اپست ِ افق apest-e ofoq
*Fr.: distance à l'horizon*
The distance separating an observer and the → *apparent horizon* of the
place. Neglecting the → *atmospheric refraction*, it is given
by: *d* = (2*Rh*)^{1/2}, where *R* is the radius of the Earth and
*h* is the observer's height. This can be approximated to:
*d* (km) = 3.57(*h*)^{1/2} for a typical value of *R* = 6378 km.
The atmospheric refraction, however, makes the thing more complex, depending on the
temperature and density variations along the line of sight. Generally, refraction
pushes the apparent horizon about 10% farther. → *distance*; → *horizon*. |