[quote name='Leon Transaxle' timestamp='1345218583' post='1775177']
I don't know.
Maybe light bulbs weren't the best example as the production of light is a inefficient process involving much heat as a by product so there are too many other variables in the equation.
Its the old candlepower unit that made me think of it.
[/quote]
Hmm, candelas and lumens and stuff? Hmmm, now you've got me unsure. Anyway, thats definitely a situation where perception comes into play, which was why I picked up on it.
As for the spuds, if you got some extra dense ones, then that would definitely be double the weight but not double the volume. (Although maybe that's just double the mass, not double the weight .. I dunno, that's physics, and I'm tired ...)