You don't feel a sideways gravitational pull from the person standing next to you, for example, or even from bigger objects like cars or buildings. However, this force between objects is usually too small for us to feel. Technically, any object with mass exerts a gravitational force on other objects. In 'classical' or 'Newtonian' mechanics, gravity is described as a force that acts between two objects, pulling them together. What does all this have to do with gravity and black holes? Read the All of the curvature is due to the much heavier ball in the middle. This is because the marbles are not heavy enough to introduce any additional curvature in the fabric. When you rolled two marbles at once, you probably noticed that (as long as they didn't collide), they did not really affect each other's motion. However, if it gets too close to the center, the marble gets sucked in and cannot escape.

As long as the marble doesn't get too close to the middle, you could probably still roll it from one end of the fabric to the other. When you try to roll the marble in a line, it follows a curved path. Now, it's impossible to get the marble to hold still - it always rolls towards the middle. No surprise there! When you place a heavy ball in the middle of your fabric, it causes the fabric to curve downward. If you roll the marble across the flat fabric, it moves in a straight line. When you hold the fabric flat and put a marble on it, it doesn't move. You might think the results of this project are obvious at first. Do the marbles appear to affect each other's motion (assuming they do not collide)?

Try rolling two marbles on the fabric at once.

Hole 7 gravity lab