Daily Energy Repost

Bohr, Einstein, Saint Augustine, and collapsing probability waves

Everything we call real is made of things that cannot be regarded as real.”

Quantum observations are quirky. A mathematical probability wave defines a photon until we observe it. The photon could be in many different locations, and the wave function determines the probability it is in a particular position. Only when we observe the photon does it manifest itself as an object at a specific point in space and time. Is it everywhere until we see it, or is it nowhere until we measure it? It may follow all possible probability paths simultaneously in multiple universes, and display particle behavior in the reference frame of our universe. These are all thoughts proposed by physicists. The quantum physicists don’t have all the answers, and neither do I.

Never-the-less observations about photons do raise interesting questions about the underlying nature of reality. Niels Bohr once said, “Everything we call real is made of things that cannot be regarded as real.” Bohr laid the scientific foundations for quantum theory and our understanding of atomic structure. Yet, he sometimes harbored an almost mystical view of reality and repeatedly questioned physicists’ ability to independently observe objects in nature.


How can you independently observe an object within a system to which you are inextricably bound? You can’t position yourself outside of the system. You can only observe the object from your position within the system. Your understanding is the outcome of how you and the object interact, not a description of the object in an independent state. Reality becomes subjective and depends on where in the system you are when you make an observation. Philosophers will recognize subjective reality as an existential concept since we are all constrained to defining the world around us through the lens of our individual experiences.

Another factor in the quantum enigma is, once the location of a photon is precisely determined, the probability function collapses. The fuzzy spatial nature of the photon transforms into a point. A single photon fired through a single small slit can potentially strike the wall behind the slit at multiple locations. This uncertainty does not result from a lack of knowledge about speed and direction, as per the analysis of motion in classical physics — this uncertainty reflects the photon’s wave-like behavior. The wave equation can only describe the probability of the photon striking at any single position. It can’t predict the actual location of the strike.

If the photon strikes at point A, then the probability it will also strike at point B goes to zero. The probability wave seems to collapse. How does the wave know when to collapse? Why can’t it produce action at multiple points, and what happens to the “information” field represented by the wave? Einstein’s view of quantum entanglement as “spukhafte fernwerkung,” — spooky action at a distance — also applies to the collapse of a probability wave.


Philosophically (not mathematically), the collapse of a probability wave is similar to the concept of time espoused by the early Christian philosopher Saint Augustine. He argued that the past is gone, and we therefore retain it only as an imperfect remnant memory. The future is yet to arrive and lacks reality. Thus the present is the only place where we exist as an active force in the universe. The present, however, is elusive, and slips away as soon as it arrives. It can only exist at the non-dimensional interface between the past and future and has no independent state of being.

The future is unknown and thus consists of an array of probabilities defining events that might or might not occur. As time moves forward and the present progresses to a point in the future, the array of possible future events collapses. A single event finally occurs when the future becomes the present. Similarly, once the photon interacts with the universe, it becomes observable, and the probability wave collapses. 

So at the macro and sub-atomic levels, our lives are dominated by uncertainty. That uncertainty manifests as a probability function that only collapses in the present when we interact with the universe. Niels Bohr’s mystical tendencies do not seem so out of place after all.

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.