A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope.
Read more about Primary Mirror: Description, Superlative Primary Mirrors
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“A fact is a proposition of which the verification by an appeal to the primary sources of our knowledge or to experience is direct and simple. A theory, on the other hand, if true, has all the characteristics of a fact except that its verification is possible only by indirect, remote, and difficult means.”
—Chauncey Wright (18301875)
“Women ... are completely alone, though they were born and bred upon this soil, as if they belonged to another class in creation.”
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