I've seen several reports that the entropy of the Universe at the time of the Big Bang was lower than it is now.
This seems impossible.
If we view entropy as a function of the number of micro states consistent with a given macro state, I cannot imagine how the entropy of what was basically a giant fire (at the time of the Big Bang) is not higher than the entropy of the current state of the Universe, which has stable planets, and life.
This is not inconsistent with the Second Law as a local phenomenon, it just says what observation plainly suggests -
Gravity caused the universe to become less complex over time, eventually supporting life.
On a smaller scale, the entropy of a fire must be higher than the entropy of a stable object, since the fire is obviously rapidly changing state, and therefore, presumably, is capable of being in a larger of number of states, while still being a fire. In contrast, a cup probably does change states somewhat, but obviously not as often, and obviously not on the same scale, in that the macro state of a cup is roughly constant.
As a result, common sense suggests that the entropy of a fire is higher than the entropy of a stable object.
Also, the temperature of the universe has consistently decreased over time:
So, why do physicists say that the entropy of the Universe around the time of the Big Bang was lower than it is today?
It doesn't make any sense, yet I've heard two reputable physicists make this claim, which is on its face almost certainly incorrect.
I'm wondering if someone can put forward a simple calculation that explains where this claim comes from, rather than simply quoting the Second Law, and saying it must be so, when available evidence strongly suggests otherwise.
This would involve taking the temperature at the time of the Big Bang, and expressing the entropy as a function of that temperature, and showing that entropy decreases as you move away from the Big Bang in time - and I don't see that happening.
The bottom line is that the universe is both colder and more structured than it once was. This means you can describe its structure with less information. So any statement that the universe has increased in entropy, or complexity, since the Big Bang, borders on nonsense, in my opinion.
It's also perfectly reasonable to assume the universe became more structured with time, since it started out so hot, that its kinetic energy overpowered any of the stabilizing forces like gravity, charge, etc.
You can pretend otherwise, but the reality is that gravity decreases local complexity over time, and other small scale forces do the same, forming atoms, eventually molecules, and then apparently, life itself.