#### Motor Daddy

**Valued Senior Member**

Say a plane is at rest on a runway that is at absolute rest. It accelerates up up and away to a constant velocity of 500 MPH and remains cruising at that velocity.

There is a person at the midpoint of the plane and a person with a ball at each end of the plane. Simultaneously each person accelerates their ball towards the mid point person. They each applied the same amount of force to the ball. The balls hit the midpoint person simultaneously.

The midpoint person says the balls were traveling in different directions at the the same velocity towards each other before they impacted him at the velocity of 100 MPH. He could not be more wrong. That is his illusion.

The person at the rear of the plane accelerated the ball to a velocity of 600 MPH, and the person at the front of the plane accelerated the ball to a velocity of 400 MPH. Both balls were traveling in the same direction at different velocities when they hit the midpoint observer.

The only way the balls could have been traveling in opposite directions is if the plane (mid point person) was at an absolute zero velocity.