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Causality: Founded On Bedrock, Or On Quicksand? - by John Prytz

The logical connection between cause and effect (causality) is one of the, if not the, most fundamental principles in the physical sciences*. If A happens, B follows. For every action there is an equal and opposite reaction. If an electron meets a positron – ka-boom! If sodium reacts with chlorine, you get table salt – not some of the time, but all of the time. Stars larger than a certain mass will end their stellar lives in a supernovae explosion. Solar and lunar eclipses, the tides, sunrises and sunsets can be determined with high accuracy mega-centuries in advance. You’d be in shock if you fired a bullet at a piece of tissue paper and it bounced back off and hit you, to say nothing of firing up the kettle for your morning coffee only to find ice inside instead of boiling hot water afterwards. Our entire lives are based around the certainty and predictability of causality. If things happen, they happen for a reason, even unusual or unexpected things. See, you weren’t aware of the steel plate behind the tissue paper, or that your better half played an elaborate joke on you having previously stashed an identical kettle in the fridge and performed some slight-of-hand! Anyway, and easily verifiable, you’ll see that physical science textbooks contain many thousands of examples of everyday, and not so everyday, cause and effect situations.


Causality is to me at least, a 100% certainty relationship. It’s not a 99.99% of the time relationship. That is, if A happens, B follows. If B happens, C follows. If C happens, D follows. Causality is not a case of if A happens, B or C follows. If C happens, D maybe follows. Now it doesn’t matter to me that causality can be reversed – if A happens, B follows. If B happens, A follows. That’s allowable because at the micro level the laws of physics aren’t time dependent. An electron and a positron can annihilate and form energy (in the guise of a gamma photon). A gamma photon can spontaneously form an electron-positron pair.


That 100% causality certainty suggests the following. There must be such a thing as predetermined or predestined outcomes. In the beginning were created trillions upon trillions upon trillions of matter particles (electrons, etc.) and force particles (like photons). They were all set in motion – in specific directions with specific velocities. The relationships between all of the elementary particles are fixed, and we call them the physical constants. The particles are fixed. The velocities and directions are fixed. The relationships are fixed - All else follows. Particle A has fixed properties.  Particle B has fixed properties. The relationship between particles of the A kind and of the B kind are fixed. Particle A meets particle B. If causality is fundamental, the outcome is 100% fixed; 100% certain. Thus, the initial ‘in the beginning’ set of conditions, once set in motion, will produce with 100% certainty, right on down the line, the exact sort of world or Universe we experience today. At the time of ‘in the beginning’, you became an inevitability. At least that’s one philosophy, but one I suggest must be so if causality is a valid concept.   


As a generalization, all of biology is ultimately based on chemistry. Chemistry is ultimately based on physics. Physics, at its fundamental core, is structured around mathematics and equations. Equations tend to equate things – obviously. Say 1 + 1 = 2, which in effect says if you cause two separate objects to come into an association, the effect is two objects in association with each other! Equations are also prediction devices. If you know the values of A, B, and C, you can predict D. If you then measure D, you find prediction (theory) and reality (fact) match – not every now and again, not only on weekends and public holidays, but all of the time. If you solve for D, knowing A, B, and C, you will have 100% confidence that in reality D is what you calculate it to be. That confidence can only arise if cause and effect operate 100% of the time. If cause and effect did not operate 100% of the time, then to use a well known literary example, Winston Smith could indeed believe that 2 + 2 = 5 and wouldn’t have to rely on Big Brother to ram the point home.


So, it’s surprising that there are those who suggest that sometimes things happen for no reason at all, like the origin of the Universe. First there was nothing; then there was something! Another example often given is an unstable radioactive atom, say an atom of uranium. It can remain in a unstable state for eons, then go ‘poof’, and for no [apparent] reason. I insert ‘apparent’ because I refuse to accept that the uranium atom goes ‘poof’ for absolutely no reason at all. But it is puzzling in that you could have two identical uranium atoms, sitting side by side, and one goes ‘poof’ and the other does not.


