1865 astronomer angelo secchi demonstrates the secchi disk which 04 20
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1865 161 years ago Historical Events April 20 3 sources

Astronomer Angelo Secchi demonstrates the Secchi disk, which measures water clarity, aboard Pope Pius IX's yacht, the L'Immaculata Concezion.

On April 20, in the year 1865, Astronomer Angelo Secchi demonstrates the Secchi disk, which measures water clarity, aboard Pope Pius IX's yacht, the L'Immaculata Concezion. This event is recorded as a Historical Events event in the history of April 20, one of 323 recorded events on this date across all of history.

Angelo Secchi was an Italian Catholic priest and astronomer from the Italian region of Emilia. He was director of the observatory at the Pontifical Gregorian University for 28 years. He was a pioneer in astronomical spectroscopy, and was one of the first scientists to state authoritatively that the Sun is a star.

Key Facts

  • This event took place on April 20, 1865 (AD era).
  • It is categorised as a Historical Events event in recorded history.
  • Referenced in 3 Wikipedia articles.
  • Wikipedia source last updated on 10 January 2026.

On This Date in History 323

Type Year Date Event
Notable Deaths 2025 Apr 20 Hugo Gatti, Argentine footballer (born 1944)
Notable Deaths 2024 Apr 20 Antonio Cantafora, Italian film and television actor (born 1944)
Notable Deaths 2024 Apr 20 Andrew Davis, English conductor (born 1944)
Notable Deaths 2024 Apr 20 Roman Gabriel, Filipino-American NFL American footballer
Notable Deaths 2024 Apr 20 Lourdes Portillo, Mexican film director, producer, and writer (born 1943)
Historical Events 2023 Apr 20 SpaceX's Starship rocket, the largest and most powerful rocket ever built, launches for the first time
Selected Events 2023 Apr 20 SpaceX's Starship launched for the first time before exploding four minutes into flight
Notable Deaths 2022 Apr 20 Gavin Millar, Scottish film director (born 1938)
Historical Events 2021 Apr 20 State of Minnesota v
Notable Deaths 2021 Apr 20 Idriss Déby, Chadian politician and military officer (born 1952)
Notable Deaths 2021 Apr 20 Monte Hellman, American film director (born 1929)
Notable Deaths 2021 Apr 20 Les McKeown, Scottish pop singer (born 1955)
Selected Events 2021 Apr 20 Derek Chauvin was found guilty of all charges in the murder of George Floyd by a Minnesota court
Historical Events 2020 Apr 20 For the first time in history, oil prices drop below zero, an effect of the 2020 Russia-Saudi Arabia oil price war
Notable Deaths 2018 Apr 20 Avicii, Swedish DJ and musician (born 1989)
Notable Deaths 2016 Apr 20 Victoria Wood, British comedian, actress and writer (born 1953)
Historical Events 2015 Apr 20 Ten people are killed in a bomb attack on a convoy carrying food supplies to a United Nations compound in Garowe in the
Notable Deaths 2014 Apr 20 Neville Wran, Australian politician, 35th Premier of New South Wales (born 1926)
Historical Events 2013 Apr 20 A 6
Historical Events 2012 Apr 20 One hundred twenty-seven people are killed when a plane crashes in a residential area near the Benazir Bhutto Internatio
Notable Deaths 2012 Apr 20 Bert Weedon, English guitarist and songwriter (born 1920)
Notable Deaths 2011 Apr 20 Tim Hetherington, English photographer and journalist (born 1970)
Historical Events 2010 Apr 20 The Deepwater Horizon drilling rig explodes in the Gulf of Mexico, killing eleven workers and beginning an oil spill tha
Notable Deaths 2010 Apr 20 Dorothy Height, American educator and activist (born 1912)
Selected Events 2010 Apr 20 An explosion on Deepwater Horizon, an offshore rig in the Gulf of Mexico, resulted in the largest marine oil spill in hi
Historical Events 2008 Apr 20 Danica Patrick wins the Indy Japan 300, becoming the first female driver in history to win an Indy car race
Notable Deaths 2008 Apr 20 Monica Lovinescu, Romanian journalist and author (born 1923)
Selected Events 2008 Apr 20 American racing driver Danica Patrick won the Indy Japan 300, becoming the first woman to win an IndyCar auto race
Selected Events 2008 Apr 20 Fernando Lugo became the first candidate not from the Colorado Party candidate to be elected President of Paraguay in 61
Historical Events 2007 Apr 20 Johnson Space Center shooting: William Phillips barricades himself with a handgun in NASA's Johnson Space Center in Hous
Notable Deaths 2007 Apr 20 Andrew Hill, American pianist, composer, and bandleader (born 1931)
Notable Deaths 2007 Apr 20 Michael Fu Tieshan, Chinese bishop (born 1931)
Notable Births 2005 Apr 20 Tallyn Da Silva, Australian rugby league player
Notable Deaths 2005 Apr 20 Fumio Niwa, Japanese journalist and author (born 1904)
Historical Events 2004 Apr 20 The Nicoll Highway in Singapore collapses, killing four workers
Notable Deaths 2004 Apr 20 Lizzy Mercier Descloux, French musician, singer-songwriter, composer, actress, writer and painter (born 1956)
Selected Events 2004 Apr 20 An incomplete tunnel leading to the Nicoll Highway MRT station in Singapore collapsed, resulting in four deaths and the
Notable Deaths 2003 Apr 20 Bernard Katz, German-English biophysicist and academic, Nobel Prize laureate (born 1911)
Notable Deaths 2002 Apr 20 Alan Dale, American singer (born 1925)
Notable Deaths 2001 Apr 20 Giuseppe Sinopoli, Italian conductor and composer (born 1946)
Historical Events 1999 Apr 20 Columbine High School massacre: Eric Harris and Dylan Klebold kill 14 people and injure 23 others before committing suic
Notable Deaths 1999 Apr 20 Rick Rude, American professional wrestler (born 1958)
Notable Deaths 1999 Apr 20 Rachel Scott, American victim of Columbine High School massacre (born 1981)
Notable Deaths 1999 Apr 20 Cassie Bernall, American victim of Columbine High School massacre (born 1981)
Selected Events 1999 Apr 20 Students Eric Harris and Dylan Klebold carried out a massacre at Columbine High School, killing 13 people before committ
Historical Events 1998 Apr 20 Air France Flight 422 crashes after taking off from El Dorado International Airport in Bogotá, Colombia, killing all 53
Notable Births 1997 Apr 20 Alexander Zverev, German tennis player
Notable Deaths 1996 Apr 20 Trần Văn Trà, Vietnamese general and politician (born 1918)
Notable Deaths 1995 Apr 20 Milovan Đilas, Yugoslav communist, politician, theorist and author (born 1911)
Notable Deaths 1993 Apr 20 Cantinflas, Mexican actor, producer, and screenwriter (born 1911)

This article draws on content from Wikipedia, available under CC BY-SA 4.0.

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