ASTRONOMICAL REFRACTION Meaning and
Definition
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Astronomical Refraction refers to the bending or deviation of light rays as they pass through the Earth's atmosphere, particularly when observing celestial objects such as the Sun, the Moon, and the stars. This phenomenon occurs due to the variation in the refractive index of the Earth's atmosphere caused by a change in air density with altitude.
When light rays from a celestial object enter the Earth's atmosphere, they encounter different layers of air with varying density and temperature. This causes the light rays to change direction slightly, resulting in a deviation from their original path. Astronomical refraction can affect the apparent position or displacement of celestial objects as observed from the Earth's surface.
The degree of astronomical refraction depends on several factors, such as the altitude of the observed object, the angle at which the light rays enter the atmosphere, and atmospheric conditions such as temperature and pressure gradients. Typically, the amount of refraction increases as the altitude of the observed object decreases, leading to a greater displacement of the object from its true position.
Astronomical refraction has practical implications for astronomers and navigators, as it can introduce errors in the measurement of celestial coordinates and the determination of an object's true position in the sky. To account for this phenomenon, correction formulas and tables are often employed to adjust the observed positions of celestial objects for the effects of astronomical refraction, allowing for more accurate calculations and predictions in the field of astronomy and celestial navigation.
Etymology of ASTRONOMICAL REFRACTION
The word "astronomical" derives from the Greek word "astronomia", which means "the science of the stars". "Astronomia" is a combination of "astron" (star) and "nomos" (law).
The term "refraction" comes from the Latin word "refractus", which means "broken" or "bent". It is derived from the verb "refringere", which means "to break" or "to bend back". Refraction refers to the change in the direction of light as it passes through a medium, such as air or water, causing it to bend or deviate from its original path.
Therefore, the term "astronomical refraction" refers to the bending of light from celestial objects (such as stars or planets) as it passes through Earth's atmosphere, which can cause these objects to appear slightly higher in the sky than they actually are.
