In honor of Serbia's
by author Rolf A. F. Witzsche
Serbian civil engineer and mathematician Milutin Milankovitch.
Milankovitch was a
Serbian engineer and meteorologist - born in 1879 he attended the Vienna
institute of technology graduating in 1904 with a doctorate in
technical sciences. He then went on to work in the University of Belgrade
where he spent time working on a mathematical theory of climate based on
the seasonal and latitudinal variations of solar radiation received by the
Milankovitch built his theory previous work done by J.A. Adhemar and James Croll of discoveries of cyclical changes in the Earth's orbit around the Sun: the eccentricity cycle, and the precession cycle. Beginning in 1875 he incorporated also the obliquity cycle, the variation of the tilt of the spin axis of the earth. Being a mathematician, Milankovitch combined all three cycles and computed from them the seasonal variations that correspond differences of solar radiation received by the northern and southern hemisphere of our planet. While the total global solar radiation received does not vary on an annual basis by the orbital cycles, it is believed that the cycles that cause solar insolation in the northern hemisphere, where the large landmasses of the Earth are located, causes the cyclical events of the ice ages.
See diagram: at http://www.detectingdesign.com/milankovitch.html
The eccentricity is expressed in seasonal differences: such as warmer summers for the hemisphere that has its summer while being closes to the Sun, or colder winters when these occur more distant from the Sun.
The eccentricity cycle is deemed to be approximately 98,000 years in length (modulated by 125,000 and 400,000-year cycles) The Earth's orbit around the sun varies from an almost exact circle (eccentricity = 0.0005) to a slightly elongated shape (eccentricity = 0.0607), (the present value is 0.017). The eccentricity is expressed in warmer summers for the hemisphere that is closes to the Sun in summertime, and colder winters for the hemisphere that is more distant at it winter.
The obliquity cycles span 41,000 years in which the earth's spin-axis tilt varies between 22.1 and 24.5 degrees (currently 23.44 degrees - the rate of change amounts to 46.85 inches/century versus the geographic axis.) The variance in tilt is expressed the severity of the seasons - less tilt means less severe seasons - cooler summers and milder winters. It is also expressed in corresponding shifts of the polar and tropical circles (1.4 km/century). For an increase of 1 degree in obliquity, the total energy received by the summer hemisphere increases by approximately 1% The cool summers are thought to allow for the yearly build up of snow and ice in high latitudes, possibly leading to the development of an ice sheet.
The precession cycles (also called axial precession) is a 25,800-year cycle of the orientation of the Earth's rotational axis, following the path of a circle around the geographic pole. The movement is deemed to be the effect of the tidal forces of the Sun and the Moon on the Earth. The change in the axis location changes the dates of perihelion (closest distance from sun) and aphelion (farthest distance from sun). The cyclical change is expressed by increasing the seasonal contrast in one hemisphere, while decreasing it in the other hemisphere.
By combing these three orbital variations, Milankovitch was able to create a mathematical model for calculating latitudinal differences in solar insolation and the corresponding surface temperature, going back 600,000 years.
During the 1940s and 1950s Milankovitch's theory was put in doubt by radiocarbon dating that indicating a lag in cooling versus the insolation and also scale-problems. The theory was revived several times from the late 60s to present, but there remain major problems that are not easily resolved, as mathematical model does not mach physical evidence, so that the Milankovitch cycles may be themselves but subsequent (at least some of them) of larger cosmic phenomena.
The major problems encountered.
And then there is the shift to the 100,000-year glaciation cycles, from the 41,000-year cycles, that had prevailed before one-million-year mark in the past.
Also, the relative distribution between the cold and warm periods have been progressively changing, with the cold periods getting longer and the interglacials shorter.
And then, there is 400,000-year problem. The computed 400,000-year cycle is only observed in climate records older than the last million years.
If the 100,000-year variations are having such a strong effect, the 400,000-year
variations might also be expected to be apparent, but it isn't observed.
The bottom line is that the ice core data doesn't mach the computed Milankovitch cycles well, which seems to indicate that much greater causes are acting upon the earth, which may the cause of the Milankovitch cycles that merely follow as an effect.
The Milankovitch-cycles theory is explained in a manner that the cause of the 100,000-year eccentricity cycle is deemed to be the result of gravitational interactions between the Earth and Jupiter and Saturn. There exists little calculated evidence that substantiates this theory.
for more, see:
Past the Milankovitch Cycles.
However, other evidence exists for the orbital variation that points to a larger cause. The effect from this cause may have already been observed by Johannes Kepler which he documented in his book, The Harmony of the World. He discovered that the spacing of the orbits is not random, but reflects an orderly principled progression. Earlier, in the 1597 in his Mysterium Cosmographicum Kepler proposed that a nested arrangement of the Platonic Solids determines the spacing between the planetary orbits. Plato is credited with discovering that only five three-dimensional, solids can be formed using regular polygons to construct them, which are called the Platonic Solids. Kepler used the potential nestling of the solids as a starting point for exploring the potential principles that govern the spacing of the orbits of the planets. His evident reasoning was that ordered phenomena must have a cause in universal physical principles that governs their order. Those have not yet been found. However many phenomena have been discovered that tend to open wider views of exploration for the phenomena that we observe. Most of these are located in plasma physics, in the twisted robe like structures of Birkeland currents flowing in space that are also reflected in the hemispheric current sheet that extends throughout the solar system to the edge of the heliosphere and is inward flowing with increasing density. Considering that the electric and corresponding magnetic forces are 39 orders of magnitude more powerful than gravity, it is not unreasonable to assume that these larger electric dynamics may have contributed to the ordering effects that have shaped the solar system, and may still shape it in response the ever-changing electric environment in our galaxy, which factors are more likely reflected in the observed orbital characteristics of the Milankovitch cycles, in the intensity changes in the solar cycles, in the changes in the hemispheric shielding of the earth from cosmic radiation, with reflective changes in the size of the heliosphere itself. These are all factors that impact on our climate. It is therefore absolute lunacy to latch onto manmade CO2, minuscule as it is, and blame it for the climatic effects of the immensely large cosmic factors. It is also being recognized increasingly that it is a fallacy to latch onto the Milankovitch cycles as a determining factor, since the observed evidence defies the computed assumptions. It is irrational to assume that our tiny planet exists isolated from, and unaffected by, the vast forces that operate in our galaxy and in the Universe itself.
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