solution
In the context of general relativity: a solution or, more precisely, a solution of the Einstein equations is a model universe that follows the law of gravity as prescribed by general relativity. See also exact ...
solid state
State of matter in which the atoms or molecules are bound so tightly to each other so that they form a solid, stable lump. In contrast with fluids, whose form adapts to whatever container they are placed in, solid bodies keep their form. ...
solar system
Our cosmic neighbourhood, consisting of a star - the sun -, eight planets orbiting the sun, numerous smaller bodies, dust and gas. In the context of relativity, the solar system is interesting as a natural laboratory in which the prediction of general ...
solar mass
The sun has a mass of 1.989·1030 kilograms [see exponential notation] what is equal to 332 946 earth masses. In astronomy, the solar mass is frequently used as a unit of mass ("Neutron stars typically have a mass of 1.4 solar masses"), sometimes written ...
singularity
Irregular boundary of spacetime in general relativity - region where spacetime simply comes to an end. Often, such boundaries are associated with spacetime curvature growing beyond all bounds and becoming infinitely large - so-called curvature singularities ...
singularity theorems
Theorems, proven by Roger Penrose and Stephen Hawking, that state under which circumstances singularities are inevitable in general relativity. As the theorems assume the laws of general relativity and certain general properties of matter, but nothing else, ...
SI
The international system of physical units, introduced in 1960. It is based on seven fundamental units; in the context of Einstein Online, the interesting ones are the metre as a measure of length and distance, the second as the unit of ...
shear
Generically, an extended body in free fall will experience deformation due to tidal effects. For instance, in a body falling towards Earth, those parts that are slightly closer to the Earth will experience a slightly stronger gravitational pull ...
