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Information about Joseph Adhemar

Joseph Alphonse Adhemar (1797 — 1862) was a French mathematician. He was the first to suggest that ice ages were controlled by astronomical forces in his 1842 book Revolutions of the Sea.

The earth's orbit is elliptical, with the sun at one focus; lines drawn through the summer and winter solstice; and the spring and autumn equinox; intersect with the sun at right angles. Currently, the earth is closest to the sun (perihelion) near the northern hemisphere winter solstice, and the earth moves faster through its orbit when closer to the sun. Hence, the period from the northern hemisphere's autumn equinox to winter and spring is shorter by around seven days than the period from spring to summer to autumn; the reverse is true in the southern hemisphere. Hence, northern hemisphere winter is shorter.

Because of this, Adhemar reasoned that because the southern hemisphere had more hours of darkness in winter, it must be cooling, and attributed the Antarctic ice sheet to this. Adhemar knew of the 22,000 year cycle of precession of the equinoxes, and theorised that the ice ages occurred in this cycle.

One immediate objection to the theory was that the total insolation during a year does not vary at all during the precessional cycle, only its seasonal distribution. Another was that the timing was wrong; however this could not be tested by the observations available at the time.

Adhemar's theory was further developed and greatly modified, first by James Croll and later by Milutin Milankovic.

Adhemar theorised about the thickness and predicted the Antarctic ice sheet (the continent had not been sighted) by comparing the depths of the Arctic and circum-Antarctic oceans. Finding the Antarctic oceans deeper (the measurements he used may not have been fully representative) and attributing this to the gravitational attraction of the Antarctic ice sheet, he postulated a truly enormous ice sheet approximately 90 km thick. Unsurprisingly, he did not convince his contemporaries.

References

  • E. Bard, Greenhouse effect and ice ages: historical perspective; Comptes Rendues Geoscience, 336 (2004) 603-638 (in French and English).
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Motto
Liberté, Égalité, Fraternité
"Liberty, Equality, Fraternity"
Anthem
"La Marseillaise"


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mathematician is a person whose primary area of study and research is the field of mathematics.

Problems in mathematics

Some people incorrectly believe that mathematics has been fully understood, but the publication of new discoveries in mathematics continues at an immense
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ice age is a period of long-term reduction in the temperature of Earth's climate, resulting in an expansion of the continental ice sheets, polar ice sheets and mountain glaciers.
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Astronomy is the scientific study of celestial objects (such as stars, planets, comets, and galaxies) and phenomena that originate outside the Earth's atmosphere (such as the cosmic background radiation).
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18th century - 19th century - 20th century
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1839 1840 1841 - 1842 - 1843 1844 1845

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In astronomy, axial tilt is the inclination angle of a planet's rotational axis in relation to a perpendicular to its orbital plane. It is also called axial inclination or obliquity.
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ellipse (from the Greek ἔλλειψις, literally absence) is the locus of points on a plane where the sum of the distances from any point on the curve to two fixed points is constant.
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The Sun

Observation data
Mean distance
from Earth 1.4961011 m
(8.31 min at light speed)
Visual brightness (V) −26.74m [1]
Absolute magnitude 4.
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solstice occurs twice a year, whenever Earth's axis tilts the most toward or away from the Sun, causing the Sun to be farthest north or south at noon. The name is derived from Latin sol (sun) and sistere
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equinox can have two meanings:
  • The moment when the Sun is positioned directly over the Earth's equator and, by extension, the apparent position of the Sun at that moment - see below.

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equinox can have two meanings:
  • The moment when the Sun is positioned directly over the Earth's equator and, by extension, the apparent position of the Sun at that moment - see below.

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right angle is an angle of 90 degrees, corresponding to a quarter turn (that is, a quarter of a full circle). It can be defined as the angle such that twice that angle amounts to a half turn, or 180° [1].
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EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
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Northern Hemisphere or northern hemisphere[1] is the half of a planet that is north of the equator—the word hemisphere literally means 'half ball'. It is also that half of the celestial sphere north of the celestial equator.
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Southern Hemisphere or southern hemisphere[1] is the half of a planet that is south of the equator—the word hemisphere literally means 'half ball'. It is also that half of the celestial sphere south of the celestial equator.
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An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²).[1] The only current ice sheets are in Antarctica and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered
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The precession of Earth's axis of rotation with respect to inertial space is also called the precession of the equinoxes. Like a wobbling top, the direction of the Earth's axis is changing; while today, the North Pole points roughly to Polaris, over time it will change.
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James Croll (2 January 1821 – 15 December 1890) was a 19th century Scottish scientist who developed a theory of climate change based on changes in the earth's orbit.

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