Object 7b

The Smurfs study the Earth tides
These greeting cards from the Royal Observatory of Belgium were edited on the initiative of Paul Melchior, former director of the Observatory, and his friend Peyo. The cards illustrate the research on Earth tides, which are induced by the Moon and the Sun. Cards displayed with the permission of IMPS.

Royal Observatory of Belgium

Inv. N/A


Paul Melchior (1925-2004), former director of the Royal Observatory of Belgium, was a friend of the cartoonist Peyo. Together they chose to illustrate the current research in Earth sciences at the Observatory using the Smurfs.
The selected greeting cards presented here highlight the research on tides, phenomena influenced by the Moon and the Sun (greetings card end 1980). Paul Melchior, a proficient tide scientist, wrote a reference book in this field (greetings card end 1978) and led the "International Centre for Earth Tides", to whose members he addressed the greetings cards.  

1978 – 1979

Tides modify the shape of the globe and cause variations in gravity. We use gravimeters to measure these variations. Most gravimeters include a proof mass suspended by a coil spring, which moves with changing gravity. In the 1970s, such instruments were used to measure the Earth tides around the world (greetings cards end 1973, 1976 and 1979).

1973 – 1974

1976 – 1977

In the early 1980s, superconducting gravimeters became available. They are much more stable than gravimeters with springs. The Royal Observatory of Belgium installed a superconducting gravimeter in Uccle in 1982, one of the first two in Europe (greetings card end 1982). This gravimeter was decommissioned in 2000, while in 1995 and 2014, new generation devices were installed at the Membach and Rochefort stations.


1982 – 1983

The quality of the superconducting gravimeters made it possible, and still makes it possible, to provide fundamental contributions to metrology (science dedicated to measurement), to the study of the tides as well as other variations in gravity. Those measurements have also allowed us to enlarge our knowledge on the structure of the Earth's interior, in accordance with the theoretical models developed at the Observatory (greetings card end 1966).


1966 – 1967

More about the "International Centre for Earth Tides" history:

Jo-El Azara
Taka Takata : Kamikaze cyclist / Kamikazefietser

Dargaud, 1973


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