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2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

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2320468 No.2320468 [Reply] [Original]

Hey, /sci/. I'm creating a fantasy/sci-fi setting and want it to conform to actual physics as closely as possible, but I also want to do cool shit with it. So I have some questions regarding thermodynamics that I hope you can help with. Note, a majority of my current knowledge on the subject is from wikipedia.

1. Is there a maximum amount of entropy than an isolated system can achieve? If so, what happens when it reaches that point?

2. Are there any other ways to increase entropy in a system other than by conversion of usable energy into heat?

If those questions are easily enough answered, cool stuff, but if you need more details about what I'm trying to do I'll provide them. I'd just as soon not though, because my intuition tells me any fantasy/sci-fi hybrid would be thoroughly ridiculed here. Thank you for your help in advance.

>> No.2320481
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2320481

I will bump with info pics ever so often, I guess.

>> No.2320485

>>2320468
>entropy than an
>entropy that an
Fix'd.

>> No.2320492
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2320492

>> No.2320504
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2320504

>> No.2320519
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2320519

Can also be Entropy and Thermodynamics general, if that will encourage people to talk.

>> No.2320534 [DELETED] 
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2320534

I'd even except a "No, go fuck yourself."

>> No.2320536
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2320536

I'd even accept a "No, go fuck yourself."

>> No.2320537

1. Heat Death

>> No.2320541

>>2320537
So the maximum amount of entropy is just determined by the maximum amount of usable energy in the system to begin with? If so, thank you.

>> No.2320548

>1. Is there a maximum amount of entropy than an isolated system can achieve?
For a given amount of energy in the system, yes. You can generally increase the entropy by heating it if you have the energy to do so.

>If so, what happens when it reaches that point?
Nothing special, you can't use it as a fuel source.

>2. Are there any other ways to increase entropy in a system other than by conversion of usable energy into heat?
Sure. Diffusion is an example.

>> No.2320549

The maximum entropy means that all the parts in the system are at the lowest possible energy state.

If the universe didn't expand, the maximum entropy it could reach would be a very thin gas(or plasma) which would be the same tempterature everywhere in the universe. No planets, no stars, no nebulae, no black holes.

If you've read or will read Vernor Vinge, in a couple of his books there's the invention of the Bobble. A spherical force-field which totally isolates what it encloses from the rest of the universe. At one point he describes how a nuclear explosion contained in a bobble will reach thermodynamic equilibrium within seconds.

>> No.2320553

>>2320548
>Nothing special, you can't use it as a fuel source.
In isolation, that is. You could very well add some other chemical and have an energy source.

>> No.2320557

>>2320548
Neat. In response to your answer of 2, is there anyway that can be uh... forced? Achieved manually? I am not able to articulate it well enough if that does not make sense.

>> No.2320563

>>2320549
>The maximum entropy means that all the parts in the system are at the lowest possible energy state.
No. For positive-temperature systems in thermal equilibrium, entropy increases when you add energy.

>> No.2320566

>>2320557
If you mix dye with water, the dye will diffuse.

>> No.2320571

>>1. Is there a maximum amount of entropy than an isolated system can achieve?

Not really. Entropy is the ratio of available energy to unavailable energy (AKA heat). As available energy approaches zero entropy approaches infinity. I've seen a few notations where the range of entropy goes from 0% to 100%, but I can't remember what they're called any more.

>>2. Are there any other ways to increase entropy in a system other than by conversion of usable energy into heat?

If the system isn't closed you can directly remove energy or insert heat to drive up the ratio. Otherwise no, not really.

>> No.2320582

>>2320571
>Entropy is the ratio of available energy to unavailable energy (AKA heat).
No. Entropy does have to do with unavailable energy, but it is an extensive property, not a ratio.

>> No.2320591

>>2320571
>>2320566
>>2320563
>>2320553
>>2320549
>>2320548
Alright, thank you. Just to make sure I'm drawing the right conclusions, I'm going to explain what I'd like to do. Note that I understand this is pseudoscience, I'm just trying to make it -believable- pseudoscience. So imagine an isolated system, separate from the universe (kind of like the aforementioned Bobble, I guess). This isolated system is sometimes accessible in a limited fashion, and its basic purpose is to allow for the total entropy of the universe to decrease by increasing its own entropy. Is this totally absurd, or do you think its within your parameters of belief when reading a work of fiction?

>> No.2320598

>>2320591
An ice cube can do that.

>> No.2320604

>>2320598
You can also put an ice cube in a thermos to make it sometimes accessible in a limited fashion.

>> No.2320605

>>2320598
If I understand it correctly, the ice cube is part of the universe, and the total entropy of a system can't decrease without the total entropy of another system increasing.

>> No.2320611

>>2320605
I arbitrarily declare my ice cube to be not part of the universe in the same way you declare your Bobble to not be part of the universe.

>> No.2320616

>>2320611
I apologize for using universe incorrectly. I'm referring to an isolated system that most stuff occupies when I say universe.

>> No.2320628

>>2320616
The outside of a thermos meets that definition.

>> No.2320644

>>2320628
While a thermos may be well insulated, I'd think that heat from outside the thermos would melt the ice cube. I'm supposing a scenario where one system has absolutely no effect on the other, except to facilitate an exchange in the level of entropy when prompted.

>> No.2320655

Alright guys, thank you for playing along and answering my questions, I will stop bothering you with my silly hypothetical.

>> No.2320656

>>2320644
So you need to imagine a very, very good thermos. Unless you're objecting to the fact that increasing the entropy of the ice cube changes its state, in which case I have to tell you that quite generally increasing the entropy of a system is going to change its state in some way.

>> No.2320693

i like how the concept of entropy is so ambiguous that you'll get a different answer every time you ask someone for just its definition.

>> No.2320717

>>2320693
No, that's because:
1. There are multiple descriptions of exactly the same thing
2. Experts will often dumb it down for a lay audience
3. Ask on 4chan, and you'll get answers from loads of people who admittedly know nothing about thermodynamics.