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From time to time,
this proposition is advanced:
'Speed of light, c, is a constant by definition. Because in 1983, an international committee
defined the meter as the distance traveled by light in vacuum during
1/299,792,458 of a second. And so c is fixed forever'.
That is wrong. Decrees can never fix anything forever. Not even the Roman Empire could not be maintained this way. Let's take a closer look.
The 'Fixed-by-Convention' Argument was first used by some critics and
sociologists of science to support the view that 'Natural Science is built upon convention and, thus, devoid of objectivity'.
Ironically, nowadays, this same argument is often used by physicists
who, in the face of the current onslaught of superluminality, are trying, in
vain, to save crumbling Relativity.
The following points can be made against the Fixed-by-Definition Argument:
[A] The
definition of the meter in terms of light travel time, in perfect or less than
perfect vacuum, does not imply that the
meter sticks and the measuring rods have become obsolete or irrelevant. That is because those meter sticks and
measuring rods have been used, right from the beginning, to build, calibrate,
and test the new light-based measuring instruments. These modern measuring devices, simply, cannot be manufactured in
any other way. Call it Measurements
Ladder. Call it Boot-strapping. Call it Vicious Circle. Or call it what you want. But that's the simple truth.
One example may illustrate this 'inarguable' fact. A prototype of the new
measuring instruments is the Michelson interferometer. Based on interference by thin films, this
ingenious device can be used to make precise length measurements by counting
the number of fringes. But how can
users translate the number of fringes to length? By consulting a standard table.
And how is the standard table constructed? By using old-fashioned meter sticks and measuring rods.
In brief, the new measurements of length and distance are operationally
based on the old ones, not the other way around.
[B] In addition
to the previous false premise, the 'Fixed-by-Convention' Argument, against
variability of c, is implicitly based on the assumption that 'Convention is a good shelter'. In other words, 'what is founded on
convention cannot be falsified'.
Tell that to the charlatans. How
easy their life could have been! The
fact of the matter is this assumption does not hold water at all.
First and foremost, there is no pure convention. Convention is supposed to be the sole
creation of the human mind. The problem is that the human mind can never come
up with anything that does not imitate and hence reflect some part of reality
either in symbols or by the virtue of its inner relations and the rules of the
game. Secondly, convention to be
convention must have its own rules.
After all, convention is a collective enterprise. And what has rules can be always beaten by
the same rules. That is because the
primary function of the rules is to catch and highlight contradictions and
violations. Finally, the new convention
of using speed of light to measure distances is not only prone to violations,
but also an ideal tool for catching them.
It doesn't take more than two persistent discrepancies in measuring the
length of the same thing to set off the alarm bells.
[C] Since it's
all about c, let's expand on it a bit further.
In the context of variability, three different kinds of light speed
have to be considered:
1. The
Muzzle Speed of Light:
This type of speed is denoted by c, and determined entirely by the internal dynamics of fundamental emitters, i.e., atoms, molecules, electrons, etc..
Historically, the value of the muzzle speed of light was fixed globally
by the ether.
Today, however, this global value hangs, loosely, in the air. There is,
simply, no good reason for why all sorts of emitters should fire their
radiation with exactly the same muzzle speed under all circumstances. Of
course, the variations in muzzle speed could be small. But they are possible nonetheless. Accordingly, it's quite possible that the
muzzle speed of light varies with
colour, as suggested by Paul Gibson, or even varies with time as
hypothesized by Moffat and others.
Some people think such variability, if found, will not imply Einstein
was wrong. It may not, but certainly
will entail major modification of his theory.
2. The
Speed of Light in Refractive Media:
Again this type of speed poses no problem to the old Ether Hypothesis.
That is because the denser the ether, the faster the speed of light, and vice
versa. Refracted speeds faster than c,
however, constitute a serious anomaly in current physics. Because refraction is interpreted on this
physics as time delay and reaction time due to re-emission and scattering of
the incident light by the medium particles. Therefore, if light runs faster, as
found by Nimtz, Wang, and others, then the anomaly cannot be explained away by
this mechanism. Let alone the damage this anomaly can inflict on Einstein's
Special Relativity.
3. The
Composite Speed of Light:
This kind of speed is defined as the resultant of the muzzle speed of light, and the speeds of the source and the observer. It's here that variability poses a direct threat to Einstein's Relativity. No convention, in the world, can hide or shelter it from the threat of this hanging sword. That is because, as H. Dingle pointed out many years ago, the Theory of Special Relativity rises and falls by the standards of kinematics alone.
[D] There is
one important point, related to the composite speed of light, not properly stressed by the proponents of
the 'Fixed-by-Convention' Argument. Einstein is widely supposed to be a genius.
And as such, it's a little harder to have him cornered! Publicly, Einstein declared that his
theory is built upon the Relativity and
the Constancy Postulates. In reality,
however, he was using a rather trivial and down-to-earth symmetry. The situation can be illustrated by the
following example.
Suppose you have $1000 in your bank account. You love this magic number
so much and you want to keep it forever regardless of any possible changes. But
how can you do it? Very simple. Change the face value of the dollar! Or better yet, create your own dollar.
So according to this procedure, if the above amount is doubled, double the face value of your
private currency. If it goes down by
half, reduce the face value of your dollar by half, and so on. The procedure can become somewhat
complicated and unreal, as in the case when you have zero or negative amount in
your account. But you can always make use of the square root of minus one and
similar mathematical tricks. In short, you cannot be proven wrong.
That is exactly what Einstein does with the composite speed of light.
He, simply, changes the units of space and time in order to keep that speed
constant.
Fortunately for the iconoclast, however, Einstein’s freedom to maneuver
is extremely strait-jacketed by nature and by his own equations of
conversion. His theory, therefore, can
be decisively falsified. For instance,
if the flight time of two beams from A to B,
within the one and the same frame of reference, is found to be
different, then Einstein’s Theory is fatally falsified. Furthermore, space and time are not just
quantities. They are, in fact,
universal logical constructs of fundamental importance. Consequently, the attempt to modify them can
lead to horrendous contradictions and corruption of reason.
Therefore, we conclude that the 'Fixed-by-Definition' Argument, against
the possible variability of speed light, is blatantly fallacious and defective
and cannot stand up under close examination.
1. Stenger, V., “Is the Speed of Light Variable?”:
http://www.colorado.edu/philosophy/vstenger/Briefs/c.pdf
2. Gibson, P., “Relativity- the Special and the
General”:
http://www.wbabin.net/gibson/gibson2.htm
3. Proceedings of the 19th IEE__ “Absence
of Transverse Doppler Shift at Microwave Frequencies”:
http://fodok.uni-linz.ac.at/fodok/publikation.xsql?PUB_ID=11801
4. Valigra, L., “Faster than the Speed of Light”:
http://www.csmonitor.com/2003/0130/p14s03-bogn.html
Absolute Velocities:
http://www.wbabin.net/physics/faraj4.htm