Misconception:
Astronauts are weightless in space because they are far enough away from Earth so as to be unaffected by Earth’s gravitational pull.

http://www.nasa.gov/images/content/106709main_image_feature_253_ajh4.jpg
http://www.nasa.gov/images/content/106709main_image_feature_253_ajh4.jpg


Source
The source of this misconception is actually a little difficult to pinpoint, but it would seem that the source is probably nothing more than the fact that no explanation is provided when we are exposed to images and video of astronauts “floating” inside space shuttles and whoever is presenting the images describes the astronauts as “weightless”. The terminology we use to describe the situation is very misleading because we learn early on that “weight” is the pull of Earth’s gravity on our bodies, so the obvious conclusion when we describe astronauts as “weightless” is that they have no weight, or that they are no longer experiencing the pull of Earth’s gravity.

Explanation
Astronauts are able to orbit Earth in shuttles precisely because gravity is very much still acting on them. At orbiting altitude the gravitational force on astronauts and their shuttle is approximately 90% of what it is on Earth, so a 200-lb. astronaut still weighs around 180 lbs. The astronaut and shuttle, rather than floating, are actually in a state of free-fall – much like passengers in an elevator when the cable snaps. The elevator and passengers are falling at the same rate, so the passengers appear to float in the elevator because the floor of the elevator is no longer pushing up on their feet. They are certainly not weightless. Their weight is why they are falling. In the case of the astronauts, they and their shuttle are constantly falling toward Earth. But, like a projectile, they are not just traveling vertically. They are also traveling horizontally – fast enough that their trajectory matches the curvature of Earth and they continuously fall past it. Just like a string tied to a rock keeps the rock from flying away when you whirl it around your head, gravity acts as a string and keeps the shuttle and astronauts falling toward Earth so they don’t fly off into space.

http://www.school-for-champions.com/science/images/force_centripetal-rope.gif
http://www.school-for-champions.com/science/images/force_centripetal-rope.gif


Solution
The simplest solution is to change the way we describe space flight. If we avoid the term “weightless” to describe astronauts, it would be significantly less likely that people would jump to the conclusion that they were not experiencing gravitational pull. Certainly every news anchor covering a space travel story would not need to launch into an elongated explanation as to why the astronauts appear to float, but using more appropriate terminology to reinforce the proper explanation would help the average viewer/listener avoid jumping to incorrect conclusions. While a simple change in terminology would not solve the problem of a general misunderstanding of gravity by the populace on the whole, a change in the way we describe the situation would help stop the constant reinforcement of this particular misconception. Widespread education on the particular topic of gravity would be required to solve the problem completely, but tearing down reinforcements of the misconception is a great first step.