The classical view on observation and measurement.
In classical physics, the human observer does not play a creative role in what is observed. Everything is observed from the so-called 3rd person perspective. In all physics experiments, any influence of the measurement on what is measured should be avoided as far as possible, although some small effect is unavoidable. For example, consider the radar detection of a vehicle’s speed. The radar photon will bounce back from the vehicle and thus have a tiny influence on the speed of the vehicle. But that effect is so small that we can safely ignore it in practice. Protesting the traffic control fine on account of this effect will be in vain. The electricity meter also uses a very small amount of energy by its measurement. But protesting the energy bill on that account will also be in vain, I am afraid.
Observation in quantum physics
However, in quantum physics – a branch of physics that has succesfully taken over the fundamental role of its parent, classical physics – this is not the case. The way we measure is of crucial influence on the behavior of that which we are measuring. There is nowadays no doubt about that effect. Is it the influence of the measuring instrument or of the experimenter? After 120 years of quantum physics success, the discussion about exactly what a measurement is is still not definitely decided. Measurement causes the so-called quantum collapse, the end of the immaterial state wave and the emergence of the material particle. John von Neumann – one of the first quantum physicists – already stated emphatically that the observed object and the measuring instrument are not physically connected in some way and thus cannot cause the quantum collapse.
This was the way he reasoned; both – instrument and measured object – are ultimately composed of fundamental particles that, when not measured, will behave like an immaterial wave of probabilities, which is their state wave. Both state waves will meet each other when doing the measurement, but will not collapse, just as two meeting waves will run unimpeded through each other without eliminating in some way the other wave. On meeting they excite their medium by summing their movements and after that they just roll on, unaffected. According to von Neumann, there is therefore no reason to assign a special influencing role to the physical measuring instrument with regard to the end of the state wave. His insight was dismissed by later phycisists, as the influence of the observer (and his consciousness) was not considered as something objectively measurable and was therefore preferred to be left out of physics. What made it even worse is that the state wave is a wave that we can formally describe, calculate and predict with physics – that is, with numbers and symbols – but that the state wave itself is not materially observable. It does not even exist in a material sense. It is a wave of probabilities and these are numbers, symbols, mathematical constructions of the mind.
Is then everything an observer?
As soon as you make a measurement, however, the immaterial wave ceases to exist and we find only one of the many possibilities, the particle, which is decidedly not a wave. This behavior is also expressed in the Copenhagen interpretation of Bohr and Heisenberg. Gradually, the insight of von Neumann, Bohr and Heisenberg – mainly because of some recent advanced quantum physical experiments such as the delayed choice experiments – has been confirmed in such a way that the observer, who is seemingly physically realising that which is observed, can no longer be ignored and is acknowledged as an essential element in the fundamental understanding of nature, which is of course something what physics aspires to. This inspired Carlo Rovelli – among others – to declare that literally every object acts as an observer of any other object in order to materialize each other. So, according to his idea, each particle only exists materially in relation to another particle. My question is then, of course, how to imagine such a process, where both particles – while not yet existing materially – are able to relate to each other and then become material as a result. In my opinion, the order of events here is wrong. Cosmologist and quantum physicist Thomas Hertog describes in ‘The origin of Time’ something similar; all things become observers causing the quantum wave to collapse and therefore matter to appear. But things are made of matter which has to collapse itself first? So – to ask the real question – what exactly do we mean by an observer and what role does it actually play?
What is an observer according to quantum physics?
In many quantum physical experiments – especially those seeking to investigate the observer effect – have until now been carried out by an instrument acting as observer. The question is whether this is the right perspective. In an complex experiment pictured in the above figure – it was based on Eugene Wigners thought experiment with two observers – Wigners idea was indeed implemented, albeit with instruments acting as observers. In such an experiment, part of the experiment is carried out within a closed environment. One of the so-called observers is residing within that closed environment and thus observes directly the result of ‘his’ experiment. The state wave is then considered to collapse by that observer observing the experiment and has by that observation collapsed into an observed particle.
