Without its bubbles, champagne is ordinary white wine, unfit for sabering or smashing against new ships. So what gives sparkling wines their sparkle? A fascinating process called secondary fermentation.
Unlike most wines, champagne goes through an additional fermentation in the bottle. Sugar and additional yeast are added when the champagne is bottled, and the yeast then slowly starts converting the sugar to carbon dioxide. The American Chemistry Society's video has more about the science of champagne. [ACS]