Here's why:

* The First Law of Thermodynamics states that energy cannot be created or destroyed, only transferred or transformed.

* This fundamental principle governs the behavior of energy in all systems, from the smallest atom to the largest galaxy.

Examples of how it applies:

* Chemical reactions: Energy is conserved during chemical reactions. For example, in combustion, the chemical energy of the fuel is transformed into heat and light energy.

* Mechanical systems: The energy of a moving object is conserved. For example, when a ball is thrown, its kinetic energy is converted to potential energy as it rises and then back to kinetic energy as it falls.

* Biological systems: Living organisms use energy from food to maintain life processes. This energy is transformed and transferred within the organism.

Therefore, the First Law of Thermodynamics is a universal principle that applies to all systems in the universe.