The diet soda and regular soda differ in the amount of solids
(sugar/sugar substitute, soft drink ingredients, etc.) that are
dissolved in the liquid. The amount of dissolved solids in a
liquid will affect the liquids density. An object will become
buoyant (float) when it is less dense than the liquid
surrounding it. Buoyancy is simply an upward acting force caused
by the fluid. Archimedes was the first person to dissect this
phenomenon and stated what is now known as Archimedes’ Principle
“Any object, wholly or partially immersed in a fluid, is buoyed
up by a force equal to the weight of the fluid displaced by the
object.” Note that one packet of an artificial sweetener is
approximately equal in sweetness to about three packets of sugar
and the artificial sweetener weighs less. The regular soda has
more solids (soft drink ingredients and sugar) dissolved in the
liquid than the diet soda so it is denser than the water
surrounding it in the aquarium causing it to sink, and the diet
soda has less solids dissolv