       
What
is Space? D.M. Marett (2010) Is the vacuum of
space a real object unto itself, or is it simply emptiness, a
nothing that does not exist in the absence of matter? From the
viewpoint of Descartes and Leibniz, without physical objects, "space"
would be meaningless because
space is the framework upon which we understand how physical objects
are related to each other. Sir Isaac Newton, on the other hand,
argued for an absolute space ("container space"), which can continue to exist in the absence
of matter. In
the 19th century, James Clerk Maxwell introduced the idea of an
electromagnetic ether - a medium of space capable of supporting the
structures of the electric and magnetic fields or light. Maxwell's idea
of space was that it had a density and a transverse elasticity - when
stressed it would impose a restoring force, much like a solid. This
made it suitable for the transmission of transverse waves that waved in
the body of the medium. It was Maxwell's challenge for an experiment to
detect this medium that led to the Michelson and Morley (M&M)
experiment of 1881 and 1887. There is good reason to believe that the
M&M experiment was the wrong one for the job, but at the time
it
confounded the understanding of researchers. This frustration opened
the way for the introduction of new theories that might solve the
dilemma, such as Einstein's relativity theory. Initially,
Einstein's theory of special relativity considered an ether of space
"superfluous" and seemed to side with Leibniz, in that relational space is the space that
defines the relations between objects,
with the implication that it cannot
exist in the absence of matter. It removed the medium of space that
Maxwell conceived of for the light waves to wave in, as this would
provide a preferred reference frame for light, and in relativity theory
there can be only relative reference frames for light. Einstein asserts
that the Maxwell-Hertz equations are simply valid in "empty" space. In
this interpretation of relativity (Dynamical Relativist
Interpretation), light and fields must consist of particles - since
there is nothing else. Energy cannot exist in space in the absence of
material objects. Space is not a "thing", it is an intellectualization
of the relation of objects to one another. It is the ultimate
"nothing." But this has a flaw - space has "properties" that cannot be
denied - it has non-zero magnetic permeability and electric
permittivity, it can support energetic structures such as electric
fields, gravitational fields, magnetic fields - and these fields
according to Quantum electrodynamics consist of particles that have
arisen spontaneously out of this "nothing". Space
has foremost the relativistic attribute that light propagates through
it at exactly C. Repeatability
(light propagates at C, magnetic permeability is always 4p
x 10-7) implies causality (space provides a structure that excludes all
velocities for light except exactly C, excludes all magnetic
permeability's except exactly 4p
x 10-7). This implies that space cannot be "nothing". Since
Einstein was obliged to admit that space has "properties" a few years
later. Einstein's general relativity (1917) re-introduced a
concept of
absolute space, and in particular, he had to try to explain
Mach's
concept of inertia. This "ether" of Einstein is not the electromagnetic
ether of Maxwell but Minkowski's "absolute worlds" hypothesis grafted
to Einstein's geometric concept of gravity. This new theory of
the
medium (Substantivalism) is not in space so much as it is in time. A
medium for electromagnetic waves is missing, the only waves conceived
of in the fabric of space-time are gravitational waves. The
Substantivalist Philosophy most consistent with Relativity might be
defined as follows: 1)
Substantivalism - spacetime is a real substance that exists
independently of physical objects. Compatible with perdurantism,
eternalism and parminedeanism (most compatible with SR). 2)
Perdurantism - Objects are 4 dimensional and extend over time. 3)
Eternalism - that all times past, present and future are equally real
(coexist). 4)
Parminedeanism -Being is fundamentally real; change is an illusion. 5)
inertia exists due to an objects motion with respect to spacetime.
Spacetime resists non-straight motion. This
is distinct from a Dynamic Relativist philosophy, mentioned earlier,
which has for its definitions: 6)
Dynamical Relativist Interpretation - spacetime does not exist
independent of real objects. Compatible with endurantism, presentism
and heracliteanism. 7)
Endurantism - 3D objects extend over a spatial region only (not across
time) but endure through time. 8)
Presentism - that only the present exists. 9)
Heracliteanism: - becoming (change) is fundamentally real. 10)
Relationalism - inertial effects can only be due to an objects motion
with respect to other objects. General
relativity says that space-time has a structure, but this structure is
determined by the matter density of the universe. This is how the
matter of the universe (the fixed stars) can provide inertia. However,
the substantivalists might say that there can be inertial forces in
space devoid of matter (Mach's principle does not hold). The metric
field does not need to be a matter field, since space-time exists as a
thing in and of itself. Thereby gravitational waves can propagate in
space-time alone. On
the other hand, a relationalist might say that the metric field is a
matter field, and if the matter of the universe is removed, nothing
would be left (space is simply a void). Gravitational waves could be
viewed as propagating in the metric field (matter field). Einstein
sees electromagnetic forces as relative to the perspective of the
observer and thereby do not exist objectively in an absolute
space.
