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)
Until the End of the World (song) sheet music published at Musicnotes.com, "Until the End of the World" is played at a tempo of 101 beats per minute in a 4/4 time signature. The basic key is E major. David Werther, a faculty associate in Philosophy at the University of Wisconsin–Madison, compared "Until the End of the World" with U2's 1987 song "Exit" in an examination of the role music can play in catharsis. He noted that both were powerful songs, but that while "Until the End of the World" allowed the possibility of purification, which he described as the cleansing of the soul "through pity and