Answer:In astronomy, geography, and related sciences and contexts, a direction or plane passing by a given point is said to be vertical if it contains the local gravity direction at that point. [1] Conversely, a direction or plane is said to be horizontal if it is perpendicular to the vertical direction. In general, something that is vertical can be drawn from up to down (or down to up), such as the y-axis in the Cartesian coordinate system.
Contents
1 Historical definition
2 Geophysical definition
2.1 The plumb line and spirit level
2.2 The flat earth approximation
2.3 The spherical Earth
2.4 Further complications
2.5 Walls and floors
2.6 Independence of horizontal and vertical motions
3 Mathematical definition
3.1 In two dimensions
3.2 In three dimensions
3.3 In the classroom
4 Discussion
4.1 Practical use in daily life
5 See also
6 References and notes
7 Further reading
8 External links
Historical definition
Girard Desargues defined the vertical to be perpendicular to the horizon in his 1636 book Perspective.
The word horizontal is derived from horizon,[2] whereas vertical originates in the late Latin verticalis, which is from the same root as vertex, meaning "highest point".[3]
Geophysical definition
Further information: Gravity of Earth and Figure of Ea
Explanation:
