April 21 in Physics History

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birthdays & deaths

Explore all birthdays & deaths of physicists occurred on this day with their short biography!

physics Events

Know all important discoveries made by physicists & events happened on this day with complete information!

April 21 in Physics History - Births – Physicists born on April 21

Jean-Baptiste Biot (21 Apr 1774 - 3 Feb 1862)

He was a French physicist and mathematician forward in the field of astronomy electricity, optics and magnetism. He developed the Biot Savart law with Felix Savart. He also contributed to geometry and in 1804 he made a 13000 feet high hot air balloon to investigate the atmosphere. He discovered optical activity in 1815 that was later used in the techniques of analyzing sugar solution.

Percy W. Bridgman (21 Apr 1882 - 20 Aug 1961)

He was an American experimental physicist who invented an apparatus that produced extremely high pressures. For his discoveries and inventions, he got the Nobel Prize for Physics in 1946. He was the first Harvard physicist who received a Nobel Prize in physics. He was known for his studies of materials at high temperatures and pressures. He started his first experimental work with static high pressures and eventually, he reached about 400000 atmospheres. During his experiments, he discovered several high-pressure forms of ice.

April 21 in Physics History - Deaths – Physicists died on April 21

Shakuntala Devi (4 Nov 1929 - 21 Apr 2013)

She was an Indian computer and astrologer who could rapidly answer 2 editions of several up to 13 digit numbers. She used her mental skills in calculating large mathematical algorithms and her calculations included using large numbers in multiplications and divisions. Her ability was not explainable though she could also quickly gave square and cube roots. Her skills were only in computation and she did not have a photographic memory for other facts.

John Michell (1724 - 21 Apr 1793)

He was a British geologist and astronaut who is considered the father of seismology. He devised a realistic estimate of the distance to the stars and discovered physical double stars. After the Lisbon earthquake of 1755 in which 70 thousand people were killed, he suggested that earthquakes set up a wave motion in the earth. He also noticed the increased frequency of earthquakes in areas near volcanoes. He discovered that if we compare the time at which the earthquake is felt, the epicenter could be calculated. He invented a device to measure very small forces call the torsion but sadly he died before carrying out the purpose of the torsion balance to determine the density of the earth.

Pierre Bertholon (28 Oct 1741 - 21 Apr 1800)

He was a French physicist and priest who is known for his studies of atmospheric phenomena, application to the growth of plants, and therapies. He also worked for public health, hydrostatics, and agriculture, Earth, and volcanoes. He was friends with Benjamin Franklin and his friend influenced him a lot. He promoted the use of lightning rods in Southern France. He also invented the electrovegetometer.

Victor Weisskopf (19 Sep 1908 - 21 Apr 2002)

He was an Austrian American theoretical physicist who was a major contributor in the court in the age of quantum mechanics. He was the doctoral student of Max Born at Göttingen. He worked with many prominent scientists such as Heisenberg, Strödinger, Bohr and Pauli. After the Manhattan Project at Los Alamos, he became associate head of the theoretical division. He developed the clouded crystal ball in the 1950s which is a model of the atomic nucleus. He also served as the director-general of CERN.

André-Louis Danjon (6 Apr 1890 - 21 Apr 1967)

He was a French astronomer who studied earth’s rotation and developed astronomical instruments to measure earthshine and brightness of the dark moon to light reflected from Earth. He also devised the standard 5 point scale for rating the darkness and color of a total lunar eclipse. His photometer consisted of a telescope in which he split the moon’s image into two identical images. By adjusting the diaphragm to dim one of the two images until the sunlight portion had the same brightness as the Earthlit portion.

Edward Appleton (6 Sep 1892 - 21 Apr 1965)

He was an English physicist who discovered the Appleton layer of the ionosphere. For his discovery, he was awarded the Nobel Prize for Physics in 1947. He founded the layer 60 miles above the ground that reflected radio waves. And after some time in 1926, he discovered another layer electrically stronger and able to reflect short waves around the earth 150 miles above the ground. The Appleton layer is a dependable reflector of radio waves and it is more useful in communication than the other layers of the ionosphere.

April 21 in Physics History - Events – Physics Events of April 21

Apollo 16 Landed On The Moon

Apollo 16 astronauts landed for a fifth manned mission to the moon surface on 21 April 1972. They landed in the central lunar highlands to explore the lunar surface, that had never been seen by previous astronauts. They traveled almost 27 kilometers using their rover and undeployed 9 experiments. They spent 71 hours on the moon’s surface and lifted off on 24 April. They reached Earth again on 27th April and later in the same year Apollo 17 was launched.

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