Final answer:
A vintage on an Australian wine label signifies the harvest year of the grapes that made the wine. The authenticity of a wine's vintage can be determined by measuring cesium-137 activity. Any pre-1950 wine with cesium-137 activity is likely a fake.
Step-by-step explanation:
The definition of the designation of a vintage on an Australian wine label indicates the year in which the grapes were harvested and used to produce the wine. The vintage year plays a significant role in the quality and character of the wine, and certain connoisseurs highly value wines from specific years, which are thought to offer particularly favorable conditions for grape growing. Given the importance of vintage, the authenticity of a wine's vintage year can be verified scientifically; a notable method involves measuring the radioactivity from cesium-137 present in the wine. Cesium-137 is a radioactive isotope released into the atmosphere during the atmospheric testing of nuclear weapons in the 1940s and 1950s and the Chernobyl disaster in 1986, and it is absorbed by living plants, including grapevines. Hence, by analyzing the cesium-137 activity in a wine bottle, researchers can validate the claimed vintage. Wines that claim a vintage prior to 1950 but exhibit cesium-137 activity are likely not genuine as the pre-1950 level of this isotope in the environment was negligible.