I thought I'd graduate at engineering

> I thought I'd graduate at engineering
> Turns out I'm going at medicine
Well I feel a little sad that I won't be studying any physics no more. So I come to thee, Veeky Forums, to help me understand a concept that never got around my head:
> Entropy
What the fuck is entropy and why it is always increasing? The Wikipedia article makes no sense at all. "disorder is more likely than order" yes yes, very good, but how the hell the universe cooling down is "disorder"? Shouldn't a higher energy state be more chaotic than a cold one? How exactly a cube of ice melting into water increasing entropy? It makes no sense at all... Why in a closed system it always increase? And how exactly that stops a perfect thermal machine from existing?

Other urls found in this thread:

physics.stackexchange.com/questions/131170/what-is-entropy-really
hyperphysics.phy-astr.gsu.edu/hbase/Therm/entrop.html
twitter.com/AnonBabble

Nobody willing to help the unintelligent soul?

Oh look, i got dubs

here is a fantastic answer

physics.stackexchange.com/questions/131170/what-is-entropy-really

but truthfully having an in depth understanding of entropy requires being fluent in the language of math and physics. not trying to be a higher than thou asshat but at a certain point it is like trying to come up with a translation for a word in Japanese that simply does not exist in English. only the original descriptive language will fully express the meaning.


As an incredibly loose and potentially cringeworthy analogy think of it like this. You can never get out more than you put in. Say i crank a wheel and 100% of that energy goes to the motion of my car. The entropy stays the same. If there is friction, wind resistance, bad fit on the gears, etcc then the amount of energy in terms of forward motion will be less than that of the energy i put in. so where did it go? friction for one, and other inefficiencies. energy which aids the car moving forward is relatively ordered as it all serves the same purpose. the heat lost to friction is disordered as it aids at no specific purpose. thus an isolated system will always increase in entropy or stay the same (be careful this is absolutely a part of it)

They say it better on a conceptual level than the rigorous definition from stackexchange

hyperphysics.phy-astr.gsu.edu/hbase/Therm/entrop.html

> Those links
Perhaps I did the right thing choosing medicine after all...

>Perhaps I did the right thing choosing medicine after all...

lmfao cheers to that, not gonna lie the masochism of conceptually trying to reason physics is why I love it so much..

What's this? Another user on /sci who actually knows what they're talking about? I was starting to lose hope.

the concept itself isn't that hard to understand, it's basically how stuff mixes. in your pic there is a time progression from left to right with the black/white mixing. The concept doesn't mean much outside the idea of mixing dissimilar things. Leave your Iced Tea on the table what happens to the over temperature of the room vs the ice. Piss in the Pacific Ocean what happens to the temperature of the Pacific ocean relative to your 37C piss? They equal out according to the limits of the "system" you predefined.

The 'system' is key, the system that is closed with a non-possible perfect insulated thermal barrier (think refrigerator walls) around it will reach it's equilibrium and nothing else will happen. it'll be perfect and homogeneous forever. Redefine the system to include the earth and that fridge is a hot/cold spot that will equalize itself to the new system when it mixes. Move the system out further to include the solar system, or the galaxy, or the local cluster, or the observable universe... eventually you'll be able to have your truly "closed" system that everything will be evenly spread out.

A cool exception to this is you. Imagine if in your OP pic your system gets to the letter P or Y as time progresses to the right, reaching equilibrium and all of a sudden creates the order represented by the letter E springs up randomly.. and that E develops into proteins, chromosomes, and simple cellular life out of nowhere... all brilliant and totally unpredictable information systems that shouldn't exist, almost like your glass of warm Tea on your table freezing randomly, which would be odd, super rare, and literally "improbable" wouldn't it.

Your ice cube analogue is flawed because you're not considering an isolated system

>chaos
>disorder

These are memes and terrible ways to explain entropy.

Try this:
"Energy spreads"

Humans are not special snowflakes. Your post was great untill that last paragraph. Organisms take in low entropy nutrition and shit out high entropy waste.

This is thermodynamically no different from countless inorganic chemical reactor system with low entropy compound inputs and waste outputs

>Why in a closed system it always increase?
isolated system actually

Entropy is a quantity that represents the amount of thermodynamically accessible microstates of a system.

It is not "disorder", per se (this is how entropy is most commonly taught to undergrads). A better way to think of it, albeit still crudely and imperfectly, is how predisposed a system may be to move towards a less ordered state.

>"Teaching people physics
>is as easy as a song:
>You think you make it simpler
>when you make it slightly wrong."

Words to live by. Ultimately, an analogy is just an analogy. Entropy isn't something you'll ever need to worry about in medicine, and it isn't something you'll ever understand until you get deep into the math.

It is most easily understood in the historical context.
Maybe you are familiar with the laws of thermodynamics. The first one basically says, that there is no thermodynamical change of state, that can destroy or create energy.
Then people realized, that there are state changes, that could be possible according two the first law, e.g. the gas in a gas bottle could go back in the bottle after opening, but those state changes are never observed.

Since thermodynamics is only an empircal science, a clever guy said: "OK, we need an additional law, that forbids these things." So he invented the word entropy and said change of entropy has to be greater than 0 for all state changes.

At that time people had the same problem like you
>wtf is entropy
There was even a kind of joke, that if you find something, that you can't explain, you should call it entropy, because nobody knows what this actually means.

With the rise of computers entropy got a context in information technology, where it describes something like the degree of order.

But in fact Thermodynamics

Source: My stat. mech prof: Haye Hinrichsen

You get a box with lots of ping pong balls in it, there are 2 kinds of balls, white and yellow.
Most of the white ball are on one side, and the yellow ones on the other side, with a few exceptions.
You close the box, you shake it a lot.
What do you expect to see, an even more ordered set of balls, or a mess ?
That's entropy increasing.

unless there's a little demon inside taking all the white balls and moving them over to one side

Fucking weaboos stay in your containment board

How the fuck are you gonna be a doctor if you can't figure shit out by reading?

Change always occur in one direction: gases expand in the direction of decreasing pressure, heat always transfers from hot to cold, etc.

Medicine really isn't all that abstract...or difficult.

The Prof at our university said we should view entropy as a concept rather than something you can fully understand. all that stuff about disorder is more confusing than helping.
You can use it optimize a process and to tell if it's even possible.