This goes against Maxwell's original idea that the magnetic lines of
force are real objective structures independent of the observer. Following
all this, if Einstein is correct, then Maxwell's wave nature of light
could be replaced with an idea of the electromagnetic energy
propagating as singularities (points) - very much like discrete
particles. To quote Einstein (1909): "Anyway,
this conception seems to me the most natural: that the manifestation of
light's electromagnetic waves is constrained at singularity points,
like the manifestation of electrostatic fields in the theory of the
electron. It can't be ruled out that, in such a theory, the entire
energy of the electromagnetic field could be viewed as localized at
these singularities, just like the old theory of action-at-a-distance.
I imagine to myself, each such singular point surrounded by a field
that has essentially the same character of a plane wave, and whose
amplitude decreases with the distance between the singular points. If
many such singularities are separated by a distance small with respect
to the dimensions of the field of one singular point, their fields will
be superimposed, and will form in their totality an oscillating field
that is only slightly different from the oscillating field in our
present electromagnetic theory of light. " By
reducing the EM oscillation to a point, there is no medium or waves
in the conventional sense. There is no good explanation
offered why
light would have a wave character, would travel at exactly C,
or be
transverse. Enter
the Quantum Electrodynamics Model of Light: Does
QEM offer any further answers? Feynman continues with Einstein's notion
that light is a particle -Feynman refers to the particle existing in
space time. Feynman
implies that the
wave-particle duality of the photon was resolved in favour of the
particle. He says quite explicitly - "I want to emphasize that light
comes in this form - particles. It is very important to know that light
behaves as particles, especially for those of you who have gone to
school, where you were probably told something about light behaving as
waves. I am telling you the way it does behave, like particles."
Feynman , QED, P. 15. He
argues that even
though wave theory correctly predicts the "why" of partial reflection,
and particle photon theory does not, QED is only concerned with
predicting the probability of the event and thereby the "why" is not
something that the theory can or will explain. P.24 of Feynman's "QED".
There
seems to be no explanation as to how the photon carries with it
frequency and polarization information. The photon is said to be
circularly polarized and to have a frequency f, but in what sense? If
the photon is a particle, how is the wave impressed upon its body? It
can't be a wave in space, since space is a void (Maxwell's ether is
dead). Even if we conceive of a sea of virtual particles to propagate
the electric and magnetic fields of the EM wave in space, one would
have to believe that the only real particle (the real photon that
triggers the photomultiplier) contains all of the frequency information
to create the field, so it must be oscillating first to guide the
virtual particles. In what way is it oscillating?
Vacuum
Polarization: To
describe fields, the "empty vacuum" must be given a rich, spontaneous
inner life. The electromagnetic field in space in QED is said to
produce virtual short-lived electron-positron pairs that change the
distribution of charges and currents that generated the original
electromagnetic field. The ether of Maxwell has been replaced by a
medium of virtual particles, miraculous in properties - they can be
spontaneously generated and then destroyed, can defy the conservation
of energy principle, and the virtual photons can be given mass due to
their short range and short lifetime. Virtual particles cannot be
detected by definition - if they persist long enough to be detected,
then they are no longer virtual. This interpretation is sometimes
referred to as the material grid of space - it has been attributed a
density that is constant in space with no clumping, and stays constant
as the universe (allegedly) expands. In fact approximately 70% of the
density of the universe has been attributed to this material grid. So
like Maxwell's ether, this virtual material grid of space has
a density. However, this material grid of QED is a matter grid - the
virtual particles have mass - even the virtual photons. In this sense
it is more like a Dynamic Relativist interpretation, where there is
only matter in space, except that they fill all of empty space with
virtual matter! The estimates of the various contributions of these
virtual particles to the density of space also doesn't add up - they
are much too big. The model cannot be "real" because the energy of
spontaneous quantum activity becomes infinitely large - these are the
so called "infinities" that Feynman had to sweep under the carpet. The
underlying problem of this new conception of space is that since the
virtual particles are by definition "undetectable", we are not much
better off than with Maxwell's original ether, which fell from grace
precisely because it was undetected. The "condensations in space" could
be something completely different from the particulate forms that have
been attributed to them, in fact, they would have to be, since their
energies don't add up. To conclude, the modern conception of space remains a contradiction - physicists have many times attempted to throw away the medium of space, only to have to re-introduce it again later - usually with models that are internally inconsistent and contradict known laws of physics. And the most important question to be left unanswered is the "why"? Why is the electron mass the mass that it is, why is the speed of light the speed that it is - the fundamental units of space have very specific values that these modern models just can't answer. Perhaps a radical re-thinking of the nature of space is needed. References:
1) http://redshift.vif.com/JournalFiles/V08NO3PDF/V08N3GRF.PDF 1) http://ls.poly.edu/~jbain/philrel/philrellectures/07.Consequences.pdf 3) http://ls.poly.edu/~jbain/philrel/philrellectures/09.Geometrization.pdf 4) http://ls.poly.edu/~jbain/philrel/philrellectures/11.InterpretingGR.pdf 5) http://web.mit.edu/physics/people/faculty/docs/wilczek_space06.pdf 6) Richard
Feynman, "QED: The Strange Theory of Light and Matter." 1988.
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