Golden Train on Springfield Squidport

"anaquarind;1579227" wrote:
Well, I didn't want to get into this, but here goes...

Actually a pound of gold (or stones, or lead) weighs more than a pound of feathers. I learned this on day one from my university physics professor. No tricks about this pound vs. that pound, just the application of Archimedes' Principle.

A pound is a measure of mass, not weight. The pound is defined against the kg, and for the remainder of this discussion I'll switch to the metric system (sorry, I'm Canadian) which will also nullify the troy-pound issue. Mass is a measure of "the amount of stuff" (in kg or pounds) and always stays the same no matter where you are, but weight is the downward force exerted by gravity (measured in newtons) and changes with location. For example, if you had a 1kg of feathers in space, it would still be 1kg, although it would have no weight.
Measuring the actual weight of a kg of feathers on earth would require the conversion of 9.8N/kg, so 1kgX9.8N/kg=9.8Newtons. The weight of a kg of gold would be 1kgX9.8N/kg=9.8Newtons... so they're the same right? Well, yes but it doesn't account for the counteracting force of buoyancy. Archimedes' Principle basically describes buoyancy in a fluid environment. The more volume an object displaces, the greater the upward force would be. It's the reason things float in water - if this upwards force is stronger than the weight pulling things down, things will float in water. Although you don't think about it, air is also considered a fluid environment, we just don't see helium balloons often enough to think about it. Since feathers take up more volume, Archemedes' Principle states that the upward force is greater than something small and dense like gold. So the 9.8Newtons of weight in feathers would be offset more by its buoyancy than the gold, so the gold weighs more.
(It's difficult to visualize, but think about weighing the pound of gold and feathers on land (for the sake of this argument let's say you measured weight in a complete vacuum where the same mass actually means the same weight), then trying to do the same thing underwater. Your feathers would probably float or at the very least weigh a fraction of what they do on land. Your gold would show up "weighing" much more. The same thing happens on land, except to a lesser degree, but the earth's atmosphere still acts like a fluid, and the same buoyancy principles apply.)

I've got to know... what is your educational background? What type of work do you do for a living? I'm extremely impressed!