Suppose a ball is thrown upwards, from the surface of the Earth. After some time, it will obviously fall down back on the surface. However, it would be deflected slightly to the sides of the initial point from which it was launched. From a person, on the Earth, this appears to be a fictitious force, called the Coriolis force, that is responsible for this deflection. However, I've learnt that this force arises because the observer is in a non-uniform reference frame i.e. the spinning Earth. Hence, they perceive this fictitious force.
However, for an observer in space, an inertial frame, how does one explain the deflection of the ball? Is it because of the ball's inertia, that it falls back to the same place, but the Earth has rotated a bit by then ? That is why it seems to be deflected in the direction opposite to the direction of rotation ?
Similarly, a compartment is orbiting a point and is connected by a thread. Inside the compartment, we have a human being. From outside, there is only the tension of the string, that acts as the centripetal force, causing the circular motion. However, it has been said, that the man inside the compartment, feels an outward deflection, that he attributes to the centrifugal force. The compartment itself does not feel any force, because it is stationary in its own frame, but the man inside feels this deflection.
How can the outside observer, explain why the man inside is feeling an outward deflection ?