82
5 Nearly Half a Million Stars
lution a system was introduced in which months were divided into ‘decades’
of ten days instead of weeks of seven, and one day into 10 h, and so on. PierreSimon Laplace (1749–1827) had played a part in this proposal. Napoleon
abolished it. In Washington, Janssen advocated a universal system of decimal
division of angles and time. Later, this was also worked out by a committee
led by the mathematician Henri Poincaré (1854–1912). For example, a day
then would have 10 h, each consisting of 100 minutes and each minute of 100
seconds. The differences with the current time-line are not even dramatic. A
hundredth of a day would then be 10 minutes, and would be equal to 14.4
current minutes, so almost a quarter of an hour; and a hundred thousandth
of a day (the new second) would measure 0.86 current seconds. According to
the proponents it was also more logical to divide a full circle into 400 units.
A right angle is then 100 ‘degrees’ and you divide that in a decimal system
again. As we know, this never got accepted. However, France did succeed in
introducing the meter via the system just mentioned, which was registered as
one forty millionth of the Earth’s circumference. But the second of time (and
the hour and minute) was defined in the Système Internationale d’Unités (S.I.)
in the old way. We all know how especially the United States still adhere to an
archaic and complicated system of distances, weights and temperatures.
The only French success was that the standard meter and kilogram were
stored in the Bureau International des Poids et Mesures in Paris, but these are
hardly of scientific importance. In the meantime, the second and the meter
have been defined on the basis of spectral transitions in atoms; the standard
meter has only historical value. Things will soon be not much different with the
kilogram; a redefinition in terms of atomic properties only awaits a somewhat
more precise determination of the Avogadro’s number, the number of atoms
in a mole, a standard quantity of a substance. It is defined as the number of
atoms in 12 grams of Carbon-12. Avogadro’s number, named after Amedeo
Avogadro (1776–1856) is about 6 × 10 23 , so a 6 followed by 23 digits before
the decimal point. To redefine the kilogram, one needs to know this number
to at least the first 8 digits, one or two more than is currently known.
5.6 Carte du Ciel
David Gill had emphasized the potential of photography for astronomy on several occasions. The director of l’Observatoire de Paris, Amiral Ernest Amédée
Barthélemy Mouchez (1821–1892), had been impressed by the presentations
and writings of Gill, and the possibility of using photography to catalog stars.
He shared this with the brothers Paul-Pierre (1848–1905) en Mathieu-Prosper
5 Nearly Half a Million Stars
lution a system was introduced in which months were divided into ‘decades’
of ten days instead of weeks of seven, and one day into 10 h, and so on. PierreSimon Laplace (1749–1827) had played a part in this proposal. Napoleon
abolished it. In Washington, Janssen advocated a universal system of decimal
division of angles and time. Later, this was also worked out by a committee
led by the mathematician Henri Poincaré (1854–1912). For example, a day
then would have 10 h, each consisting of 100 minutes and each minute of 100
seconds. The differences with the current time-line are not even dramatic. A
hundredth of a day would then be 10 minutes, and would be equal to 14.4
current minutes, so almost a quarter of an hour; and a hundred thousandth
of a day (the new second) would measure 0.86 current seconds. According to
the proponents it was also more logical to divide a full circle into 400 units.
A right angle is then 100 ‘degrees’ and you divide that in a decimal system
again. As we know, this never got accepted. However, France did succeed in
introducing the meter via the system just mentioned, which was registered as
one forty millionth of the Earth’s circumference. But the second of time (and
the hour and minute) was defined in the Système Internationale d’Unités (S.I.)
in the old way. We all know how especially the United States still adhere to an
archaic and complicated system of distances, weights and temperatures.
The only French success was that the standard meter and kilogram were
stored in the Bureau International des Poids et Mesures in Paris, but these are
hardly of scientific importance. In the meantime, the second and the meter
have been defined on the basis of spectral transitions in atoms; the standard
meter has only historical value. Things will soon be not much different with the
kilogram; a redefinition in terms of atomic properties only awaits a somewhat
more precise determination of the Avogadro’s number, the number of atoms
in a mole, a standard quantity of a substance. It is defined as the number of
atoms in 12 grams of Carbon-12. Avogadro’s number, named after Amedeo
Avogadro (1776–1856) is about 6 × 10 23 , so a 6 followed by 23 digits before
the decimal point. To redefine the kilogram, one needs to know this number
to at least the first 8 digits, one or two more than is currently known.
5.6 Carte du Ciel
David Gill had emphasized the potential of photography for astronomy on several occasions. The director of l’Observatoire de Paris, Amiral Ernest Amédée
Barthélemy Mouchez (1821–1892), had been impressed by the presentations
and writings of Gill, and the possibility of using photography to catalog stars.
He shared this with the brothers Paul-Pierre (1848–1905) en Mathieu-Prosper