Common Science 



FIG. 38. The horse goes forward by pushing backward on the earth with his feet. 



you took forward, just as the big ball that a performing 

 bear stands on turns backward as the bear tries to walk 

 forward. 



The usual way of saying this is, " Action and reaction 

 are equal and opposite." If you climb a rope, the 

 upward movement of your body is the action ; but you 

 have to pull down on the rope to lift your body up. 

 This is the reaction. 



Without this law of action and reaction no fish could 

 swim, no steamboat could push its way across the water, 

 no bird could fly, no train or machine of any kind could 

 move forward or backward, no man or animal could 

 walk or crawl. The whole world of living things would 

 be utterly paralyzed. 



