Johann Heinrich von Mädler

Johann Heinrich von Mädler

Johann Heinrich von Mädler
Born (1794-05-29)May 29, 1794
Died March 14, 1874(1874-03-14) (aged 79)
Nationality Germany
Fields astronomy

Johann Heinrich von Mädler (May 29, 1794, Berlin – March 14, 1874, Hannover) was a German astronomer.

Life and Work

His father was a master tailor and when 12 he studied at the Friedrich‐Werdersche Gymnasium in Berlin.[1] He was orphaned at age 19 by an outbreak of typhus, and found himself responsible for raising three younger sisters. He began giving academic lessons as a private tutor and in this way met Wilhelm Beer, a wealthy banker, in 1824.

In 1829 Beer decided to set up a private observatory in Berlin, with a 95 mm refractor telescope made by Joseph von Fraunhofer, and Mädler worked there. In 1830 they began producing drawings of Mars which later became the first true maps of that planet. They were the first to choose what is today known as Sinus Meridiani as the prime meridian for Mars maps.

They made a preliminary determination for Mars' rotation period, which was off by almost 13 seconds. A later determination in 1837 was off by only 1.1 seconds.

They also produced the first exact map of the Moon, Mappa Selenographica, published in four volumes in 1834–1836. In 1837 a description of the Moon (Der Mond) was published. Both were the best descriptions of the Moon for many decades, not superseded until the map of Johann Friedrich Julius Schmidt in the 1870s. Beer and Mädler drew the firm conclusion that the features on the Moon do not change, and there is no atmosphere or water.

In 1836, Johann Franz Encke appointed Mädler an observer at the Berlin Observatory, and he observed with its 240-mm refractor. In 1840, Mädler was appointed director of the Dorpat (Tartu) Observatory in Estonia (then Russian Empire), succeeding Friedrich Wilhelm Struve who had moved to Pulkovo Observatory. He carried out meteorological as well as astronomical observations. He continued Struve's observations of double stars. He remained in Tartu until he retired in 1865, and then returned to Germany.

By examining the proper motions of stars, he came up with his "Central Sun Hypothesis", according to which the center of the galaxy was located in the Pleiades star cluster and that the Sun revolves around it. He got the location wrong.

He published many scientific works, among them a two-volume History of Descriptive Astronomy in 1873.

Notwithstanding several singular scientific errors J. H. von Mädler, without doubt, is one of the great and eminent astronomers of the 19th century. The craters Mädler on the Moon and Mädler on Mars are both named in his honor.

The conventional tropical year according to von Mädler

Next to his other numerous and important works, von Mädler made calculations concerning the true length of the tropical year with precision never attained before, though this fact is little known. Based on his results, he proposed to Russia, which at this time used the conventional tropic year according to Sosigenes of Alexandria of exactly 365 days 6 hours (cf. Julian Calendar), besides dropping 12 days to equal Gregorian Calendar dates in the year 1900, but then, first proposed by von Mädler himself, a new 128-year rule for additional common years. (The only odd thing in Mädler's proposal was, that neither the year 1900, nor 2028, 2156 etc. [=1900 +128 +128...] were themselves divisible by 128.)

But (according to von Mädler) if the years 3200, 6400, 9600, 12,800, 16,000 and so on are NOT leap years the duration of the mean Gregorian year will then be 365.2421875 days (10,000 divided by 3200 gives 3.125) and this approaches very closely the real duration of the mean tropical year which lasts 365.24219 days. So that a very little error of only 3.125 - 3.100 = 0.025 days in 10,000 years will then be made.

Neither the Tsar nor Orthodox clergy accepted this unsolicited proposal. After the Bolshevik Revolution in Russia, Lenin adopted the western (papal) calendar, with its conventional tropic year of 365.2425 days (i.e. 365d. 5h 49min. 12s) due to Christopher Clavius (1537-1612). But this was astronomically true about 6000 years ago. The conventional tropical year according to Simon Newcomb (1835-1909) was 365.2422 days (= 365d. 5h 48min. 46.08s). But this is no more than an approximate value. The real tropical year 2000.0 (measured by Pierre Bretagnon) was 365.242190517 days, that is about 365d. 5h 48min. 45.26s. That is also very close to the conventional tropic year according to von Mädler: 36531128 or 365.2421875 days, exactly 365d. 5h 48min. and 45s or 365d. 6h. minus 11min 15s. But because the real tropical year shortens about half a second per century, this will exactly attain the von Mädler-proposed value in only a few decades. Thus, we can well expect that yet we can count on the conventional tropic year according to von Mädler.


  1. The Biographical Encyclopedia of Astronomers. New York: Springer. 2007. p. 723. Retrieved 3 October 2014.


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