Been reading Bernhard Schutz's A
First Course in General Relativity.
Here a few thoughts stimulated by this book.
Apologies in advance for your having to think this through.
It is a (tacit or explicit) axiom of modern physics that only sensuous
data
received in the present exist; "sensuous"
here includes all that an observer-subject can sense with the
aid of apparatuses such as microscopes, vibrating membranes in
microphones, telescopes, radio-telescopes, gravitational
interferometers, etc. etc.
For relativity physics, all observations are relative to the
observer-subject in its respective reference frame receiving
signals in the form of electromagnetic (including, in
particular, the visible colour spectrum) or gravitational
waves, which all move at the absolute speed of light, c =
300,000 km/s, either in a straight line (special relativity)
or on a curved line (general relativity). The motion of such
waves is the absolute motion. All scientific observation is
relative to and solely dependent upon receiving such e-m and
gravitational waves. The angels of modern
physics are photons and gravitons which, at their specific,
differentiated frequencies, carry information. Gravitation
itself is equivalent to the curvature of four-dimensional
space-time in co-ordinates (x. y, z, t). The specific way in
which these four co-ordinates are related to each other in the
metric of the Riemann tensor, R, determines whether the space-time in question is either
flat or curved. If R=0 everywhere, the space-time is flat.
For modern physics, it is solely by virtue of the e-m and
gravitational signals an observer-subject receives that the
observer can 'see' or 'hear' the universe. Such signals bear
energy, i.e. are pure potential and actual motion, that is
registered by the recipient medium, such as the eye's retina,
AS difference, i.e. information. Because these
signals only reach an observer at the speed of light, looking
out into the universe is looking back in linear time, t,
which, in relativity theory, for convenience, is not measured
in seconds, but in metres, that is, the metres travelled by
light in a given time interval. By convention and for ease of
mathematical manipulation, the speed of light c is set equal
to 1. Hence modern physics both mathematizes and spatializes
time entirely.
First it was optical telescopes, starting with Galileo's, that
enabled scientists to see further out into the universe than
the naked eye is capable of. The light signals carried the
information necessary to see better. Optical telescopes got
better and better, with larger and larger lenses and ever
improved resolutions allowing ever finer differentiation to be
seen in the light-messages. Starting after WWII, telescopes receiving radio, gamma rays, x-rays, etc. entered the fray, enabling e-m radiation also
outside the visible, optical spectrum to be received and hence
'seen'. These radiation signals (spectrometry) allowed
completely new phenomena in the sky to be observed for the
first time, which in turn greatly modified the theoretical
models (i.e. equations) developed to understand the information-signals
received. Phenomena such as black holes, quasars, pulsars, neutron stars were now 'visible' for the scientific
observer-subject via the signal data received and their often
very laborious analysis, which has become a major branch of
modern physics.
E-m radiation received from the sky is itself subject to
disturbance by other e-m radiation from other sources. The
further the e-m radiation has travelled to the observer, the
more it has been corrupted by this noise from having to pass
through and by other matter with its own e-m radiation. It cannot get through so-called 'decoupled' plasma-matter at all, which supposedly predominated in the young universe. By
using multiple observers and analyzing very large amounts of
data ('messages'), the noise can be filtered out to get to the
underlying 'core' message. Everything depends, of course, on
the sensitivity of the receiver-apparatuses. The signals
received carry energy which activates the sensors in the
receiver apparatus with a certain amplitude. The more
sensitive the apparatus (e.g. radio telescope), the further the
observer can 'see' or 'hear' into the universe.
Gravitational waves were detected directly for the very first
time in 2015 by the LIGO interferometers in the U.S. These
waves are extremely hard to detect, for their energy is low,
which means low amplitude which has to be sorted out from the
various sources of noise (extraneous information), principally
seismic noise from vibrations at low frequencies, thermal
noise from heat sources at
middle frequencies, shot noise from quantum effects at
higher frequencies. On the other hand, gravitational waves are
not affected by the intervening matter like e-m radiation is,
enabling better 'hearing' further back in linear time. With
the advance from the Earth-based LIGO interferometers to the space-based LISA interferometers within the next
couple of years, cosmologists hope the improved
sensitivity to be able to detect the less-noisy
gravitational signals coming from further back in
the universe's linear time. Thus they hope to
'hear' the young universe, to 'see' its highly
energetic state with its relativistic velocities
close to the speed of light. Such relativistic velocities
cannot be achieved
on Earth even with
the most powerful
particle
accelerators (the
Large Hadron
Collider at CERN).
