Apollo 13: What is Weightlessness?

Weightlessness and How it Applies to Apollo 13

     Weight is defined as a body's relative mass or the quantity of matter contained by it, giving rise to a downward force. So when you look at the word weightlessness, it implies that there is a lack of gravity. This is impossible, because in order to get a lack of gravity, you need to get infinitely far away from any other object, as per the formula for the force of gravity, which is:

g= G * ((m1*m2)/(r^2)).

Before we proceed into what exactly weightlessness is, we better define weight in terms of forces.

Weight is not actually the force of gravity but actually the force normal to the force of gravity. The normal force is a contact force from the object one object is contacting, equal and opposite to the applied force. 

When talking about weightlessness, one must also mention orbital motion and "Zero-G." How do things stay in orbit when there is clearly only one force.

There is a velocity tangent to the orbit path and perpendicular to the acceleration. So long as the velocity is large enough proportionally to the acceleration, the object will continue orbiting in free-fall--as there is a net force implied by the acceleration. In essence, the object is "falling infinitely," or "falling around the object it is orbiting." And by virtue of it being in free fall, there is no normal force and as such there is weightlessness.

Overall, I would give the movie a GP, as director Ron Howard wanted the movie to be authentic in terms of the weightlessness.