The Personal Website of Mark W. Dawson

Containing His Articles, Observations, Thoughts, Meanderings,
and some would say Wisdom (and some would say not).

The Arrow of Time

1. Introduction
2. The Classical Definition of Time
3. The Problems of the Classical Definition
4. The Redefinition of Time
5. Final Thoughts
6. Further Readings
7. Disclaimer

Introduction

The arrow of time refers to the question of what is the meaning of time, why and how time flows, and what is the physical nature of time? In the books “Now: The Physics of Time’ by Ricard A. Muller, “The Order of Time” by Carlo Rovelli, and “Time Reborn: From the Crisis in Physics to the Future of the Universe” by Lee Smolin these three eminent physicists address these issues. This observation is based on these books and my own belief in the nature of time.

I should point out that I am NOT a scientist or engineer, nor have I received any education or training in science or engineering. This paper is the result of my readings on this subject in the past decades. Many academics, scientists, and engineers would critique what I have written here as not accurate nor through. I freely acknowledge that these critiques are correct. It was not my intentions to be accurate or through, as I am not qualified to give an accurate nor through description. My intention was to be understandable to a layperson so that they can grasp the concepts. Academics, scientists and engineers’ entire education and training is based on accuracy and thoroughness, and as such, they strive for this accuracy and thoroughness. When writing for the general public this accuracy and thoroughness can often lead to less understandability. I believe it is essential for all laypersons to grasp the concepts of this paper, so they make more informed decisions on those areas of human endeavors that deal with this subject. As such, I did not strive for accuracy and thoroughness, only understandability.

The Classical Definition of Time

Entropy is the only quantity in the physical sciences (apart from certain rare interactions in particle physics; see below) that requires a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says, the entropy of an isolated system can increase, but not decrease. Hence, from one perspective, entropy measurement is a way of distinguishing the past from the future. However, in thermodynamic systems that are not closed, entropy can decrease with time: many systems, including living systems, reduce local entropy at the expense of an environmental increase, resulting in a net increase in entropy. Examples of such systems and phenomena include the formation of typical crystals, the workings of a refrigerator and living organisms, used in thermodynamics.

Much like temperature, despite being an abstract concept, everyone has an intuitive sense of the effects of entropy. For example, it is often very easy to tell the difference between a video being played forwards or backwards. A video may depict a wood fire that melts a nearby ice block, played in reverse it would show that a puddle of water turned a cloud of smoke into unburnt wood and froze itself in the process. Surprisingly, in either case the vast majority of the laws of physics are not broken by these processes, a notable exception is the second law of thermodynamics. When a law of physics applies equally when time is reversed it is said to show T-symmetry, in this case entropy is what allows one to decide if the video described above is playing forwards or in reverse as intuitively we identify that only when played forwards the entropy of the scene is increasing. Because of the second law of thermodynamics entropy prevents macroscopic processes showing T-symmetry.

When studying at a microscopic scale the above judgements cannot be made. Watching a single smoke particle buffeted by air it would not be clear if a video was playing forwards or in reverse and in fact it would not be possible as the laws which apply show T-symmetry, as it drifts left or right qualitatively it looks no different. It is only when you study that gas at a macroscopic scale that the effects of entropy become noticeable. On average you would expect the smoke particles around a struck match to drift away from each other, diffusing throughout the available space. It would be an astronomically improbable event for all the particles to cluster together, yet you cannot comment on the movement of any one smoke particle.

The Problems of the Classical Definition

In the early 20th century the eminent scientist Dr. Arthur Eddington postulated the entropy was the cause of the arrow of time. Entropy is an idea that comes from a principle of thermodynamics dealing with energy. It usually refers to the idea that everything in the universe eventually moves from order to disorder, and entropy is the measurement of that change. Dr. Eddington believes that entropy was the reason for the arrow of time. It has been the accepted explanation of times arrow since it was postulated, as no other scientific idea on time has arisen that provides a satisfactory explanation to scientists. Yet this idea has some inherent problems that in many ways make it unsatisfactory. The biggest one is that although that, in general, all thermodynamic systems will proceed from order to disorder over long periods of time, in shorter periods of time some systems proceed from disorder to order (think of large clouds of gas in space (disorder) that start to clump and then become a star (orderly)). Why are times arrow not affected by going from a disordered state to an ordered state if entropy is the reason for times arrow? Dr. Muller’s book discusses these and many other problems with entropy being the cause of times arrow.

