My Love Affair with the Second Law of Thermodynamics

Second Law of ThermodynamicsIn love with the law – the second law of thermodynamics…

When I was a child, I used to like to bake. As I stirred the various ingredients together, I thought that if I moved the dough around faster and faster the integrity of each ingredient would be restored. I would see, perhaps, the clear round white of the egg with the yellow yolk inside. However, no matter how long I stirred, that pleasure was not vouchsafed me.

The Second Law of Thermodynamics

Later in my life, I heard about the Second Law of Thermodynamics (for short, Second Law1). You experience this when

You mix batter for a cake,

You accidentally drop an egg on the floor,

You run your car into a tree,

You burn a hole in the carpet,

Our planet grows older and

Our solar system grows older and

Our galaxy grows older and

The universe grows older.

You get the idea; what has happened is irreversible. The why? Because of the 2nd Law. There is an equation (don’t run away) for this:


The “S” is the amount of disorder that may occur in any physical change; “dS” is the change in the amount of disorder. The equation states that change produces2 disorder; it makes clear the meaning of Second Thermo.

In his wonderful book, In Pursuit of the Unknown – 17 Equations That Changed the World, Ian Stuart says that he once asked a group of people how many of them could describe the law. None of them could. He then notes that asking this question is the scientific equivalent to asking, “Have you read a work of Shakespeare’s?” If you are asked to give an explanation of Second Thermo, here is a simplistic answer:

If you are in a car going 50 miles and hour and stop, the kinetic energy that produced the motion is turned into heat. You cannot take that heat energy and use it to make your car resume the 50 miles per hour speed once more.3

A physicist once told me that in time the universe will eventually consist of clouds of swirling dust. The moon will no longer go around Earth; Earth will no longer go around the sun. All cyclic movement will have ceased, causing time to disappear. He called this new era the Age of Eternity. Second Thermo at work.

There is a film short, Renaissance. It starts with a still scene of a room filled with a pile of all types of broken objects. As you watched, the shards slowly swirled and then came to rest. The objects appeared a bit more organized. Once again the swirl occurs and comes to rest, producing even more organization.

This action continues until you can see the emergence and finally the completion of a beautifully furnished room. The film is my child baking dreams become true.

—Ellen Hetland Fenwick

1 The American Heritage Dictionary of the English Language: The physics of the relationship between heat and other forms of energy.”
2 It never decreases.
3 With the development of autos like the Toyota hybrid Prius, part of the heat (only part) that is generated by the process of deceleration is changed into electricity. A fee to Second Thermo must be paid.

Note: You might also enjoy Static Friction and Kinetic Friction AKA Sliding Friction


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