The story
Parvati shaped a son from the turmeric paste of her bath and set him to guard her door. When he refused Shiva entry, Shiva cut off his head, and then, to console Parvati, gave him the head of an elephant and made him chief of his ganas and the god worshipped first. His birthday is the Chaturthi of Bhadrapada.
On this night the Moon is not looked at, for the Moon once mocked Ganesha and was cursed; anyone who sees him that night risks false blame, as Krishna did over the Syamantaka gem.
How it is celebrated
Families install Ganesha at midday after the prana pratishtha, worship him morning and evening with aarti and modaks, and visit each other's Ganapatis. In 1893 Lokmanya Tilak turned the household festival into a public one, and today huge images in community pandals, such as Mumbai's Lalbaugcha Raja, draw millions. On the last day, Anant Chaturdashi in Maharashtra, processions carry the images to the sea or rivers with drums and dancing and the cry "Ganpati Bappa Morya, pudhchya varshi lavkar ya", "come again soon next year". Many now use clay images and immerse them at home.
Eco-friendly Ganeshas
Images of plaster of Paris and chemical paints pollute the lakes and seas where they are immersed. Many families and mandals now choose images of natural clay (shadu) painted with natural colours, or seed Ganeshas that grow into plants, and immerse them in a tank or a bucket at home, using the clay afterwards in the garden.