Speculum metalSpeculum metal is a mixture of around two-thirds copper and one-third tin, making a white brittle alloy that can be polished to make a highly reflective surface. It was used historically to make different kinds of mirrors from personal grooming aids to optical devices until it was replaced by more modern materials such as metal-coated glass mirrors.
Chord (geometry)In geometry, a chord (from Latin chorda'catgut, string') of a circle is a straight line segment whose endpoints both lie on a circular arc. If a chord were to be extended infinitely on both directions into a line, the object is a secant line. The perpendicular line passing through the chord's midpoint is called sagitta (Latin for "arrow"). More generally, a chord is a line segment joining two points on any curve, for instance, on an ellipse.
Astronomical objectAn astronomical object, celestial object, stellar object or heavenly object is a naturally occurring physical entity, association, or structure that exists within the universe. In astronomy, the terms object and body are often used interchangeably.
AltitudeAltitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context (e.g., aviation, geometry, geographical survey, sport, or atmospheric pressure). Although the term altitude is commonly used to mean the height above sea level of a location, in geography the term elevation is often preferred for this usage.
Celestial navigationCelestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the surface of the Earth without relying solely on estimated positional calculations, commonly known as dead reckoning.
MirrorObject that reflects an imageA mirror reflecting the image of a vaseA first-surface mirror coated with aluminium and enhanced with dielectric coatings.
Isaac NewtonSir Isaac Newton ( ; 4 January 1643 [O.S. 25 December 1642] – 31 March 1727 [O.S. 20 March 1726]) was an English polymath who was a mathematician, physicist, astronomer, alchemist, theologian, historian and inventor. He was a key figure in the Scientific Revolution and the Enlightenment that followed.
Angular distanceAngular distance or angular separation is the measure of the angle between the orientation of two straight lines, rays, or vectors – typically in three-dimensional space – or the central anglesubtended by the radii through two points on a sphere. When the rays are lines of sight from an observer to two points in space, it is known as the apparent distance or apparent separation.
LongitudeInternational Terrestrial Reference SystemSpatial Reference System Identifier (SRID)Universal Transverse Mercator (UTM)
Royal SocietyBritish learned societyThe Royal Society of London for Improving Natural Knowledge, commonly referred to as the Royal Society, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, recognising excellence in science, supporting outstanding science, providing scientific advice for policy, education and public engagement and fostering international and global co-operation.
Robert HookeRobert Hooke (; 18 July 1635 – 3 March 1703) was an English polymath who was active as a physicist ('natural philosopher'), astronomer, geologist, meteorologist, and architect. He is credited as one of the first scientists to investigate living things at microscopic scale in 1665, using a compound microscope that he designed. Hooke was an impoverished scientific inquirer in young adulthood who went on to become one of the most important scientists of his time.
Board of LongitudeThe Commissioners for the Discovery of the Longitude at Sea, or more popularly Board of Longitude, was a British government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.*As an Amazon Associate I earn from qualifying purchases.