Thermodynamics, time and change
When the great Italian engineer Michele Besso died in 1955, his good friend Albert Einstein wrote in a letter to Michele’s sister:
»Michele has left this strange world a little before me. This means nothing. People like us, who believe in physics, know that the distinction made between past, present and future is nothing more than a persistent, stubborn illusion«.
To explain what this means, Carlo Rovelli, writes in his book Seven Brief Lessons on Physics, about heat. Understanding the laws of thermodynamics is crucial to understanding the question of time. Rovelli exemplifies with a spoon that is placed in a cup of hot tea. Heat moves from hot things to cold things, but not vice versa, and therefore the spoon becomes hot. There is an exchange of heat over time. In every case where there is no exchange of heat, the future behaves exactly like the past. As soon as there is heat, the future is different from the past. If there is no friction, a pendulum can swing forever. The future of the pendulum is predictable. If there is friction, if there is heat, the pendulum would slow down, and we would be able to distinguish the future from the past.
This means, the difference between the past and the future exists only when there is heat. Rovelli writes:
»The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder«.
Heat means friction, movement, change. When there is movement, there is a change over time.
The change is not predictable though. Even for the tea spoon. It heats up because the tea and the spoon interact through a specific number of variables. The value of these variables is not enough to make a prediction of the future exactly. It is enough to say that the tea with optimum probability will heat up the spoon. As unlogic as it sounds, it is not impossible that the tea will become hotter when the cold spoon goes in, it is just extremely improbable, writes Rovelli:
»Heat does not move from hot things to cold things due to an absolute law: it only does so with a large degree of probability«.
Time is a word that describes the indefinite continued progress of existence and events in the past, present, and future regarded as a whole. The general conception is that the past is what has been, the present is the time that we live in now, and the future is what has not yet been. But it is not as simple as that. Modern physics suggests that the now is an illusion. That the universal flow of time is a generalization that simply does not work.
Then what is the present? We say that the past no longer exists, and that the future does not yet exist. That only the things of the present exist. But according to Rovelli, there is nothing that corresponds to the notion of the ‘now’ in physics.
Confused? If you hold the now up against the here, it might help: Here corresponds to the place where a speaker is. It is obvious that two different people are here different places, that the word depends on, where it is spoken. The word now also corresponds with the instant, the word is spoken. Therefore, the two words here and now, are what is called indexical. They point to the context in which they occur. If things that are not here exist, then things that are not now should also exist.
What if you do not put the teaspoon in the tea? What if you leave it on the table and pour the tea over it? What if you choose to do something highly unpredictable. Then your surroundings change over the course of time. When you create heat, friction, motion, action - then you create change. If you make someone come over to your here and now, change their perspective, you might even change even more. You still cannot predict the future, but you can take actions and make changes that with a certain probability can get you where you want to be. With no motion, there is no distinction between past and future.
If we keep to our old ways, others will act and thereby define in what way the future might change. The future is created where there is motion. By behaviour, conversation, interaction, culture, the future is constantly altered. And most of it is unconcious. If we dare to regard time as a whole, that we can manipulate, there are good news: Not only is the past and the present now.
The future is now. And it belongs to those who move.