Question

Why is entropy of the universe increasing?

Answer 1

The idea of entropy refers to the spontaneous changes that occur in everyday phenomena, as well as the universe's inclination toward disorder. In the year $1850$ , a German physicist named Rudolf Clausius proposed this idea.

Complete answer:
Entropy is defined as a measure of randomness or disorder of a system.
Energy always flows downhill, leading to an increase in entropy. Entropy is the spread of energy, and energy spreads out as much as possible. It flows from a hot (highly energetic) region to a cold (lowly energetic) region on its own.
As a result, energy is dispersed evenly between the two regions, and the two regions have temperatures that are equal. On a much greater scale, the same process occurs. Every star, including the Sun, emits energy into the universe.
The stars will eventually cool down, and the heat will have dispersed to the point where there will be no warmer or cooler objects. It will be the same brutally cold temperature throughout. There's no need for anything to modify its behaviour once everything is at the same temperature. The universe will have completely run down, and the entropy of the universe will be at its highest point ever.
The entropy ${S_1}$ of the hot region is defined as
${S_1} = \dfrac{q}{{{T_1}}}$
Therefore, during the energy transfer, the change in entropy is
$\Delta S = {S_2} - {S_1} = \dfrac{q}{{{T_2}}} - \dfrac{q}{{{T_1}}} = q\left( {\dfrac{1}{{{T_2}}} - \dfrac{1}{{{T_1}}}} \right)$
Since ${T_2} < {T_1},\dfrac{1}{{{T_2}}} > \dfrac{1}{{{T_1}}}$ and $\Delta S$ is positive.
The system's total entropy increases. Because energy never flows in the opposite direction, the universe's total entropy is always increasing.

Note:
In an isolated system, the more disorder there is, the higher the entropy. Entropy increases when reactants break down into a larger number of products during chemical reactions. A system with more randomness has a higher temperature than one with a lower temperature. It is evident from these instances that when regularity decreases, entropy increases.