But then, let’s look at a macro case. Say we have two identical twins standing side-by-side. All of a sudden one keels over dead – the other doesn’t. Would you consider that mysterious? Probably not, as an autopsy might reveal that the one who kicked the bucket had a heart attack.


So, what about those two side-by-side ‘identical’ uranium atoms where one goes ‘poof’ and one doesn’t go ‘poof’. Did it happen for no reason? Unfortunately, it’s way more difficult to perform an autopsy on a ‘poof-ed’ uranium atom, but that doesn’t mean that it didn’t suffer the micro equivalent of a heart attack. I think the alternative to the ‘no reason’ argument is that there was some, ever so subtle and maybe in-deterministic quantum event that triggered the ‘poof’ in one. Perhaps something caused the phenomena called ‘quantum tunneling’ inside the uranium atom’s nucleus forcing it to spit out an alpha or beta particle or maybe a gamma ray. The escape, the ‘poof’, turned the previously unstable radioactive atom into a stable non-radioactive atom. As a best guess, maybe the uranium atom that went ‘poof’ had its nucleus hit by a passing neutrino or cosmic ray that triggered the quantum tunneling that caused the ‘poof’. We may never know exactly what that something was, but it was a something, not a nothing.


Akin to the radioactive atom example, there are those who suggest that quantum physics have undermined causality. That’s because in quantum physics one of the central planks is the uncertainty principle, better termed the Principle of Indeterminacy in the professional literature. In effect, the guts are that the very act of measuring something changes the characteristic(s) or nature of what you are trying to measure. A macro example would be you wanting to measure the temperature of your cup of coffee. Alas, sticking a thermometer into the cup in itself changes the temperature from what it was before you stuck the thermometer in.


A micro example – say there’s this electron traveling along minding its own business, and say you want to stick your nose into its business by wanting to know where it is now, how fast its traveling, and in what direction its heading. Now to detect this electron, something else has be interact with both the electron (firstly) and hence with you (or more likely as not your recording or measuring instrument). Unfortunately,  that interaction with the electron, say a photon hitting it and then the deflected photon being detected by you (or your instrument), knocks the electron away from the position it was in, changes its velocity and its direction or pathway you were interested in. You now ain’t got a clue where the electron is which is what you were trying to establish in the first place. Ultimately, the position, a combination of its velocity and pathway, become only a probable or possible or indeterminate or uncertain or even, to our perception, a random one. There’s a certain probability the electron is now within a certain range; a higher probability or certainty it’s within a larger range and a even greater probability it’s within an even greater range. Probably the only thing you’re 100% certain about is that it’s somewhere in the Universe! So even though you can’t know exactly where the electron is to the Nth degree, it’s somewhere and it’s in an exact place (has coordinates) and has a pathway, and there’s a reason behind it. That’s a micro example of say a small marble hitting a large marble and deflecting the large marble’s position, velocity and direction. There’s still cause and effect in operation.


What about the duality nature of light? Sometimes light (photons) acts like a wave, sometimes like a particle. [The same applies to other fundamental particles, like electrons.] Even though this is considered strange doings (to us anyway used to nature in the macro realm), there’s still no violation of causality. Identical experiments, regardless who, where or when performed, produce identical results. It’s just that experiment #1, #3 and #5 produce wave-like behavior 100% of the time, and experiment #2, #4 and #6 produce particle-like behavior, again, 100% of the time. If a total novice comes along and does experiment #2, you can bet particle-like behavior will result. Confusing? Yes. Do we have a long road ahead of us before we come to terms with this duality and what nature is trying to tell us? Yes. Is wave/particle duality a violation of causality? No.