But outside this closed environment there is a second observer for which the content of that closed environment – the larger box with the experiment and the first observer in it – is still an uncollapsed state wave as long as the second observer has not yet observed the contents of the larger box. Only when that second observer can observe the contents of the larger box will for ‘him’ the state wave end, making the measurement of the particle becoming a fact. As far as the second observer is concerned it is then that the particle becomes manifested with its physical properties. Who of these observers is now the person who triggers the materialisation of the measured particle with its properties?
The figurines inside and outside the boxes, representing the observers, are physical measuring instruments and lack therefore any consciousness that could interpret their observation. So, is an interpretating consciousness really necessary here? The experimenters apparently do not think so. Anyhow, the outcome of the experiment implicated surprisingly that we could start to doubt the existence of an objective material world in which consensus rules, in which a fact is simply a fact, regardless of who did observe it.
Is consciousness really needed? Is interpretation necessary?
Can a physical instrument observe its environment and then interpret its observation? I would like to draw attention here to something that I do not think a physical instrument can do, however advanced it may be, namely interpretation, giving meaning to perception. That’s the core of the case here. What is interpretation? Can a physical instrument do that? The experimenters think so, which fits their materialistic image of the world in which man, and any organism, is only a complex machine. Something that can – in principle – be described as the result of its parts. The observers brain is according to them merely an advanced computer, coincidentally created in the evolutionary process of survival of the most suitable biological machines. The mind, emerging from the brain, can therefore be replaced by an advanced but non-biological machine such as ChatGPT, an AI. Interpretation by the mind is – in that vision – not different from a calculation. So, the question is; is there any difference between an organic living observer and an observing instrument? And what is the difference? In trying to answer this question, we have to simplify the discussion and look at the essential differences between a simple ‘acting’ measuring instrument – a central heating thermostat – and an organic observer.
Can a physical instrument be an observer?
What is the difference between the central heating thermostat and the biological entity that depends on its central heating thermostat for a pleasant ambient temperature? Is there a fundamental difference, fundamental in the physical sense? The thermostat ‘senses’ the ambient temperature, determines if it deviates from the optimal value, and then activates or deactivates the central heating boiler. Is that interpretation? Is that a measurement? These seem to me to be essential questions, although I suspect that they cannot be answered with a 100% waterproof answer. But I will try.
What causes the state wave to collapse?
We could therefore ask the following question. How is it possible that a physical instrument, which itself is not observed and thus is in a state wave, will cause the state wave to collapse or reduce? (The “collapse of the wave function” is also known as the “reduction of the wave packet). Consider the central heating thermostat. It does its job, even if no one is present because you have forgotten to lower the ambient temperature for a few days of absence. When you return home after a few days of absence you will notice that the house is warm, that the thermostat is still set on higher temperatures, so you must conclude that during your absence the boiler has been burning fuel for nothing. That conclusion – fuel burned for nothing – is interpretation. This unconscious thermostat was not able to understand that, otherwise it would have chosen to lower the desired ambient temperature. Can you still say that this unconscious thermostat is an observer? If so, did the thermostat collapse the state wave that contains your unobserved central heating boiler, all the radiators and the air in your home into a materiality? Every time it measured the temperature? How?
Real observers are interpreters
I think indeed that a real observer should be able to interpret his observations. Interpretation is assigning a meaning to an observation. That’s not what an instrument does. I have to tell the thermostat first, by programming it, which is a pleasant temperature. It cannot do that by itself because such an instrument has no knowledge of ‘pleasant’. Now you might argue that an advanced AI like ChatGPT could do it. But to do that, ChatGPT should first search through a huge database with data on what are pleasant temperatures for human beings. And how is ChatGPT’s database fed with these data? Indeed. By human beings who have recorded what they experience as a pleasant temperature. Had they not done so, ChatGPT would not be able to produce an answer on the question of what a pleasant temperature is. You might get an answer on the question of what ambient temperature a biological human being needs. But that’s not what is meant by pleasant. Pleasant is not a numerical expressible experience. Always, and without exception, the question of the meaning of an observation, its interpretation, has to be traced back to an observation by a conscious being. A being that was able to consciously interpret his perception as pleasant or unpleasant, red or green, hard or soft, wet or dry, beautiful or ugly. These experiences are certainly not numbers. I hope you will realize that, without living people, the ‘pleasantness’ of a temperature wouldn’t make any sense. The thermostat has no inkling of ‘pleasantness’. Of course it can be programmed to produce pleasant temperatures, but that always takes someone to think what that means and to translate it subsequently into the numbers a machine can process.
