History of the telescope a wider field of view than a classic Cassegrain. During the period 1850–1900, reflectors suffered from problems with speculum metal mirrors, and a considerable number of "Great Refractors" were built from 60 cm to 1 metre aperture, culminating in the Yerkes Observatory refractor in 1897; however, starting from the early 1900s a series of ever-larger reflectors with glass mirrors were built, including the Mount Wilson 60-inch (1.5 metre), the 100-inch (2.5 metre) Hooker Telescope (1917) and the 200-inch (5 metre) Hale telescope (1948); essentially all major research telescopes since 1900 have been reflectors. A number of 4-metre class (160 inch)
The World Until Yesterday The World Until Yesterday The World Until Yesterday: What Can We Learn from Traditional Societies? is a 2012 popular science book by American intellectual Jared Diamond. It explores what people living in the Western world can learn from traditional societies, including differing approaches to conflict resolution, treatment of the elderly, childcare, the benefits of multilingualism and a lower salt intake. "The World Until Yesterday" has had a mixed reception. Abby O'Reilly of "The Independent" called it "essential reading" that "cements [Diamond's] position as the most considered, courageous and sensitive teller of the human story writing today." In "The New York