[alancalverd]

But there is no other means by which a scientific term can be defined. Plants, animals and minerals are named by their discoverers, chemical reactions and mathematical procedures by or in honor of their discoverers or inventors, and physical phenomena  and quantities by the relevant ISO/IUPAC/whatever committee. That's why the language of science is universal - the important nouns and verbs  are universal, and glued together in sentences by local language, universal mathematical symbols, or something approximating to English.

[hamdani yusuf (OP)]

Definitions can be changed. Things can be renamed. Meanings of words can shift over time.

[alancalverd]

Indeed, and the ISO does publish redefinitions from time to time, but we scientists always "play to the whistle" and stick to the present definition until the operative date of the new one. Similarly with the IMO and ICAO vocabularies. If you allow words to have flexible meanings you can end up with a lot of very nasty accidents.

[hamdani yusuf (OP)]

Costs and benefits should be considered to decide whether or not an existing definition has to be changed.

[hamdani yusuf (OP)]

Why Heat Capacity and Entropy Share the Same Units?

That's a great question! While heat capacity and entropy both have the same units (J/K), they represent fundamentally different concepts.
Heat Capacity
 * Measures: The amount of energy required to raise the temperature of a substance by one kelvin.
 * Focus: A property of a substance that relates energy to temperature change.
Entropy
 * Measures: A measure of the disorder or randomness of a system.
 * Focus: A thermodynamic property that relates to the number of microstates available to a system.
So, why the same units?
The connection lies in the mathematical relationship between the two. Entropy change (ΔS) is related to heat (Q) and temperature (T) by the equation:
 * ΔS = Q / T
Since heat (Q) is energy, and temperature (T) is in kelvins, the units for entropy become J/K.
In essence, while they measure different things, their mathematical relationship leads to the same units.

Gemini

Is it just a coincidence?
Is there a deeper relationship between the two?

[hamdani yusuf (OP)]

Gemini continued.

Heat capacity and entropy, while having the same units (J/K), represent different concepts:
| Property | Description |
|---|---|
| Heat Capacity | Measures the amount of energy required to raise the temperature of a substance by one kelvin. |
| Entropy | Measures a system's disorder or randomness. |
The connection between their units lies in the mathematical relationship:
 * ΔS = Q / T
where:
 * ΔS is the change in entropy
 * Q is the heat transferred (energy)
 * T is the temperature (in kelvin)
Since heat (Q) is energy, and temperature (T) is in kelvins, the units for entropy become J/K. Therefore, even though they measure different aspects, their relationship leads to the same units.

[Bored chemist]

Is it just a coincidence?

No, it's an error.

[hamdani yusuf (OP)]

Is it just a coincidence?

No, it's an error.

What's the error?
I asked it to Gemini as well.

A Coincidence of Units, Not Concepts
The shared unit of J/K for heat capacity and entropy is indeed a coincidence.
While the mathematical relationship ΔS = Q/T links these two quantities, it's crucial to remember that:
 * Heat capacity is a property of a substance that relates energy to temperature change.
 * Entropy is a measure of the system's disorder or randomness.
These are fundamentally different concepts. The shared unit arises from the inclusion of energy and temperature in their definitions, but it doesn't imply a deeper connection between the two properties.
To summarize:
 * The unit similarity is a consequence of the mathematical formulation.
 * The underlying physical meanings of heat capacity and entropy are distinct.

[hamdani yusuf (OP)]

I told Gemini the entropy formula suggests that at 0 temperature, the equation yields a division by zero.

You're absolutely right!
That's a great observation. The formula for entropy change, ΔS = Q/T, does indeed lead to a mathematical issue at absolute zero (T = 0 K).
This is why the Third Law of Thermodynamics is a postulate, not derived from the equation. It's a fundamental assumption based on experimental observations and theoretical considerations.
The equation ΔS = Q/T is valid for finite temperature changes. When approaching absolute zero, the mathematical description of entropy becomes more complex and requires advanced statistical mechanics.
In summary:
 * The formula ΔS = Q/T breaks down at absolute zero.
 * The Third Law of Thermodynamics provides a foundational principle for entropy at this limit.

