The Copenhagen Interpretation of Quantum Mechanics: An Introduction and Worldview Assessment Jeremy Royal Howard Jeremy Royal Howard holds a By the science of physics we discern scient intelligence could know the future Ph.D. in Christian Apologetics and something of the powerful logic that exhaustively if it could grasp perfectly in Worldview Studies from the Southern stands behind the world. In tracing the an instant all the forces, components, and Baptist Theological Seminary. He has ominous sweep of faraway giants in the relations that compose the natural realm.1 held numerous church positions, includ- dark of space, in following the mechan- But foretelling the future based on physics ing head pastor, and currently works as ics of nutrient transport in the human was never more than fairy tale. The fact is an independent writer. He is co-author circulatory system, in setting man’s feet humans are not omniscient and everyday of The New Eve: Smart, Bold Femininity on the surface of that lesser of two great mechanical systems can exhibit chaotic in a World of Opportunity (Broadman lights, the moon—in these and countless behavior.2 Thus, mechanical determin- & Holman, forthcoming 2008) and other exercises we are not eyeing cold ism is an ideal that is inapplicable to co-editor of The Men’s Fraternity Bible trivia about our world; we are learning any system. Nevertheless, the inability (Broadman & Holman, 2007). yet again something of He who stands of Newtonian mechanics to eliminate back of it all. chaotic elements is more a result of the Physics does not yield a full-blown investigator’s limited knowledge of relevant theology, but by its light we see evidence factors than genuine irregularity in of a God of order, consistency, and deeply the natural order.3 This is an important powerful intellect. Physicists believed distinction from the tendency among this once. From Newton’s ascendancy physicists who adhere to the Copenhagen to the dawn of twentieth century, most interpretation (CI) of quantum mechanics scientists held some form of Christian (QM) to attribute quantum chaos not to belief. They also assumed it would be investigative incapacities but to the very possible to describe all physical entities by nature of quantum entities. In summary, Newtonian physics. On this assumption, though determinism based on Newtonian tracing the activities of any inanimate mechanics is impractical, it nevertheless object should be as simple as obtaining remains the case that, in principle, the values for position, momentum, and Newtonian outlook sets up an expectation trajectory, and then projecting outcomes that future states of a mechanical system by Newton’s laws. Underlying this are can be predicted by accounting for all presuppositions that the world is rational present variables. Order begets order in in structure and operation and that the a mechanistic universe. scientifi c investigator is a mere observer Given the success of the Newtonian rather than a participant in the experi- program, scientists operating up to the mental results he obtains. dawn of the twentieth century expected Confi dence in classical mechanics was that even the microphysical world would so pervasive that some believed an omni- prove to be orderly. The realization that it 38 is not jolted physicists out of a centuries- them and follow them through the testing long habit of mind, and the result has apparatus. In other words, it appears that been an “outrage” that has not abated in a certain “peer infl uence” is afoot, as if a century of years.4 photons dialogue with one another across time and distance, take note of the experi- Introduction to Quantum mental machinery arrayed around them, Mechanics and then decide whether to be particles or “Quantum” refers to the smallest units waves. This uncanny behavior leads to into which a thing can be divided. In QM, an obvious problem for the experimenter. it refers to the tiny packets of energy by While the act of measuring macroscopic which atomic exchanges occur. Atoms systems changes the native state only do not trade energy in regular portions; negligibly (for instance, measuring wind rather, they absorb and emit energy fi t- speed slows the wind only insignifi- fully. For example, an atom may retain its cantly), many theorists believe measuring entire quantity of energy for an indetermi- a quantum system actually makes it what nate amount of time and then discharge it is! It is as if the scientist is more “cre- in an unpredictable exothermic fl urry a ator” than “explorer.” Hunt for a particle, quanta of that energy. This irregularity and a particle you fi nd. Seek a wave, and evokes a host of questions, chief of which it is there in place of the particle. Search is: are quantum entities lawless? Experts for the quantum reality that exists apart are divided over whether or not this ques- from your biasing the situation, and you tion has been answered. will