出典:Wiktionary
nullsurface (複数形 nullsurfaces)
出典:Wikipedia
出典:『Wikipedia』 (2010/05/17 14:30 UTC 版)
In the theory of relativity, a null surface is a 3-surface whose normal vector is everywhere null (zero length with respect to the local Lorentz metric), but the vector is not identically zero. For example, light cones are null surfaces.