The Copenhagen interpretation Born, Heisenberg, Schrödinger, Bohr (1925-1927)

1. The Copenhagen interpretationBorn, Heisenberg, Schrödinger, Bohr (1925-1927) • Even though the Copenhagen interpretation is supposed to be the “orthodox” interpretation, there is widespread disagreement on it because… • …it requires a process (called wavefunction collapse) for which there is no known physical explanation. • The disagreement is between those who believe a physical explanation might be possible and those who don’t.

2. In this interpretation… • Space and time are assumed to be objectively real. • Prior to an observation, the universe is assumed to be divided between a quantum wavefunction that cannot be observed and a classical object that can be observed.

3. The wavefunction is assumed to be a solution to the Schrödinger equation, the fundamental equation of quantum physics • The wavefunction is assumed to exist whether or not there are observations. • It represents the probability (not the certainty) that a specific result (e.g., a position) will be obtained if the observer makes a specific type of measurement (e.g., of position). • It describes all of the possible results (e.g., all of the possible positions) that could be obtained , but cannot predict which result will actually be obtained.

4. Wavefunction collapse • At the moment of observation, the wavefunction is assumed to change irreversibly from a description of all of the possibilities (e.g., of position) that could be observed to a description of only the event that is observed. • This is called wavefunction reduction, or wavefunction collapse.

5. The next observation • After an observation and wavefunction collapse, a new wavefunction emerges. • It represents all of the possibilities that are allowed by the previous observation. • Another observation results in another wave function collapse, etc. • In this interpretation, a sequence of observations result from a sequence of wavefunction collapses. • Without wavefunction collapse, there are no observations.

6. Wavefunction collapse (cont.) • Any solution to the Schrödinger equation must at all times contain as many possibilities as were present initially. • No mechanism that obeys the Schrödinger equation (i.e., no physical process) can change the number of possibilities. • This means that no physical process can cause collapse. • Thus, collapse requires a nonphysical agent.

7. What is the only nonphysical agent that we know of? • Most physicists do not like to admit that collapse might be caused by Awareness. • Awareness, being nonphysical, does not obey the Schrödinger equation. • Therefore, Awareness might collapse the wavefunction.

8. Wavefunction collapse (cont.) • Even if there were a physical mechanism for wavefunction collapse, it would produce nothing but a collapsed wavefunction. • A collapsed wavefunction is not aware. It is only a collapsed wavefunction. • Awareness exists on a different level from the objects of awareness. • What “we” are aware of cannot be what is aware. • Awareness is self-evident. It needs no proof. That “we” are aware is the only thing that “we” can be certain of because Awareness does not change. • All objects of Awareness change with time.

9. The problem of the observer • What do we mean by an observer? • In the Copenhagen interpretation, a sequence of observations results from a sequence of wavefunction collapses. • An example of a sequence of observations is a sequence of thoughts, feelings, emotions, body sensations, and perceptions, i.e., a sequence of mind states. • (These can be thought of as a sequence of arisings in Awareness.)

10. The Copenhagen interpretation does not require separate observers • It requires only observations. • The separate “observer” is only a mental construct (which could result from a sequence of wavefunction collapses).

11. If there are observations but not separate observers… • There is no separation… • …and there is no suffering. • “We” think there is more than one “observer” because “we” have been taught so. • Suppose “we” have been taught wrong! • Then the best thing “we” can say about all of “our” suffering is that it has told “us” that there must be a better way!

12. The Copenhagen interpretation could be purely subjective • The Copenhagen interpretation normally requires an objective wavefunction that collapses at the moment of an observation. • However, suppose there is no wavefunction and no wavefunction collapse. • Then an observation would consist of simply a sequence of mind states. • This would be a purely subjective interpretation.

13. For example, • Christopher Fuchs has created a subjective interpretation in which quantum probabilities are interpreted as Bayesian probabilities. • Bayesian probabilities are probabilities that an agent’s belief will change to a new belief as a result of new data (from new observations). • At the present time, Fuchs’ interpretation requires an external object to be observed. • However, if the observation were purely subjective, then his interpretation would be a completely subjective interpretation of quantum theory!