A Medium for the Propagation of Light Revisited

Abstract

Electromagnetic waves are waves that propagate through the vacuum of space. Although it is well known that mechanical waves require the presence of a medium for wave propagation, it is commonly thought that electromagnetic waves do not require a medium for propagation. The purpose of this essay is the demonstrate, using logic and common sense, that electromagnetic wave propagation (i.e., light) also requires the presence of a medium. Using the logic and math associated with wave propagation in a material medium, the composition of the medium for the propagation of light is retroductively deduced.

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Vancouver Canada, BC 2017 Proceedings of the CNPS 1
A Medium for the Propagation of Light Revisited
Lori Gardi
lori.anne.gardi@gmail.com
Although it is well known that mechanical waves require the presence of a medium for wave propagation, it
is commonly thought that electromagnetic waves do not require a medium. The purpose of this essay is to
demonstrate, using logic and common sense, that electromagnetic waves (i.e., light) also requires the presence
of a medium for propagation. Using the analogy of wave propagation in a material medium, the composition
of the medium for the propagation of light (the aether) is deduced, the null result of the Michelson-Morley
experiment is explained, and an alternate experiment to detect the luminiferous aether is proposed.
Keywords: aether, light, sound, propagation, waves, medium, Michelson-Morley, gravity waves, LIGO, virtual
particles
1. Introduction
The luminiferous aether has been hotly debated topic
for more than 100 years. Although it is commonly
thought that light does not require a medium for prop-
agation, the debate is all but over. First, we must all
agree that waves do not travel in the traditional sense as
a car travelling down a highway or a particle travelling
through a particle accelerator. Waves propagate, i.e., the
mechanism for travelling waves is much different than
the mechanism for travelling particles. This is an impor-
tant point.
It is well known that a sound that you hear propagates
through the medium called air. When I speak a word,
I am not emitting a sound. A sound is not leaving my
mouth and travelling to your ear. What I am doing is I
am setting up a perturbation in the medium called air.
The perturbation generates a wave pattern which then
propagates through the air, at a constant velocity (the
speed of sound in air), until it reaches the detector, in
this case, the ear. Here is another example. I am sitting in
a pool of water. When I sit still, nothing happens. When I
start waving my arms in the water, then you will see some
waves. Am I emitting these waves? Obviously not. I am
perturbing the medium called water which manifests as a
wave that then propagates through said medium. In other
words, something must be waving in order for a wave to
appear. The act of waving perturbs the medium.
Here, I argue a similar thing for light. When you turn
on a light, what is actually happening? Does the light
bulb emit particles of light or photons that then travel
through space to a detector? Does the detector then catch
the photons? Doesn’t it make more sense that the light
bulb is setting up a perturbation in a medium? Why
should light waves behave so much differently than all
other waves? Short answer; they don’t. In this essay, it
is argued that light and sound are exactly the same, only
propagating in different media. This has been argued
many times in the past [1] [2] [3], but most physicists
still believe that light propagation does not require a
medium. The null result of the Michelson-Morley exper-
iment is usually sited as support for this belief system,
however, there may be another explanation for this null
result that wasn’t considered historically. This will be
the subject of this essay.
Claims:
1. All waves are caused by perturbations (waving).
In order for a wave to form, "something" must be
waving.
2. All wave propagation requires a medium. There are
no exceptions.
2. On the Speed of Sound
The equation used to calculate the speed of sound
through a material medium is as follows:
v=sKs
p(1)
Here, Ksis the stiffness coefficient (or the modulus of
bulk elasticity for gases), and pis the density coeffi-
cient. Stiffness is the resistance of an elastic body to
deformation by an external force, and density is mass
per unit volume. In general, a material with a large
mass per unit volume (density) will tend to exhibit
a slower speed of sound, and a material with a large
stiffness coefficient will tend to exhibit a faster speed
of sound. (The opposite is true of low density and less
elastic materials.) In reality, it is much more compli-
cated than that. A rarefied medium, e.g., rarefied air,
which has a lower mass per volume, will also have
a lower stiffness coefficient. In this case, the speed
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2 L. Gardi: A Medium for the Propagation of Light Revisited Vol. 10
of propagation in rarefied air is much slower than in
non-rarefied air, even though the density coefficient is
lower. In general, rarefied materials exhibit a slower
speed of propagation than the non-rarefied materials.
