Telescopes typically use concave glass mirrors to focus light from outer space, but these can be expensive and fragile. Liquid mirror telescopes use a spinning vat of mercury, the motion of which creates a parabola to achieve the same effect for a lower price.

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12 Questions About the History of Space Exploration Answered

The universe formed roughly 13.8 billion years ago. We humans have been exploring a small portion of the universe beyond Earth for only the past seven decades. What have we accomplished so far? Lots! This list provides a just a few answers, so be sure to learn much more in Britannica’s article