/LIK7NlUh">Greek</a> σφαῖρα, sphaîra) is a <a href="/facts/Geometry/wTQf5ffQ">geometrical</a> object that is a <a href="/facts/Solid_geometry/tHH3JFoq">three-dimensional</a> analogue to a two-dimensional <a href="/facts/Circle/9fy5ggKn">circle</a>. Formally, a sphere is the <a href="/facts/Locus_(mathematics)/t4swdGJq">set of points</a> that are all at the same distance r from a given point in <a href="/facts/Three-dimensional_space/KAqKWUbS">three-dimensional space</a>. That given point is the <a href="/facts/Center_(geometry)/oKPIwkY3">center</a> of the sphere, and r is the sphere's <a href="/facts/Radius/9Gr9deYD">radius</a>. The earliest known mentions of spheres appear in the work of the <a href="/facts/Greek_mathematics/ealke3z8">ancient Greek mathematicians</a>.
The sphere is a fundamental surface in many fields of <a href="/facts/Mathematics/pxTouaz4">mathematics</a>. Spheres and nearly-spherical shapes also appear in nature and industry. <a href="/facts/Bubble_(physics)/99TogqIG">Bubbles</a> such as <a href="/facts/Soap_bubble/eq1CIYkW">soap bubbles</a> take a spherical shape in equilibrium. The Earth is <a href="/facts/Spherical_Earth/YEpM38jY">often approximated as a sphere</a> in <a href="/facts/Geography/TRd1Toyo">geography</a>, and the <a href="/facts/Celestial_sphere/TYAtXgor">celestial sphere</a> is an important concept in <a href="/facts/Astronomy/0ArJVM1p">astronomy</a>. Manufactured items including <a href="/facts/Pressure_vessels/5mGeFbpQ">pressure vessels</a> and most <a href="/facts/Curved_mirror/X1c0aVmK">curved mirrors</a> and <a href="/facts/Lens/ejlH6n5c">lenses</a> are based on spheres. Spheres <a href="/facts/Rolling/rfmy2YIl">roll</a> smoothly in any direction, so most <a href="/facts/Ball/8WmjNhx7">balls</a> used in sports and toys are spherical, as are <a href="/facts/Ball_bearings/UarVS4gr">ball bearings</a>.

Sphere open-in-new

Sphere