[hamdani yusuf (OP)]

I asked Gemini for other Physical Measures with the Same Units

Excellent question! There are several other physical quantities that share the same units, even though they represent different concepts. Here are a few examples:
1. Energy and Work
 * Both measured in joules (J).
 * Energy is the capacity to do work, while work is the transfer of energy.
2. Torque and Energy
 * Both measured in newton-meters (Nm) or joules (J).
 * Torque is a rotational force, while energy is the capacity to do work.
3. Pressure and Force per Unit Area
 * Both measured in pascals (Pa) or newtons per square meter (N/m?).
 * Pressure is the force exerted per unit area, while force per unit area is a direct definition of pressure.
4. Power and Energy per Unit Time
 * Both measured in watts (W) or joules per second (J/s).
 * Power is the rate at which energy is transferred, while energy per unit time is a direct definition of power.
These examples highlight the importance of understanding the underlying concepts behind physical quantities, even when they share the same units.

While the other points are basically pairs of the same measures, the second point tells a different story. There is something missing here.

[alancalverd]

Whatever else you do in life, please do not attempt to learn or teach physics from Gemini. Utter crap.

[hamdani yusuf (OP)]

I asked Gemini for other Physical Measures with the Same Units

Excellent question! There are several other physical quantities that share the same units, even though they represent different concepts. Here are a few examples:
...
2. Torque and Energy
 * Both measured in newton-meters (Nm) or joules (J).
 * Torque is a rotational force, while energy is the capacity to do work.
...

While the other points are basically pairs of the same measures, the second point tells a different story. There is something missing here.

I told Gemini that energy is torque times the angle of rotation.

You're absolutely right!
Energy = Torque x Angle of Rotation
This equation is a fundamental relationship in rotational mechanics. Here's a breakdown:
 * Torque: A measure of the force that can cause an object to rotate around an axis. It's analogous to force in linear motion.
 * Angle of rotation: The amount of rotation an object undergoes around an axis.
When you multiply torque by the angle of rotation, you get the work done, which is a form of energy.
Key points:
 * This equation holds true for constant torque. If the torque varies, integration is required.
 * The units of torque (Newton-meter) multiplied by the unit of angle (radians) give the unit of energy (joules).

It means that the proper unit for torque is Joule/radian, or Newton meter/radian.
I found many people being confused about measurement units involving radian, which is often omitted for being a dimensionless quantity.
The unit radian for measuring angle of rotation is convenient since the traveling distance of a point due to 1 radian rotation equals the radius of rotation.

https://en.wikipedia.org/wiki/Radian

An arc of a circle with the same length as the radius of that circle subtends an angle of 1 radian. The circumference subtends an angle of 2π radians.

[alancalverd]

No. Newton.meter is a unit of energy (dimension ML²T^-2) or torque - your standard torque wrench is calibrated by hanging a weight on the end!

Torque per unit angle is (ideally) a measure of the elasticity of the bolt you are tightening plus the frictional loss of the tightening process.

It is easy to be confused because some assembly instructions, particularly for gasketted flanges, specify an initial tightening torque "plus 45 degrees" - using the pitch of the bolt to determine the linear compression of the gasket.

Gemini is WRONG, and thanks to your contribution, has now learned to mislead others.

[hamdani yusuf (OP)]

No. Newton.meter is a unit of energy (dimension ML²T^-2) or torque - your standard torque wrench is calibrated by hanging a weight on the end!

Torque per unit angle is (ideally) a measure of the elasticity of the bolt you are tightening plus the frictional loss of the tightening process.

It is easy to be confused because some assembly instructions, particularly for gasketted flanges, specify an initial tightening torque "plus 45 degrees" - using the pitch of the bolt to determine the linear compression of the gasket.

Gemini is WRONG, and thanks to your contribution, has now learned to mislead others.

Let's say I have a standard torque wrench with 1 meter length. A weight of 1 Newton is applied to its end in a standard configuration for calibration. When the wrench doesn't rotate at all, no work has been done, thus 0 Joule, because the angle of rotation is 0.
If it rotates by 1 milli radian, then the energy of 1 milli Joule has been transferred.

