|AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy
|Gravity, black holes and physics
GRAVITATION AND THE GLOBAL STRUCTURE OF THE UNIVERSE:
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
concepts, that we did not manage to fully include in the
continuity of interpretation of astrophysics and cosmology.
"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 . 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" :
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.
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...
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" ..?.. 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...
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
and general theory of relativity
|Gravity, black holes and space-time physics :
|Gravity in physics
|General theory of relativity
|Geometry and topology
|Unitary field theory
|Anthropic principle or cosmic God
|Nuclear physics and physics of ionizing radiation
|AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy