The technology has moved on. Traditional mirror balls need suspending, a motor to rotate then and a pin spot or two to highlight. The new alternatives turn all that on it's head, literally. So a one piece unit, sits or suspends, with a rotating hemispherere with gaps which the light projects through. Some great extra easy functionality too which we love to use. With light control through DMX they can also variably dim and strobe, vary rotation speed and direction, and with modern LED bulbs can change and blend colours too.
And then there's the scale. In October, London saw the largest ever spinning mirror-ball, about 1.5 tons and house sized, alongside the Millennium Bridge, with integrated LCD screens and live twitter feed too. Described as the Death Star of mirror balls. While it was designed to be a reminder for the clocks to go back an hour, given it was sponsored by a Vodka brand, that's the pub and club association well re-enforced.
So while the machinery has moved on, things are not that much different 70 years on. Those mirror-balls and mirror ball effects are still there in the pubs and clubs, keeping a similarly watchful eye on all that boy-meets-girl dancing fun.