> Okay, fast thought experiment. Take a person, put him in scuba gear (so he won't suffocate) and then lock him in a big airtight plastic baggie. Put the plastic baggie on the scale. It's a /big/ scale, so none of the baggie is hanging off of the sides of the scale. The person's feet, for example, contact the scale just through the plastic.
>
> Now the person jumps. (The bag is big enough that even when the person jumps all the way up, the bag still touches the scale.)

Heh. Put some scuba gear on some time and try jumping. Falling over is about as close as you'll get. I think somebody calculated the total weight of all the stuff an average scuba diver wears as something like 60-70 kilos.

Brunnen-"maybe we could fill the bag with water...and put a dead fish of undetermined density in there too..."G