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
    • 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
    • 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

From the Cabinet of Physics: Many Ways to Look at Centrifugal Force

By Bill Higgins  |  10 Jun 2016

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

This entry is part 13 of 23 in the series From the Cabinet of Physics

Today, in exploring the effects of centrifugal force, we see no fewer than seven gadgets demonstrated. Our curator does a lot of cranking.

1. As a spinning glass globe rotates faster, colored liquid within it rises to form a belt or ring around its middle.

2. An array of pendulums starts out hanging vertically, but the pendulums spread out as rotation speeds up.

3. A spring-loaded sphere, arranged to slide on a horizontal bar, moves outward as the bar spins, compressing the spring.

4. Two flexible strips of metal form two circular hoops, outlining an imaginary sphere. As they are spun, they are centrifugally deformed. We see that the shape they outline becomes less like a sphere and more like a pumpkin.

This demonstration makes a point of interest to planetary scientists: Many planets—Earth and Jupiter are good examples—bulge slightly at their equators, and are flattened at their poles, because of their rotation. The effect is more subtle than the dramatic bulging we see in the spinning hoops, but perhaps witnessing this apparatus helped students visualize an important piece of geophysics.

5. As glass vessel rotates, the flat surface of colored liquid within it changes in shape. The liquid’s surface becomes a bowl shape, low in the middle, high at the edges of the glass—a paraboloid.

Since a parabolic shape is ideal for applications in acoustics, radio, and optics, such as making the mirror of a reflecting telescope, and an accurate parabolic shape is not easy to make, many an engineer has contemplated the surface of a spinning liquid and daydreamed.

In the 1980s at the University of Arizona’s Steward Observatory, J. Roger P. Angel found a practical way to build a huge spinning furnace. He cast large telescope mirrors from molten glass. The speed of the furnace’s rotation and the diameter of the mold determined the shape of the resulting paraboloid. Then the furnace kept spinning as the glass was allowed to cool. The glass solidified into the desired shape, ready for testing and polishing.

By this means, in 1985 Professor Angel’s team produced a mirror 1.8 meters in diameter. This became the primary mirror of the Vatican Advanced Technology Telescope (VATT) on Mount Graham in Arizona. So astronomers of the Vatican Observatory may have a special reason to smile when they see the surface of a spinning liquid. Angel’s group went on to cast mirrors for many more telescopes, including four 8.4 meter behemoths for the Giant Magellan Telescope array.

6. As it rotates, a dangling metal ring responds to forces that leave it spinning in a horizontal plane.

7. With an apparatus similar to example 6, a loop of chain is spun. Centrifugal effects force the chain into the shape of a circle, and also bring its motion into a horizontal plane.

These seven demonstrations flash by in less than four minutes, but they establish that the Cabinet of Physics was well-equipped to present students with the phenomena of centrifugal motion… as long as the person doing the demonstration had a sturdy cranking arm.

The Foundation for Science and Technics, or Fondazione Scienza e Tecnica, of Florence, Italy, has made available many videos exploring the Cabinet of Physics, a large collection of antique scientific demonstration instruments.  The Foundation’s homepage may be found here, and its Youtube channel, florencefst, 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

From The Backyard: Seasons Change

By Fr. James Kurzynski  |  27 Mar 2023

Conjunction of the Moon and Pollux – March 29-30

By Robert Trembley  |  27 Mar 2023  |  Sacred Space Astronomy

Conjunction of the Moon and Mars – March 28

By Robert Trembley  |  27 Mar 2023  |  Sacred Space Astronomy

Ask an AI about the History of Astronomy

By Mr. Christopher Graney  |  25 Mar 2023

Archives

      • 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 in this Series:
"From the Cabinet of Physics"

78  |  What Do We Lose When We Sacrifice Science?

By Br. Guy Consolmagno  |  27 May 2021  |  Sacred Space Astronomy

69  |  To err is human… to admit it, is science

By Br. Guy Consolmagno  |  25 Mar 2021  |  Sacred Space Astronomy

12  |  From the Cabinet of Physics: In the Days before PowerPoint

By Bill Higgins  |  18 Jun 2016

14  |  From the Cabinet of Physics: Tracing the Pathway of a Spark

By Bill Higgins  |  27 May 2016

15  |  From the Cabinet of Physics: Seven Mirrors and a Spectrum

By Bill Higgins  |  20 May 2016

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