I just assume that in addition to the ability to ask a question on Quora, you also have the ability to search for meanings of words on the Internet (e.g. with Google).I then conclude that you have done so and have not found a satisfactory answer. In addition, I do not have to contribute links to sites such as Wikipedia, or Berkeley, where these things are explained in depth.
Then, there is still an option left:
Entropy is actually ‘ diffusion to the maximum ‘.This is simplistic, but a good start to learn to understand it.
Imagine a bottle of water (completely pure water).Now imagine that you throw a scoop of salt in it (for the one who knows, don’t come up with that after saturation sinks the rest to the bottom, that doesn’t matter).
Salt is a crystal and has the property to exert influence on the fabric around the crystal.The crystal falls apart and forms charged particles that try to ‘ levelling ‘ themselves with the fabrics around it. This causes the ‘ salt particles ‘ (ions) to move as far as possible from each other between the surrounding fabric.
Entropy goes a step further.
Everything that is arranged close to each other will eventually fall apart and be arranged far from each other. Even worse, everything will go back to a state in which it has no power to exert effect on anything else.
This is also why life by definition ends in entropy (maximum dispersion) where the body by loss of all its internal processes and energy/movement decays to basic pieces (cells fall apart and so on) and distributes themselves over the environment.
Similarly, in the universe, where energy is needed for a force and a force eventually loses its amplitude (range).So everything falls that momentum loses apart. Also the Earth, the Sun, the galaxy, the cluster, etc., will eventually come apart by loss of energy, that they lose their integrity and lapse into particles that drift apart until they all reach the maximum distance of have achieved each other.
“But the universe still expands?Surely there is never a maximum distance? ‘
Yes and No.Why does the universe expand? By the initial energy. As long as that energy is moving, the universe will be in motion and expand. When the energy is insufficient to move the matter, the expansion will stop and what is going to happen is not yet clear. A ‘ cold death ‘ in maximum of entropy or a ‘ shrinking universe ‘, in which the matter is reunited by the basic force, namely attraction, is not certain. After all, a force is energy and if there is no more energy, there is also no force, not nuclear, not electromagnetically and also no more attraction.
But entropy is a phenomenon that is clearly demonstrably in closed systems (and how infinitely our universe may be, it behaves very well as if it were closed).