Ka
Kaleidoscope
e 6.1, Jack J.
J Miller, “R
Review of Th
he Speed of
o Light: Co
onstancy and
Co
osmos by David
D
A. Grrandy”
Review
w of The Speed
S
of Light:
L
Con
nstancy and Cosmo
os by Davvid A. Gra
andy
JACK J.. MILLER
Modern physsics is a playground fo r philosophy. Our study of the un
niverse has revealed
M
myriad of co
ounterintuitive truths an
nd unsettling conclusions: if some of the fund
damental
a vast m
constantts of nature that define our universse differ by one part in 1010, for exxample, mattter as we
know it would not exist.
e
avid Grandyy’s book is an attemp
pt to deal with
w
one of
o these con
nstants of nature –
Da
the spee
ed of light, c – and pre
esents a brieef overview of its imporrtance in on
ne aspect off modern
physics, Einstein’s special
s
(as opposed
o
to
o general) theory of re
elativity. Speecial relativitty is the
extension off the “Copernican Princip
ple” that we
e don’t live in
n a special p
place: every observer
natural e
sees a d
different reality, and the
ere is no ‘un
niversal’ refe
erence frame to define a truth sho
ould they
disagree
e. Experimen
ntally verified
d countless thousands of
o times, spe
ecial relativitty comes with a few
conclusions that so
ome might find
f
unsettliing: there are no such things as ssimultaneous events,
ght is consta
ant in all
informattion cannot travel fasterr than the sspeed of light, and the speed of lig
frames of referencce, including those whiich are non-stationary. The deveelopment off special
relativityy lead to th
he abandonment of th
he concept of a Luminiferous Æth
her, an all-p
pervading
medium through wh
hich light wa
as presumed
d to propagate, which would
w
provid
de a reference frame
heory is, at heart, a maathematical toolkit for transformin g between different
for all. Einstein’s th
of reference, and one studied by un
ndergraduate
es around th
he world.
frames o
Grrandy’s thesis is an attem
mpt to show
w that, as cre
eatures of th
his universe, we are bou
und to be
influence
ed by its law
ws. He provid
des a selecteed overview
w of special relativity,
r
wh ich is mostly
y correct,
and doe
es not dwell on its ascendance from
m the confused and con
ntradictory u
understandin
ng at the
time. This is followe
ed with a sojjourn into th
he philosoph
hy of observ
vation, drawiing from a myriad
m
of
authors from different periods. He preseents variouss contempla
ations of th
he nature of visual
nce, together with a wide variety of thoughts on
n what light is.
experien
Un
nfortunately, I found Grandy’s
G
textt wanting in
n several ke
ey areas. Mo
ost notably, modern
physics has spent much
m
of the
e last centurry dealing with
w
what lig
ght is: it is a mutually inducing,
propaga
ating set of orthogonal electric and
d magnetic waves
w
(a fac
ct never men
ntioned in the book,
despite being know
wn since 186
65); it is the gauge boso
on of the electroweak p
part of the Standard
122
Kaleidoscope 6.1, Jack J. Miller, “Review of The Speed of Light: Constancy and
Cosmos by David A. Grandy”
Model Lagrangian; it is the quantised excitation of the electromagnetic field. The picture modern
particle physics has of light is complex, consistent, experimentally verified, and complete
with a several interesting philosophical problems – problems which Grandy does not discuss.
Explaining these statements and coming up with a consistent theory of visual experience would be
a Herculean task: Grandy does not attempt it. Instead, we are given an oft-anachronistic
scattergun of quotations from various authors who have attempted this task, often before
the modern scientific understanding of light and vision. Grandy expands Einstein with Derrida;
he quotes Heidegger with Descartes. A critical, chronological development of the understanding of
light, together with an expanded discussion of the philosophical problems with physics, would
have been far preferable to a series of quotations and barely contextualised ideas. Grandy also
touches on the problem of the perception, and argues that we cannot ever understand light – or
comprehend special relativity – as it is such an integral part of our being.