This is an important point that we will come back to later.
3. On the Speed of Light
One of the equations used to calculate the speed of
light is as follows:
c=s1
ε0µ0(2)
Here, ε0corresponds to permittivity (of free space) and
µ0corresponds to permeability (of free space). With a
little adjustment, we can make this equation look exactly
like the speed of sound equation (1):
c=sµ−1
0
ε0(3)
Here, inverse permeability, µ−1
0, plays the role of the
stiffness coefficient. This makes logical sense since ma-
terials that are more permeable (like a sponge) tend to
be less stiff than materials with a lower permeability, and
vice verse. Analogously, the ε0parameter plays the role
of the density coefficient, Ks. This also makes logical
sense since permittivity is directly proportional to dielec-
tric polarization density (polarized particles per unit vol-
ume). In this manner, the equation to calculate the speed
of light in the vacuum of space (using vacuum permittiv-
ity and permeability) can be made to look exactly like the
equation used to calculate the speed of sound in a mate-
rial medium. Although this does not prove that there is
a medium for the propagation of light, it does imply that
a medium could exist. If there is a medium, then what is
its composition?
Logically speaking, if empty space is a medium,
then that medium cannot be made of ponderable matter
(particles with mass), since the vacuum of space is by
definition, empty of matter. If the vacuum of space is not
ponderable matter, then what is it? Well, it must be made
of something other than ponderable matter. But if the
vacuum of space is not made of ponderable matter, then
it doesn’t exist, right? This is not necessarily true. We
currently cannot directly observe dark matter, but we can
infer its existence by the behaviours of the galaxies and
galaxy clusters. We also cannot directly observe dark
energy, but its existence can be inferred by the apparent
accelerated expansion of the universe. By analogy, just
because we cannot directly observe the medium for the
propagation of light doesn’t mean that it does not exist.
The fact that light propagates at a finite velocity implies
that a medium should exists. That said, if the medium
is not made of ponderable matter, then what could it
be possibly made of? Can we intuit the medium for
the propagation of light by studying the propagation of
sound waves through a "ponderable matter" medium?
4. On the Speed of Sound in NaCl
In this section, we will analyze the behaviour of a pon-
derable material medium called sodium chloride, NaCl,
commonly known as salt. These experiments were done
by Menahem Simhony at the Hebrew University in Is-
rael [5] [6]. In his experiments, Simhony noticed that
the clear salt crystal, NaCl, becomes cloudy and electri-
cally conducting when exposed to UV light of around 8
eV. With this exposure, Na and Cl ion pairs are released
from the crystal lattice medium and are free to wander
(conduct) within the medium. When the UV energy is
removed, the ions fall back into the lattice and the 8 eV
energy (used to free the ions) is released, after which the
crystal becomes clear again.
Using equation (1), the speed of sound within the
NaCl lattice can be calculated by replacing the stiffness
coefficient , Ks, with the binding energy of NaCl within
the lattice, and the density coefficient, p, with the mass
per unit volume of the NaCl medium. The assumption
here is that the binding energy of a material determines
its stiffness (and indirectly the elastic properties) of the
medium. For these calculations, the unit volume of a
single NaCl pair was chosen.
v=sKs
p=rA
B+C=3700[m/s](4)
Here, A=1.3052 ×10−18 is the binding energy of the
NaCl bond, B=3.818×10−26 is the mass of the sodium
ion, and C=5.720 ×10−26 is the mass of the chlorine
ion. This equates to 3700 [m/s] which is in fact the speed
of sound within the NaCl medium.
