if the universe was empty and there was 2x 60kg balls, one at either side of of an otherwise empty universe, its claimed they would start moving towards eachother due to gravity and eventually meet

How could this happen, how is gravity able to give instructions to both objects over such a huge distance, how does one ball even 'know' that the other exists before it starts moving?

apparently it could take something like 100 billion years for these 2 balls to hypothetically meet in theory

does the move begin 'instant' (even if its only like 1 metre a year or something) or would it take a few years for them to register eachother's existence and begin the slow crawl to eachother?

is gravity's actions restricted by something similar to the speed of light, ie the 2 balls wouldnt know the other exists for the first few billion years and remain stationary