Do the equations
worked out by
physicists to
capture the motion
of matter continue
to hold up for the
very young,
compact universe
with its highly
energetic (high-temperature) matter
moving close to
the absolute speed
of light? The
cosmologists are
still waiting from
the differentiating
message
from long ago.
Cosmology itself
rests on the
observation that
on the very, very
large scale,
beyond that of
galaxies and even
clusters of
galaxies, the
universe is
homogeneous in
every direction
and also
isotropic, i.e. it
is moving outward
in all directions
from any given
observation-point
at all, either accelearting or decelerating. These
observations have
led modern
cosmology to
postulate the expanding
universe. From
this postulation
and the
observation of the
expansion
velocity, assumed uniform, it's
easy to calculate
backwards to the
time zero when the
universe was just
a dot. This is the
event of the
Big Bang at
around 14
billion years
ago. As
a dot, however,
ultimately-small
Planck dimensions
are attained and
quantum dynamics
with quantum
indeterminacy come
into play. To date
there is no
unified theory of
gravity (curved
space-time) and
quantum dynamics,
not for want of
trying. Einstein
spent the later
part of life in
vain trying to
formulate
mathematically a
unified quantum-gravity theory. What a
bummer!
Undaunted,
cosmologists aim
nevertheless to
get closer and
closer to the Big
Bang event by
receiving
especially
relatively
noiseless
gravitational
signals from
further and
further out, i.e.
back in time.
Astoundingly, the
universe for the
modern cosmologist
is an evenly
expanding sphere
from ANY
observation point
at all in the
universe. This
conception,
remarkably enough,
corresponds to
Greek cosmological
conceptions with
their emphasis on
circles and
spheres when
accounting for the
observed motions
in the sky and the
structure of the
cosmos.
But there is at
least one major
difference. In Timaios,
Plato casts a
cosmos consisting
not merely of
matter in motion,
as modern physics
does, but of
"bodies" (_somaton_
Tim. 34b2)
"encapsulated"
(_periekalypsen_
34b4) by the
psyche (_psychae_). The psyche
for the Greeks is
the principle of
life, i.e. of
self-movement. All
that is living is
capable of, has
the power of
self-movement. The
cosmic psyche
embraces the
bodies of the
cosmos, endowing
them with
self-movement in
the sky. The
cosmic movement of
bodies is governed
by the psyche as
its "despot and
ruler" (_despotin
kai arxousan_
34c6). Plato then
differentiates
this psychically
encapsulated and
governed cosmos by
mixing
unchangeable being
and changeable
becoming to form
indivisible
sameness
(_tau'ton_35a4)
and divisible difference
(_heteron_35a4).
The realm of
difference is then
differentiated
further into seven
according to
arithmetic
proportions. The
realm of the same
is forced into a
"circuit of the
same and similar"
(_tautou kai
homoiou
periphorai_ 36d1),
the realm of
difference is
split into "seven
unequal circles"
(_hepta kuklous
anisous_ 36d2).
The
thoughtful part of the all-encapsulating psyche,
_nous_ or mind, ensures that the cosmos is ordered
according to arithmetically rational proportions.
One does not have to wonder, then, that Werner
Heisenberg, the famous German mathematical
physicist who first developed the matrix
formulation of quantum mechanics, along with the
unsettling quantum indeterminacy for the movement
of dynamic states, took a strong orientation in
his work precisely from Plato's Timaios
(cf. his autobiography, Der Teil und das Ganze).
In his mathematical quantum theory, Heisenberg
followed above all principles of symmetry and
simplicity, the main 'aesthetic' criteria in
mathematics. And if you delve into Einsteinian
general relativity theory, you'll also find that
the challenging mathematical language he
especially developed for it (tensor mathematics),
which aims at maximizing compact brevity through
symmetries built into the notation, reduces in the
end to wondrously simple-looking equations.
In contrast to modern relativity physics, the
cosmic psyche and its mind is not reliant on
receiving messages from the absolute motion of
electro-magnetic and gravitational radiation. Its
_nous_ (reason) is all-encompassing, enabling it
to 'see' the entire cosmos in its arithmetic structure,
as furthered developed in Timaios. Thus
does the cosmos presence rationally for the mind.
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