What a festive way to examine what happens to the heart in different gravitational situations! Small groups place a water-filled balloon in different locations (on a table top, in a tub of water, and held in a vertical position), drawing the shape of the balloon each time. An article is included about g-force and orthostatic hypotension, a fascinating read to help address Common Core State Standards for scientific literacy! Although this is a fun instructional activity, if you are short on time, it can easily be left out of the unit.