In the Triwizard Tournament in the HP and the Goblet of Fire film, a cannon is used at the start of each of the three tasks. It can be seen e.g. in this video clip:
Having been convinced by @Au101 that the cannon is canon, my question is:
why is there such a thing as a cannon in Hogwarts?
It's easy to make loud bangs with magic, and the Reducto curse can probably do the same amount of damage as a cannonball. We know wizards don't tend to use firearms, so why was an exception made in this case? Why would wizards even know about such Muggle devices, when they can perform all the tasks of a cannon with magic?