In the first seal of the Law, all things are impermanent, “all things” means all physical and mental phenomena. Everything is constantly changing, and Shakyamuni made this statement of the ephemeral nature of all things first as a fact that people must experience in daily life. Clearly the operations of the mind are fluid, but even such apparently stable objects as rocks and trees are constantly undergoing change. From the minutest physical particles to the largest celestial bodies, nothing ceases to move for a moment. Modern scientific theories about this kind of flux make it easier than in the past to accept the idea that all things are impermanent.
Basic Buddhist Concepts