in Modern Physics
The phenomena of the
cosmos require an observer in order to be learned about and understood by
us. The observer can take many forms, for example:
Some Personal Speculations
1. A person
watching amoeba through a microscope
2. A person watching an ocean sunset
3. A spacecraft monitoring a distant asteroid (and transmitting data to
4. A person conducting an experiment in a laboratory
The ideal observer
is one who causes no unnecessary perturbations to the system being observed.
An observation made by such an observer is called an objective observation.
In our school physics and chemistry, we routinely assume that our observations
But reality seldom,
if ever, provides us with ideals. The real observer always causes an unnecessary
perturbation of some kind. Scientists must remain alert in their efforts
to minimize the magnitudes of these perturbations. The extent to which
they succeed determines the level of confidence they can claim in their
results and, therefore, the certainty they can expect in their knowledge
In the 20th century,
physics was forced into the position of re-evaluating the role of the
observer, both in relativity and in quantum mechanics. In relativity,
the absolutes of Newtonian physics were banished, and observations obtained
by observers in different frames of reference became all that was available.
These observations were linked through a system of coordinate transformations.
In quantum mechanics,
the observer and the system being observed became mysteriously linked
so that the results of any observation seemed to be determined in part
by actual choices made by the observer. This situation is represented
by the wave function, a function in the complex domain that contains information
about both the cosmos at large and the observer's apparent state of knowledge.
I have long been fascinated
by these developments and have developed a model to help me both to understand
them and to explain them to others. I wish to share this model with you...
Let us ask a simple
question: When you look up at night and "see" a star, what is
"really" going on? A Newtonian philosopher might answer that
you are "really seeing" the star, since, in Newtonian physics,
the speed of light is reckoned as being infinite. An Einsteinian philosopher,
on the other hand, would answer that you are seeing the star as it was
in a past epoch, since light travels with finite velocity and therefore
takes time to cross the gulf of space between the star and your eye. To
see the star "as it is right now" has no meaning since there
exists no means for making such an observation.
A quantum philosopher
would answer that you are not seeing the star at all. The star sets up
a condition that extends throughout space and time-an electromagnetic
field. What you "see" as a star, is actually the result of a
quantum interaction between the local field and the retina of your eye.
Energy is being absorbed from the field by your eye, and the local field
is being modified as a result. You can interpret your observation as pertaining
to a distant object if you wish, or concentrate strictly on local field
This line of argument
brings us to an interesting notion: that of the interaction boundary.
Let us assume an observer and a system to be observed-any observer and
any system. Between them, imagine a boundary, and call it an interaction
boundary. This boundary is strictly mathematical; it has no necessary
physical reality. In order for the observers to learn about the system,
they must cause at least one quantum of "information" (energy,
momentum, spin, or what-have-you) to pass from themselves through the
boundary. The quantum of information is absorbed by the system (or it
might be reflected back) and the system is thereby perturbed. Because
it has undergone a perturbation, it causes another quantum of information
to pass back through the boundary to the observer. The "observation"
is the observer's subjective response to receiving this information. In
a simple diagram, the situation looks like this:
O | S
where O and S represent
the observer and the system, the vertical line represents the interaction
boundary, and the arrows represent the information exchanged in the act
In this scheme, no
observation can be made without first perturbing the system. The observation
is never one of the system "at rest," but of the system perturbed.
the state of the system before the perturbation and
represents the state immediately after, then the observation approaches
the ideal only if
If I is the information
selected by the observer to send across the interaction boundary, then
it is apparent that
must be a function of I: i.e.,
Thus, the observation
is affected by choices made by the observer, as quantum mechanics seems
to teach. In the case of atomic and some molecular phenomena, the inequality
does not hold; in
so that the perturbation is comparable in magnitude to the state itself.
Because all information is exchanged in quanta (modern physics does not
allow for the "smooth exchange" of arbitrarily small pieces
of information), this situation necessarily gives rise to an inescapable
uncertainty in such observations. The quantum theory takes this uncertainty
into account as the Heisenberg Uncertainty Principle.
Uncertainty is not
strictly a law of Nature, but is a result of natural laws that reveal
a kind of granularity at certain levels of existence. Observers in modern
physics truly become participants in their observation, whatever that
observation might be.