As far as I know, nothing can ever die. No thing can die. All things, or forms, can and will change. All things are forms. All forms are temporary, a word associated with temporal, or the temporal realm.
All things are comprised of energy. The first Law of Thermodynamics states: Energy is conserved (the quantity of energy) or remains symmetric under all transformations (paraphrased). So all the energy that ever was in the Universe is still in the Universe. Energy isn't spent. There is no energy 'Life Span'. There is an energy 'Life Cycle' - if we choose to describe it in terms.
All things are energy. People are energy. So, Life span, or Life cycle?
The closest to what might be called an answer to the questions "What is eternal? Are we eternal?" might be found in the laws of thermodynamics. Thermodynamics deals with energy.
laws of thermodynamics
any of three principles governing the relationships between different forms of energy
- The first law of thermodynamics (law of conservation of energy) states that the change in the internal energy of a system is equal to the sum of the heat added to the system and the work done on it
- The second law of thermodynamics states that heat cannot be transferred from a colder to a hotter body within a system without net changes occurring in other bodies within that system; in any irreversible process, entropy always increases
- The third law of thermodynamics (Nernst heat theorem) states that it is impossible to reduce the temperature of a system to absolute zero in a finite number of steps
- Also called: zeroth law of thermodynamics the principle that if two bodies are each in thermal equilibrium with a third body then the first two bodies are in thermal equilibrium with each other