• acute angle – an angle of less than 90°; (an obtuse angle is an angle greater than 90°);
  • axiom – a fundamental assumption based upon no other assumption or assumptions more fundamental than it;


  • Big Bang – white hole at origin for a light cone, measuring Planck's length in spatial extent (10-33 cm in diameter); see The Universe is Round Article, especially illustration at end of article;


  • continuity – a smooth, unbroken, and uninterrupted series of points adjacent in every linearly independent direction; space and time, together, each being inseparable from the other, constitute the space-time continuum;
  • continuum – the continuity of all space and time locations together, in smooth, continuous proximity in every spatial and temporal direction, and in any combination thereof;
  • cosmological constant – number corresponding to the curvature of space-time; see The Conventional Universe Article; see The Shape of Space Article;



  • energy – everything lying within space and time that is not space and time; this includes all light (all radiation) and all matter; nature consists solely of energy and gravity; in terms of energy, space and time are effectively made of light; this light and everything else in the universe, are shaped by the distribution of energy in it (expressed in nature as gravity);
  • Euclidian – conventional, three-dimensional, flat space extending infinitely (like the space around us seems to be almost effectively is, but really is not, because space and time curve with respect to matter);


  • flat space – a space continuity that has the same amount of 'room' anywhere in it because it effectively lacks any kind of curvature whatsoever (just as the space nearby seems to us to be the same);
  • [reference] frame – synonym for frame of reference, a set of space and time measures corresponding to a unique motion and gravity; an entire chapter, Chapter Six, page 28 (specifically, page 30), is dedicated to its description;


  • geometry – a collection of fixed space (and optionally time) measures and labels of distances and angles;


  • hyperbolic space – a continuity that provides far more "room" than flat space does, without additional dimensions, because its curvature provides the additional "room" necessary, so allowing; the space-time of our universe is curved in this very way, as reflected in its expansion;
  • hyperspace – a space with one dimension fewer than the number corresponding to the encompassing space;
  • hyper-dimensional – shapes and spaces (i.e. geometry) involving more than three dimensions and which can include time also as a dimension;


  • isomorphic – universally the same (identically structured) in every direction, at any time (i.e. everywhere, always);


  • light cone – the visible universe; see The Universe is Round Article, especially illustration at end of article;
  • linearly independent – (in this text) a synonym of orthogonal, (see orthogonal, below and dimension, above) ; see The Dimensions of Nature Article;
  • Lobachevskian space – hyperbolic space in which the farther the distance away, the more densely packed and less disperse the contents of the space;
  • Lorentz transformations – a set of four equations universal for translating the measures and locations of one reference frame into what they would be in another frame; the equations of relativity are derived from the Lorentz transformations.


  • massive – having the property of mass (manifest as weight and inertia); matter has mass, light (radiation) and gravity do not have mass;
  • mathematics – a precise, formalized language, based upon logic; math is the language of science;
  • matter – energy that has temporal extent (mass); light and gravity are momentary and thus have no temporal extent (having only spatial extent);


  • obtuse angle – an angle greater than 90°; (an acute angle is an angle of less than 90°);
  • orthogonal – lines are linearly independent, or orthogonal, when each crosses the other while never lying within the lesser dimensionality of any such intersecting line; each line corresponds to its own unique dimension; see The Dimensions of Nature Article; (see also dimension, above);


  • perpendicular – a single unique case, among an infinity of other orientations, of orthogonal (see orthogonal, above);
  • physical theory – theoretical physics, that is, either Relativity, the Theory of Quantum Mechanics or both together; see Stronger than Fact Article;


  • qualitative – based upon conceptual notions expressed as ideas, principles, and/or properties;
  • quantitative – based upon measures expressed in terms of numeric quantities and relationships;
  • quantum mechanics/quantum theory – the theory of energy (as opposed to relativity, the theory of space and time), the Theory of Quantum Mechanics;


  • radiation – any and all forms of light; (the term is also applied to high speed, massive particles of extraterrestrial origin, which, by virtue of being massive are not light); see Riding a Beam at the Speed of Light Article;
  • relativity – short for the Theory of General Relativity, which is the theory of space, time, big motion, and gravity; see Relativity in Ten Minutes Article and Bending Space and Time Article;


  • singularity – a point of zero size lacking a correspondence to any single, defined tangent, but instead, to many; although the continuity of relativity's geometry includes physical singularities; singularities flatly do not exist for (non-continuous) energy;
  • space-time – the four-dimensional, inseparable combination of spatial distance and temporal extent in our universe;


  • tangent – a straight line, flat surface, three-dimensional space, or four-dimensional combined space/time frame of reference, is tangent to a curve at the single point where the straight line(s) of the tangent intersect(s) the curve of a circle, spherical surface, or spherical space, respectively, at single, unique point (region); see The Universe is Round Article, especially illustration at end of article;
  • tangent space – a tangent, stipulated, effectively flat, spatial volume, corresponding to a single moment that intersects a curved, spherical special sphere in four dimensions (like the four dimensions of space-time); (see 'tangent' above); see The Universe is Round Article, especially illustration at end of article;
  • theoretical physics – (also called physical theory or the theoretical model) a body of ideas that describe nature more accurately than any model ever conceived, and which underlies ANY and ALL genuine and accurate science; theoretical physics is based upon two scientific theories, relativity, for space and time, and quantum mechanics, for energy;
  • [scientific] theory – a body of ideas that has never been demonstrated to have ever failed to accurately model reality); see Theory Stronger than Fact Article;


  • visible universe – the scope (i.e. physical extent) of our unique and individual light cone; see The Universe is Round Article, especially illustration at end of article;