Foucault’s Pendulum ~ 1851
In the background of the
stamp is an silhouette map of France the homeland of Jean Foucault
(1819- 1868). Foucault (pronounced "Foo-Koh") was born on September
19, 1819. He studied medicine, but changed to the physical sciences at
the Paris Observatory. Foucault's life is marked by many
distinguishing achievements. He was the first scientist to photograph
the sun. He was able to measure the speed of light in a laboratory
using a system of rotating mirrors. He proved that humans have
binocular vision, with the brain combining images from the two eyes
into a single image. He is also credited with improvements on mirrors,
lenses, prisms, arc lamps, telescopes, and gyroscopes. He died in
In 1851 Jean Foucault hung a 61 pound ball on a 200
foot cable and started it swinging in the Panthéon in Paris. A pin on
the bottom of the ball traced the path of the swinging ball in wet
sand. In 24 hours the path moved 270°. Since a swinging pendulum does
not change its direction the change is attributed to the movement of
the environment, specifically the building in which the pendulum was
hung, thus demonstrating the rotation of the earth.
If the pendulum were hung at the North Pole it would
seem to rotate 360° in 24 hours. If it were hung at the equator it
would not change at all. The formula for the apparent rotation is
n=360sinF. Since Paris is about 48.6°, the apparent rotation was about
270° in 24 hours.
The stamp was issued to observe the bicentennial of the
National Conservatory of Arts and Crafts in 1994.
The Ozone Layer
In the 1970s
scientists of the British Antarctic Survey observed a drop in
atmospheric ozone over the Antarctic. A hole in the ozone layer was
detected in the 1980s. This permits damaging ultraviolet radiation,
which may cause skin cancers, eye damage, immune system damage and
damage to the ecosystem.
The ozone hole reached it maximum size in 2000, 11
million square miles, three times the size of the United States.
International agreements regulating the release of ozone destroying
chemicals into the atmosphere has slowed the damage to the ozone
Also in 2000 Brazil issued this stamp to mark the
"International Day for the Preservation of the Ozone Layer."