Using the logic of this example, we can now speculate
as to the makeup of the luminiferous aether. First, we
make a guess that it is made up of "particle pairs" of
some sort, however, it cannot be made up of "atomic"
particle pairs (like NaCl) because the vacuum of space
is by definition empty of ponderable matter. Here, it is
assumed that the vacuum of space is made of and/or
filled with something, but what could this something be?
5. On the Medium for the Propagation of
Light
In physics, there is a phenomenon referred to as
electron-positron annihilation. This occurs when elec-
trons and positrons get close together and collide. The
result of one collision is the annihilation of an electron
and a positron with a release of two gamma ray photons,
each with an energy of 0.511 MeV or 1.022 MeV in to-
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Vancouver Canada, BC 2017 Proceedings of the CNPS 3
tal. In the NaCl experiment, the free roaming Na and Cl
ions fell back into the lattice with the release of the 8 eV
of energy that was used to extract the ions from the lat-
tice in the first place. What if the same thing is happen-
ing with electrons and positrons? What if the electrons
and positrons are not annihilating, but instead, are merely
falling back into a lattice or medium of some kind? If
this is the case, then the 1.022 MeV energy release (af-
ter collision) can be considered as the binding energy
of an electron-positron pair in a medium consisting of
bound electron-positron pairs. Using the NaCl analogy,
the speed of propagation of such a medium can be calcu-
lated as follows:
v=rA
B+C=299792458.0[m/s](5)
Here, Ais the binding energy of the electron-positron
pair in the medium (A=1.637421×10−13 [J]) and B+C
is the mass per unit volume of the electron-positron pair
(B+C=1.821876582 ×10−30 [kg]). Notice that this
evaluates to exactly the speed of light. This suggests
that the vacuum of space consists of a medium of bound
electron-positron pairs. This is, for all intents and pur-
poses, Dirac’s sea [7]. Although these electron-positron
pairs are not ponderable in of themselves (since they are
charge condensed and mass condensed), they do become
apparent when unpaired (ponderable) atoms and ions en-
ter the medium. Figure 1 is a 2D schematic of how a sea
of electron-positron pairs might self-organize in the pres-
ence unpaired charges.
From Figure 1, it is clear to see that the sensation
we experience as charge could very well come from a
field or medium consisting of a sea of bound particle-
antiparticle pairs. This may explain why both electrons
and protons "have" the same charge even though they
have different masses and are of different sizes. It is
possible that particles do not have the property of charge
in of themselves, but instead, they experience charge
the same way, via the particle-antiparticle medium. It
should also be noted that equation (5) apples to all
particle-antiparticle pairs, not just electron-position
pairs. For example, if we insert the binding energy and
mass per unit volume for a proton-antiproton pair into
equation (5), we will still get the speed of light. We
could use quark-antiquark pairs as well and get the same
answer. Thus, a medium of particle-antiparticle pairs
would explain where all the virtual particle-antiparticle
pairs come from in quantum field theory.
6. On the Detection of the Aether: Part I
The null result of the Michelson-Morley experiment
is often sited as evidence that the aether does not exist.
The MM experiment measures the speed of light in two
perpendicular directions as the earth orbits around the
sun. The hypothesis is as follows: If the aether exists,
then the measured speed of light should be different in
the direction of motion through the aether as compared
to a direction at right angles. This experiment has been
done many times with increasing sensitivity over the
years [4], and a difference has never been detected.
Given this null result, the consensus is that the aether
does not exist. This hypothesis, however, is merely an as-
sumption. A literature search will show that an acoustic
Michelson-Morley experiment has never been officially
performed. Unofficially (independently) however, a
Michelson-Morley type experiment has been performed
in air using an ultrasonic range finder [8]. Interestingly,
this experiment also produces a null result. Given these
results and the logic of the MM experiment, we must
conclude that air does not exist. Obviously, this is not
the case. It seems that direct detection of the aether is
not be possible using the MM experimental setup. Using
light emitters and detectors to detect the medium for the
propagation of light may be akin to circular reasoning.