fi nd yourself shutting down your machinery on your way out the door. The Problem of Light The odd manner in which atoms man- Quantum Probabilities age energy is but one of the quantum Physicists use “wavefunction” as a anomalies which seem to belie Newtonian catch-all term that signifi es that all we expectations about an orderly, rational can know about a quantum system are world. Consider light. Is it made of waves probabilities about things like position, or particles? Particles are site-specifi c. If a momentum, and energy.6 Thus, whereas particle happens to be resting on the tip Newtonian mechanics aimed at precise of your nose just now, it cannot presently description of entity and event, QM settles be found anywhere else in the universe. for probabilistic descriptors of both. What A wave, on the other hand, has spread. It a quantum entity happens to be and do is can be here, there, and all around. at best statistically described. For instance, Scientists wishing to determine whether if an experimenter isolates a radioactive photons are particulate or wave-like run atom, he can be confi dent that it is set to into a diffi culty, however, for experiments decay at some future time. However, he seem to indicate that photons can behave does well to go on with her daily activi- as either particles or waves depending ties, for the exact time of the impending on what kind of measurement the scientist decay event is unknown. He may predict conducts.5 Experiments also imply that it broadly as a function of probability, but photons “decide” how to behave based on never narrowly as a function of regular the destinations of photons that precede mechanistic process. Newton and his 39 mechanics, it seems, are detained at the This advice, a veritable charter state- door to the quantum domain. ment for the CI, amounts to the following: Give up trying to conceptualize QM. Live Non-locality with the paradoxes, celebrate them even, In classical physics, cause-and-effect but forego the search for rationality. is a local phenomenon. If billiard ball D suddenly darts across the billiard bed and Formalism and Interpretation lands inside a pocket, the sensible physi- How can QT be fruitful and yet myste- cist will look for an immediate local cause rious? The answer lies in the distinction for D’s sudden change of momentum. between formalism and interpretation. Has either the cue or the cue ball struck The formalism is “a set of equations and it? Anyone suggesting that a cue ball on a set of calculational rules for making pre- a nearby table sent D racing would rightly dictions,” while the interpretation offers be dismissed from the discussion. ontological explanations for the observed Not so in quantum billiards. After sev- phenomena.9 One is about math; the other enty years of trying to dispel it, genuine about meaning. non-locality seems to be a settled fact In QT, it is the interpretation that is of quantum reality. Quantum particles mysterious. Since the formalism is all that share a common past may carry on one needs to conduct experiments, most affecting one another even in the event practicing physicists use the formalism that they become too widely separated and entirely ignore the controversy over to allow for any form of contact action or interpretation. Since a key difference physical communication. between the CI and alternative views is the question of whether or not quantum The Current State of Quantum indeterminacy is a refl ection of nature Mechanics itself or just current conceptual and Despite its anomalies, quantum theory investigative limitations, the tendency for (QT) is one of the most successful sci- physicists to practice QM in disregard to ence theories in history, leading to many its interpretation means physics has got- technological advancements.7 If it works, ten on quite well without solving a vital it must be right. Right? Maybe not. The ontological question: have we or have fact is physicists are in the dark about the we not found genuine acausality in the meaning of QM. physical world? Where one comes down on this question is not dictated by the for- Nobody understands quantum mechanics. So do not take the lec- malism or the empirical results obtained ture too seriously . just relax and in the laboratory. Rather, the decision is enjoy it. I am going to tell you what decided on one’s personal philosophical nature behaves like. If you will simply admit that maybe she does convictions.10 Thus, it is no surprise that behave like this, you will fi nd her most physicists regard the interpretation a delightful, entrancing thing. Do not keep saying to yourself, if you of QT as baggage that is best left curbside, can possibly avoid it, “But how can for scientifi c fact is far more relevant than it be like that?” because you will philosophical opinion when one is in the get “down the drain”, into a blind alley from which nobody has yet hunt for a research grant.