The horizontal direction, usually labelled the X direction, is then automatically determined. One can start off by designating the vertical direction, usually labelled the Y direction. In the context of a 1-dimensional orthogonal Cartesian coordinate system on a Euclidean plane, to say that a line is horizontal or vertical, an initial designation has to be made. Alternatively, one can start by designating the horizontal direction. Through any point P, there is exactly one vertical and exactly one horizontal. The horizontal is perpendicular to the vertical. Mathematical definition In two dimensions For example, even a projectile fired in a horizontal direction (i.e., with a zero vertical component) may leave the surface of the spherical earth and indeed escape altogether. When the curvature of the earth is taken into account, the independence of the two motion does not hold. The notion dates at least as far back as Galileo.
Vertical displacement of a projectile is not affected by the horizontal component of the launch velocity, and, conversely, the horizontal displacement is unaffected by the vertical component. Neglecting the curvature of the earth, horizontal and vertical motions of a projectile moving under gravity are independent of each other. Independence of horizontal and vertical motions On a larger scale the gravitational field of the earth, which is at least approximately radial near the earth, is not radial when it is affected by the moon at higher altitudes.
On a smaller scale, a mountain to one side may deflect the plumb bob away from the true zenith. It is a non homogeneous, non spherical, knobby planet in motion, and the vertical not only need not lie along a radial, it may even be curved and be varying with time. The situation is actually even more complicated because earth is not a homogeneous smooth sphere. Only on the equator and at the North and South Poles does the plumb line align with the local radius. This Euclidean Three Space is measured with Right Line Geometry also known as Surveying.įor a spinning earth, the plumb line deviates from the radial direction as a function of latitude. Furthermore, a plane cannot both be a horizontal plane at one place and a vertical plane somewhere else. Horizontal planes, e.g., walls, may be parallel to each other or they may intersect at a vertical line. In the flat earth scenario, where the earth is notionally a large (infinite) flat surface with gravitational field at a right angle to the surface, the earth surface is vertical and any plane parallel to the earth surface is also vertical. Modern rotary laser levels that can level themselves automatically are robust sophisticated instruments and work on the same fundamental principle. A water level device may also be used to establish horizontality. Alternatively, a spirit level that exploits the buoyancy of an air bubble and its tendency to go vertically upwards may be used to test for horizontality. In physics, engineering and construction, the direction designated as vertical is usually that along which a plumb-bob hangs. You are never kicked out for views like the above but without exception anyone who has any criticism of 'Michael Whitman'(sic) is first warned to stop posting those views and if they persist they are kicked out.Spirit level bubble on a marble shelf tests for horizontality Non-political being defined as any criticism that they are pro-Nazi is political and swiftly erased and the accuser removed from the group. This is a recent and representitive example from the 'non-political' Tiger Tank Facebook page. They attract a large following of people who know bugger all about history and are fooled into believing all the the 'Mods' lies and propaganda. I have lost too many arguments to be confident in my own infallibility!įacebook is (in my opinion) the place where the real fanboise now dominate, What happens is a few hard-core true believers set up their own page and through bullying and removal of all opposing views create the perfect platform for uncritical worship of all things German. Believers in 'German superiority' sometimes have a point and you have to get used to the idea that 'you' may lose the argument. You are always going to meet people who hold views that are different from 'yours'. True that fanboise do post there but the number of informed posters who can (and do) counter and destroy their arguments is legion and thus they ill-informed quickly get a lesson in sourcing their fictions.
Having been around the internet for some 18 years now and having the scars to prove it I can say with some authority that AHF is not a fanboise site.
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