This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

Share this

Free weekly newswire

Sign up to receive all our latest news direct to your inbox.

Physics on film

100 Second Science Your scientific questions answered simply by specialists in less than 100 seconds.

Watch now

Bright Recruits

At all stages of your career – whether you're an undergraduate, graduate, researcher or industry professional – brightrecruits.com can help find the job for you.

Find your perfect job

Physics connect

Are you looking for a supplier? Physics Connect lists thousands of scientific companies, businesses, non-profit organizations, institutions and experts worldwide.

Start your search today

Blog

Michael Faraday, wagon wheels and sandpiles…

chuckwagon.jpg
Courtesy: WPCA

By Hamish Johnston

…what do they have in common?

The answer can be found it the latest issue of Physical Review Letters.

In 1831* Michael Faraday published a paper in the Journal of the Royal Institute of Chemistry about what has come to be called “the wagon wheel effect”. The most familiar example is the illusion that a spoked wheel rotates in the wrong direction as a wagon moves across the screen in a motion picture.

This effect can usually described as a simple function of the angular frequency of the wheel and the frame rate of the film. However, under certain conditions the illusion defies this simple explanation — suggesting that part of the effect is related to how our nervous system and/or brain processes flickering images.

Writing in PRL three physiologists at McGill University argue that the flickering images picked up by the eyes amount to a periodic forcing of nonlinear neural oscillations. These oscillations occur naturally in the nervous system at frequencies of 1-100Hz, whereas a movie projector usually operates at 24 frames per second — so there might be something to it.

1831 was a busy year for Faraday. He also published a paper in the Philosophical Transactions of the Royal Society that introduced “Faraday heaps” to the world. When a tray of sand is shaken up and down, a number of small heaps are formed. These combine into larger heaps and eventually the tray contains jut one large heap.

While physicists understand why the single heap is the most stable configuration — a mathematical description of the merging process had remained elusive….until now.

Writing in the same issue of PRL and international team filmed the evolution of Faraday heaps in the lab and used these data to derive a set of differential equations that describe the process.

So that’s two 178 year old mysteries solved…

*According to PRL Faraday’s wagon wheel paper was published in 1831 — but according to the Royal Society of Chemistry website, this journal only began in 1841. Another mystery to ponder!

This entry was posted in General. Bookmark the permalink.
View all posts by this author  | View this author's profile

Leave a comment

Your e-mail address will not be published. Required fields are marked *

Guidelines

  • Comments should be relevant to the article and not be used to promote your own work, products or services.
  • Please keep your comments brief (we recommend a maximum of 250 words).
  • We reserve the right to remove excessively long, inappropriate or offensive entries.

Show/hide formatting guidelines

Tag Description Example Output
<a> Hyperlink <a href="http://www.google.com">google</a> google
<abbr> Abbreviation <abbr title="World Health Organisation" >WHO</abbr> WHO
<acronym> Acronym <acronym title="as soon as possible">ASAP</acronym> ASAP
<b> Bold <b>Some text</b> Some text
<blockquote> Quoted from another source <blockquote cite="http://iop.org/">IOP</blockquote>
IOP
<cite> Cite <cite>Diagram 1</cite> Diagram 1
<del> Deleted text From this line<del datetime="2012-12-17"> this text was deleted</del> From this line this text was deleted
<em> Emphasized text In this line<em> this text was emphasised</em> In this line this text was emphasised
<i> Italic <i>Some text</i> Some text
<q> Quotation WWF goal is to build a future <q cite="http://www.worldwildlife.org/who/index.html">
where people live in harmony with nature and animals</q>
WWF goal is to build a future
where people live in harmony with nature and animals
<strike> Strike text <strike>Some text</strike> Some text
<strong> Stronger emphasis of text <strong>Some text</strong> Some text
WordPress Appliance - Powered by TurnKey Linux