Aristotle and time

Bust of Aristotle. Marble, Roman copy after a Greek bronze original by Lysippos from 330 BC; the alabaster mantle is a modern addition.
Source: Wikimedia Commons
Born: 384 BC, Stagira, Chalcidian League
Died: 322 BC (aged approx. 62), Euboea, Macedonian Empire

It turns out to be interesting to compare Aristotle’s ideas about time with my insights about time and quantum physics. There are striking similarities.

A quote from Physics, book 4.11:

But neither does time exist without change; for when the state of our own minds does not change at all, or we have not noticed its changing, we do not realize that time has elapsed, any more than those who are fabled to sleep among the heroes in Sardinia do when they are awakened; for they connect the earlier ‘now’ with the later and make them one, cutting out the interval because of their failure to notice it.

So, just as, if the ‘now’ were not different but one and the same, there would not have been time, so too when its difference escapes our notice the interval does not seem to be time. If, then, the non-realization of the existence of time happens to us when we do not distinguish any change, but the soul seems to stay in one indivisible state, and when we perceive and distinguish we say time has elapsed, evidently time is not independent of movement and change. It is evident, then, that time is neither movement nor independent of movement.

Aristotle says here that time does not exist without change being perceived by our [consciousness]. If no change is experienced, then we also won’t experience time. So time is not the same as change or movement, but it is not independent of it.

Now we perceive movement and time together: for even when it is dark and we are not being affected through the body, if any movement takes place in the mind we at once suppose that some time also has elapsed; and not only that but also, when some time is thought to have passed, some movement also along with it seems to have taken place. Hence time is either movement or something that belongs to movement. Since then it is not movement, it must be the other.

If we observe a ‘before’ and an ‘after’, which is observing a change, then there is time. But time is not equal to change. Time results from the comparison between two now moments. We define the sequence of nows ourselves by assigning it an ‘before and’ after ‘.

When, therefore, we perceive the ‘now’ one, and neither as before and after in a motion nor as an identity but in relation to a ‘before’ and an ‘after’, no time is thought to have elapsed, because there has been no motion either. On the other hand, when we do perceive a ‘before’ and an ‘after’, then we say that there is time. For time is just this-number of motion in respect of ‘before’ and ‘after’.

The ‘now’ itself does not change, but the moments recorded in every ‘now’ do.

The delayed quantum eraser

This vision of Aristotle on time reminds strongly of the conclusions about time that can be drawn from studying the results of delayed choice quantum eraser experiments. In a simple double-slit experiment, observable interference will always occur behind the double-slit. A pattern of dark and light bands. It invariably shows up whether photons, electrons, atoms or even larger molecules are sent through a double slit.

Electron interference buildup over time. Provided with kind permission of Dr. Tonomura
Source: Wikimedia commons

In the delayed choice experiments, in principle, photons are sent through a double slit, and simultaneously information is collected about which slit the photon has passed. The measured information about the passed slit is randomly either recorded or irrevocably destroyed in order to determine the effect of available information about the passed slit on the interference pattern. The experimental results are in line with the predictions of quantum mechanics but nevertheless very intriguing.

  • If information is available about through which slit the photon has passed, the result of the experiment is affected in such a way (no interference) that the conclusion has to be that the photon state wave must already have collapsed in the slit manifesting a physical photon there.
  • The experiment is set up in such a way that the moment in time when that information is measured and recorded follows in time sequence after the photon appeared (manifested) in the slit.

At first glance, this looks like an effect back into the past, retrocausality. However, this doesn’t mean that we can change the past. Once measured, the past is irrevocably fixed. But as soon as we involve the active observer, retrocausality is no longer needed as an explanation. The observer will by his conscious observation only fix the order of events at that moment . It is then not the instrumental detection of the slit passage that exerts an effect on the interference behavior of the photon. History – the sequence of now moments – is fixed by the observer’s attention. That’s time.

