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[28] [42] Lockwood and Fröhlich, 2007, found "considerable evidence for solar influence on the Earth's pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century", but that "over the past 20 years, all the trends in the Sun that could have had an influence on the Earth ...
The bulk of the work, however, is a collection of tabulated precomputed values that provide the position of the sun at any point in time. Newcomb's Tables were the basis for practically all ephemerides of the Sun published from 1900 through 1983, including the annual almanacs of the U.S. Naval Observatory and the Royal Greenwich Observatory.
Irradiance in space is a function of distance from the Sun, the solar cycle, and cross-cycle changes. [2] Irradiance on the Earth's surface additionally depends on the tilt of the measuring surface, the height of the Sun above the horizon, and atmospheric conditions. [3] Solar irradiance affects plant metabolism and animal behavior. [4]
Ibn Yunus observed more than 10,000 entries for the Sun's position for many years using a large astrolabe. [184] The first reasonably accurate distance to the Sun was determined in 1684 by Giovanni Domenico Cassini. Knowing that directly measurements of the solar parallax were difficult, he chose to measure the Martian parallax.
Most sun charts plot azimuth versus altitude throughout the days of the winter solstice and summer solstice, as well as a number of intervening days.Since the apparent movement of the Sun as viewed from Earth is nearly symmetrical about the solstice, plotting dates for one half of the year gives a good approximation for the rest of the year.
Solar maximum is the regular period of greatest solar activity during the Sun's 11-year solar cycle. During solar maximum, large numbers of sunspots appear, and the solar irradiance output grows by about 0.07%. [2] On average, the solar cycle takes about 11 years to go from one solar maximum to the next, with duration observed varying from 9 to ...
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All days of the year, solstices included, have the same length of 12 hours. Solstice day arcs as viewed from 20° latitude. The Sun culminates at 46.56° altitude in winter and 93.44° altitude in summer. In this case an angle larger than 90° means that the culmination takes place at an altitude of 86.56° in the opposite cardinal direction.