If you kick a football it will accelerate away from you, but only while you are kicking it and it does that in both cases. And if you have got as far as F=ma th

If you kick a football it will accelerate away from you, but only while you are kicking it and it does that in both cases. And if you have got as far as F=ma then you will presumably be bright enough to apply it to gravity and the shape and material of any hill as well as the action of your foot. Besides, the people who are saying that the system is too complex to make a prediction are not saying that there will be no effect. There is an increase in the energy going into this system and saying that things are so complex that we should bet on there being no effect is not saying that there is no global effect, but that there is a global effect that more or less exactly counterbalances the initial effect and that to me sounds like wishful thinking from the viewpoint that nature is somehow magically in balance.