AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy | Gravity, black holes and physics |
Chapter 5
GRAVITATION
AND THE GLOBAL STRUCTURE OF THE UNIVERSE:
RELATIVISTIC COSMOLOGY
5.1. Basic
starting points and principles of cosmology
5.2. Einstein's
and deSitter's universe. Cosmological
constant.
5.3. Fridman's
dynamic models of the universe
5.4. Standard
cosmological model. Big
Bang.
5.5. Microphysics
and cosmology. Inflationary
universe.
5.6. The
future of the universe
5.7. Anthropic
principle and existence of multiple universes
5.8. Cosmology and physics
5.8. Cosmology and physics
Is is gratifying to say, that contemporary relativistic cosmology has already emerged from the stage of unfounded speculations and idle theorizing (it is no longer "mythology"...) and has become an important part and extension of astrophysics and the natural sciences. Can give a consistent picture of the structure and evolution of the universe as a whole; this picture is built on the proven laws of physics and its predictions agree well with the observations. Let us therefore consider some general aspects of the relationship between cosmology and physics.
The methodology of physical cognition consists of three main elements: observation , experiment and theory . In the early stages of the development of physics, the first of these methods - observation - played a decisive role; let us recall only Newton's law of gravitation based on astronomically observed Kepler's laws of planetary motion. However, Newton was already doing mechanical experiments that resulted in his three basic laws of motion. With the further development of physics, accompanied by a profound improvement in experimental techniques, the role of observation declined rapidly. Especially since the early 20th century, when for the reveal the laws of the microstructure of matter, it was necessary to use more and more sophisticated and costly experiments (eg powerful yet accurate accelerators in conjunction with subtle detection electronics), the method of observation seemed already entirely historic and the relationship between physics and astronomy is one-way: physics in its laboratories reveals the fundamental laws of nature, that allow to explain and predict astronomically observed phenomena in space.
Fig.5.12. A wide range of sizes of objects in our world, explored
by various fields of physics and natural sciences using various
tools.
(it is discussed in more detail in §1.0
"Physics - fundamental natural science",
passage "Methods and tools of
nature research", monograph
"Nuclear physics and ionizing radiation physics")
In recent years, however, this relationship has begun to
change. Indeed, contemporary relativistic cosmology has shown
that the universe, in its very hot and dense initial phase, was a
kind of unique "laboratory" of high-energy physics, in which the processes took
place intensively, that we are now trying to observe with the
greatest effort on massive accelerators, and even those phenomena
whose laboratory implementation is not hopeful in the foreseeable
future. The cosmological consequences of current theories of elementary particles (especially unitary theories)
have proven to be so clear and obvious, that their confrontation with astronomical observations distant universe *) makes it
possible to set strong constraints on the parameters of these
theories of elementary particles, and sometimes even their
verification or rejection.
*) In addition to optical
observations (including spectroscopic) with increasingly larger
and more powerful telescopes and radio telescopic
observations using large antenna systems (interconnected), it is
primarily a detailed measurement of the properties of microwave relic
radiation - its homogeneity, fluctuations (depending on
the angular distance and wavelength), polarization. Already at
the time of the separation of radiation from matter, there were
germs of future structures in the universe, so these photons
passed through places with different gravitational potentials,
which led to small changes in their energy and wavelength - a
slight cooling or heating. These fluctuations
should be visible even now, as slightly warmer and colder
"spots" in the otherwise isotropic distribution of
relic radiation - they represent a kind of "paleontological
imprint" of the structures of the early universe - see
§5.4, part "Microwave relic radiation - a messenger of
early space news". The temperature
difference is very small, of the order of 10-5 degrees, so the relevant methods of their data
measurement are constantly being improved *). In the future, then
the detection of primordial gravitational waves
(see §2.7 "Gravitational waves", passage "Detection of gravitational waves"), or detection of relict neutrinos
(for details on neutrinos and their detection, see eg the passage
"neutrino" in §1.2" Radioactivity "of the
book"Nuclear Physics and Physics of Ionizing Radiation").
*) For a detailed study of relic radiation, the COBE
satellite (Cosmic Background Explorer) was launched in 1989, in
2001 WMAP satellite (Wilkinson Microwave Anisotropy Probe), in
2007, an even more sensitive PLANCK probe was launched.
At first glance, it might seem that nuclear and
particle physics, dealing with the smallest known particles of
matter, has very little to do with cosmology, which, on the other
hand, examines the largest possible objects in the universe.
However, current research refutes this view. Both in the form of
elementary particles and in cosmology, it was possible to develop
so-called standard models, which explain very
well the results of almost all physical experiments and
astronomical observations. On the other hand, they raise new
questions and problems - how to "find common
ground of things"?
