The IERS was established in its present form in 1987 by the International Astronomical Union and the International Union of Geodesy and Geophysics, replacing the earlier International Polar Motion Ser ...
The phrase originated in classical antiquity, when astronomers and natural philosophers divided the lights in the sky into two groups. One group contained the fixed stars, which appear to rise and set ...
1 millisecond is 0.001 seconds, 2 ms is 0.002 seconds etc.1 millisecond (1 ms) — cycle time for frequency 1 kHz; duration of light for typical photo flash strobe; time taken for sound wave to travel ...
Discovery history of the secular acceleration Edmond Halley was the first to suggest, in 1695, that the mean motion of the Moon was apparently getting faster, by comparison with ancient eclipse observ ...
Among the ancient Greeks, several of the Pythagorean school believed in the rotation of the earth rather than the apparent diurnal rotation of the heavens. The first was Philolaus (470-385 BCE) though ...
Auroras or aurorae are classified as diffuse and discrete. The diffuse aurora is a featureless glow in the sky that may not be visible to the naked eye, even on a dark night. It defines the extent of ...
To completely describe the state of a plasma, we would need to write down all the particle locations and velocities and describe the electromagnetic field in the plasma region. However, it is generall ...
Plasma is loosely described as an electrically neutral medium of positive and negative particles (i.e. the overall charge of a plasma is roughly zero). It is important to note that although they are u ...
In physics, a charged particle is a particle with an electric charge. It may be an ion, such as a molecule or atom with a surplus or deficit of electrons relative to protons. It can be the electrons a ...
A torus can be defined parametrically by:x(\theta, \varphi) = (R + r \cos \varphi) \cos{\theta} y(\theta, \varphi) = (R + r \cos \varphi) \sin{\theta}z(\theta, \varphi) = r \sin \varphi whereθ, φ ar ...
Kristian Birkeland, Carl St?rmer, and Nicholas Christofilos had investigated the possibility of trapped charged particles before the Space Age. Explorer 1 and Explorer 3 confirmed the existence of th ...
The defining criterion is that the bulk velocity of the fluid (in this case, the plasma of the solar wind) drops from "supersonic" to "subsonic", where the speed of sound in a plasma is defined asc_s^ ...
In the early 20th century geologists first noticed that some volcanic rocks were magnetized opposite to the direction of the local Earth's field. The first estimate of the timing of magnetic reversals ...
When William Gilbert published de Magnete in 1600, he concluded that the Earth is magnetic and proposed the first hypothesis for the origin of this magnetism: permanent magnetism such as that found in ...
The magnetic moment is defined as a vector relating the aligning torque on the object from an externally applied magnetic field to the field vector itself. The relationship is given by \boldsymbol{\ta ...
