Why objects tend to minimize their energy ?

[hugo_faurand]

Hello everyone !

About one year ago I read a book called "Insoluble mais vrai" which is a popular science book.
In one chapter, the author , David Louapre, wrote :
"Sauf qu'il faut se souvenir qu'en physique, le mouvement naturel des corps les conduit à minimiser leur énergie."

Translated in english :

" Remember that in physics, objects' natural motion tends to minimize their energy."

It didn't disturbed me up to now. But I'm not quite sure that I understand the sentence. Yes, when you throw something and it's free falling, it minimzes its energy until reaching the ground or something else. But is there a demonstration of that principle and above all, why ? Why objects minize their energy ?

Thanks in advance.
Hugo

(Sorry if it remains some mistakes, as you've understood I'm not english.)

 

[atyy]

Within classical physics, it is not fruitful to ask "why" for fundamental questions.

Also, while minimization of energy is ok for a popular science book, when you get to more advanced studies, the principle might be more accurately said to be minimization of action, or even more accurately to be stationarity of action.

In quantum physics, the principle of least action of classical physics can be derived from the path integral formulation of quantum mechanics as a saddle point approximation.

https://en.wikipedia.org/wiki/Principle_of_least_actionhttp://www.scholarpedia.org/article/Principle_of_least_action

 

[Dale]

I agree with @atyy. It seems like the book is referring to the “principle of least action” which should be called the “principle of stationary action” but that doesn’t sound as catchy.

 

[stevendaryl]

Okay, there might be a confusion about what is meant by "objects tend to minimize their energy". It might be a way of referring to the principle of least action, which is about the paths of particles---they tend to travel in straight lines unless acted upon by forces.

Or it might be about the "ultimate" fate of moving objects. If you throw a ball into the air, it has a certain energy (kinetic plus potential). It drops to the ground, and maybe bounces a few times. But eventually, it comes to rest on the ground. So its energy is less than you gave it when you threw it into the air.

This rule of thumb about the ultimate fate of moving objects is actually not about energy, but is about entropy. Energy is conserved, so it's not really the case that the energy of the object disappears. Instead, the energy of the object is transformed into vibrations of the ground and heat. If that is what is at issue, then the real question is not "Why do objects minimize their energy?" but "Why, over the long term, does energy tend to dissipate into vibrations and heat?" The answer to that question is provided by statistical mechanics. There are many more ways that energy can be divided up into vibrations and heat than there are ways that energy can be used for the motion of large objects. So it's just probability are that interactions will favor dissipation of energy.

 

[Dale]

Good point @stevendaryl , without more context it is not possible to determine if the author is referring to the principle of least action or the second law of thermodynamics