At present, in the mutual interest of
physics and cosmology are the fundamental principles of
our world. In cosmology, these are questions of the origin
of our universe, the basic laws
which control him, his ultimate destiny. In
particle physics, these are questions of the nature of
matter: how did matter originate ?; what is its
structure - what are its basic building "stones" and
how do these interact ?; what are the mechanisms of these
building blocks that create such complex objects as galaxies,
stars, planets - and ultimately living matter? This creates a
very remarkable connection between the
microworld and the megaworld...
All the most basic aspects of matter and
the universe seem to rooted in those first prime fractions of a
second after the Big Bang, when the properties of the physical
interactions themselves were formed. The laws of physics that
prevailed in these extreme conditions are not yet well known
- we do not know what the structure of space and time
was then, what was the number of dimensions, how matter was
formed. At that time, the macroworld and the cosmos, then
non-existent in the present sense, intertwined with the
microworld of quantum laws (cf. also the
passage "Very Early Universe" in §5.4). Some aspects of these phenomena may never be
clarified..?..
However, some current (and especially
future) concepts of unitary theories of fields,
interactions and elementary particles (mentioned
in Appendix B, especially in §B.6 "Unification
of fundamental interactions. Supergravity. Superstrings."), could shed some light
here, in co-production with experiments of high-energy
particle interactions on successively built large
accelerators (see " Charged particle accelerators "). The finer the details of
the structure of matter we want to penetrate - and thus also the
greater the depth of knowledge of the structure of the universe -
the higher the energy of the particles we must use. It can be
said that high-energy particles are certain "probes"
into the deepest details of the structure of matter and at the
same time into the earliest moments of the evolution of the
universe.
Two seemingly very remote parts of physics - the theory of elementary particles examining the smallest objects and cosmology examining the largest of the whole universe - thus combine to form a unified picture of the world. The successes of research in one area can be very penetrating in the other area of knowledge. It is this dialectical unity of the microworld, macroworld and megaworld that is the characteristic trend in contemporary fundamental physics.
Physically, we humans are just a tiny powder in the universe. Spiritually, however, we go far beyond this insignificance: we are able to know and understand the vast universe - its structure, its functioning, its evolution ... |
At the end of the chapter on cosmology, we will
briefly mention some rather non-standard and hypothetical
speculations, that we did not manage to fully include in
the continuity of interpretation of astrophysics and cosmology.
To all 4 questions mentioned below, an adequate skeptical answer
is "Probably
not!".
"Holographic"
universe ? Probably not !
Loss of information in a black hole.
Holographic principle.
In Chapter 4, we discussed the properties of black
holes in detail. When a black hole is formed by gravitational
collapse, all information about the individual properties of the
collapsing matter is lost to the outside world, except for the
total mass, charges and rotational momentum - §4.5 "A black hole
has no hair", a black hole has no
microscopic structure. He refers to this unusual situation as the
"paradox of information loss" - see
also the discussion in the final passage of chapter 4.7 "Quantum evaporation: return of matter from a black hole?". From the point of view of statistical physics
(and information theory), entropy is a measure of the disorder
of a given system [167]. This enormous amount of lost information
is then a measure of the black hole's entropy. The
proportionality between the surface of the horizon and the
entropy of the absorbed matter was later given the rather
misleading name "holographic principle"
:
Holographic principle
A holographic image in optics is created in such
a way that a beam of coherent light (from a laser) is split into
two parts, one of which hits the photographic layer directly, and
the other part after reflection from the imaged object. Both of
these beams interfere and create a structure of thin interference
stripes on the photographic emulsion, carrying information about
the phase differences of the two beams. If we then irradiate this
two-dimensional image with coherent light (again from a laser),
the reflected rays reconstruct the same phase differences that
created the image - the impression of a three-dimensional image
of the original object is created. The holographic image has the
interesting property that even from a fragment of the hologram we
can see the entire three-dimensional image, albeit with a lower
resolution.
The two-dimensional surface of the black hole's horizon carries
all the information (appropriately reduced - "the black hole
has no hair") about the three-dimensional configurational
masses absorbed in the black hole, just as a two-dimensional
hologram carries information about a three-dimensional object.
However, the similarity with holography ends here, because
specific detailed information about the absorbed matter (except
for the mass M, the momentum of the rotational moment J
and possibly the electric charge Q) is lost and cannot be
reconstructed in any way.
However, some
experts in the field of astrophysics and unitary field theories
(started with G.'t Hooft and L.Susskind) liked the holographic
idea and led them to believe that in a similar way all
information about other systems, not only black holes, could be
locate on the surface (area) of the area in which they are
located. A thought experiment with a very large black hole could
indirectly point to this, around whose horizon the usual laws of
physics would apply as in a state of weightlessness, in a
free-falling locally inertial system there would be only tiny
tidal forces. Below the horizon, based on the holographic
proportionality between the surface of the black hole's horizon
and its entropy, we can imagine that all information about the
matter inside is localized on the horizon, whose surface
maintains information about the entire internal space..?..
However, this
interpretation is not very physically correct, because the
theorem "a black hole has no hair" and the
proportionality between the surface of the horizon and entropy
applies to the outer, not the inner, space of the black hole..!..
