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Which weighs more? A ton of feathers or a ton of lead?


It's an old puzzler regarding the comparative weights of a ton of lead and a ton of feathers, and some people think they always know the answer. But maybe it's not as obvious as it might seem.

To a simple view, it seems a deep question. Obviously the feathers are very light and yet there's a whole ton of them so that is very big. Feather beds can weigh quite a lot, but a ton of feathers would be a truckload. Lead, in contrast, is about eleven times heavier than water for the same volume, so a ton of lead can be imagined as a metre square by 9cm thick. Yet, although the lead is very "heavy", a concept known as "density", a ton of it is not very big in the space it takes up.

A practical approach would be to get a weighing scale balance and set it up with a ton of lead on one side and a ton of feathers on the other. This would not be easy, as the choice of instrument would be a puzzling question in itself. However, as both the ton of feathers and the ton of lead both weigh "a ton", the expected result would be that they weigh THE SAME!

But then, that's science, isn't it?! Gives a pure result. Some people might instead prefer to argue the point, perhaps having a fierce debate that they were right and the other person had got it wrong. For example "The lead has GOT to weigh more because it's heavier than feathers!" or "A ton of feathers is so big that it MUST weigh more than the lead!". Others would take a more equalist view, saying that everyone's point of view is valid and that if anyone wants to believe that the lead or the feathers is heavier, then that is true from their perspective. Indeed there are people who would say that it is entirely a matter of personal belief which weighs more and that faith can give a true personal measurement of the feathers or lead situation and that scientific measurement is irrelevant.

I'm with the scientific approach myself and in such a situation I would be keen to get a set of scales to prove the fact and defy various people's faulty beliefs on this kind of thing!

Also, if it turned out that a ton of feathers and a ton of lead didn't weigh the same, it would require further investigation!

Now I'd guess there will be some people thinking this is all a bit silly, as it's obvious that a ton of feathers and a ton of lead weigh the same because they've read it in a book, or because it's just "true". But, how about if the experiment was conducted on the moon?! Would the feathers and lead still weigh the same?

Curious as it may seem, there is a discrepancy. If the initial ton of feathers and the ton of lead are weighed on the earth and balanced up to be the same, and then the experiment is taken to the moon and balanced up again, the feathers now outweigh the lead! With this kind of thing it's no good trying to explain it away as experimental error! The feathers weigh a measurable amount more than the lead.

This is not because the gravity is one sixth on the moon. There's still "a sixth of a ton" on each side of the balance. The reason for the difference is that on the moon the feathers no longer have the buoyancy of the air which they had on the earth. (If you have doubts about this, consider it's the opposite effect of what would happen if the experiment were performed underwater, where the lead would sink about as expected and the feathers would weigh not much at all, and that's even before they floated off). These effects are put to use with the idea of Density Scales


Other stuff: Orbits of satellites in space , floating of a snooker ball on a pint of mercury , How long is a piece of string? , Pescu , Space , mass or weight , etc. Truths , misconceptions , and a great many other things. Oh really?