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  2. Empirical evidence for the spherical shape of Earth - Wikipedia

    en.wikipedia.org/wiki/Empirical_evidence_for_the...

    In practice, this method is not reliable because of variations in atmospheric refraction, which is how much the atmosphere bends light traveling through it. Refraction can give the impression that Earth's surface is flat, curved more convexly than it is, or even that it is concave (this is what happened in various trials of the Bedford Level ...

  3. Bedford Level experiment - Wikipedia

    en.wikipedia.org/wiki/Bedford_Level_experiment

    The Old Bedford River, photographed from the bridge at Welney, Norfolk (2008); the camera is looking downstream, south-west of the bridge. The Bedford Level experiment was a series of observations carried out along a 6-mile (10 km) length of the Old Bedford River on the Bedford Level of the Cambridgeshire Fens in the United Kingdom during the 19th and early 20th centuries to deny the curvature ...

  4. Atmospheric refraction - Wikipedia

    en.wikipedia.org/wiki/Atmospheric_refraction

    Diagram showing displacement of the Sun's image at sunrise and sunset Comparison of inferior and superior mirages due to differing air refractive indices, n. Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. [1]

  5. Angle of incidence (optics) - Wikipedia

    en.wikipedia.org/wiki/Angle_of_incidence_(optics)

    In computer graphics and geography, the angle of incidence is also known as the illumination angle of a surface with a light source, such as the Earth's surface and the Sun. [1] It can also be equivalently described as the angle between the tangent plane of the surface and another plane at right angles to the light rays. [2]

  6. Caustic (optics) - Wikipedia

    en.wikipedia.org/wiki/Caustic_(optics)

    There have been many different approaches to address the continuous problem. One approach uses an idea from transportation theory called optimal transport [10] to find a mapping between incoming light rays and the target surface. After obtaining such a mapping, the surface is optimized by adapting it iteratively using Snell's law of refraction ...

  7. Collimated beam - Wikipedia

    en.wikipedia.org/wiki/Collimated_beam

    The light from stars (other than the Sun) arrives at Earth precisely collimated, because stars are so far away they present no detectable angular size.However, due to refraction and turbulence in the Earth's atmosphere, starlight arrives slightly uncollimated at the ground with an apparent angular diameter of about 0.4 arcseconds.

  8. Refraction - Wikipedia

    en.wikipedia.org/wiki/Refraction

    Refraction occurs when light goes through a water surface since water has a refractive index of 1.33 and air has a refractive index of about 1. Looking at a straight object, such as a pencil in the figure here, which is placed at a slant, partially in the water, the object appears to bend at the water's surface.

  9. Atmospheric optics - Wikipedia

    en.wikipedia.org/wiki/Atmospheric_optics

    The reddish color of the Sun when it is observed through a thick atmosphere, as during a sunrise or sunset. This is because long-wavelength (red) light is scattered less than blue light. The red light reaches the observer's eye, whereas the blue light is scattered out of the line of sight. Other colours in the sky, such as glowing skies at dusk ...