Ceremonial ship launching is the process of transferring a vessel to the water. It is a naval tradition in many cultures, dating back thousands of years. It has been observed as a public celebration and a solemn blessing. In addition to the size and weight of the vessel, ship launching imposes stresses on the ship not met during normal operation, and represents a considerable engineering challenge, in addition to a public spectacle. Ship launching involves many superstitions intended to invite good luck, such as christening by breaking a sacrificial bottle of champagne over the bow as the ship is named aloud and launched.