Time sequence created by observer

In short, quantum physics seems to confirm Aristotle’s ideas about time. Now we can see an important difference between experienced time and clock time. The latter was introduced by Newton in the 16th century as the only model of time of importance in physics. With that the observer was sidelined and was no longer an important player in the physical universe. But quantum physics seems to restore experienced time as something that also plays a role in physics. The conscious observer acting as an information processor becomes thus an active participant in the universe again.

Beyond Weird & The Quantum Handshake

To keep up to date with the subjects on my website I have to read quite a bit. And a lot of highly interesting material on quantum physics is being written and published. But occasionally I come across something that impresses me particularly and seems worth of special attention. Especially when it considerably broadens or clarifies my view on quantum physics and its interpretations. Therefore highly recommended stuff for visitors of my website. So, I’ll discuss two books here. The first one I want to discuss is: “Beyond Weird – Why Everything You Thought About Quantum Physics is .. different” by Philip Ball.

Beyond Weird

I am grateful to the student who put this book in my hands. Philip Ball is a science journalist who has been writing about this topic in Nature for many years. You don’t need to be able to solve exotic Schrödinger equations to follow his fascinating and utterly clear explanation of the quantum world and the riddles it presents. Also, he clears some misunderstandings up about this subject. Such as the word quantum, which is actually not the fundamental thing in quantum physics but rather an emerging phenomenon. The state wave is not quantized but fundamentally very continuous. He desctibes how quantum physics in its character and history deviates from all previous physical theories. It is a theory that is not built by extrapolation on the older theories. You can’t imagine what happens in the quantum world as you can do with, for example, gravity, electric currents, gas molecules, etc. The mathematical basis of quantum physics, quantum mechanics was not created by starting from fundamental principles but was the result of particularly happy intuitions that worked well but whose creators could not fundamentally explain what they were based on. Examples are: The matrix mechanics of Heisenberg, the Schrödinger equation, the idea of ​​Born that the state function gives you the probability of finding the particle at a certain place when measured. It was all inspired intuitive guesswork that laid the foundation for an incredibly successful theory we still don’t really understand how and why it works. Ball makes presents a good case for the idea that quantum mechanics seems to be about information. It is a pity, in my opinion, that he ultimately appears to adhere to the decoherence hypothesis. That is the point in his book where the critical reader will notice that what was until then comparably good to follow step by step suddenly loses its strict consistency and that from there one has to do with imperfect metaphors. His account remains interesting but isn’t that convincing anymore. Despite that, the book is highly recommended for anyone who wants to understand more about the quantum world and especially about quantum computers.

The Quantum Handshake

A completely different type of book is “The Quantum Handshake – Entanglement, Nonlocality and Transactions” by John Cramer. His interpretation of quantum physics seems, in my opinion incorrectly, not to be placed on the long list of serious quantum interpretations. Not a big group of supporters. In any case, I had never heard of his interpretation until it was brought forward by someone at a presentation about consilience I attended a short time ago. The subject made me curious because the state wave seems to stretch out backward and forward in time as I see it. Cramers’ hypothesis is that the state wave can also travel back in time, creating a kind of ‘handshake’ between the primary departing state wave and the secondary backwards in time reflected state wave. The reflected state wave traveling back in time arrives at the source thus exactly at the time of departure of the primary wave. This handshake between both waves effects the transfer of energy without the need for the so-called quantum collapse. The measurement problem where the continuous state wave instantaneously changes into an energy-matter transfer would then be explained as the result of a energy transfer by the handshaking state waves. However, in order to finally be able to complete that energy-matter transfer from source to measurement device, Cramer has to assume that the state wave is “somewhat” material-physical. This ephemeral quality of the state wave is considered as a severe weakness in his interpretation. Nevertheless the book provides worthwhile reading for those who want to delve into the various interpretations of quantum physics, also and especially because of Cramer’s discussion of a large number of experiments with amazing implications such as, for example, quantum erasers and delayed choice experiments where retro causality appears to occur. His idea of ​​a state wave that is traveling back in time – which is not forbidden in the formulations of quantum mechanics – remains a fascinating possibility.

