P l a y - b a l l   s u n d i a l
     
  A child likes to play with a ball so the children will find a spherical sundial very interesting . This sphere has to be transparent so that sunrays can enter and we can see through and through. The most common portable type of sundial is one with the use of a triangle to cast a shadow. This is oriented to the north with the help of a compass to show the right time . In this spherical type of sundial there is some water and a floating disc on which there is a vertical triangle with markings for the corresponding hours.  
                                                  
 

The advantage of this sundial is that even if the ball rolls , the disc will always remain horizontal. There is one magnet fixed in the disc which is not visible and this magnet will keep the disc always oriented to the north. In this way we don't need to orient the disc to the north. This disc will also show us the direction . One half part of the disc will will have the marking for corresponding hours and on the other half part will have the map of the world which will tell us the corresponding situation in an other country. On the sphere we can make the lines of longitude and latitude along with the world map. These graphics has to be made of thin lines so that these lines do not restrict the sunrays to enter .

The other side of the dial (floating disc) can have one more sundial which is caliberated according to some other country and it can tell us the time of that country even if we are using it in India. In this case I would like to caliberate the dial according to U.K. because for the solar eclipse in August '99 U.K. is the first land mass.

 

 
   
 

Using the same principle the sundial can be made as small as a wrist watch. The sundial wrist watch has some water and a floating disc with hidden magnet and a small vertical triangle as shown in figure. This sundial can be made of diameter from 6'' to 10'' so that it will be light and comfortable for the children.

 
     
 
       Amit Rajwade
Maneesh Goyal       
 
 

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