Artist's rendering of the International Prototype Kilogram (Image: Greg L)
According to researchers at Newcastle University in the United Kingdom, the kilogram is very likely getting heavier. How can this be? Mainly because we’re talking about the definitive kilogram, the International Prototype Kilogram (IPK) kept at the International Bureau of Weights and Measures in Paris. But because this is the kilo against which all kilos are defined, in a theoretical sense at least, all kilograms will technically be heavier too.