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Antikythera mechanism. The Antikythera mechanism (fragment A – front and rear); visible is the largest gear in the mechanism, about 13 cm (5 in) in diameter. The Antikythera mechanism ( / ˌæntɪkɪˈθɪərə / AN-tik-ih-THEER-ə, US also / ˌæntaɪkɪˈ -/ AN-ty-kih-) [1] [2] is an Ancient Greek hand-powered orrery (model of the Solar ...
Earth's rotation. Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise . The North Pole, also known as the Geographic North ...
An easy way to do this is to set a clock or watch so it shows "sundial time" which is standard time, plus the equation of time on the day in question. [d] The hour-lines on the sundial are marked to show the positions of the shadow of the style when this clock shows whole numbers of hours, and are labelled with these numbers of hours.
A nocturnal is a simple analog computer, made of two or more dials, that will provide the local time based on the time of year and a sighting of Polaris, the North Star, and one or more other stars. In the northern hemisphere, all stars will appear to rotate about the North Star during the night, and their positions, like the progress of the ...
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface. The rotation of a star produces an equatorial bulge due to centrifugal force. As stars are not solid bodies, they can also undergo differential rotation.
The north and south celestial poles are the two points in the sky where Earth 's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers at Earth's North Pole and South Pole, respectively. As Earth spins on its axis, the two celestial poles ...
Diurnal motion (from Latin diurnus 'daily', from Latin diēs 'day') is an astronomical term referring to the apparent motion of celestial objects (e.g. the Sun and stars) around Earth, or more precisely around the two celestial poles, over the course of one day. It is caused by Earth's rotation around its axis, so almost every star appears to ...
On the topographic maps of the U.S. Geological Survey (USGS), for example, a diagram shows the relationship between magnetic north in the area concerned (with an arrow marked "MN") and true north (a vertical line with a five-pointed star at its top), with a label near the angle between the MN arrow and the vertical line, stating the size of the ...