Quantum physics and time

From Wikipedia: Vlatko Vedral is a Serbian-born (and naturalised British citizen) physicist and Professor of Physics at the University of Oxford and CQT (Centre for Quantum Technologies) at the National University of Singapore and a Fellow of Wolfson College. He is known for his research on the theory of Entanglement and Quantum Information Theory. As of 2017 he has published over 280 research papers in quantum mechanics and quantum information and was awarded the Royal Society Wolfson Research Merit Award in 2007. He has held a Lectureship and Readership at Imperial College, a Professorship at Leeds and visiting professorships in Vienna, Singapore (NUS) and at Perimeter Institute in Canada. As of 2017, there were over 18,000 citations to Vlatko Vedral’s research papers. He is the author of several books, including Decoding Reality.

Watch this movie “Living in a quantum world” from Vlatko Vedral on YouTube: At the end of his presentation a question from the audience about time and quantum physics is asked (at about 1: 10) and in his answer he describes the behavior of a super-accurate clock and what happens to the last digits when you lift that clock half a meter in the gravitational field. And then he wonders what it means when you imagine that clock to be in a quantum superposition at the two different heights in the gravitational field. A superposition of two different timelines. Fascinating.

By the way, the first part of his presentation – about 45 minutes – is actually a very compact version of my quantum physics book. Everything is presented in an almost blazing speed: interference, the Mach-Zehnder interferometer, Schrödinger’s cat, the Copenhagen interpretation against the multiverse interpretation, delayed choice experiments, interference with very large molecules shot through double slits, the orientation of our robin on the earth’s magnetic field in its annual migration, the 100% efficiency of chlorophyll. Highly recommended.

Dark Matter, Antimatter and Anti-time

Our Big Bang model universe is not symmetric in time. This doesn’t perhaps disturb you, but it disturbs physicists who think symmetry rules all. A new cosmology model, published in 2018, suggests that our Universe has a mirror image in the form of an “antiuniverse” that existed before the big bang. Read the summary on f, read the complete article at or view Neil Turok’s presentation on YouTube below.

We like symmetry

In the anti-universe, according to the idea of Boyle, Finn and Turok, time moves in the opposite direction of our universe, everything is made up of antimatter and is also mirrored with respect to us. This fulfills three important symmetry conditions that our universe without an anti-universe does not meet. This is called CPT symmetry. So, very attractive because we like symmetry. At the Big Bang, both universes arose at the same time and developed in opposite directions. But there’s more. The model explains the fact that we hardly seem to find antimatter in our universe. It also predicts the dark matter that we seem to find in our universe as a heavy variant of the neutrino and it also predicts the amount of dark matter we calculated. So it seems to agree with theory. Until now, I was not a big fan of dark matter as an explanation for the excessive rotational speeds of the stars in the periferies of their galaxies, the Electric Universe offers a very credible model there, but this might just ‘convert’ me.

L. Boyle/Perimeter Institute for Theoretical Physics

Finally, this hypothesis seems to offer a attractive confirmation of the idea that we experience time by increasing entropy. In the anti-universe, its entropy should grow in the opposite direction. From our perspective, the clocks in the anti-universe are running backwards and the people there are getting inexorably younger to end up being squeezed into their mothers’ wombs.

Where is it located?

The question remains, of course, where that anti-universe is located. But maybe that’s the wrong question. Dimensions like space and time are an experience, a product of the mind, the energetic changes in matter and of our memory.

Waiting for he Big Crunch

Ultimately, if the universe and the anti-universe stop expanding and gravity eventually wins, both universes could reunite at the so-called Big Crunch. Which would probably be followed by another Bang and Anti-Bang, time and anti-time, matter and anti-matter. So why worry?