Retrograde Motion Study

If you have trouble understanding retrograde motion, you aren't alone. The planets seem to move forward for a while, and then some may seem to stop, turn around and begin to go backwards. Eventually, they hit the brakes again, and turn around and go forward again. It certainly looks confusing. If you forget for a moment about bodies in space and use examples right here on Earth, the strange motion of the planets will be a little easier to understand. It all depends upon your "point of view."

If you were to ride in an automobile that drove so smoothly that you had no sense of motion, you might experience the sensation more fully, but you can experience enough in any vehicle.

When your car is parked alongside another vehicle at a stop light, you can check this out for yourself. Look at the car next to you. If, as you watch the other car, your car moves forward sooner at the green light than they do, they will seem to move backwards. They didn't put their car in reverse, but from your "point of view," they moved backwards.

Consider the solar system as a very large example of an automobile race track. All of the cars are in their various lanes...some were lucky, and got inside lanes, closer to the sun. They will be able to go around the sun in much less time than those planets that had to take the farthest, outside lanes. You are in the third lane out from the sun. The cars in the first two lanes, a Lincoln Mercury and a Toyota Venus will travel much faster than you will. You will travel a little faster than the Jeep Mars Rover, and those cars in the outside lanes, such as the Pontiac Saturn and the Chevrolet Jupiter will travel much slower than you.