Throughout our lives, we are dogged by a question that challenges our perceptions of time and space: Is it safe to eat food you’ve dropped if you pick it up quickly enough?

The good old five-second rule. It’s been the subject of household debates and innumerable science fair projects, with some claiming it’s real and others denouncing it as bunk. And now this famous rule of thumb is in the headlines again, with a new study putting it to a yet more rigorous test…