Reading: Develop the model
The weightlessness puzzle
A spacecraft circling Earth is not beyond the reach of gravity. Gravity supplies the inward acceleration needed to continually bend the craft's path. Inside, astronauts and their cabin accelerate together under gravity, so a freely floating object is not pressed against the floor as it would be on a supported surface. This condition is called apparent weightlessness, not zero gravity.
Free fall can follow a curve
An object falling near Earth's surface speeds downward when released from rest. Give a hypothetical object sufficient sideways speed and a gravity-directed acceleration, and its path can curve around Earth. The idea of orbit as continuing free fall connects a familiar falling object with a circular-orbit model. The model depends on initial sideways velocity as well as gravity; it does not mean every fall becomes an orbit.
Radial direction matters
At any point of a uniform circular orbit, instantaneous velocity is tangent to the circle. Gravitational acceleration points toward Earth's center. The magnitude can remain constant for a perfect circular path even while the vector directions keep changing. In an elliptical orbit, both distance and speed change; our classroom circle calculator explicitly does not represent that general case.
What could spoil the model?
Air drag, propulsion, Earth's nonspherical gravity, other celestial bodies and collisions are missing from an ideal two-body circle calculation. Low Earth orbit still experiences residual atmosphere. Numerical predictions are teaching models, not flight design or astronaut safety procedures.