What weighs more, a kilo of feathers or a kilo of iron? The answer will surprise you

The article examines the classic riddle of a kilo of iron versus a kilo of feathers, explaining that while their mass is identical, buoyancy in air causes a tiny difference in measured weight, as demonstrated in an experiment by the University of Trento.

The article examines the classic riddle: what is heavier, a kilo of iron or a kilo of feathers? The simple answer is that both weigh a kilogram, but the article explains that when measured in air, buoyancy (lift) affects the result. A kilo of feathers takes up more volume and therefore displaces more air, reducing its measured weight compared to a kilo of iron. The theoretical difference is only about 0.77 grams. The article describes a 2014 experiment by the University of Trento in Italy, where a bronze plate and a polystyrene block were compared on sensitive scales in a vacuum chamber, demonstrating the effect of air. The National Institute of Standards and Technology (NIST) notes that this effect is a significant source of error in precise mass measurements. The article concludes that the answer depends on whether you weigh in air or in a vacuum.