|MadSci Network: Physics|
National Geographic has an item for sale: an hourglass inside a tube of water. In trying to guess why the hourglass rises in the tube, as the sand in the glass falls, we came upon another question: which has greater buoyancy - a container filled with air, at normal air pressure, or that same container with a vacuum? I'm the answer to our question has to do with the air being compressed (slightly) under the sand, and decompressed, sightly, above the sand.
Re: What is the difference of boyancy between air and vacuum filled containers?
Try the links in the MadSci Library for more information on Physics.