"The mirrors guiding this light, made of sandwiched layers of silicon and molybdenum, are ground so precisely that, if scaled to the size of Germany, they would have no bumps bigger than a millimetre"
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https://www.economist.com/business/2020/02/29/how-asml-becam...>
Also, I've heard some say that if China were to try and develop its own ASML like lithography machine, it would take at least 10 years. I wonder if anyone could throw any light on that claim?