In physics, students sooner or later learn about Maxwell’s demon. That’s a little feller that sits inside a box filled with say molecules of carbon dioxide at standard temperature and pressure. There’s a partition in the middle of the box with a hole and a lid covering the hole. Now these molecules are moving about at different velocities. It’s the job of the demon to open the lid covering the hole whenever a carbon dioxide molecule with an above average velocity moves from the left side of the box to the right side. And the demon opens the lid whenever a slower than average molecule is moving from the right side to the left side. The upshot of that, is that because molecular velocity is just temperature, the right side of the box will get warmer; the left side will get cooler, even though at the start the box was a uniform temperature. Now if that actually happened, you’d be pretty amazed, for its contrary to what we associate cause and effect to be. But, there’s no violation of physical law here. Now and again, something highly improbable can, and does, happen. By chance, you could have a situation where faster moving molecules just happen to all tend to move to the right and slower moving molecules move to the left. Causality is preserved.


Another case could be that all the molecules happen to move in the same direction at the same time and all end up in one corner of the box. Again, it’s highly improbable, but not impossible. And again, there’s no violation of cause and effect. Just like there is no violation of causality of you get dealt a royal flush! To a golfer, a hole-in-one is rare, an unexpected and unpredictable and random event, but it doesn’t violate causality. Ditto the breaking up of a rack of billiard balls with the cue ball and having them all go into various pockets. In either case, golf or billiards, if the initial conditions or circumstances that led up to the hole-in-one or pocketing all the balls in one shot are repeated, exactly repeated down to the Nth detail, the outcome the next time around will be identical. Cause and effect are 100% repeatable under identical conditions. Change the conditions (the cause) and you change the effect.


These above two examples are summed up by the quantum mantra that if it’s not forbidden, it’s compulsory – at least if you wait long enough. Of course in the case of the box and the carbon dioxide molecules, although the outcomes suggested will come to pass, you might have to wait multi-billions of years to observe it – probably even longer!


To hammer home the point, just because something is expressed in probabilities (events that can appear to be random but ultimately have patterns) doesn’t mean causality doesn’t operate – we just don’t have enough of the necessary details, and to the necessary level of precision, down to the degree required to predict with as close to 100% certainty as makes no odds. That’s unavoidable in the micro world. Absolute prediction in the macro world is often a theoretical luxury, but still, in theory, one can come to terms with it. Take a dice – if you knew exactly its initial position when tossed, its trajectory, its rotation rate, the exact condition of atmospheric parameters (temperature, pressure, viscosity, air currents, etc.), any slight imperfections in the cubic shape, and so on and so on, you could predict with confidence what number would come up - but not to the extent of 100% - always expect unexpected chaos, some factor(s) you hadn’t anticipated but perhaps should of! Alas, when you’re at the gaming table, trying to calculate all the relevant factors in your head in real time are beyond – well, even a super computer. But, be certain that whatever number does come up that cause and effect determined the outcome. It didn’t happen for lack of any reason at all.    


Let’s look at another quantum level example. Say we have two pairs of two electrons each, one pair in the Great Galaxy of Andromeda, the other in our own Milky Way Galaxy. In each galaxy respectively, both electrons are approaching each other at the same velocity and at the same angle and since all electrons have the same mass and electric charge, the two electrons should deflect, either as a direct result of a collision (if the velocities are high enough) or because they repel prior to contact because  have like charges. I’d suggest, even though this is a quantum level event (probability and uncertainty rule), that in other galaxies, the two electrons will deflect in a 100% identical manner. The cause is identical, thus the effect will be identical.


Thus far I’ve been talking about cause and effect as if it were totally a one-to-one relationship. That’s not true of course. While there are many ways (causes) to commit suicide – it’s only one effect (you’re dead). There are numerous ways a deck of cards can be organized (causes) that can deal you a pair of red kings – but the outcome is only one effect. One exact ordering of the deck can not give you a pair of red kings one time and a pair of black kings next time, assuming the same number of players, the same game, and dealing in the same order. Getting back to physics, as Einstein realized, both gravity (cause) and acceleration (cause) can give rise to the same effect; say being pushed back in your seat.


