Cover your work surface with an even layer of newspaper. Place the large foam ball on top of it.
Spray the ball with an even layer of yellow paint. Allow it to dry according to the manufacturer's directions.
Paint the small ball with an even coat of blue paint. Allow it to completely dry. Paint green continents over the blue. Again, allow it to dry completely.
Insert one end of a skewer to the middle bottom of the large yellow ball. Feed the other end of the second skewer into the middle side, perpendicular to the bottom one, inserting the tip into the middle.
Place the bottom skewer in the glass jar, holding it in the middle. Pour the sand over the skewer, until it is 1 inch from the top. This will hold the sun in place and allow it to rotate.
Insert the small foam ball onto the end of the skewer that still sticks out from the sun, pressing the tip in to the middle of the ball to hold it firmly.