One of the issues about time is that in scientific theory the equations that are utilized allow for both the forward and backward movement of time, or to put it another way there is no reason for why time moves forward rather than backward. For example, if a pool ball strikes another ball we can utilize science to determine the paths of both balls. But science can also be utilized to determine the path of the pool balls by examining the end position of the balls to determine what their path was. This is because science utilizes the initial state of an object, the forces or energy applied to the initial state, and the resultant final state of the objects (forward). So, if you knew the final state of the object, and the forces or energy that were applied to the object, you could determine the initial state of the object (backward). The same equations are utilized no matter if you start from the initial or the final state, as long as you knew the forces or energy applied. So why does time in our universe progress forward (past to present to future) rather than backward?

Another problem is traveling through time and its paradoxes. The most famous one is if you could travel back in time to before your father was conceived, and killed your grandfather, you would never have been born. If you hadn’t been born you could not have traveled back in time to kill your grandfather, and therefore you would have been born to go back and kill your grandfather, ad infinitum. Another paradox is if you travel forward in time and bring back information that will change the future. If the future has been changed then the information you bring back will have been changed. Therefore, you could not have brought back the same information because it has changed, and therefore you could not have changed the future in the same way. Current science has no answer to these paradoxes, but it allows for the possibility of its equations if you allow for traveling back and forth between time. And the entropy postulation does not disallow time travel (as times arrow can move both backward and forward depending on your entropic state in limited periods of time).

A further problem is the issue of free-will. Science tries to be deterministic within a problemistic universe. What place is there for free will if all things were deterministic within problematic constraints. For example, I could sit in front of a glass of water and ignore it, or I could take a drink and place the glass of water in another position. In science, the final position could be determined by the end state and the forces or energy applied, to determine the initial state. But what if I have ignored the glass of water; its final state would be its initial state, as no forces or energy were applied. How can science determine if was my free-will to either ignore or take a drink of water that resulted in its end state? This begs the question if I have free will, or if I must have done what I did based on the final state of the glass of water?

The three books mentioned in the Introduction delve into these issues and other problems with time in physics. It is not possible to recap or explain the physics problems with time in this short article but suffice it to say that the problems are many and varied. I would direct you to these books if you wish to gain a fuller understanding of the physics problems with time.

The question then is why is the arrow of time so important to physics? It is important because without a good understanding of time it is not possible to have a full understanding of Gravity or Quantum Physics. And Gravity or Quantum Physics are at the core of modern physics and modern technology. Indeed, today’s technological world is not possible without understanding Gravity and Quantum Physics. And all modern electronics utilize Gravity and Quantum Physics as the basis for their operations.

The Redefinition of Time

Drs. Muller, Rovelli, and Smolin each have their own unique ideas of what time is. I personally believe that Dr. Muller is on the right track, but I am intrigued by Dr. Rovelli’s ideas on time, and I am not quite sure if I understand Dr. Smolin. Therefore, I will constrain myself to an issue in Dr. Muller’s explanation of time for the rest of this article.

Dr. Richard A Muller:

Dr. Muller’s postulation is that time is a fundamental property of the universe and is constantly being created. His suggestion is also that time ran faster at the beginning of the universe, and that time slowed over the expansion of the universe. Therefore, if you can measure an interval of time near the beginning of the creation of the universe you could discover that time ran faster at the beginning then it does now. Unfortunately, his suggestion to determine if this is true is not currently possible, and very unlikely to be possible in the near future. I believe Dr. Muller is essentially correct, but I also believe that he did not consider some other issues as follows. Please note that in the following comments I treat time intervals as discreet packets for clarity purposes, although time may be contiguous.

Mr. Mark Dawson:

If Dr. Muller is correct than an interval of time at the creation of the universe is less than a current interval of time, so, therefore, there were more time intervals occurred at the beginning of the Universe then in the same duration of a current time interval. If you think of expanding wave crests as in the following diagram, then at the beginning the wave crests are narrowly spaced but over time they grew further apart. If this is true for time, the question arises on how to measure the age of the universe; by utilizing our current time intervals as a measuring stick or by counting the number of time intervals that have occurred since the creation of the universe. (i.e. in our expanding wave crests analogy do we measure by the number of crests that have been created since the start, or do we measure from the start to the end by utilizing the distance between the crests at the end as a measuring stick). As the universe was created approximately 14 billion years ago by our current time intervals there may have been many more billions of time intervals since the creation of the universe, if time intervals have changed.

