: What is entropy in thermodynamics and mechanics?
In: Physics
Entropy is the tendency of everything to always move towards uncontrolled chaos. So in mechanics and thermodynamics, it’s the actions and reactions moving steadily towards a more and more uncontrolled state. Perfect example is a nuclear reaction. Once started it is essentially uncontrolled and unrecoverable without extreme intervention. Or a truck that lost it’s brakes. Ever see a runaway ramp? It’s a stretch of rocks and gravel on the bottom of a downslope of a hill. Truck looses brakes it can veer off and hit it, it used momentum and friction to slow a truck down.
Entropy is disorder. Think of a brick wall. If I build the wall, it’s going to be very ordered once I finish, each brick in the correct place. Over time, the wall will fall apart because things naturally want to move towards higher entropy. Once some bricks fall or crumble, the wall will be more disordered and have higher entropy.
It takes some work or effort to make things ordered. It took effort from me to build the wall and even if it takes what seems like a very long time, eventually the universe can’t sustain that work forever without more work to keep the wall the way it was when I built it.
At it’s most simple; heat and energy have a tendency to want to spread out across space. Entropy is a measure of how strong that tendency is for any given piece of matter at any given time.
It’s a measure of how many different ways you can arrange all the little pieces of a set while still seeing the same properties of the set as a whole.
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