Imagine for a moment that ideas have mass. This means they would be governed by the laws of motion.
It takes effort to put something into motion. Once it’s moving it will tend to keep going at the same speed in the same direction until another force is applied to it.
Ideas can gain momentum, seemingly take on a life of their own. Just remember, if it’s your idea and you’re not steering it, it may not end up where you expect or want it.