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  • neelkantha42

!yportnE esreveR

Keywords: Reverse entropy; disorder; time directionality

Hello Everyone! I recently watched the first half an hour of the new film, Tenet, by Christopher Nolan. Later, it was a bit violent, so that was a disappointment😕... Anyhoo, it was talking about entropy and how it influences our experience of the passage of time.

But what is entropy? Well, me in 2017 would say that it was the collective amount of disorder in the universe. But me in 2021 would quite heavily criticise this definition. Why? Because "disorder" implies an "order" and "order" implies a preference. But preferences change from person to person, scenario to scenario and so that would not properly describe such an important attribute of the universe such as the passage of time itself. Also, as experimentation by humans is replaced more and more by simulation using computers without preferences, describing "order" to a machine will be a very arduous and demanding task. Instead, I would supply a different definition: Entropy is the total number of possible configurations in a system. Think about it, when a glass shatters, there are more ways the fragments could be spread out than when they were together. Of course, as the size of the universe is always increasing, the number of configurations always increases and so entropy always increases. But what if the universe starts shrinking (like in a Big Crunch)? Then entropy could be reversed! That would allow events to happen in time rolling backwards, as in the videos below:

In the video below, count how many instances show reverse entropy.

Scores for answers: (For actual answer see footnote)

0: Are you reading this page?

1 or 2: You're getting the hang of it!

3 or 4: Warm, but not like pie!

5 or 6: Could be a detective someday...

7 - 9: When did I give you the answers?

10+: I don't know what video you've been watching!

So, to answer the question regarding the flow of causality (in the title pic), there is a short and a long answer:

Short answer: A

Long answer: C! This is because as there is a unique corresponding effect for each cause (model A), there is also a unique corresponding cause for each effect (model B). This might be confusing as "effects" can be shared between causes (e.g. both jogging and swimming have the "effect" of burning calories) but these "effects" should actually be called consequences and effect should mean the collective sum of these consequences. For example, a detective cannot figure out a whodunnit using just one clue (consequence), but with all the clues together (effect), the culprit would be caught and put behind bars for a long time. Similarly, the universe may constantly be deducing the past by analysing the effect of the present. This might sound absurd, but in a similar way, the traditional view of the propagation of time (phew, that was a lot to say!) suggests that the universe is constantly determining the effect in the future with the causes in the present. Thus, there is no way to deduce the propagation of time from a "3rd person" perspective (from outside our continuum). In fact some physicists, such as Carlo Rovelli (2), state that time does not propagate at all, or in other words, both the past and the future are determined and that we go through the "block of time" from the start to the end, experiencing the present as we go along. They say that as the rate of entropy growth is neither positive nor negative, but rather 0 (given that every quantum reaction makes sense both backwards and forwards), there is no way to distinguish the past from the future in terms of entropy and so instead of there being a temporal entropy gradient (meaning that the past had low entropy and the future will have high entropy), there is an ever-present continuum of time that contains a coherent string of matter configurations. Notice how entropy underlies and imbues the concept of time directionality. In the diagram below, I present 5 (out of the many) possible views of space-time and entropy below:

Matrixism: Spacetime is an illusion and everything can be expressed by only variables and trace tables.

Presentism: Only the present exists.

The Growing Block (3): All past and present is determined. The future does not exist yet.

Possibilism: All past and present is determined. The future exists, but is not definite.

Eternalism: All past, present and future is determined.

Personally, I can see from the point of view of each of these 5 perspectives. I would say the majority of people I come across would agree with a Growing Block model, but some people agree with the other views. What view do you agree with or think could explain our actual experience of entropy and time?

Please share your thoughts in the comments below and C u soon!


  1. There are actually 8 main instances in the second video that show reverse entropy.

  2. Carlo Rovelli relates to an eternalistic view of the universe in "The Order Of Time".

  3. Some people consider the Growing Block model to be another form of possibilism as in both the Growing Block and the other form of possibilism, there is free will.

  4. Here is another fun reverse entropy video:



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