Vertical
From Simple English Wikipedia, the free encyclopedia
An object is in a vertical position when it is in an "up-down" direction, roughly speaking perpendicular to the horizon or horizontal.
[edit] Some specifications
- The concept of verticality only makes sense in the context of a clearly measurable gravity field, i.e., in the 'neighborhood' of a planet, star, etc. When the gravity field becomes very weak (the masses are too small or too distant from the point of interest), the term vertical loses its meaning.
- In the presence of a simple, time-invariant, rotationally symmetric gravity field, the vertical directions passing by different points in space (and not belonging to the same vertical direction) intersect at the center of mass of that gravity field. This means that no two different vertical directions are ever parallel to each other.
- In general, a vertical direction will only be perpendicular to a horizontal plane if both are specifically defined with respect to the same point: a plane is only horizontal at the point of reference. Thus both verticality and horizontality are strictly speaking local concepts, and it is always necessary to state to which location the direction or the plane refers to.
