Minding Matter - Adam Frank Flashcards
Many prominent researchers advocate for a universe fully reducible to matter.
However, after more than a century of profound explorations into the subatomic world, our best theory for how matter behaves (quantum mechanics) still tells us very little about what matter is.
With its emphasis on probability waves, essential uncertainties and experimenters disturbing the reality they seek to measure, quantum mechanics made imagining the stuff of the world as classical bits of matter (or miniature billiard balls) all but impossible.
For physicists, the ambiguity over matter boils down to what we call the measurement problem, and its relationship to an entity known as the wave function. Back in the good old days of Newtonian physics, the behaviour of particles was determined by a straightforward mathematical law that reads F = ma. (Force = mass x acceleration)
The equation F = ma gave you two things that matter most to the Newtonian picture of the world: a particle’s location and its velocity.
Many materialists still carry the baggage of that old classical picture.
The equation F = ma was true whether you were looking at the particle or not. All of that fell apart as scientists began probing at the scale of atoms early last century. In a burst of creativity, physicists devised a new set of rules known as quantum mechanics. A critical piece of the new physics was embodied in Schrödinger’s equation.
When calculations are done with the Schrödinger equation, what’s left is not the Newtonian state of exact position and velocity. Instead, you get what is called the wave function.
The wave function does not give you a specific measurement of location and velocity for a particle; it gives you only probabilities at the root level of reality.
It’s not just position and velocity that get smeared out. The wave function treats all properties of the particle (electric charge, energy, spin, etc) the same way. They all become probabilities holding many possible values at the same time. Taken at face value, it’s as if the particle doesn’t have definite properties at all.
NOTE: the spin of a particle is an immutable property. It’s always spinning at one and the same rate. It does not slow down.
This is what the German physicist Werner Heisenberg, one of the founders of quantum mechanics, meant when he advised people not to think of atoms as ‘things’.
Even at this basic level, the quantum perspective adds a lot of blur to any materialist convictions of what the world is built from.
According to the standard way of treating the quantum calculus, the act of making a measurement on the particle kills off all pieces of the wave function, except the one your instruments register.
What exactly is quantum mechanics telling us about the world? What does the wave function describe? What really happens when a measurement occurs? Above all, what is matter?
There are today no definitive answers to these questions.
The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction and denies the actuality of wavefunction collapse. Many-worlds implies that all possible alternate histories and futures are real, each representing an actual “world” (or “universe”).
According to the Copenhagen interpretation, physical systems generally do not have definite properties prior to being measured, and quantum mechanics can only predict the probabilities that measurements will produce certain results. The act of measurement affects the system, causing the set of probabilities to reduce to only one of the possible values immediately after the measurement. This feature is known as wave function collapse.
As yet there is no way to experimentally distinguish between these widely varying interpretations. Which one you choose is mainly a matter of philosophical temperament.
The attraction of the many-worlds interpretation, for instance, is its ability to keep the reality in the mathematical physics. In this view, yes, the wave function is real and, yes, it describes a world of matter that obeys mathematical rules, whether someone is watching or not. The price you pay for this position is an infinite number of parallel universes that are infinitely splitting off into an infinity of other parallel universes
Physics from the Copenhagen perspective is no longer a description of the world in-and-of itself. Instead, it’s a description of the rules for our interaction with the world. As the American theorist Joseph Eberly says: ‘It’s not the electron’s wave function, it’s your wave function.’
Today, it is hard to reconcile the confidence of materialist beliefs with the multiple interpretations of quantum mechanics.
What do the quantum rules imply about the nature of reality.
