# gnomon

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## gnomon

(nō`mŏn): see sundialsundial,
instrument that indicates the time of day by the shadow, cast on a surface marked to show hours or fractions of hours, of an object on which the sun's rays fall.
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## gnomon

(noh -mon) A device used in ancient times to measure the altitude of the Sun and hence to determine the time of day and time of year. It consisted of a vertical shaft of known height (such as an upright rod or pillar) that cast a shadow of measurable length and direction on a graduated horizontal base. The ratio of height to shadow length gave the tangent of the altitude angle. The term is also applied to the metal projection on a sundial, used for the same purpose.

## Gnomon

an ancient astronomical instrument consisting of a vertical column on a horizontal platform. The altitude and azimuth of the sun can be determined from the length and direction of the column’s shadow. The shortest shadow during the day indicates the direction of the north line. In ancient times the gnomon was used to determine the inclination of the ecliptic to the equator and the geographical latitude of locations. In modern times the gnomon finds use only as a sundial.

## gnomon

[′nō·mən]
(engineering)
On a sundial, the inclined plate or pin that casts a shadow. Also known as style.
(mathematics)
A geometric figure formed by removing from a parallelogram a similar parallelogram that contains one of its corners.
References in periodicals archive ?
Caddy (1990) described appropriately chosen gnomonic time intervals over an organism's life history as a series of time intervals in which a constant proportion of the population dies within each selected interval.
For Panopea globosa, the number of gnomonic intervals was determined by dividing its life history into a predetermined number of biological units (life stages).
Two thousand vectors of natural mortality for gnomonic time of Panopea globosa were estimated based on the following assumptions: (1) the main source of uncertainty and variability was the mean annual fecundity and (2) a noninformative distribution (U) of [delta].
In accordance with knowledge of the life span of Panopeci globosa, the seven gnomonic divisions selected a priori represented a suitable representation of realistic time subunits for this species.
The duration of gnomonic intervals was 17,166 days (47 y for Panopea globosa).
With regard to the gnomonic method, the statistical procedure depends first on the duration of early embryogenesis, which can vary over a range of physical environments.
The results presented here suggest that an approach based on gnomonic time represents biological developmental stages realistically throughout the life cycle of long-lived clams, including Panopea globosa.
Modelling natural mortality with age in short-lived invertebrate populations: definition of a strategy of gnomonic time division.
Natural mortality and life history stage duration of Pacific sardine (Sardinops caeruleus) based on gnomonic time divisions.

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