Since its debut nine years ago, Hublot’s Big Bang collection of wristwatches has ballooned to include a diverse range of styles, from sleek and highly mechanical to fun and colorful. Though the line has become extremely varied over the years, the circular shape of the watches’ cases has never changed—until now. The Hublot Spirit of Big Bang is the latest addition to the collection and a radical departure for the series, thanks to its unique tonneau case, which derives its name from the French word for “tun” (a…