Practical Use in Daily Life
The concept of a vertical line is thus anything but simple, although, in practice, most of these effects and variations are rather small: they are measurable and can be predicted with great accuracy, but they may not greatly affect our daily life.
This dichotomy between the apparent simplicity of a usual concept and an actual complexity of defining (and measuring) it in scientific terms is because the typical linear scales and dimensions of relevance in daily life are 3 orders of magnitude (or more) smaller than the size of the Earth. Hence, the latter appears to be flat locally, and vertical directions in nearby locations appear to be parallel. Such statements are nevertheless approximations; whether they are acceptable in any particular context or application depends on the applicable requirements, in particular in terms of accuracy.
In graphical contexts, such as drawing and drafting on rectangular paper, it is very common to associate one of the dimensions of the paper with a vertical, even though the entire sheet of paper is standing on a flat horizontal (or slanted) table. In this case, the vertical direction is typically from the side of the paper closest to the user to the opposite side (farthest away). This is purely conventional (although it is somehow 'natural' when drawing a natural scene as it is seen in reality), and may lead to misunderstandings or misconceptions, especially in an educational context. For example, Girard Desargues defined the vertical to be perpendicular to the horizon in his Perspective of 1636.
Vertically can literally be translated as up-and-down not side-to-side
Read more about this topic: Vertical Direction
Famous quotes containing the words daily life, practical, daily and/or life:
“We have lost the art of living; and in the most important science of all, the science of daily life, the science of behaviour, we are complete ignoramuses. We have psychology instead.”
—D.H. (David Herbert)
“A beautiful woman is a practical poet, taming her savage mate, planting tenderness, hope and eloquence in all whom she approaches.”
—Ralph Waldo Emerson (1803–1882)
“The daily lesson of slum life, visualised, reiterated, of low standards, vile living, obscenity, profanity, impurity, is bound to be dwarfing and debasing to the children who are in the midst of it.”
—Albion Fellows Bacon (1865–1933)
“Whoever takes a view of the life of man ... will find it so beset and hemm’d in with obligations of one kind or other, as to leave little room to suspect, that man can live to himself: and so closely has our creator link’d us together ... that we find this bond of mutual dependence ... is too strong to be broke.”
—Laurence Sterne (1713–1768)