Vic Stenger
"Reality
Check" in Skeptical Briefs September,
2003
Since
I have been writing a column called "Reality Check" for several years now,
perhaps it is time for me to say what I think is really real. The best
definition I can think of is inspired by a comment made by Samuel Johnson
in 1763. As described in Boswell's Life of Johnson,
We
stood talking for some time together of Bishop Berkeley's ingenious sophistry
to prove the nonexistence of matter, and that every thing in the universe
is merely ideal. I observed, that though we are satisfied his doctrine
is not true, it is impossible to refute it. I shall never forget the alacrity
with which Johnson answered, striking his foot with mighty force against
a large stone, till he rebounded from it, "I refute it thus."
So,
I define something as real when it kicks back after you kick it. In simple
terms, this describes the processes of everyday observations, but also
the most sophisticated scientific experiments. When we look at an object
with our naked eyes, light from some source bounces off the object into
our eyes. Or, the object itself may emit light. In either case, the object
and the light receptors in our eyes recoil from the momentum that is transferred
in the process and generates an electrical signal that is analyzed by our
brains.
Scientific
observations are basically the same. Not only visible light, but the whole
electromagnetic spectrum from radio waves to gamma rays are available to
joggle reality, along with sensors far more precise than the human eye
to detect the jiggles that are returned. What's more, other particles,
such as electrons and neutrinos, are also available as probes and computers
are utilized to supplement the analytic capability of our brains. In short,
science is not some special method of learning about the world. It is an
enhancement of the only method by which we humans, in fact, learn about
the world--empirical observation. The stuff of reality that kicks back
when you kick it is called matter.
And, that's all there is.
In
the 1930s, Edward Milne described a procedure by which we can make observations
using only a clock to provide quantitative measurements aboutwhatever
is out there in reality. This procedure implements the notion that objective
reality responds to our probing and that our familiar space-time model
of reality is basically a description of this process, a model we have
built to describe the data.
Suppose
we have a device that can emit a sequence of electromagnetic pulses (tightly
grouped bunches of photons) with a fixed time intervalor
period controlled by
the ticks of a clock. We can think of them as radar pulses, but, in principle,
any part of the electromagnetic spectrum can be utilized. Further suppose
that we have a device that will detect any electromagnetic pulses returned
to us and we use the clock to measure their period along with the time
interval between the first pulse transmitted and the first returned.
Consider
the case where we observe returning pulses with the same period as the
emitted pulses but delayed by a certain amount. We can then make a model
to describe this observation. We imagine that "out there" is an object
that reflected the pulses back to us. We further imagine that the object
is separated from us by a dimension called space.
The pulses are pictured as "traveling through space," taking a certain
time to reach the object and return.The
object is modeled as being separated from us by a "distance" equal to half
the observed time delay, multiplied by an arbitrary constant c called
the "speed of light." The only purpose of this constant is to allow us
the flexibility of expressing distance with different units than time,
a rather silly idea.
Next
consider the case where the period of the returned pulses has a larger
value fromthose transmitted. We
model this by saying that the object is "moving" away from us and so the
reflected pulses arrive at a lower rate as each succeeding pulse must travel
a greater distance. Specifically, we hypothesize that the object is moving
away at a speed v along
the line between us, which can be calculated from the transmitted and received
pulse periods (homework exercise).
Similarly,
in the case where the returned pulse rate is lower, we say that the object
is "moving" toward us. Of course, this is just the familiar Doppler effect.
However, note how we have not presumed a concept if space but introduced
it as an operational element of a model that describes observations.
We
can extend the picture to two and three spatial dimensions by aiming our
sender and receiver in various directions. In this way we measure the vector
velocity whose magnitude is the speed. Accelerations can also be measured
as the time rate of change of velocity.
This
illustrates how space, time, and motion are human constructs, defined operationally
in terms of clock measurements. They are not real. They do not kick back.
In fact, one does not quite know how to kick them. Still, somethings out
there are real, as evidenced by the fact that they do kick back when you
kick them. But whether they are really localized objects moving around
in space, or something entirely different that can still be modeled that
way, we will never know,
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Vic Stenger's latest book is Has Science Found God: The Latest Results in the Search for Purpose in the Universe. His web site is at http://spot.colorado.edu/~vstenger.