# Entropy in everyday life

Discussion in 'General Philosophy' started by wegs, May 20, 2019.

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3. ### DaveC426913Valued Senior Member

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Depends on whether we're talking about logarithmic measurements, or logarithmic formulae.

• The decibel unit is expressed as a logarithm of sound volume.
• The Richter scale is a logarithm of earthquake intensity.
• Saying CEOs make 7-figure salaries is measuring salaries logarithmically.
• You could draw a chart of enclosure sizes, showing closets in the centimetre range, houses in the metre range and factories in the decametre range.
Those are all measurements. You graph them logarithmically. I'm trying to think of some natural processes that have a logarithmic formula.

5. ### DaveC426913Valued Senior Member

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Actually, no.

The kg is a unit of mass. It is the same whether on the Earth or the Moon.

The Newton is the unit of weight. It equals 1 kg·m/s^2.

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8. ### exchemistValued Senior Member

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ΔG = -RT lnK?

9. ### DaveC426913Valued Senior Member

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I was hopin' for something a little less cryptic.

I found some real-world examples of logarithmic correlations:

https://www.quora.com/What-things-i...arithmic-function-but-looks-like-linear-to-us

Here are some others. The curved lines show logarithmic relationships between the absolute intensity of the stimulus and the perceived magnitude.

Last edited: May 30, 2019
10. ### exchemistValued Senior Member

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Oh well if you want one of those, you can have the pH acidity alkalinity scale.

The earlier one is the formula that relates the change in free energy of a chemical reaction to its equilibrium constant, i.e. the ratios of concentration (or pressure) of reactants and products at equilibrium for that reaction.

11. ### Michael 345New year. PRESENT is 72 years oldlValued Senior Member

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Agree

Is why I need time (ha ha) out

Rookie mistake

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12. ### DaveC426913Valued Senior Member

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As I thought through some examples I realized that there are two types of logarithmic representation. Most of them are nothing more than ways of visualizing data and using an easy to represent scale.
The Richter scale is one such example. The data is represented logarithmically -because the difference between 1 and 1.1 would be vanishingly small at the scale of 9 - it would essentially be 9 and 9.00000001. So we alter the scale in representations.

But that doesn't mean the physics of an earthquake itself is logarithmic in nature.

Electric shocks and sound volume are logarithmic though. There is a measurable correlation between input and output, and it is logarithmic.

I am not sure about pH scale though. Is the logarithm merely for easy visualization? Or is there a formula that shows the chemistry itself obeys a logarithmic scale?

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13. ### arfa branecall me arfValued Senior Member

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Lots of physical systems exhibit exponential behavior.

An easy example is water in a tank or reservoir with a tap. Open the tap and the water pressure decreases exponentially over time (as the volume of water in the tank decreases).
Capacitors discharge through a fixed resistance exponentially.
I think it might be true in general, that energy tends to disperse exponentially.

It also might be true that any such process has a Taylor expansion. So what happens if you take logarithms of Taylor expansions? What can be visualised by doing that, and does it correspond to anything physical?

14. ### wegsMatter and Pixie DustValued Senior Member

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Exponential = rate of change, yes?

15. ### DaveC426913Valued Senior Member

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Ah. Good point.
Heat loss is exponential too.

16. ### exchemistValued Senior Member

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The pH one is a log scale like the Richter scale. A tenfold increase in H+ concentration is one "click" up in acidity on the scale.

But the Gibbs free energy one is not. That free energy change is proportional to the log of the equilibrium concentration ratios.

There is a related one in electrochemistry (Nernst equation): https://en.wikipedia.org/wiki/Nernst_equation

Both derive from statistical thermodynamics, in which population distributions of species change in response to exponential energy change. Terms with exp(-E/kT) appear all over the place. So naturally it follows that equations for the energy are expressed in terms of the log of the numbers in the population distribution.

Last edited: May 31, 2019
17. ### DaveC426913Valued Senior Member

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Yep. That much I know. What I am not sure of is whether there is indeed some physical manifestation of it that is logarithmic.

18. ### Write4UValued Senior Member

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Albert Bartlett explains the "physical manifestation" as a natural logarithmic phenomenon in detail. He begins his lecture with: "The greatest shortcoming of the human race is our inability to understand the exponential function."

Last edited: May 31, 2019
19. ### wegsMatter and Pixie DustValued Senior Member

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And just like that, the discussion about entropy is done.

I'm reminded today of why I stopped posting here. The rudeness can be overwhelming at times.

20. ### DaveC426913Valued Senior Member

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If you have specific questions, with specific answers, the thread has a good chance of staying on topic. But you've got to admit, even your questions are sort of stream-of-consciousness, even if they have a common theme. We are following your lead.

Personally, I would be pleased as punch if I started a thread that generated enough interest to last 300 posts, regardless of how its content fluorished and multiplied.

Last edited: May 31, 2019
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21. ### wegsMatter and Pixie DustValued Senior Member

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...

Last edited: May 31, 2019
22. ### Beer w/StrawTranscendental Ignorance!Valued Senior Member

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Entropy, hmm...

I saw a person with a shirt that read: Youth is a gift of nature... Middle age is a work of art.

Next time I see him I'll tell him disorder increases with time, hence, he's lying to himself and that he is really going loony tunes stupid.

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23. ### wegsMatter and Pixie DustValued Senior Member

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And just like that, Beer brought back entropy. lol

I saw a funny meme: ''Entropy: the ultimate Thermodynamics Game. You can't win. You can't break even. You can't even quit the game.''