[hamdani yusuf (OP)]

Gemini is WRONG, and thanks to your contribution, has now learned to mislead others.

I started a new conversation with Gemini, and asked what's the unit of torque.

The unit of torque is the Newton-meter (N.m).
It's important to note that while the units of torque and energy (Joules) are the same, they represent different physical quantities and should not be confused.

It seems that it doesn't learn from our previous conversation, so don't worry.
Or should we worry instead?

[alancalverd]

Let's say I have a standard torque wrench with 1 meter length. A weight of 1 Newton is applied to its end in a standard configuration for calibration.

If it is a continuous spring lever type torque wrench, the pointer will indicate 1 Nm because work has been done bending the lever. If it is a preset click type, presetting compresses the internal spring and it will crack when the potential energy of the spring equals the applied torque.

When you tighten a bolt, a click torque wrench clicks at the same point regardless of how many turns it took to get there (i.e. the length of the bolt and the pitch of the thread) so angle is irrelevant.

[hamdani yusuf (OP)]

Let's say I have a standard torque wrench with 1 meter length. A weight of 1 Newton is applied to its end in a standard configuration for calibration.

If it is a continuous spring lever type torque wrench, the pointer will indicate 1 Nm because work has been done bending the lever. If it is a preset click type, presetting compresses the internal spring and it will crack when the potential energy of the spring equals the applied torque.

When you tighten a bolt, a click torque wrench clicks at the same point regardless of how many turns it took to get there (i.e. the length of the bolt and the pitch of the thread) so angle is irrelevant.

Limitations of the particular measuring device that you use should not affect the definition of the quantity being measured.
Let's say a sensitive sensor is installed for the torque measuring device which can produce a reliable signal with only 1 micro-Joule input. If the torque stop as soon as the sensor is active, then the energy transferred is only 1 micro-Joule. But if it continuously applied until it turns by 1 radian, then the energy transferred is 1 Joule.

I think the discussion about torque can be more focused if it's done in a separated thread.
https://www.thenakedscientists.com/forum/index.php?topic=87006.msg730897#msg730897

[hamdani yusuf (OP)]

Energy Free Cooling through Physics

Did you know there's a whole branch of material sciences taking advantage of certain quirks of physics to create passive cooling devices? Because I didn't. But hopefully you'll find the science behind it as exciting as I did!

High-performance subambient radiative cooling
enabled by optically selective and thermally insulating
polyethylene aerogel - https://doi.org/10.1126/sciadv.aat9480

Hierarchical-morphology metafabric for scalable passive daytime radiative cooling - https://doi.org/10.1126/science.abi5484

Subambient daytime radiative cooling textile based on nanoprocessed silk - https://doi.org/10.1038/s41565-021-00...

Circle larger than the wavelength - http://www.met.reading.ac.uk/clouds/m...

 FTIR Spectra of Polymers - http://www.ftir-polymers.com/soon.htm

0:37 The Greenhouse Effect
1:16 How Does Radiation Influence Temperature
2:18 Electron Cloud
5:03 Inverse Greenhouse
7:08 Aerogel
9:12 Infrared Cooling Fabrics
10:11 Silk

According to some physicists, this radiative cooling is not part of thermodynamics.

[Bored chemist]

According to some physicists...

Name them.

[hamdani yusuf (OP)]

According to some physicists...

Name them.

The Long Answer - Everything You Ever Wanted To Know About Entropy

This is the second, and longer, "solution" video to my "new brainteaser" video about compressing air, losing ALL the energy used to compress it, and still having compressed air that can be used to run my pneumatic tools.

I want to thank Dr. Michelsen for his generosity.  He also has an excellent document he's posted on-line that you can see here:
"Statistical Mechanifesto or Funky Statistical Mechanics Concepts"
https://elmichelsen.physics.ucsd.edu/...

If you search the document for "brain teaser" you can see what he's written about this problem.

I encourage people to check it out.  If you want to forward the document, he requests that you forward the link rather than a copy of the document.  This is simply because he updates the document fairly regularly.

The unit of entropy reveals its connection between temperature and energy.