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The two points P and P ' (red) are antipodal because they are ends of a diameter PP ', a segment of the axis a (purple) passing through the sphere's center O (black). P and P ' are the poles of a great circle g (green) whose points are equidistant from each (with a central right angle). Any great circle s (blue) passing through the poles is ...
Name Standard symbol Definition Field of application Archimedes number: Ar = fluid mechanics (motion of fluids due to density differences) : Asakuma number: As = heat transfer (ratio of heat generation of microwave dielectric heating to thermal diffusion [6]
Measure of the separation of equal and opposite electric charges C⋅m L T I: vector Electric displacement field: D →: Strength of the electric displacement C/m 2: L −2 T I: vector field Electric field strength: E →: Strength of the electric field V/m, N/C L M T −3 I −1: vector field: Force: F →: Transfer of momentum per unit time ...
diameter: meter (m) distance: meter (m) direction: unitless impact parameter meter (m) differential (e.g. ) varied depending on context differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S: square meter (m 2)
Any two great circles intersect in two diametrically opposite points, called antipodal points. Any two points that are not antipodal points determine a unique great circle. There is a natural unit of angle measurement (based on a revolution), a natural unit of length (based on the circumference of a great circle) and a natural unit of area ...
Both definitions are also valid for the diameter of a sphere. In more modern usage, the length d {\displaystyle d} of a diameter is also called the diameter. In this sense one speaks of the diameter rather than a diameter (which refers to the line segment itself), because all diameters of a circle or sphere have the same length, this being ...
For example, one sphere that is described in Cartesian coordinates with the equation x 2 + y 2 + z 2 = c 2 can be described in spherical coordinates by the simple equation r = c. (In this system— shown here in the mathematics convention —the sphere is adapted as a unit sphere , where the radius is set to unity and then can generally be ...
an object of diameter 1 AU (149 597 871 km) at a distance of 1 parsec (pc) Thus, the angular diameter of Earth's orbit around the Sun as viewed from a distance of 1 pc is 2″, as 1 AU is the mean radius of Earth's orbit. The angular diameter of the Sun, from a distance of one light-year, is 0.03″, and that of Earth 0.0003″. The angular ...