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.
When we pass Jupiter or Mars or Saturn, for example, these more outward planets in orbit â which move more slowly than Earth in orbit â appear to reverse course in our sky for a couple of months. A schematic of how retrograde motion works when Earth (T) passes an outer planet (P) as they both orbit the sun (S). The changing viewing angle from Earth makes the projection of the planet against the celestial sphere (A) move backwards (A2-A4) as we pass the slower planet. Credit: Wikipedia user Rursus.