Finger (unit)
5, 6 = finger width
2, 3 = hand width , fist
1, 4 = hand span
Others: fist
The unit of measurement finger or the finger width (the finger width) is, together with the foot and the cubit, one of the few length measures that go back to prehistoric times. The manageable length corresponds to about 2 cm, thumb width about 2½ cm.
Antique unit of measure
The oldest evidence of the finger as a measure of length date back about 5000 years ago from Mesopotamia and ancient Egypt , where it Ubanu or Djeba was called. In ancient times, feet were usually divided into sixteen fingers. Since the foot size is usually around 30 centimeters, the finger width measures around 18 to 19 millimeters , depending on the valid foot definition .
The ancient Greeks and Romans also used the width of the daktylos or digitus as the smallest main unit to measure length . Below that there was, for example, half a finger's width or a third of a finger's width . 18 finger widths make a pygm .
The finger width as a measure is also mentioned in the Bible ; according to J. M. Dold, its length should have been 0.63 Swiss inches. As a Roman measure, it was called Digitus transversus and was 0.61 Swiss inches in length.
Anglo-American
Finger or digit is one of the measures of the Anglo-American measuring system :
- 1 digit = ¾ inch = 19.05 mm (exactly. According to the definition 1 inch = 25.4 mm, 1956): as such only in use in the USA (rarely).
Further use today
Today the measure is still often used in medicine and abbreviated as QF (cross finger ). It often remains unclear (especially in paediatrics ) whether the patient's finger width or the doctor's finger width is meant. The duodenum is so named because it is twelve finger widths ( duodenum ); the fingers of the person being examined and not of the examiner are always decisive here.
The filling level, especially of alcoholic beverages in the individual drinking glasses , is sometimes still given in finger widths today (the filling line in the serving measure indicates that the filling is in accordance with standards ).
Finger width for angle estimation
In free-eyed astronomy, the finger width serves as an approximate measure for small angles . With an outstretched arm, it measures about 1.5 degrees (3 moon diameters ). The thumb width is about 2 degrees. With three fingers (with narrow hands almost four) you can estimate an angle of 5 ° (5 ° can also be estimated with the fist )
- For example, the Orion Nebula lies 5 ° below the Orion Belt , the rather striking row of three bright stars. With 3 fingers you can find the little cloud in a few seconds.
See also
Individual evidence
- ↑ JM Dold: Ratio of the coins, dimensions and weights of all countries to the new Swiss. J. Weilenmann, Uster 1853, p. 40.
- ↑ The moon as a star and planet pointer. kuffner-sternwarte.at.