Conscious interpretation is always the final act of an experiment
The fact that a conscious interpreter is ultimately required, in my view, applies without exception to any experiment. Even for a run of the enormous Large Hadron Collider in Geneva. Ultimately, the result is always observed by a conscious being that assigns meaning to it. We may eventually get informed of the meaning by a publication, but it is usually not mentioned in the publication that there was always a person involved in the interpretation of the results. That is so obvious that it does not need to be mentioned explicitly. This means that an essential element of the experiment is never mentioned in reports. The observation was X, and that means Y. And that last part of it — and that means Y — that’s what it’s all about. That’s the interpretation of a person and therefore the actual experience of the world. That conclusion creates in the Copenhagen Interpretation by observation also all the previous events in the experiment as someting that did happen. As in previous example about the central heating, the history of the unwanted fuel consumption during your absence has become a fact after and because of your observation. That fact is then, after the quantum collapse brought on by your observation on returning home – unfortunately – no longer an immaterial probability distribution. It became what we call a fact. That’s something for which there can exist consensus.
What then is the role of a recording measuring instrument?
We have spoken enough of the observer for this moment and will now focus on the other question. What is a measuring instrument in this context? The requirement seems to be that it should be able to register. This means that a certain class of passive measuring instruments won’t qualify. Think of the yardstick, for example, which does not itself make a registration of length. It is a completely passive measuring instrument in contrast to an advanced central heating thermostat that remembers the indoor temperature pattern to anticipate the next moment of starting or stopping the boiler. So, registering ability seems at first glance a valid criterion, measuring plus recording. So, is a voltmeter connected to a recorder an observer or not? Is a photon detector connected to a coincidence detector in an advanced double-slit experiment an observer or not?
In order to answer that question, try therefore to think about how a recording measuring instrument might affect – by some yet unknown physical process – the registered object in its wave state and, above all, why another very similar instrument would not do so. Take, for example, a solid length of iron rod. That rod doesn’t seem a recording instrument, until you realize that the rod expands or shrinks according to its temperature. So, the rod measures the temperature by its length. If the rod is long enough and cleverly connected to a marker pen and a moving roll of paper, this would record the temperature evolution history. The change in the length of the rod provides the information on the temperature evolution. In this way you can consider the rod with marker and paper as a recording measuring instrument. Because we are able to use the rod in an ingenious way, as a registering instrument that we considered from another point of view as passive, it would thereby become an observer who would cause the quantum wave to collapse. I hope you see the inconsistency.
So you will not easily identify any arbitrary iron rod as an observing measuring instrument. If you start thinking about measuring instruments in this way, then the idea of an instrument as an observer becomes inconsistent and therefore highly questionable. Whether an instrument registers, or not, would then be not determined by its physical properties but by the way in which we employ it, and this is of course a case of human reflection. Ultimately, therefore, we must begin to acknowledge that even with an instrument that measures and records the result, the real observation – the observation that makes the quantum collapse happen – happens only if the result is observed finally by a conscious observer. If we accept that as an explanation then we may have an acceptable, useful, and consistent criterion for the definition of a measurement and also for the triggering of the quantum collapse, which is the material manifestation of the world.
So in the end we have to acknowledge that a conscious observer is needed for a real measurement, no exceptions. The measuring instrument is then nothing but an extension of our senses – which are also physical measuring instruments – and cannot be the cause for the quantum collapse, evoking the appearance of matter in our world. That has a profound meaning for our experience of the world. We are essential in the (hi)story. We are an essential part of the world, of the universe. By observing the world and thus experiencing the world consciously we create it.
Paul J. van Leeuwen graduated in applied physics in Delft TU in 1974. There was little attention to the significance of quantum physics for the view on reality at that time. However, much later in his life he discovered that there is an important and clear connection between quantum physics and consciousness.
What he learned between then and today resulted in a post academic course in quantum physics for non-physicists. A little bit later he decided to put the contents of that course, and more, in a book published in Dutch: Kwantumfysica, Informatie en Bewustzijn – and started a website on the subject. He translated the Dutch version of his book in English, titled: ‘Quantum Physics is NOT Weird’.