A Vertical Sundial

Applet

If you prefer to view the applets offline, you can download them. Just unzip astro-applets.zip, and open astro-applets.html in your browser.

If you can't run this applet properly, please download the latest version of the Java Runtime Environment (JRE) at http://java.sun.com/j2se/.

This applet was made together with Tey Meng Khoon and Frederick H. Willeboordse of CITA (Centre for Information Technology and Applications) for the course Heavenly Mathematics: Cultural Astronomy.

Video Clip

I have recorded a video clip that explains this applet. It's available in several formats.

• 
  
  RealVideo SureStream, click on the embedded player or click on the link to view in a separate window. The quality and file size of the clip is determined by the preference settings in your RealPlayer.
• RealVideo LAN/150Kbps, click on the link to view in a separate window or right-click to download and view it from your hard disk. This file is big, so this is only for people with fast connections.
• 
  QuickTime, click on the picture to view in a separate window or right-click the link to download and view it from your hard disk. This file is big, so this is only for people with fast connections.

If you can't get any sound in the QuickTime file, you may need to download the latest version of QuickTime.

Discussion

This Java applet shows a vertical sundial. It shows the shadow, and also traces out the path of the tip of the shadow.

• Is this useful for telling the time? Try to understand why a useful sundial must have the gnomon (the “stick”) parallel to the earth's axis.