Tobias Mayer

Tobias Mayer ( also Majer; born February 17, 1723 in Marbach am Neckar, † February 20, 1762 in Göttingen ) was a German astronomer, Geo and cartographer, mathematician and physicist. Although he had never studied at a university as an autodidact, he was a renowned scientist of his time.

Life and work

Mayer grew up in Esslingen am Neckar in poverty. From 1729 to 1741 he attended the local German school and grammar school. Since mathematics was not offered in the Latin School, Mayer formed in this discipline continues autodidact. Due to his great talent, he was temporarily promoted by the mayor of the city of Esslingen. After his father's death in 1731, Mayer received accommodation in the orphanage. His mother died he published the first map of Esslingen, in 1741 a book on geometry and mathematics, 1745, " Mathematical Atlas " and a book on military architecture in 1737. 1739. When he took a job in 1746 at JB Homann cartographic institute in Nuremberg, he had thus already published two papers in geometry. Mayer revealed the inaccuracies of the cards used at that time by talking about each drew two common cards and large differences, especially in east-west direction vorfand. The determination of the longitude of a city was only possible with great uncertainty.

In 1751 he married Mary Victoria, born Gnüge ( 1723-1780 ), and the following year his son Johann Tobias was born, who was also a physicist later. The father is in some texts referred to erroneously as Johann Tobias Mayer. After the baptism book and original publications whose first name is but simply Tobias.

Because of its improvements in the field of cartography and because of his reputation as a scientist, he was appointed in 1751 to the Chair of Economics and Mathematics at the University of Göttingen. 1752-1756 he completed publications on length determination, astronomy, geophysics, mathematics, and measuring instruments. In the years 1757-1762 he published in spite of the Seven Years' War further work on astronomy, but also to the earth's magnetic field and color theory.

In 1754 he became head of the newly established observatory, which was housed in a tower of the city wall. With great enthusiasm and success, he worked there until he died in 1762 of typhoid fever.

Scientific achievements

Astronomy

His first major astronomical work was a careful study of the libration of the Moon ( cosmographic news, Nuremberg 1750). His posthumously published in 1775 by Lichtenberg map of the moon was half a century to none. Mainly based on Mayer's fame but his lunar tables, which first appeared in 1752 in the print. 1755 he submitted an expanded version of these tables with the British government. They were so accurate that the moon position to within 5 arc seconds and thus the longitude at sea could be determined accurate to within 0.5 °.

For a solution to the so-called length problem was found, which had up to that time prevented safe navigation on the high seas. Another solution to the same problem developed about the same time, the English clockmaker John Harrison: it was based on time measurement by means of newly developed watches that exactly on board a sailing ship were sufficient even under the harsh conditions on the high seas.

S scientific theory on which were based the lunar tables, was posthumously published under the title Theoria lunae juxta systema Newtonianum 1767 in London. Also posthumously published in 1770 in London his improved version of these tables. Mayer's widow brought these tables to England in person. In recognition of Mayer's merits to the solution of the linear problem they received from the British Government a premium of £ 3,000. Already in 1714, the British Parliament had established an annual award in the amount of 20,000 pounds for the length problem and a committee, the Board of Longitude, used for it.

Mayer's lunar maps were later taken up by, among others, Johann Hieronymus Schroeter.

The lunar crater T. Mayer was named after him.

Invention of Repetitionskreises

Middle of the 18th century occurred on slight discrepancies between the predictions of Newton's theory of gravitation and the actually observed planetary locations. These differences were about the moon up to 5 minutes of arc, resulting in the determination of longitude on Earth could result in an uncertainty of 2.5 degrees. Depending on latitude, this meant a discrepancy or inaccuracy navigation by up to 150 nautical miles. The necessity of precise observations to create a better theory of motion of the moon constructed Tobias Mayer, a new astronomical measuring instrument, the so-called repetition or Repetitionskreis. The device was first used in land surveying and consisted of two relatively rotatable and lockable separate sighting devices with a telescope.

To measure you aiming for the angle between two terrestrial points, one of which is a reference point. This process is repeated several times. For example, after three Peilungsvorgängen the disc indicates the triple of the desired angle. The advantage of this method is that the inevitable occurring measurement error is less than the one-time adjustment and reading of the circle. Although Mayers invention itself brought no fundamental innovation, but reduced its repetition principle, the angular error of the practical measurement. Repeated angle measurements brought the land surveying hitherto unattainable accuracy. This repetition principle transferred Mayer now on an astronomical mirror circuit. Determine the required angular difference between Moon and Star by repeated measurements and then dividing by the number of sightings. Thus it succeeded Mayer, set up from 1755, his lunar tables with an accuracy of approximately one minute of arc. Later, the astronomer called F.X. by Zach (1754-1832) the Mayersche mirror circuit as the greatest invention of the 18th century astronomical ..

The first models of the new device were made in 1750 in Göttingen, and from about 1757 by John Bird in London. Mayer soon realized that the refinement that he could achieve using such an instrument for his lunar theory was suitable for a reliable method for determining the length at sea. But only three years after Mayer's death, measurements of the English "Board of Longitude ," that the accuracy of location determination could be improved to the lake with Mayer's method to about 60 nautical miles. From 1785 these devices became known as Borda circles and experienced widespread.

Mayer's solution to the longitude problem

The figure at right illustrates the principle of the solution for the longitude problem first in his work by Johannes Werner " In hoc opere haec continentur Nova translatio primi libri geographiae Cl ' Ptolomaei ... " (Nuremberg, 1514) was mentioned. Mayer has improved on the basis of Newtonian theory and more accurate astronomical observations required to calculate tables of lunar positions crucial.

Except for a small parallactic displacement of the moon appears with simultaneous observation at the same time at the same position of the fixed stars - although this observation are taken from different locations on the Earth. At the same time this means at the same universal time. At a certain date depends on the deviation of the true local time, which can be determined by observation of the sun, only on the longitude of the observer. As the Moon moves in its orbit around the earth per hour to about 33 minutes of angle against the fixed stars to the east, can be carried out by appropriately accurate measurement of the angular distance between the Moon and bright fixed stars in its vicinity, the deviation of the true local time in universal time and thus the longitude of the observer determine - if enough accurate data on the position of the moon in the fixed stars as a function of universal time are available.

Museum

The birthplace of Tobias Mayer houses since 1996, Tobias Mayer Museum. It lies close to the birthplace of Friedrich Schiller Torgasse 13 in Marbach am Neckar. The museum was and is established and maintained by Tobias Mayer club.