The news about Arecibo got me looking into big telescope installations recently. I’m curious, why are there two super huge radio dishes (Arecibo and FAST), but nothing that size for optical or IR or something?
In: Engineering
These dishes act as mirrors that focus light onto one point. This is fairly easy to build for radio waves because simple things like concrete to nearly perfect reflections of radio waves. As others have mentioned, radio’s long wavelength allows a lot of error for “good enough” focusing.
But yea, turns out building a perfect mirror 300 meters across is incredibly difficult. Typically what we do instead is build individual hexagonal mirror sections then assemble these hexagons on site to create the telescope itself.
And there are a few giant visible light telescopes in the works. None are as big as Arecibo, Arecibo is gigantic still incredibly difficult to do with visible light, but we have the aptly named Extremely Large Telescope in Chile and Thirty Meter Telescope in Hawaii.
A little further from earth we are also getting the James Webb Space Telescope launching soon hopefully.
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