This may also help explain the Hyperinflation period of the Big Bang. Hyperinflation occurred in the early universe when the size of the universe increased exponentially in a very short period of time. A short period of time with our current understanding of time intervals. If, however, time intervals were very much shorter during hyperinflation then by its standard of time intervals many more time intervals occurred during the hyperinflation period. Therefore, hyperinflation occurred in a short time frame by our time interval standards but over a long timeframe by hyperinflation time interval standards.

This may also affect the speed of light as the speed of light is measured over a time interval. Lightspeed may just be constant within a time interval, and perhaps there is a relationship between a time interval and the speed of light. If there is a relationship, then the speed of light may have varied over the evolutionary time of the universe.

All of this is very, very, very speculative but perhaps worthy of a pause for consideration by those much more knowledgeable and experienced than me.

Final Thoughts

I realize that my thoughts on this subject are entirely speculative, and speculation by a person not qualified to be taken seriously. However, I present them in the hope that another qualified scientist would consider them and maybe spark their curiosity. If so, then perhaps I may have contributed in a very small manner to the advancement of science. I think of one of my favorite locations “Everyone in life has a purpose, even if it's to serve as a bad example.” It may be that my speculation is a bad example of a layperson injecting themselves into the serious business of science. Either way, this speculation may start a serious inquiry or cause a chuckle which would contribute to the humor in life.

Further Readings

Below are the books I would recommend that you read for more background information on these scientists. They were chosen as they are fairly easy to read for the general public and have a minimum of mathematics. Time Reborn by Lee Smolin may be more difficult as he delves into the quantum physics in more detail than the other two books.

• Now: The Physics of Time by Richard A. Muller
• The Order of Time by Carlo Rovelli
• Time Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin

For a brief introduction on these topics I would recommend the Oxford University Press series “A Very Short Introduction” on these subjects:

• Quantum Theory: A Very Short Introduction by John Polkinghorne
• The Laws of Thermodynamics: A Very Short Introduction by Peter Atkins
• Cosmology: A Very Short Introduction by Peter Coles
• Gravity: A Very Short Introduction by Timothy Clifton

Some interesting website with general scientific topics are:

• Ask a Mathematician / Ask a Physicist
• Ask the Physicist!
• Physics and Astronomy Ask the Experts
• The Skeptic's Dictionary
• Understanding Science – how science really works

Disclaimer

Please Note - many academics, scientist and engineers would critique what I have written here as not accurate nor through. I freely acknowledge that these critiques are correct. It was not my intentions to be accurate or through, as I am not qualified to give an accurate nor through description. My intention was to be understandable to a layperson so that they can grasp the concepts. Academics, scientists, and engineers entire education and training is based on accuracy and thoroughness, and as such, they strive for this accuracy and thoroughness. I believe it is essential for all laypersons to grasp the concepts of this paper, so they make more informed decisions on those areas of human endeavors that deal with this subject. As such, I did not strive for accuracy and thoroughness, only understandability.

Most academics, scientist, and engineers when speaking or writing for the general public (and many science writers as well) strive to be understandable to the general public. However, they often fall short on the understandability because of their commitment to accuracy and thoroughness, as well as some audience awareness factors. Their two biggest problems are accuracy and the audience knowledge of the topic.

Accuracy is a problem because academics, scientist, engineers and science writers are loath to be inaccurate. This is because they want the audience to obtain the correct information, and the possible negative repercussions amongst their colleagues and the scientific community at large if they are inaccurate. However, because modern science is complex this accuracy can, and often, leads to confusion amongst the audience.

The audience knowledge of the topic is important as most modern science is complex, with its own words, terminology, and basic concepts the audience is unfamiliar with, or they misinterpret. The audience becomes confused (even while smiling and lauding the academics, scientists, engineers or science writer), and the audience does not achieve understandability. Many times, the academics, scientists, engineers or science writer utilizes the scientific disciplines own words, terminology, and basic concepts without realizing the audience misinterpretations, or has no comprehension of these items.

It is for this reason that I place understandability as the highest priority in my writing, and I am willing to sacrifice accuracy and thoroughness to achieve understandability. There are many books, websites, and videos available that are more accurate and through. The subchapter on “Further Readings” also contains books on various subjects that can provide more accurate and thorough information. I leave it to the reader to decide if they want more accurate or through information and to seek out these books, websites, and videos for this information.