The total amount of energy in the universe is fixed, but

disorder is increasing

The correct answer is option 3. disorder is increasing.

Let us delve into the concept of the fixed total amount of energy in the universe and why the increase in disorder (entropy) is the correct explanation.

Conservation of Energy:

The first law of thermodynamics states that energy can neither be created nor destroyed in an isolated system. This principle ensures that the total energy content of the universe remains constant over time. Energy can, however, change forms. For instance, energy can transform between potential energy (such as gravitational or chemical potential energy) and kinetic energy (energy of motion), as well as between thermal, electrical, and other forms of energy.

Entropy and Disorder:

Entropy (\(S\)) is a measure of the disorder or randomness in a system. It quantifies the number of microscopic configurations that correspond to a macroscopic state of the system. The second law of thermodynamics states that the entropy of an isolated system tends to increase over time, or at best, remain constant in reversible processes. This law implies that natural processes lead to an increase in disorder or randomness within the system and its surroundings.

Connection to Options:

Option (1) Matter is increasing: The total amount of matter in the universe can change over cosmological timescales due to processes like particle creation or annihilation. However, this does not directly affect the fixed total amount of energy in the universe.

Option (2) Gravitation is decreasing: Gravitational potential energy can convert into kinetic energy and vice versa. However, gravitational interactions do not affect the fixed total amount of energy in the universe; they merely involve energy transformations.

Option (4) Lightning is increasing: Lightning is a localized phenomenon involving the conversion of atmospheric electrical potential energy into other forms like heat, light, and sound. While significant locally, lightning events do not influence the fixed total amount of energy in the universe.

Entropy and the Universe's Energy:

The increase in entropy (disorder) is directly related to the fixed total amount of energy in the universe. As energy undergoes transformations and interactions, entropy tends to increase because energy disperses and becomes more evenly distributed among particles and systems.

This increase in entropy aligns with the fixed total energy because while the total energy content remains constant, its distribution and the number of possible arrangements (microstates) of energy tend to increase, reflecting an overall trend towards greater disorder.

Conclusion:

The correct statement about the fixed total amount of energy in the universe is that disorder (entropy) is increasing. This is because entropy's increase is a direct consequence of the second law of thermodynamics, which governs the behavior of energy in isolated systems. While energy is conserved, the processes that occur tend to increase the overall disorder or randomness within the universe, reflecting the irreversible nature of natural processes governed by entropy. Therefore, option (3) disorder is increasing provides the best explanation in the context of thermodynamics and the fixed total amount of energy in the universe.