global warming definition. The term attached to the notion that the Earth's temperature is increasing due to the greenhouse effect. Note: Whether global warming is actually happening is a subject of scientific debate.
Like jet airplanes, space rockets work on a principle called action and reaction (another name for Newton's third law of motion). The massive force (action) generated by hot gases firing backward from a rocket's engines produces an equal force (reaction) that pushes the rocket forward through space.
Also as you will see later, the Turtle class inherits a method named forward() from its immediate superclass named SimpleTurtle. This method causes the turtle to move forward by 100 pixels. Thus, the third statement in Listing 1 causes the turtle to move from the center of the world to the position shown in Figure 1.