Why does a marble in a merry-go-round move towards the edge? When the marble is viewed from with respect to the ground, it experiences a net inward acceleration, and hence force. However, when the marble is displaced slightly, it moves towards the edge. Why? My first answer would be centrifugal force, but isn't it fictitious? 
EDIT: 
The marble isn't the center of the conversation here. It's the outward force. The marble and the merry-go-round can be substituted with just about anything. A car on a bend, a child being spun around by someone or a centrifuge. My question is simply, why does any of these "things" get pushed outwards. A simple answer would be centrifugal force. But isn't that fictitious? 
The reason why I asked about the marble and merry-go-round is because of a thought experiment involving the two in Physics by Resnick and Haliday. 
 A: Imagine first an object with perfect circular motion (on the left in the image below) - a ball on the end of a rod for example. It starts with some initial velocity (green line), the radial acceleration (red line) varies this velocity such that it continues along a circular path.
Some none perfect transfer of the force - your marble on a merry go round, for example - would experience the same radial acceleration but not sufficient that it removes all component of the objects velocity in one direction. 
In the image below the ball starts with it's velocity entirely in the $y$ direction and then, at the top, the ball has it's velocity entirely in the $x$ on the left hand side but the right still has some component in the $y$ - hence the ball moves a little in the $y$ direction too. 

A: Objects are not pushed outwards relative to the ground. There is no outward force in this frame of reference. If the object is suddenly released (as in a catapult) it flies off at a tangent wrt the ground, with the velocity it had at the instant of release (Newton's 1st Law). This motion requires no force. This velocity is perpendicular to the initial radius, so the object will eventually cross the circumference of the circle.
In the frame of reference of the rotating platform, the object gets further from the centre, but it also veers off to one side tangentially. (Looking down on a platform rotating anti-clockwise, the object veers clockwise.) The radial component of this motion is attributed to Centrifugal Force, while the tangential component is attributed to the Coriolis Force.

Source: Hyperphysics website.
