I remember being asked this question at my grandfather’s knee. Of course the popular answer, which is wrong, is they both weight the same. Yes, they have different weights, an ounce of gold is heavier than an ounce of paper.
An ounce of gold weights 31 grams, and an ounce of paper weight 28 grams. Gold is measured in ounces troy, and most other things, including paper, are measured in ounces avoirdupois.
A similar question is why do cars in Britain have a better miles per gallon than in the US – it is not because Americans have bigger cars. A US gallon is 3.7 litres and a UK gallon is 4.5 litres, Americans have smaller litres.
ColinPaice 