Even ask them about fairly simple and prosaic things about gravitational acceleration, the apparent lack of gravity in free fall (when of course you wouldn't be falling if there were really no gravity) and you will see that most people will understand little and many will outright dispute a lot that we now know about gravity. (religion.blogs.cnn.com)
For future long distance space missions such as Mars, which will take an estimated three years for the round trip, scientists want to study the effect of lack of gravity on human bones, the heart and other organs. (educationworld.com)