The action begins with the sphere being about two feet in diameter. The sphere begins to rapidly race straight away from the viewer. The sphere also increases its size just as rapidly. The net result is that the visual image of the sphere always remains the same.
Time passes. The sphere becomes as big as a house, then as big as a town, then as big as the moon, and then as big as the sun. This might continue.
The picture does not change, but the perception may continually change if the viewer wills the action to be there or believes that it must be there. Of course, very few of us were brought up to believe that white things in the sky might behave this way, but we still need to be careful. Perceptions are partly the result of something we do and are prepared to do. They are not merely the direct result of the things that we observe.