# gnomon

## Definitions

• WordNet 3.6
• n gnomon indicator provided by the stationary arm whose shadow indicates the time on the sundial
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Webster's Revised Unabridged Dictionary
• Gnomon (Astron) A style or column erected perpendicularly to the horizon, formerly used in astronomocal observations. Its principal use was to find the altitude of the sun by measuring the length of its shadow.
• Gnomon The index of the hour circle of a globe.
• Gnomon (Geom) The space included between the boundary lines of two similar parallelograms, the one within the other, with an angle in common; as, the gnomonbcdefg of the parallelograms ac and af. The parallelogram bf is the complement of the parallelogram df.
• Gnomon (Dialing) The style or pin, which by its shadow, shows the hour of the day. It is usually set parallel to the earth's axis.
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Century Dictionary and Cyclopedia
• n gnomon On a sun-dial, the triangular projecting piece which by its shadow shows the hour of the day; also, any index to a sun-dial or to a meridian-mark, especially a very large one. The early gnomons used for astronomical purposes were vertical pillars or obelisks.
• n gnomon The index of the hour-circle of a globe.
• n gnomon A piece of a parallelogram left after a similar parallelogram has been removed from a corner of it. Thus, in the figure, EFGBCD is a gnomon.
• n gnomon An odd number; one of the terms of an arithmetical series by which polygonal numbers are found. Also called gnomonic number.
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Chambers's Twentieth Century Dictionary
• n Gnomon nō′mon the pin of a dial, whose shadow points to the hour: the index of the hour-circle of a globe:
• n Gnomon nō′mon (geom.) the name given to the sum of any three of the parts of a rectangle when divided into four parts by cross-lines parallel to its sides: interpreter, as in Bengel's Gnomon Novi Testamenti
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## Etymology

Webster's Revised Unabridged Dictionary
L. gnomon, Gr. one that knows, the index of a sundial. See Gnome
Chambers's Twentieth Century Dictionary
Gr. gnōmōn, an interpreter—gnōnai, to know.

## Usage

### In literature:

AF is a gnomon at Alexandria; SB a gnomon at Svene; IS and JK represent the sun's rays.
"A History of Science, Volume 1(of 5)" by Henry Smith Williams
If the gnomon of a sun-dial be divided into two equal, and also into two unequal parts, what would be its value?
"The Adventures of Mr. Verdant Green, Vols. I to III" by Cuthbert Bede
The other dial had some half-worn hour-marks, but no gnomon.
"Passages From the English Notebooks, Volume 1" by Nathaniel Hawthorne
Before you go outdoors draw on the platform of the sundial a straight line from angle B of the gnomon to the front edge of the platform.
"The Library of Work and Play: Gardening and Farming." by Ellen Eddy Shaw
Its shape may be compared roughly to a gnomon, with one longer and one shorter arm.
"The Seven Great Monarchies Of The Ancient Eastern World, Vol 4. (of 7): Babylon" by George Rawlinson
It is meant to serve as the gnomon of a gigantic dial, traced in lines of white marble in the pavement of the square.
"Roman Mosaics" by Hugh Macmillan
The first astronomical instrument was the gnomon.
"Essays on Education and Kindred Subjects" by Herbert Spencer
No doubt, however, it was a sun-dial, or gnomon of some kind.
"The Story of Eclipses" by George Chambers
They had obelisks and exact gnomons to mark the equinoxes and solstices.
"Celebrated Travels and Travellers" by Jules Verne
The Gnomonical part is treated of in the Ninth Book.
"An Abridgment of the Architecture of Vitruvius" by Vitruvius
Above the slab, a Cupid, with outspread wings, held an arrow that served as a gnomon.
"The Confessions of Arsène Lupin" by Maurice Leblanc
On leaving the temple he glanced at the gnomon or sundial, which at that height marked the time for all Rome.
"Sónnica" by Vicente Blasco Ibáñez
They had gnomons to indicate the solstices.
"History of the Intellectual Development of Europe, Volume II (of 2)" by John William Draper
The gnomon was throwing a long shadow westward across the VII.
"The Idyl of Twin Fires" by Walter Prichard Eaton
The gnomon at once cast a pointed shadow on that side of the circle opposite the sun, but there were as yet no marks for the hours.
"Bevis" by Richard Jefferies
No moving shadow, no gnomon, no sun-dial would be possible.
"Astronomical Myths" by John F. Blake
Gnomonic projection is a projection of a sphere in which the centre of sight is the centre of the sphere.
"Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 2" by Various
A similar use of a vertical pole as a primitive gnomon for a sun-dial seems to have been common to many uncivilized peoples.
"Old-Time Gardens" by Alice Morse Earle
The first astronomical instrument was the gnomon.
"Illustrations of Universal Progress" by Herbert Spencer
Upon the brass face appeared slightly raised Roman numerals and the triangular gnomon cast its shadow across the four.
"The Secret of the Sundial" by Mildred A. Wirt, AKA Ann Wirt
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### In poetry:

Falls; it is longer than ye wist:
It preaches, as Time's gnomon can,
This monument in London mist!
"Ballade Of Cleopatra's Needle" by Andrew Lang
Around this sun-dial daughter May
Sometimes holds a holiday;
She is the matron, makes the tea;
The kettle by the gnomon stands:
We think the scene right fair to see,
As all scenes are when love commands.
"The Sun-Dial" by William Bell Scott

### In science:

Star coordinates in the tangent plane are computed from the Tycho-2 catalogue by gnomonic projection, after transformation of the catalogue coordinates from mean to observed place.
Results from the Wide Angle Search for Planets Prototype (WASP0) I: Analysis of the Pegasus Field
The gnomonic pro jection uses initial estimates of the optical axis location on the sky and the barrel distortion coeﬃcient.
Results from the Wide Angle Search for Planets Prototype (WASP0) I: Analysis of the Pegasus Field
Gnomonic projections of Healpix (Gorski et al, 2005) maps of the QUBIC synthesized beam for a monochromatic instrument with point-like (top-left) or 3 mm detectors (top-right), a 25% bandwidth instrument with point-like (bottom-left) and 3 mm detectors (bottom-right).
QUBIC: The QU Bolometric Interferometer for Cosmology
These curves have a spiral behavior and a gnomonic growth (i.e. made of successive self-congruent parts).
Motions of Curves in the Projective Plane Inducing the Kaup-Kupershmidt Hierarchy
During the ﬁrst two years we made mostly visual observations of ma jor showers without plotting the meteors onto the gnomonic star maps.
1996--1998 Polish Visual Meteor Database
Baseline distances needed are 7500 km for one detector, and 2500–3500 km for the other. For these distances, the smallest triangle apex angle (and the best production efficiency) is about 50°, when detectors are in opposite directions (in a gnomonic projection) from vertically aligned rings.
Accelerator design concept for future neutrino facilities
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