Physicists have spent an awfully long time dealing with the fundamental problem that
nature is made out of the very things one wishes to investigate. It is often impossible, therefore,
to perform experiments that investigate a phenomenon without the results of that experiment
changing the exact experiment performed. One cannot simply ignore the rest of the universe
when measuring the property of a sample. It is this idea, in fact, that lead to quantum mechanics
in the first place: objects are small if the disturbance made by measuring them is large compared
to the value of the quantity one is measuring.
This idea is not new, and yet it is one that Grandy alludes to as a novel revelation: light’s
odd behaviours are hidden from our everyday experience. I propose that this fact is entirely
unsurprising: our everyday experiences are on a world where c is largely compared to any velocity
v we are likely to experience. The relevant factor for special relativity,
γ = (1− v
2
c2
)
−1
is therefore
almost unity at any speed humans have directly travelled at relative to earth. As v approaches c,
however, ・ diverges and the world becomes far stranger: colours shift, distances, times and
masses distort, and the very geometry of space bends, all proportional to ・. This seems
fantastical directly because of our local experience: our intuition about how the world behaves is,
in general, wrong. Nature knows exactly what tools she has to use; we do not. It is a fallacy,
therefore, to suggest something as problematic if one cannot ‘common-sensically’ understand why
it is the case: our ‘common sense’ is often wrong; Grandy quotes authors who do just this.
Grandy spends a lot of time discussing how one can never truly see light, per se, but only
rather images of other things. This statement is almost tautologous, for light is just an integral
part of our cosmos. We cannot understand what it is like to be a photon any more than we can
understand what it is to be an atom of hydrogen. When it comes to vision, the whole apparatus of
the eye is a brilliant example of why biology is difficult. Without a chemical changes occurring due
to a photon being absorbed in a single molecule of cis-retinal, I would never be able to detect
that a photon had arrived on my retina; without countless billions of molecules of retinal
(and more parallel imaging apparatus), I would never be able to receive an image of a tree.
123
Kaleidoscope 6.1, Jack J. Miller, “Review of The Speed of Light: Constancy and
Cosmos by David A. Grandy”
Without a brain that layers information in many different ways across many levels of organisation1
in a way that is, of course, not yet fully understood, I would never be able to perceive the picture
of a tree as a tree. Yet the philosophical problem of perception still stands: I can never know that I
am really looking at “a tree”, or that I am now observing a tree in the same universe as everyone
else – or that a tree to me is the same as anyone else. Grandy states that the constancy of the
speed of light has an effect on the apparatus of our vision. This is true, but perhaps not for the
reasons he states: c is implicit in the mechanistic explanation offered above; were c not constant,
we would likely not live in a causal universe. Unfortunately special relativity does nothing for the
problem of perception.
Unlike the universe, Grandy’s book has little structure. It does not appear to have a coherent
argument, and is more a pastiche of a selected number of thoughts about the speed of light. In
most cases, these authors were writing before the modern understanding of the nature of our
universe – making the physics somewhat out of date – or, alternatively, present phenomenological
arguments that fundamentally seem to be descriptions of the lack of understanding of light on
behalf of others. The Egyptian God Ra, as well as the Christian one both make rather unexpected
appearances. If you approach this book expecting to be educated in special relativity, there are far
better introductions. If you instead wish for a grounding in the history and philosophy of
electromagnetism (a rich field), again, there are other more focussed texts in the field. Widely read
philosophers of science who wish to critically examine the author’s argument may, however, find
challenging and novel snippets that they enjoy.
Jack J. Miller
Department of Physics
The University of Oxford
[email protected]
Jack J. Miller MPhys (Hons. Oxon.), AMInstP, AFHEA is in the final year of a DPhil (PhD) in
Condensed Matter Physics, and has an interest in the history and philosophy of electromagnetism.
1
For a good, accessible introduction to how phenomena as complex as consciousness can
arise from deterministic systems with a finite set of rules, see the Pulitzer-prize winning
Gödel Escher Bach by Douglas Hofstader.
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