Why do astronauts in the Space Shuttle experience weightlessness?

Astronauts in the Space Shuttle experience weightlessness because they are in a state of free fall. In orbit, the Space Shuttle and its occupants are moving forward at a high speed while also being pulled by Earth's gravity. This creates a situation where both the Shuttle and the astronauts inside are falling toward Earth, but because they also have sufficient horizontal velocity, they continuously miss it. This is known as being in orbit.

As a result, everything in the Shuttle, including the astronauts, is falling at the same rate. When in free fall, there is no normal force acting on the astronauts, which gives them the sensation of weightlessness. It's important to note that gravity is still present and acts on both the shuttle and the astronauts; it is just that the uniform acceleration downward results in the feeling of floating, as if there is no weight.

This contrasts with other answers that suggest different reasons for weightlessness, such as being in a vacuum, which does not inherently cause weightlessness, or the use of anti-gravity suits, which do not exist. The misconception that gravity does not affect them in space is also incorrect, as gravity is indeed the force that keeps the shuttle in orbit. Thus, the correct answer highlights the true reason behind the experience