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
I watched a YT video of some scientist talking about this. He said the hard part is not melting down all the glass into a big puck, it’s the cooling and tempering of such a monstrosity. Molten glass is exceedingly delicate when cooling; if you cast a cup and leave it on an open table to cool, it will burst. You have to put the glass in a kiln and bring it down slowly, over the course of hours. The biggest castings in the world for the biggest telescopes in the world take several hours to melt, but almost a year to cool! Then after that, you have to be able to lift and support the thing, which requires feats of engineering, and the more mirror you have, the more work it takes to grind and polish the whole thing; I heard that the error on one side of these mirrors to the other is less than 1/4 the width of a human hair, and it has to be, or the mirror is unusable. And then you have to move one of the most expensive and delicate objects ever made by man across the planet and up a mountain to the observatory.
Think about that. Even if we could cast a single piece of glass the size of Arecibo, *HOW WOULD YOU MOVE IT INTO PLACE*?
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