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Scientists maintain that scientific investigation must adhere to the scientific method, a rigorous process for properly developing and evaluating natural explanations for observable phenomena based on reliable empirical evidence and neutral, unbiased independent verification, and not on arguments from authority or popular preferences. Science therefore bypasses supernatural explanations, it instead only considers natural explanations that may be falsifiable.
Fields of science are distinguished as pure science or applied science. Pure science is principally involved with the discovery of new truths with little or no regard to their practical applications. Applied science is principally involved with the application of existing knowledge in new ways, including advances in technology.
Mathematics is the language in which scientific information is best presented, often it is the only way to formulate and present scientific knowledge. Therefore whether mathematics is a science in itself or the framework of science is a matter of perspective.
The three major types of atomic line filters are absorption-re-emission ALFs, Faraday filters and Voigt filters. Absorption-re-emission filters were the first type developed, and so are commonly called simply "atomic line filters"; the other two types are usually referred to specifically as "Faraday filters" or "Voigt filters". Atomic line filters use different mechanisms and designs for different applications, but the same basic strategy is always employed: by taking advantage of the narrow lines of absorption or resonance in a metallic vapor, a specific frequency of light bypasses a series of filters that block all other light.
An 18th Century Persian astrolabe used for determining the time at both day and night. The points of the curved spikes on the front rete plate, mark the positions of the brightest stars. The name of each star being labeled at the base of each spike. The back plate, or mater is engraved with projected coordinate lines. From the Whipple M