Astronomy Practice Exam

Which condition contributes to astronauts experiencing weightlessness?

1. The absence of gravity

2. Being in free fall

3. A decrease in speed

4. The design of the spacecraft

The correct answer is: Being in free fall

Weightlessness experienced by astronauts is primarily due to being in free fall. When a spacecraft orbits the Earth, it is essentially falling towards the planet due to gravity, but because it is also moving forward at a high speed, it keeps missing the Earth. This creates a condition where both the spacecraft and the astronauts inside are accelerating downwards at the same rate as the gravitational pull. As a result, they do not feel the normal sensation of weight that we experience on the surface of the Earth. In free fall, all objects fall at the same rate regardless of their mass, resulting in a microgravity environment inside the spacecraft. This is what allows astronauts to float and experience what is commonly referred to as zero gravity or weightlessness, even though gravitational forces are still acting on them. The other conditions listed—absence of gravity, a decrease in speed, and the design of the spacecraft—do not accurately describe the phenomenon that leads to the sensation of weightlessness in orbit. Gravity is still present, and it is the specific motion of the spacecraft in free fall that creates this unique experience for astronauts.