Why does the second law of thermodynamics not apply to the universe

The 2nd law does apply to the universe as a whole.
Sounds like you learned the meme definition of entropy. Spend some time understanding what entropy is and your question will be answered.

>>7754841

Gravitational clumping lowers entropy.

>>7754870

No it don't. Clumping releases photons so the entropy still goes up overall.

>>7754841
>I mean, under the big bang theory, it goes from extremely small, compact, homogenized, and featureless to, well, this; all sorts of orders, classifications, distinct types of matter, irregular forms, separate structures. That seems like a patent DECREASE of entropy

Wrong way around. That's a massive increase in entropy.

Entropy can be essentially thought of as a measure of information. (In fact, there is a deep unity between thermodynamics and information theory.) The less information something contains, the less its entropy.

This is why, for instance, a uniform perfect crystal at absolute zero has no entropy - because it is totally uniform, featureless, and immobile, and thus encoding no information.

So the featureless, homogenized origin of the universe has incredibly low entropy, and the messy, lumpy, chaotic modern universe has plenty.

>>7755148
>featureless
That seems like a lack of information, aka high entropy.

>>7754841
The big bang was a very low entropy state.
>>7755568
Nope. Imagine a big, random jumble of particles, like in a gas. For a given macroscopic state, there will be millions of microscopic state - if you jiggle a few atoms around, the macroscopic phenomena stay the same. Hence it requires a great deal of info to specify the exact state.

For an ordered crystal, changing a few atoms will have a massive effect on the macroscopic properties, destroying the crystal structure. There is essentially just one microscopic state for every macroscopic state, so we can specify the exact microscopic state using a handful of classical macroscopic variables. We don't need to go plotting the position of every single particle. In the case of a crystal, you could also use information about the number of particles, the crystal structure and overall shape. Normally in thermodynamics one works in the infinite volume limit (thermodynamic limit), so the notion of shape and number of particles disappear. For example, if I tell you that you have atoms of type A, and B, and that they are arranged in fcc lattice, there is just one microscopic state that can come from this.

If you just think of entropy as a measure of disorder, then an empty, perfectly symmetrical chunk of space is clearly lower in entropy than a big bubble of space filled with random splashes of matter and wrinkly spacetime geometry.

>>7754841
entropy =\= disorder, you pop sci faggot

>>7754841
you know that putting work (energy) into a system can turn disorder (entropy) int order. I.E. tree growing because of sunlight

>>7755750

I second this.

Entropy is a function of the number of microstates: different configurations of a many-point system such that they all result in the same macroscopic state. This is from the exact definition of entropy (from the Boltzmann Hypothesis).

Putting all the Universe's energy in a very small space means there is a very limited number of particles that can exist, and all of them are going to be in the same ultra-high-energy state, more or less. That means low number of microstates = low entropy.

When you expand the Universe, you can now have so many different arrangements of particles with so many different energy distributions, all resulting in the same macroscopic state (for example, if you swap the energies of two hydrogen nuclei inside the Sun or two stars in a galaxy, there would be no noticeable difference in the behavior of the Sun or said galaxy). That's a very large number of microstates = large amount of entropy.

>>7755750
Not that guy, but I think I understand microstates better now. Thanks and well put