Maxwell's demon

Maxwell's demon was an imaginary entity hypothesized in an attempt to disprove the Second Law of Thermodynamics.

This law states that, on average, in a closed system the disorder (known more formally as entropy) must never decrease. On further statistical analysis, it is found that, although it is possible, it is incredibly unlikely.

In this video I attempt to demonstrate this idea.

I'd like to welcome my new subscribers, thank you very much for showing an interest. In return I hope to continue interesting you!

Category:

Entertainment

Tags:

• maxwell's
• demon
• cards
• trick
• effect
• second
• law
• of
• thermodynamics
• entropy

[Ripley747]

Not the most accurate of thermodynamic explanations or demonstrations, but I realize after watching that wasn't the point of the video. Cool trick though for sure. I suspect I know how it coulda been done, but not really sure. I see you're already in a debate with about 50 different people about the accuracy of your science so I will let you duke it out with them:).

[mrwhite692000]

@Ripley747 Thanks for your comments! Yeah, it's just a trick I needed an idea for. Notice how "I attempt to demonstrate this idea". I'm a physics graduate - I could split hairs over this - but it's just a bit of fun! However, debating is also fun so please feel free to join in!

[Ripley747]

@mrwhite692000 Well, then I'll throw this out there. Not debating, just curious on your thoughts. What are your thoughts that even Maxwell's Demons don't violate the 2nd law? If you're unaware of this concept, it states (paraphrasing) Maxwell's Demons would require more entropy to function properly since it would create more entropy overall. That is, the "trap door" would produce more entropy in order for it to distinguish the difference between a high energy and low energy molecule. Thoughts?

[mrwhite692000]

@Ripley747 yes, it's a fair assumption to make and, yes, there are real Maxwell's demons out there in the world but they must, at least, produce as much entropy as they reduce. See my reply to StefSSU and you'll see my thoughts on this. It all depends on how you define what a Maxwellian demon actually is.

[mrwhite692000]

Here is the message that I have so evidently failed to communicate to you:

"Several physicists have presented calculations that show that the second law of thermodynamics will not actually be violated, if a more complete analysis is made of the whole system including the demon... a real-life Maxwell's demon would need to have some means of measuring molecular speed, and that the act of acquiring information would require an expenditure of energy."

- Wikipedia

[mrwhite692000]

Well if you've taken nothing from this discussion then that's you're own fault, not mine. Same goes for wasting your own time.

Additionally, the fact that, as Maxwell's demon is defined as not expending work to achieve the task may well be impossible but what I was disagreeing with is that Maxwell's demons do actually exist. It is possible to separate out mixtures such as is described, however, you must do work to achieve this end.

[discosqueakyfly]

So, contrary to your original response, you agree with me? Did I really just waste this much time for you to contradict your original statement to StefSSU about how the idea could not be deemed impossible? I had hopes of something actually coming from this... but I suppose one should not expect to learn physics from a guy doing card tricks. I mean, no offense, but if I wanted to chase my tail I'd take lessons from the dog. Peace.

[mrwhite692000]

The demon may well be defined as doing this task of sorting molecules out without doing work but this, in reality, is impossible. You need energy to do work. A consequence of doing work is that you always increase the entropy of the system except in the case where the process is reversible, in which case the entropy stays the same.

[discosqueakyfly]

Okay, but back on point, the same quote you used earlier also said Maxwell's demon does its job "without expenditure of work" (or energy, as I've shown means basically the same according to the laws of physics.) Yes, the system in equilibrium can't do the work itself, so Maxwell's demon comes and does it without using any energy and thus without offsetting the decrease in entropy of the system. Therefore it would be impossible, no? Nothing like that exists in nature.

[mrwhite692000]

Well since you're saying energy can be used then I'm afraid this is simply not true by the conservation of energy.

The Wikipedia definition of thermodynamic equilibrium is good enough. Check out the Wikipedia article on heat engines and look at the subsection "efficiency". You'll find when Tc=Th you can't do any work. This can be generalised to any system that can do work, i.e. Maxwell's demon.