Because the direction of time (time’s arrow) is symmetrical at the micro level – there’s no law(s) or principle(s) of physics that demands that time has to flow in one, and only one direction, you can have cases where cause and effect likewise show time symmetry. That is, A can cause B; but B can also cause A. Obvious examples include how an electron and a positron meet and annihilate producing energy. Or, energy can produce an electron-positron pair. Familiar examples happen all the time in chemistry, where chemical reactions are reversible. An atom of oxygen can combine with an atom of carbon to form carbon monoxide. Or, a molecule of carbon monoxide can dissociate back into carbon and oxygen. In either case, causality operates.


Sometimes you need two causes to produce one effect. Say you need this pill and that pill to treat one disease.


Can one cause give rise to a multitude of effects? - At a simple and fundamental level, probably not. In physics you usually associate one cause with one repeatable effect. A common example is the Doppler Effect – a racing ambulance or police car or fire engine with sirens going full blast passes you (cause) as you’re standing on the sidewalk. You hear a higher than normal note as the vehicle approaches you, and a sudden drop to a lower note as the vehicle passes you and recedes into the distance. That sudden change is the effect. Another not so common example, given above, an electron meets a positron (cause), and ka-boom (effect). In chemistry, two parts hydrogen and one part oxygen make water. That’s it. Of course cause and effect can be reversed. One can break down water (cause) into hydrogen and oxygen in a two to one ratio.


However, in more complex systems, one cause can give rise to lots of repercussions. For example, an asteroid impacts Planet Earth 65 millions years ago. One effect is a large crater in the planet. Another effect is the demise of non-avian dinosaurs (and other species as well). A third effect is a layer or iridium at the Cretaceous-Tertiary boundary.

The cause of the dinosaur’s demise ultimately gave an effect – the rise of the mammals and humans as the dominate life forms on the planet. Humans of course have in turn produced many other effects on the planet, all of which would have been bypassed had that asteroid missed us all those millions of years ago!


A viral infection (cause) can give rise to a fever (effect), and a sore throat (effect), and chills (effect), and a runny nose (effect), and sneezing (effect), etc.


Of course one cause can result in a chain reaction or a snowballing effect or the butterfly effect. One particle (initial cause) impacts a nucleus (effect) which then spews out more particles (a cause) which hits more nuclei which sends out even more particles hitting more nuclei until you have a runaway chain reaction, which, if it happens fast enough is the explosion (final effect) of an atomic bomb.


A butterfly flapping its wings (cause) at location X can produce an air current which reinforces an existing air current which continues on down the line to ultimately produce a drought (effect) in location Y and a typhoon (2nd effect) that hits location Z.


I maintain you can’t have an effect without a cause, but can you have a cause without an effect – can something happen without affecting anything else? Put this way, say a cause has an effect – could that effect in turn have no further influence on anything, anytime? While such incidents would be rare indeed, IMHO, I can imagine possible scenarios. One example that comes to mind is an isolated proton in the remote void of outer space that disintegrates or decays into an electron, a neutron and an antineutrino. It’s certainly possible that any one of the three effects, the neutron, the electron or the antineutrino could in theory travel throughout the void for all eternity without ever coming into any association with anything else, just because in the void, ‘anything else’ is so few and far between that it’s possible for something to keep on keeping on – an ultimate micro hermit.


One can have a lot of fun playing around with causality, but it’s like playing a game within the rules. Playing the game without any rules, without any causality, only produces chaos.


Conclusion: I think the fundamental difference here is, is that when some people use the word “chance”, they mean something happened for no reason – no causality – and there is no underlying fine print. I would argue that causality still exists; the fine print exists, we just don’t see it; haven’t discovered it, or fully understand it yet. My notion of the fine print; that undiscovered country; the details, apply whether to a macro system or to a micro (quantum) system. What the fine print is not, IMHO, is a god or equivalent.



*In the biological sciences, even under the most tightly controlled laboratory conditions of temperature and pressure, etc., the experimental organism will do what it damn well pleases! (Nudge, nudge; wink, wink.)


Science librarian; retired.

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