The
"holographic principle" was further generalized in
connection with the construction of superstring theory:
"Information (degrees of freedom) about a system inside a
volume V
can be localized (encoded) on the surface ¶V of this volume, while the information
density does not exceed one bit per Planck surface lp2".
The holographic
principle is generally the statement that information
about an N-dimensional region (its interior) is
encoded at the N-1 dimensional boundary of that
region. Within the general theory of relativity, it is
theoretically supported only at the horizons of black holes. In
other cases, it is only an extrapolation and analogy - an
unsubstantiated hypothesis... So the universe
is apparently not "holographic".
However, holographic concepts are sometimes used in
different variants of superstring theory.
Is our
entire universe inside a gigantic black hole ?
The development of black hole astrophysics in the 1960s - 1980s
and the attractiveness of these "exotic" objects led to
yet another bizarre hypothesis: That our entire universe (with all the galaxies, nebulae, stars, planets and
other structures that can be seen through telescopes or inferred
from detection of electromagnetic or corpuscular radiation and
possibly gravitational waves) could be
located inside a gigantic black hole,
existing inside an even larger whole - the multiverse (however, there is no direct connection with the
multiverse hypothesis in the previous §5.7 "Anthropic
principle and the existence of multiple universes"). The origin of this
universe could then be explained by an equally bizarre idea: that
the Big Bang was a kind of "big bounce", where
the gravitational collapse in the previous universe created a
"wormhole" *), the outlet of which opened into
a new expanding universe..?..
*) We critically discussed the questions of
hypothetical wormholes and their relationship to black holes in
§4.4., the passage "Wormholes
- bridges to other universes?".
So, all unverified assumptions.
Furthermore, from an astrophysical point of view, it would not be
consistent with the cosmological principle (discussed already in §5.1, passage "Cosmological principle") of global homogeneity and isotropy of the universe. In
the outward direction, towards the horizon of the black hole, a
sparser distribution of galaxies would be observed than towards
the center, towards the "singularity". No
"edge" of the universe at the horizon, nor condensation
in the direction towards the center and possibly fall into the
singularity, is not observed.
Some astrophysicists like the idea of the
universe inside a black hole, but mainly popularizers and those
interested in the fields of philosophy, culture and social
sciences, they find it exciting and mysterious. However, it does not
correspond to the real universe that we observe and live
in which...
The
universe as a giant quantum computer ?
Successful analyzes and computer simulations of many processes in
the universe using powerful computers with sophisticated software
have given some authors the impression that this is not just a
random sucsess of erudite astrophysicists and computer experts,
but because the universe itself is a kind of gigantic
software system, that we are just trying find out. And
from the point of view of evolution, the Universe is a kind of autodidactic
system..?.. Surely most experts do not mean this completely unfounded
science fiction hypothesis literally, but rather
metaphorically! "We could be living in the digital world
depicted in the Matrix without knowing it" ..?.. Probably
not! The literal hypothetical that "the universe is
a computer" is definitely not true. Instead, a more
plausible claim should be: "A number of processes in
the universe can be software algorithmized" and
analyzed on large computers (possibly
quantum computers in the future), allowing
them to better understand, simulate, and extrapolate into the
future. Philosophically, this suggests that the universe
is knowable in terms of the idea of the material
unity of the world...
Cosmic
consciousness - the universe as a "living thing" that
is aware of itself ?
This sci-fi idea is too subjective and anthropomorphic
to discuss in detail in our (astro)physics treatise.
Astrophysics and cosmology view the
universe as a barren and inhospitable place
consisting almost entirely of empty space and inanimate matter.
Life is extremely precious. On Earth, matter organized itself to
a high level of complexity by special mechanisms and gradually
created living beings ("Stars,
planets, life in the universe"). We don't yet know if this has happened in other places
in the universe...
Some philosophers, alternative naturalists and environmentalists,
in the spirit of anthropomorphism, would like to see the universe
not completely "dead", but the Universe as a living,
evolving and learning system with which we humans would live in
harmony with each other, because a better and sustainable life on
Earth, without crises and devastation of the natural environment.
This is certainly a positive motivation. However, somewhat
misleading here can be the idealistic motivation against
materialism, which wrongly equates objective
"enlightened" scientific materialism, which helps
to protect nature by better knowledge of
reality, with vulgar human materialism, leading to
selfishness, consumer society and the devastation of nature.
"The universe knows itself - through
us" (C.Sagan)...
Of course, there is no
objective confirmation of this idea...
5.7. Anthropic principle and the existence of multiple universes |
Appendix A:
Mach's principle and general theory of relativity |
Gravity, black holes and space-time physics : | ||
Gravity in physics | General theory of relativity | Geometry and topology |
Black holes | Relativistic cosmology | Unitary field theory |
Anthropic principle or cosmic God | ||
Nuclear physics and physics of ionizing radiation | ||
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