Why does an astronaut feel weightless while orbiting the Earth in a space ship despite the presence of gravity?

Introduction / Context:
Astronauts in orbit around the Earth often appear to float freely inside their space craft, and this situation is commonly described as weightlessness. Many people wrongly believe this means there is no gravity in space. This conceptual physics question tests the correct explanation based on orbital motion and free fall rather than the mistaken idea of zero gravity.

Given Data / Assumptions:

• The astronaut and the space ship are in a stable orbit around the Earth.
• Gravitational attraction from the Earth is still present at orbital altitude, only slightly weaker than at the surface.
• There is no physical contact with the ground or any support surface providing a normal reaction force.
• Air resistance is negligible inside the sealed cabin, and there is no significant thrust acting most of the time in stable orbit.
• We are interested in the apparent weight felt by the astronaut, not in the actual gravitational force magnitude.

Concept / Approach:
Weight is the force with which a body presses on a support, usually equal to the normal reaction exerted by that support. In orbit, both the astronaut and the space ship are in a continuous state of free fall around the Earth due to their orbital motion. They are constantly falling toward the Earth, but their tangential velocity keeps them moving around it. Because astronaut and ship accelerate together, there is no normal reaction on the astronaut feet or body, so the astronaut feels weightless. Gravity is still acting, but the apparent weight is zero.

Step-by-Step Solution:
Step 1: Recognise that in a circular orbit, gravity provides the centripetal force needed to keep the space ship and astronaut moving in a curved path.Step 2: Both astronaut and space craft have the same acceleration toward the centre of the Earth because both are acted upon by the same gravitational field.Step 3: Since there is no solid support resisting this common free fall, the normal reaction on the astronaut from the floor or walls is essentially zero.Step 4: With no normal reaction, the astronaut experiences no sensation of weight, so an apparent weightlessness is observed, even though gravity is still present.

Verification / Alternative check:
As a check, imagine briefly firing the rocket engine to produce an upward acceleration greater than gravity; the astronaut would then feel heavier as the normal reaction increases. In contrast, if the engine produced just the right upward acceleration to balance gravity in a stationary hover, the astronaut would feel normal weight. The orbital situation is different because there is no upward thrust balancing gravity; instead, both astronaut and ship are freely falling. Experiments on parabolic flights, which create short periods of free fall inside an airplane, show the same weightless sensation, confirming that free fall is the key reason.

Why Other Options Are Wrong:
Option b is wrong because gravity at typical orbital heights is still a large fraction of surface gravity. Option c is incorrect since inertia alone does not remove weight; it just resists acceleration. Option d is not accurate for a stable orbit, because the rocket engine is usually off and does not exactly cancel weight. Option e is irrelevant, since magnetic field has almost no effect on the weight sensation of an astronaut.

Common Pitfalls:
Many students confuse zero gravity with zero weight, assuming that if a person floats then gravity must be absent, which is not true. Another mistake is to think that being far from Earth automatically removes gravity, even though gravitational influence extends very far. It is essential to distinguish between gravitational force and apparent weight, which depends on the normal reaction from a support. Remember that in orbit the astronaut is in free fall, sharing the same acceleration as the space craft, and this is what produces weightlessness.

Final Answer:
Because the space ship is in continuous free fall due to its orbital motion around the Earth.