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.
Momentum describes how strong a moving thing is. Things that aren't moving have no momentum. Moving things have less momentum if they are light or moving slowly, and more momentum if they are heavy or moving fast. Because of momentum, a planet or a star that is moving in space will generally keep moving in the same direction unless something happens to push it another way. The Sun keeps going around the Milky Way, and the Earth keeps going around the Sun.