exchemist
Valued Senior Member
The small steps explain the most common phenomenon that we can observe: inertial motion. Until now, the only explanation of inertial motion was: inertial motion is due to mass. Massive bodies go straight line and do not change speed because they resist an acceleration when we try to accelerate them. Thats all there is, and its not a physical explanation, its only a deduction from a principle. We are not accelerating them when they are on inertial motion, and they are not resisting to any force, so why are they going on moving?
We cannot detect either what causes gravitation, but we are looking for it because we can observe gravitation at work. Meanwhile, we develop theories that help us understand gravitation. Why not develop theories that can help us understand inertial motion? After all, we can also observe it at work, no? SR was about inertial motion, and it was also about light, why not try to improve it?
But it IS a physical explanation, and one that is intuitive. A "heavy" object requires a bigger force to change its direction of motion. Why would that need further explanation? It is almost a definition of mass.