Infinity is a mathematical concept not a physical one.
Oh really, tell me then. how far can you travel before you reach the end. And as far as gravity goes, we know it exist, we can calculate gravity force from the amount of mass of a subject, yet, we do not know why it exist. We do not know what causes it, why does greater mass attract lesser mass?
See post 27
Infinity is not a distance just like 3 is not a distance both are mathematical concepts. For example there are 3 feet in a yard but 3 is not a distance. If I was doing Calculus right I would be using concepts of infinity it may or may not have anything to do with distance or any measurement.
The attraction is mutual. The apple exerts a gravitational pull on the Earth, proportional to its mass.