Thermodynamics in the 21st century

[VincentG]

Thank you to Matt Brown for introducing me to Ludwig Boltzmann. He was at the precipice of a major breakthrough in attempting to quantify the molecular energy that we call "heat".

This article seems rather timely for the current state of the forum.

https://scitechdaily.com/how-chaos-theo ... f-physics/

[matt brown]

So many of these past legends never lived to 50, imagine where we might be if they had all lived to 70. Boltzmann passes by unnoticed by most, even within science. Today, we would call him a physicist, but during his time, science wasn't clearly organized. History does not follow a linear path and has many twists and turns. One of the weirdest is that by 1900, mainstream physicists did NOT believe in the molecular theory !!! The nickel tour is that physicists thought energy ruled the universe and subordinated any matter to largely irrelevant (makes me wonder how they got thru each day). However, all chemists had bought into the molecular theory a century earlier ~1800. Boltzmann believed the molecular theory, but struggled to unify it with thermodynamics. He was one of the few guys that kept the kinetic theory alive thruout the later 1800s and early 1900s until Einstein's 1926 Nobel Prize secured the kinetic theory.

It's a sad reflection of our society that so many know a lot about Ludwig Beethoven, but nothing about Ludwig Boltzmann. Another guy that passes by largely unnoticed is James Clerk Maxwell who is usually ranked second to only Newton (Einstein getting third place).

[VincentG]

Agreed Matt.

Can someone help provide insight to #5? Was this written before caloric theory was abandoned and heat was viewed as a thing other than molecular speed itself? How could they assume that the gas molecules lose no energy to impact? That would be the definition of perpetual motion and mean that no entropy would occur.

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[matt brown]

Agreed Matt.

Can someone help provide insight to #5? Was this written before caloric theory was abandoned and heat was viewed as a thing other than molecular speed itself? How could they assume that the gas molecules lose no energy to impact? That would be the definition of perpetual motion and mean that no entropy would occur.

The kinetic theory was debated for decades, so yes, this was written before the caloric theory was abandoned. According to the Equipartition of Energy theory, all internal energy is kinetic energy (for an ideal gas). A large, heavy, oxygen molecule moves slower than a small, light, hydrogen molecule, but similar to mv^2, each has the same kinetic energy. Since both have the same energy, no energy is transferred during collisions. OK, this covers 2 things in motion colliding, but what about gas molecules hitting a fixed wall (cylinder or piston)? If the moving gas molecules hit a fixed surface, no energy is lost since no...work...was done, but if something moves (think piston) then work is done and gas molecules loose energy. So, yep, a rigid box full of gas molecules is perpetual motion.

[VincentG]

So, yep, a rigid box full of gas molecules is perpetual motion.

To be more clear, I understand that if the temperature inside and outside the box are equal, there is no change in internal energy, and therefore "perpetual". But if the temperature(energy) inside is higher, the gas obviously loses energy upon impact with the walls.

Ok so molecular theory is still half baked then...

[matt brown]

We tend to accept the heating part without question (constant volume heating) as if related to our cooking experiences, but the cooling part makes us question this whole scheme (oops, theory). Yeah, exactly how the 'heat' move back and forth. As per another post, I'm clueless and prefer to accept the conclusions without knowing the process/es.

[VincentG]

It appears Ben & Jerry were onto something of the sort with their thermoaccoustic cooling device.