Well, it could, but it would be rather little. You can calculate the gravity affecting the marble using this formula:F1= F2= g x m1 x m2/r^2So because you are asking a marble, the marble will be mass 1. Because the earth is the other object, it will be mass 2. So seeing that the marble is rather small in mass, therefore, gravity or the weight of the marble wouldn't really affect its momentum.