I have always been fascinated about how time works, is it just a clock on the wall? Something we use to govern our life by? We inhabit time as fish live in water. Our being is being in time.
Reality is very different from what it seems. The Earth appears to be flat but is spherical. Neither is the structure of time what it seems to be: it is different from the uniform, universal flowing. I discovered this when I started reading up on it in the great book “The Order of Time” by Carlo Rovelli.
Past and future are different from each other. Pain comes after the wound, not before it. A glass window can break into a thousand pieces, and the pieces cannot re-form the window. We cannot change the past; we can have regrets, memories. The future instead is uncertainty, desire, hope. We can live towards it because it does not yet exist. Time is not a line with two equal directions but an arrow with different extremities.
Heat
Heat always passes from a hot object to a cold object, This is the only basic law of physics that distinguishes the past from the future.
The arrow of time appears only where there is heat. Every time there is a difference is manifested between the past and the future, heat is involved.
Entropy, denoted by S is a measurable quantity that increases or remains the same but never decreases.
∆S≥0
Delta S is always greater than equal to zero, this is the second law of thermodynamics. It's the nub in the fact that heat always passes from hot to cold, never the other way round.
Blur
It was Ludwig Boltzmann, who truly understood what the equation ∆S≥0 means. The difference between the past and the future does not lie in the elementary law of motion. But it is the natural disordering that leads to gradually less particular, less special situations.
Boltzmann had shown that entropy exists because we describe the world in a blurred fashion. He had demonstrated that entropy is precisely the quantity that counts how many are the different configurations that our blurred vision does not distinguish between.
Heat, entropy, and the lower entropy of the past are notions that belong to an approximate, statistical description of nature.
Entropy, as Boltzmann fully understood, is nothing other than the number of microscopic states that our blurred vision of the world fails to distinguish.
The equation which states precisely this is carved on Boltzmann’s tomb in Vienna, above a marble bust.
The difference between past and the future refers only to our blurred version of the world.
If there is a pack of 52 cards and we arrange it by even numbers then odd numbers. That’s our version of the deck, if we were to arrange the cards in order of color or hearts first that changes that version of the deck. Similarly, the past and the future refer to this blurred version of the world.
