In the experiments below, Δ α represents the change in α over time, which can be computed by α prev − α now . If the fine-structure constant really is a constant, then any experiment should show that Δ Δ α α α α = d e f α α p r e v − − α α n o w α α n o w = 0 , or as close to zero as experiment can measure. Any value far away from zero would indicate that α does change over time. So far, most experimental data is consistent with α being constant.