Skip to content
Vatican Observatory
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Latest
    • Overview
    • Resources
    • Press
    • Audio
    • Video
    • Research
    • Authors
      • FAQs
    • Newsletter
    • Tucson Meteor Cameras
  • Podcast
  • Education
    • Overview
    • Resource Center
    • Image Gallery
    • Summer School
    • Books
    • Software
    • Additional Resources
    • ACME
    • Ambassadors
  • Shop
  • Calendar
  • Support
    • VATT 30th Anniversary
    • Overview
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Fr. Coyne Fundraiser
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
  • Specola Vaticana
  • Contact
    • Contact
  • About
    • Overview
    • Team
    • FAQ
  • Telescopes
    • Overview
    • Telescope Images
  • Latest
    • Overview
    • Resources
    • Press
    • Audio
    • Video
    • Research
    • Authors
      • FAQs
    • Newsletter
    • Tucson Meteor Cameras
  • Podcast
  • Education
    • Overview
    • Resource Center
    • Image Gallery
    • Summer School
    • Books
    • Software
    • Additional Resources
    • ACME
    • Ambassadors
  • Shop
  • Calendar
  • Support
    • VATT 30th Anniversary
    • Overview
    • Donate Now
    • Smart Ways to Give
    • Sacred Space Astronomy
      • View Content
    • Fr. Coyne Fundraiser
    • Bequests / Trusts
    • The Foundation
      • Newsletters
      • Annual Reports
  • Press
  • Specola Vaticana
  • Contact
    • Contact

How Frs. Riccioli and Dechales Argued that Science Shows the Earth to be at Rest – The Coriolis Effect

By Mr. Christopher Graney  |  19 Jul 2017

Share:
  • Share on Facebook
  • Share on Twitter
  • Share on LinkedIn
  • Share via Email
Hurricane Sandy from 2012. Credit:NOAA. Hurricane Sandy from 2012. Credit:NOAA.

The Coriolis Effect is an apparent deflection of projectiles and falling bodies that is caused by the rotation of the Earth.  It is named for Gaspard-Gustave de Coriolis, a French scientist who described it mathematically in the early 19th century.  It is responsible for the rotation of weather patterns such as hurricanes.  But it turns out that a century and a half before Coriolis did his work, other scientists were discussing the Coriolis Effect.  These scientists were Jesuits—Fr. Giovanni Battista Riccioli, who discussed the effect in his 1651 book Almagestum Novum, and Fr. Claude François Milliet Dechales, who discussed the effect and included some nice simple diagrams of it in his 1674 book Cursus seu Mundus Mathematicae.

What is interesting about this is that Riccioli and Dechales were discussing an effect that they did not believe to exist.  Their whole point was that, were Earth rotating like Copernicus says, that rotation would produce observable effects—deflection of projectiles and falling bodies.  Since these effects are not observed, that is an argument against Copernicus, and in favor of an immobile Earth.

Now, they were wrong about the effect not existing.  The effect exists, but it is much harder to observe than one might expect.  Indeed, even Isaac Newton and Robert Hooke in 1679-1680 tried, without success, to use the effect to prove Earth’s rotation.

From a 1690 edition of Cursus seu Mundus mathematicus. Click here for the entire page. Dechales’s cannon illustration, from a 1690 edition of Cursus seu Mundus mathematicus. Click here for the entire page.

How does the Coriolis Effect work?  Well, let’s let Dechales explain it—he explains it well, using very clear illustrations.  First the deflection of falling bodies:

A ball F, hanging from the top of a tower directly above point G, is dropped.  While the ball descends, point G is carried [by Earth’s rotation] into I.  I propose the ball F to be unable to arrive at point G (now at I).  This is because the ball when positioned at F has a momentum [impetus] requisite for passing through arc FH (through which the tower top moves while the ball descends) which is greater than that requisite for arc GI.  Therefore, if the ball is dropped, it will not arrive at point I, but will advance forward farther [to L].

