On the Nature of Light
By Reason McLucus
19th Century beliefs about the nature of light continue to hamper a
study of light.
Early 19th Century physics was characterized by support for
various theories that were subsequently disproved such as the theory
that atoms were the smallest particles of matter and an atom
of one element could not be converted to another
element. J.J. Thomson disproved the first theory with his
discovery of the electron in 1897. Physicists
also discovered that the processes of nuclear fission and nuclear
fusion could change an atom of one element to an atom of another
Unfortunately the 19th Century debate suggesting that light must BE a
particle or BE a wave survives. The confusion comes in part
from the fact that in some situations light acts like a particle
other situations acts like a wave.
The standing joke when I studied light in the 60's was about the
university that taught that light was a wave on Monday, Wednesday
and Friday; and taught that light was a particle on Tuesday, Thursday
and Saturday. My professor took a different approach. He
taught light as a wave for half a semester and light as a particle the
continues to hamper an understanding of light (i.e.,
Some physicists have tried to get around the dichotomy by
suggesting that light consists of particles that may actually be
something called wavicles.
This idea implies a misunderstanding of what a wave is. A wave
involves particles forming temporary sets which
momentarily function in unison. Air molecules
normally move around like ping pong balls in a bingo machine.
However, when a sound wave passes through air the separate
temporarily function as if they were entangled with each other as
they pass along the sound energy to adjacent air molecules.
Once the wave has passed the air molecules return to
Physicists ignore the fact that if light is a form of energy it
cannot be a particle or be a wave although particles or waves might
transfer it from one location to another like particles and waves
transfer kinetic energy from one location to another. Particles
are ultimately matter, not energy. Waves involve the movement of
matter. Particles and waves transfer energy, but they are
If I throw a baseball the kinetic energy produced by the movement
of my arm is transferred to the baseball which then transfers that
kinetic energy to whatever it hits, such as a bat, a glove or perhaps a
window. An underwater earthquake may transfer its kinetic energy
to a tsunami wave which may then transfer that energy to objects
on a shore a
thousand miles away.
Waves transfer kinetic energy much more effectively than
particles. The energy used to move a guitar string wouldn't
propel a particle very far. However, that movement produces a
wave which can travel a hundred feet or more and reach anyone in
an auditorium. Such kinetic energy waves are commonly called
"sound waves" because they produce a physical sensation in the human
ear which the brain interprets as sound.
Waves can transfer complex sounds from many instruments to the human
ear in a manner that allows all the sounds to be heard even though they
come from different locations. Light waves would be more
likely to be able to transfer light in a variety of colors and
intensities in a way that allows the eye to recognize different
than would individual particles emitted from various locations.
In a classic experiment in quantum physics an individual photon
carrying light energy
approaching two different gates will go through one gate on some
occasions and the second gate on other occasions. If light from
Mars were leave the surface as individual photons they would quickly
become jumbled together so no details could be seen from Earth.
Although there are situations in which the transfer of light can be
explained as involving particles (photons), many situations such
reflections can only be explained as involving waves. If
particles produced a mirror image, objects that aren't directly
in front of the mirror would be reflected as being on the opposite side
of the room because the particles would hit the opposite side of the
mirror. Some reflective surfaces can produce the effect of
light going around a corner.
One of the problems about light as a wave is the need for something to
be "waving" as Professor Michael Fowler points out in
Some type of aether
has long been suggested as what might be waving.
However, an aether would only be necessary to transfer light
waves through space. Physicists have long ignored the
possibility that electrons in atoms could transfer
light waves just as easily as they transfer electricity.
The transfer of light waves by electrons would explain why the passage
of light through some substances causes heating but not other
The process would be similar to the process by which the passage of
electricity causes heating.
Resistance to the passage of
electricity causes heating. Resistance to the passage of
electromagnetic radiation could function in the same way.
A possible explanation for the fact that radiation passes through the
atmosphere with minimal heating would be that electrons in gas
molecules could pass along a wave without resistance because the
molecules move independently. Electrons in solids might
have less ability to pass along radiation without resistance because
the atoms they are part of are held in place in a
Air molecules can transfer sound waves even though they normally move
in a highly disorganized fashion because they can temporarily act as if
they were all connected together and acting in unison to transfer
complex sounds. Why couldn't electrons, which can transfer
energy through a wire in a highly organized manner, temporarily
organize to transfer electromagnetic waves.
Water waves may cause small boats to begin
moving back and forth because all of the boat must move at the same
time rather than having adjacent molecules move independently as
water molecules do. Moving
electromagnetic waves through a
solid might require entire groups of atoms to move in order
electrons to transfer the energy as a wave just like an
entire boat must move for the kinetic energy in water waves to be
transfered to the other side of the boat. The motion of
atoms is what physicists define as heat.
The issue of how a light wave could move through space
remains. Some type of "aether" would
be the most likely
Physicists claim there must be some type of matter they cannot detect
because the matter they can detect seems insufficient to be all the
matter of the universe. They usually describe this matter as
but transparent matter would be even harder to detect
than matter that was dark.
Dark objects don't
emit or reflect light, but they can block light if they pass
between the source of the light and the observer. Light can pass
through transparent matter without being easily detected.
Transparent matter can be very difficult to detect. In some cases
it may be detectable because some frequencies of light don't pass
through, or because the light that passes through isn't as bright.
Astronomers have noticed that light coming from distant galaxies seems
to have been shifted toward the red end of the light spectrum.
The greater the distance from earth the greater the red shift.
Some have suggested that this red shift indicates
the relative velocities
of earth and the distant galaxies. However, the shift could also
be due to passage through transparent matter such as what has
traditionally been called an aether.
A problem with the theory that the shift indicates movement away from
earth is that everything seems to be moving away from earth, but the
Hubble telescope images indicate that some distant galaxies are moving toward each
other, including the movement of our galaxy toward the Andromeda
galaxy. Thus it would be more likely that some distant galaxies
would show movement toward earth with a shift toward the blue end of
the spectrum instead of a uniform red shift. Also the relative
motion would vary among galaxies rather than being uniform based on the
distance from earth.
The false dichotomy that light must BE a wave or BE a particle
continues to hamper an understanding of light in the 21st
Century. If light is a form of energy it cannot be a particle or
a wave because both involve matter. However, both particles and
waves could transfer light energy from location to another just like
particles and waves transfer kinetic energy from one location to
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light, electromagnetic radiation, red shift, photons, dark
matter, aether, electrons, waves, particles, dichotomy, kinetic