12 Issues for the Future
255
fundamental constants, and that controversial concepts such as wave function collapse are no longer needed. We therefore arrive at a similar point of
contention to the one that we encountered in Chap. 3 when assessing the
leprechaun and his acts of magic: what do we count as an assumption when
applying Occam’s Razor?
The debate on this question is sure to proceed for many years to come, as
it revolves around what is acceptable evidence for a scientific theory, which
is not something on which there is universal agreement among physicists.
Traditionally, successful scientific theories should be testable, i.e. at least, in
principle, now or sometime in the future, be capable of being falsified by
experiment or observation. The trouble is that the multiverse theory can
explain anything at all, and so cannot be falsified. As such, at this time it
probably belongs more in the domain of metaphysics than physics. This may
not be a life sentence, however. Other physical theories began their existence
in this manner, and became accepted later as genuine theories, after emerging
technology provided a way of putting them to a practical test.
For an excellent summary of competing views on this topic, see: Universe
or Multiverse? by Carr and Ellis [22]. In the following Sections we address
some less esoteric issues in earth-bound physics, which also warrant further
discussion.
12.8 The Past is Never Dead. It’s Not Even Past
[23]
In Chap. 5, we encountered Wheeler’s Delayed Choice Experiment, where
choices made at the time of an observation appear to influence what has
already occurred in the past. In this experiment we saw that our decision
whether to use a wave detector (e.g. a sheet of photographic plate that
allows us to build up an image of interference fringes), or particle detectors (which respond to individual particles) affects the wave/particle nature of
light passing through two slits. In the first case, light behaves as a wave and in
the second as a stream of photons. This behaviour appears to be influenced
by the observer’s decision on which detector to use, even if that decision is
made after the light has already passed through or by the slits.
It is this apparent retrocausality in the behaviour of the light that creates
so many philosophical and conceptual difficulties in the interpretation of this
experiment. John Wheeler, the proposer of the original thought experiment,
had this to say: There is an inescapable sense in which we, in the here and now
… have an inescapable, an irretrievable, an unavoidable influence on what we
255
fundamental constants, and that controversial concepts such as wave function collapse are no longer needed. We therefore arrive at a similar point of
contention to the one that we encountered in Chap. 3 when assessing the
leprechaun and his acts of magic: what do we count as an assumption when
applying Occam’s Razor?
The debate on this question is sure to proceed for many years to come, as
it revolves around what is acceptable evidence for a scientific theory, which
is not something on which there is universal agreement among physicists.
Traditionally, successful scientific theories should be testable, i.e. at least, in
principle, now or sometime in the future, be capable of being falsified by
experiment or observation. The trouble is that the multiverse theory can
explain anything at all, and so cannot be falsified. As such, at this time it
probably belongs more in the domain of metaphysics than physics. This may
not be a life sentence, however. Other physical theories began their existence
in this manner, and became accepted later as genuine theories, after emerging
technology provided a way of putting them to a practical test.
For an excellent summary of competing views on this topic, see: Universe
or Multiverse? by Carr and Ellis [22]. In the following Sections we address
some less esoteric issues in earth-bound physics, which also warrant further
discussion.
12.8 The Past is Never Dead. It’s Not Even Past
[23]
In Chap. 5, we encountered Wheeler’s Delayed Choice Experiment, where
choices made at the time of an observation appear to influence what has
already occurred in the past. In this experiment we saw that our decision
whether to use a wave detector (e.g. a sheet of photographic plate that
allows us to build up an image of interference fringes), or particle detectors (which respond to individual particles) affects the wave/particle nature of
light passing through two slits. In the first case, light behaves as a wave and in
the second as a stream of photons. This behaviour appears to be influenced
by the observer’s decision on which detector to use, even if that decision is
made after the light has already passed through or by the slits.
It is this apparent retrocausality in the behaviour of the light that creates
so many philosophical and conceptual difficulties in the interpretation of this
experiment. John Wheeler, the proposer of the original thought experiment,
had this to say: There is an inescapable sense in which we, in the here and now
… have an inescapable, an irretrievable, an unavoidable influence on what we