Then, the deflection of projectiles:

Likewise, consider a cannon discharged in the direction of one of the poles [of the Earth].  During the time in which the ball would traverse the distance MO, the cannon [originally at M] would be carried to N, while the target [originally at O] would be carried to P.  While the ball was at M, it had from the rotation of the Earth momentum able to carry it through arc MN (which is greater than arc OP) during the time required to travel from M to O.  But the ball, separated from the cannon, conserves this momentum whole [totum hunc impetum conservat].  Therefore it should run through a distance greater than OP, and consequently not hit the target.

From a 1690 edition of Cursus seu Mundus mathematicus. Click here for the entire page. Dechales’s cannon illustration, from a 1690 edition of Cursus seu Mundus mathematicus. Click here for the entire page.

Note how Dechales illustrates the cannon ball passing to the right of the target.

You can read all about this in this month’s issue of Physics Today!  Just click here.  For a more detailed discussion from the Cornell University ArXiv preprint server, click here.

 

 

 

Share:
  • Share on Facebook
  • Share on Twitter
  • Share on LinkedIn
  • Share via Email

Sacred Space Astronomy

The Vatican Observatory’s official digital community and online magazine.

Become a Member

Recent Posts

Phillis Wheatley: Faith & Science

By Mr. Christopher Graney  |  23 Sep 2023  |  Sacred Space Astronomy

ⓜ Full Moon-th Meetup: 29 September, 2023

By Robert Trembley  |  22 Sep 2023  |  Sacred Space Astronomy

Spectacular Prominence

By Deirdre Kelleghan  |  22 Sep 2023  |  Sacred Space Astronomy

From the Vatican Observatory Faith and Science pages (Younger Readers): Johannes Kepler – Discovering the Laws of Celestial Motion

By Faith and Science  |  21 Sep 2023  |  Sacred Space Astronomy

Archives

      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • October
      • September
      • August
      • July
      • June
      • May
      • April
      • March
      • February
      • January
      • December
      • November
      • August
      • June
      • March
      • January
      • November
      • October
      • December
      • November
      • April
      • May
      • January
      • December
      • September
      • May
      • March
      • December
      • November
      • February

More Posts by
Christopher M. Graney

Phillis Wheatley: Faith & Science

By Mr. Christopher Graney  |  23 Sep 2023  |  Sacred Space Astronomy

Black Holes at Seven Pines (3): The Ultimate Storehouse of Memory

By Mr. Christopher Graney  |  16 Sep 2023  |  Sacred Space Astronomy

The Time and Place for the Integration of Science and Faith

By Mr. Christopher Graney  |  9 Sep 2023  |  Sacred Space Astronomy

Black Holes at Seven Pines (2): The Basics

By Mr. Christopher Graney  |  2 Sep 2023  |  Sacred Space Astronomy

Astronomy in Art & Architecture: The Sun and 19th-century Tombstones

By Mr. Christopher Graney  |  26 Aug 2023  |  Sacred Space Astronomy

Somerville, Mary (1780-1872)

By Mr. Christopher Graney  |  22 Aug 2023  |  Resources

View More

Newsletter

Upcoming astronomical events, scientific breakthroughs, philosophical reflections… just a few reasons to subscribe to our newsletter!

Vatican Observatory
  • About
  • Telescopes
  • Latest
  • Podcast
  • Education
  • Shop
  • Calendar
  • Support
  • Press
  • Specola Vaticana
  • Contact
Privacy Policy  |   Cookie Policy  |   Disclosure Statement

Podcast:

  • Apple Podcasts Listen onApple Podcasts
  • Spotify Listen onSpotify
  • Google Podcasts Listen onGoogle Podcasts
  • Stitcher Listen onStitcher
  • Amazon Alexa Listen onAmazon Alexa
  • TuneIn Listen onTuneIn
Made by Longbeard