Liquid Mirror Telescopes
Liquid-mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is Mercury (element), mercury, but other liquids will work as well (for example, Fusible alloy, low-melting point alloys of gallium). The liquid and its container are rotated at a constant speed around a vertical axis, which causes the surface of the liquid to assume a Parabola, paraboloidal shape. This parabolic reflector can serve as the primary mirror of a reflecting telescope. The rotating liquid assumes the same surface shape regardless of the container's shape; to reduce the amount of liquid metal needed, and thus weight, a rotating mercury mirror uses a container that is as close to the necessary parabolic shape as feasible. Liquid mirrors can be a low-cost alternative to conventional large telescopes. Compared to a solid glass mirror that must be cast, ground, and polished, a rotating liquid-metal mirror is much less expensive to manufacture. Isaac Newton noted t ...
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