In other words, the logic of the MM-experiment may be
inherently flawed.
7. Similarities Between Sound and Light
There are many similarities between sound and light.
For example, both sound and light carry energy from one
place to another. Both sound waves and light waves ex-
perience wave interference. They both exhibit Doppler
shift. Both experience reflection, refraction and diffrac-
tion. Refraction is the bending of a wave when it moves
between media with different propagation speeds. Both
sound and light refract toward the normal of the gradient
when moving from a fast medium to a slow medium.
Another similarity has to do with the speed of sound
in a rarefied medium. Earlier, it was noted that the speed
of sound actually slows down in rarefied air even though
the density is lower than the non-rarefied air. Rarefied
mediums actually reduce the stiffness constant of the
medium which also affects the speed of sound in said
medium. If light propagates in a medium, then the speed
of light should also slow down when the medium is
rarefied.
As sound waves propagate in matter, light waves prop-
agate in aether. This is the hypothesis. Here it is argued
that when matter is present, then aether is rarefied and
when aether is present, then matter is rarefied. When
matter is rarefied, sound slows down and when aether
is rarefied, then light slows down. In materials that trans-
mit both light and sound, for example NaCl, aether is rar-
efied AND matter is rarefied. The vacuum of space is not
empty, it is just empty of matter, but full of aether. In a
similar manner, an opaque material medium is empty of
aether but full of matter. When matter is present, aether
is rarefied and vice verse. Without recognizing the exis-
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4 L. Gardi: A Medium for the Propagation of Light Revisited Vol. 10
Figure 1. This figure depicts how a medium of electron-positron pairs might self-organize in the presence of ions or charges
within the medium. The image on the left shows unlike charges in the medium and the image on the right shows like charges in the
medium. Image source: "Diracs equation and the sea of negative energy" by Don Hotson
tence of the aether, this reciprocal nature of matter and
aether cannot be realized.
Now, the only difference between sound and light
appears to be that sound is a longitudinal wave and light
is a transverse wave. Therefore, instead of saying that
light and sound are exactly the same, only propagating
in different media, we are going to say that photons and
phonons are exactly the same (only propagating in differ-
ent media). Phonons are the sound equivalent to photons
(ie. they oscillate transverse to the direction of motion),
only they propagate in solid media. Technically, solids
support the propagation of both transverse waves and
longitudinal waves. In seismology, longitudinal waves
are referred to as pressure waves or P-waves and trans-
verse waves are referred to as shear waves or S-waves.
This line of thinking also suggests that there may be a
(previously undiscovered) longitudinal component to
light propagation. Longitudinal electromagnetic waves
would be very difficult to detect since the displacement,
perpendicular to the direction of motion would be very
small. That said, there may be an experiment that is well
suited to the detection of such waves as explained in the
next section.
8. On Detection of the Aether: Part II
The Michelson-Morley experiment failed to detect the
aether. Earlier, we suggested that the logic supporting
this experiment may be inherently flawed since it uses
light emitters and detectors to detect the light medium.
There is, however, another experiment that might be bet-
ter suited to detecting the medium for the propagation
of light that does not rely on light emitters and detec-
tors. To explain this, we are going to use the analogy of
wave propagation in ponderable matter. As mentioned in
the previous section, earthquakes generate both P-waves
and S-waves. P-waves are compression waves that prop-
agate in the direction of the compression. These waves
are very subtle and therefore, much more difficult to de-
tect. S-waves move particles perpendicular to the direc-
tion of travel and thus propagate slower than P-waves.
S-waves are much easier to detect as they create more of
a disturbance. In the analogy presented herein, S-waves
are analogous to transverse electromagnetic waves and
P-waves are analogous to longitudinal electromagnetic
waves which, according to the standard model of elec-
tromagnetism, do not exist. Without a medium, it is dif-
ficult to reconcile the existence of longitudinal waves in
the vacuum of space.
