# Entropy? Siri is no help

I’m working on something. How can the net amount of entropy of the universe be massively decreased?

The answer can take a while…

Please close GQ – this was the Last Question.

And AC said: “[LET THERE BE LIGHT!]” And there was light

Is there really a way to figure this out? Even on the Straight Dope Message Board, I think you are asking a little too much. I mean, these people have not helped me that much, and my questions are much less philosophical and much easier to address. And, now you are calling for all of the quantum mechanics and theoretical physicians, which the Straightdope is full of, to answer this question? Well, hope for the best, but be prepared for the worst.

I do not understand entropy as well as some of the aforementioned people do. And, even they don’t understand it as well as they think they do. But, I suspect that the level of entropy in a universe can be reduced by half, if someone in that universe were to create another universe through high science & technology and manipulation of colossal energies. But they better get it right, because if they don’t they could really mess things up for the people in the first universe.

Perhaps if Siri and Alexa and Cortana and Google Assistant get together, they can solve this problem?

Is there an “Ask A Theoretical Physicist” hotline?

Isn’t that impossible by the second law of thermodynamics?

You beat me to this, which is tragic.

I’ll have to give a serious answer.

If we understand the universe at all, the overall entropy of the universe can not be reduced. We can reduce entropy in a subset of the universe, by increasing it more outside that subset (freezing water decreases the entropy inside the freezer, but increases it more outside).

If you can time travel (another impossibility) you can reduce entropy.

The universe starts at t=0 but whether the universe starts at entropy =0 is an open question, not yet understood (IMNA Physicist, so I maybe wrong).

In his book “A brief history of time” Stephen Hawkins explained how he came up with the idea that black holes will lose mass by radiation and will eventually dissipate. He said that idea was a direct result of the laws of entropy.

While “INSUFFICIENT DATA FOR MEANINGFUL ANSWER” might be a glib nerdy reference (and also probably the answer you got from Siri, because the folks who programmed Siri are after all nerds), it’s also about the best answer you’re going to get. We no of no way to do it. We have no reason to believe there’s any way to do it. If there is any way to do it, we have no clue what it would be.

Well, if I expend more energy then aren’t I increasing entropy faster than when I expend less energy?

For example, is entropy increasing faster when I am on running on a treadmill or sleeping?

Of course, that is on a mighty small scale but it’s a start.

Oh, sure, we can change the rate at which entropy is increasing. We can make it increase quickly or slowly. But we can’t decrease it.

Just to take pity on any poor non-nerd who might stumble across this thread, many of the responses to the question refer to the story the last question by Isaac Asimov

You are correct.

However, it is important to point out that “insufficient data” ALSO means that it can’t be ruled out “as yet”, either. There may come a time when there IS sufficient data for a meaningful answer.

Can I reset the universe back to initial conditions by dividing by zero on my HP 15C?

it depends what value of zero it uses.

Divide by cucumber error.

If you want to go down the rabbit hole, you can always check out conformal cyclic cosmology.

Basically, it claims, and I’m going to simplify this a whole lot, is that there is no difference between two photons 1mm apart in a 1mm sized universe, and two photons 1 billion light years apart in a billion light year sized universe, scale invariance, it is called.

So, as entropy increases, and eventually everything is diluted to where there are only photons, then you end up with the same conditions as the early universe before the big bang.

It’s a bit sketchy, and doesn’t have a whole lot of following, but if it is correct, then your answer is to just wait a little while.

I suppose this the right place to ask this related question:

Does the idea that the universe is expanding, and its expansion is accelerating, have anything to do with entropy? It seems consistent to me that an infinitely expanding universe would lead to maximum entropy. But the 2nd law of thermodynamics was in place well before we knew that the universe would expand forever, as opposed to eventually reversing expansion and then contracting due to gravity.