Five-hundred-meter Aperture Spherical radio Telescope (FAST)

FAST

Fr.: FAST

The 500 m diameter → radio telescope
which is the largest → single-dish antenna
in the world.
It is an Arecibo type telescope nestled within a natural basin in China's remote and
mountainous Dawodang, Kedu Town, in southeastern China's Guizhou Province.
The → reflector consists of 4,450 triangular panels,
each with a side length of 11 m. More than 2,000 → actuators
are used, according to the feedback from the
measuring system, to deform the whole reflector surface and directly correct for
→ spherical aberration. Several detectors are used to
cover a frequency range of 70 MHz to 3 GHz.

An aberration of a spherical lens or mirror in which light rays converge not to a single
point but to a series of points with different distances from the lens or mirror.
Spherical aberration is corrected by using parabolic reflecting
and refracting surface

A type of → astrolabe
in which the observer's horizon is drawn on the surface of a globe,
mounted with a freely rotating spherical lattice work or 'spider'
representing the celestial sphere.
The earliest description of the spherical astrolabe dates back to
the Iranian astronomer Nayrizi (865-922).

The branch of astronomy that is concerned with determining the apparent positions and motions of
celestial bodies on the celestial sphere.
Same as → positional astronomy.

A coordinate system using an origin (O) and three perpendicular axes
(Ox, Oy, Oz), in which the position of a point (P) is given by three
numbers (r, θ, φ). The coordinate r is the distance from the
origin, θ the angle between the z-axis and the r direction, and
φ the angle between the projection of r on the xy-plane and
the Ox-axis. The coordinate φ is also called the
→ azimuthal angle.

The branch of geometry that deals with figures on the surface of a sphere
(such as the spherical triangle and spherical polygon). It is an example of a
non-Euclidean geometry.

A solution of some mathematical equations
when → spherical polar coordinates are used in investigating physical
problems in three dimensions. For example, solutions of
→ Laplace's equation treated in spherical polar coordinates.
Spherical harmonics are ubiquitous
in atomic and molecular physics and appear in quantum mechanics as
→ eigenfunctions of
→ orbital angular momentum.
They are also important in the
representation of the gravitational and magnetic fields of planetary
bodies, the characterization of the
→ cosmic microwave background anisotropy,
the description of electrical potentials due to charge
distributions, and in certain types of fluid motion.

The term spherical harmonics was first used by William Thomson (Lord
Kelvin) and Peter Guthrie Tait in their 1867 Treatise on Natural Philosophy;
→ spherical; → harmonic.

spherical latitude

ورونای ِ کرهای، ~ سپهری

varunâ-ye kore-yi, ~ sepehri

Fr.: latitude sphérique

The angle between the → normal to a spherical reference
surface and the → equatorial plane.

A triangle drawn on the → surface of a
→ sphere. A spherical triangle, like a plane triangle,
may be right, obtuse, acute, equilateral, isosceles, or scalene.
The sum of the angles of a spherical triangle is greater than 180°
(π) and less than 540° (3π). See also → spherical excess.