If longitudinal electromagnetic waves do exist, 1) they
will be very subtle and difficult to detect and 2) they will
travel faster than the transverse electromagnetic compo-
nent (aether S-wave). That said, according to relativity,
no-thing can travel faster than the speed of light, how-
ever, waves are not things and they do not travel, they
propagate. The argument here is that the subtle longitu-
dinal waves of the aether can and do propagate slightly
faster than the speed of light, analogous to the P-waves of
seismic theory. Although the Michelson-Morley experi-
ment was ill suited to detect longitudinal electromagnetic
waves, there is another experiment that may be much bet-
ter suited to detect these waves. This experiment is called
LIGO.
On September 14, 2015, such a signal was detected
by LIGO, allegedly caused by the collision of two black
holes 1.3 billion light years from Earth. According to
the above analogy, what was detected was, for all intents
and purposes, the P-wave of an earthquake in the aether
(an aether-quake if you may) likely caused by the black
hole collision. According to the earth quake analogy,
this P-wave should have been followed by an S-wave
(transverse electromagnetic wave), and it was. A tran-
sient gamma ray signal was detected approximately 0.4
seconds after the detection of the so called gravitational
wave [11] [12]. Of particular interest is the fact that the
signal detected by LIGO is morphologically very similar
to a seismic P-wave (see Figure 2). It should also be
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Vancouver Canada, BC 2017 Proceedings of the CNPS 5
noted that relativity does not predict that a gamma ray
signal should necessarily follow a gravitational wave.
That said, if all future "gravitational waves" are followed
by a gamma ray signal, then the idea of a medium for the
propagation of light (as outlined in this essay) should be
revisited.
Figure 2. On the top is a close up of the P-wave of the M8.3
September 25, 2003 Hokkaido, Japan earthquake recorded at
West Lafaytte, Indiana. Below that is a graph of the gravity
wave detected on September 14, 2015 at 09:50:45 UTC, by
LIGO in Hanford, WA
9. Discussion
Using the analogy of waves propagating in a solid
medium, it could be argued that the aether is solid of
some kind, since solids can and do transmit transverse
waves. There are, however, other possibilities. It has
recently been discovered that superfluids behave some-
what like a solid in their ability to conduct transverse
(shear) waves, contrary to what was previously thought.
A group of physicists at Northwestern University have
shown that at sufficiently low temperatures, superfluid
helium-3 exhibits a collective behaviour that supports the
propagation of shear waves [9]. Another possibility lies
in the research associated with Bose-Einstein conden-
sates (BEC). It is found that (transverse) electromagnetic
waves can propagate in a BEC when it consists of atoms
with dipole moments [10]. Therefore, it is possible that
a medium made of (polarizable) electron-positron pairs
might behave as Bose-Einstein condensate. The author is
leaning toward a BEC consisting of particle-antiparticle
pairs (generalized as vortex-antivortex pairs [13]) as the
medium for the propagation of light.
10. Conclusion
A change in perspective shows that light may in fact
propagate in a medium, contrary to common thinking.
Using the analogy of calculating the speed of sound
in NaCl (i.e., salt), the medium that supports the prop-
agation of light waves is deduced to be a medium of
bound particle-antiparticle pairs. It was shown how
the logic of the Michelson-Morley experiment may be
inherently flawed and that the null result reported by
these experiments does not preclude the existence of a
medium. It was also shown how another experiment,
called LIGO, may be better suited to directly detect the
luminous aether medium. Here, the gravitational wave
detected by LIGO in 2015 is thought to be analogous
to the detection of the P-wave of an earthquake in the
aether. Of course, there does exist another aether detector
that has been around for much longer than LIGO or any
other experiment that man has dreamed up. They are
called "eyes".
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