|AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy||Physics and nuclear medicine|
Nuclear and radiation physics
1.0. Physics - fundamental natural science
1.1. Atoms and atomic nuclei
1.3. Nuclear reactions
1.5. Elementary particles
1.6. Ionizing radiation
1.0. Physics - fundamental natural science
In this introductory chapter we will try to outline some methodological aspects of the construction of physics and its integration into the context of other science and scientific knowledge in general. These methodological notes may be interesting, for example, for students and those interested in non-physical professions who want to get a comprehensive picture of the physical aspects of the study of nature. And maybe they can stimulate the joy of some readers to learn how our beautiful world and the whole universe works ...
Nature and its
We will not explicitly define the concept of nature , about which everyone has a more or less clear intuitive idea. We will adhere to the universalist concept that nature is absolutely everything that is , it has an objective existence . So it is basically the whole Universe with galaxies, stars, planets including the Earth, our terrestrial nature - mountains, rivers, sea, all flora and fauna, all atoms and subatomic particles anywhere on Earth and in space. Even we humans and cells in our body with complex biochemical reactions, all our creations.
After all, even some "mental" processes and ideas, if (at least in principle) it is possible to identify and locate their "coding" in the neural network of the brain, can be included in the general term "nature".
At the heart of all scientific research lies the process of categorization . Reality, which is too complex and diverse in its complexity *), is divided into simpler groups according to certain criteria - categories, that we examine separately. The results of the research of individual categories can then be generalized and possibly synthesize - to summarize them into a more general framework, encompassing a wider group of phenomena - the whole. The analytical and synthetic approach, in their dialectical unity, forms a general method of scientific cognition of reality.
*) The world is full of "hiding places". Science seeks to "hunt" fragments of knowledge from these hideouts and put them into a mosaic of complex and objective human knowledge .
Constant inquisitive questions " why? " can lead us to the basic principles of nature ...
Knowledge: science + experience
The knowledge of every (educated) person is based on two components :
¨ Science , providing objective, universal and reproducible knowledge. However, these communicated findings may not always be properly understood and interpreted.
¨ An experience that may be subjective and sometimes erroneous, but if it reflects reality, can provide a sharper and more concrete insight into reality.
The unity of these two components creates a common and clear human mind , enabling us to orient ourselves correctly in the events of our world through critical thinking . Physicists and other naturalists, as well as forensic people of various specializations, believe only in the objective observations, measurements and reasoning based on them, confirmed by independent observers and researchers. Unreproducible, unverified and controversial claims ("One Lady Said", "The Jurassive Genius Speculated") cannot become part of scientific knowledge ..!..
The more complex situation is with phenomena inaccessible to our sensory knowledge - phenomena in the microworld or very distant universe, where we must rely on research using instrumental methods (test tubes, accelerators, detectors, telescopes, etc.) and learn to analyze, reflect and apply the facts found. With the heroic efforts of researchers, these complex methods have succeeded in gaining far-reaching, previously unsuspected, knowledge about the internal structure of matter and the structure and evolution of the universe that are objective and "work" ...
Gradual knowledge of nature, universe, life is sometimes similar to a ladder , whose "rungs" are partial discoveries, the results of experiments, astronomical observations. However, unlike the ordinary ladder from which we pluck fruit from the trees in the garden, we do not see the end of this "ladder of knowledge": more and more steps are continuously built as you climb the ladder of knowledge. The question is whether sometime in the future we will encounter the last, "final rung of the ladder of knowledge", or we will discover the secrets of nature and the universe one after the other constantly..?.. Experience to date shows, that each new level of knowledge and solution of a certain problem brings new and new questions, often even deeper and more fundamental ...
- Education - Wisdom
The present world is full of information. However, knowledge at the level of information does not necessarily mean education and wisdom. Knowledge itself can be empty . In order for knowledge and information to gain real meaning and value - to turn into education and then to wisdom, a comprehensive multi- stage path of knowledge must be carried out :
¨ Acquisition of factual information and knowledge - study, communication with others, personal experience, observation, scientific research.
¨ Internal understanding of this information, searching for their interrelationships and their context in other areas.
¨ Putting knowledge and skills into practice, their confrontation with various changing circumstances.
¨ Ask new questions about the nature these phenomena and events, try to find an explanation. To draw from them conclusions useful for "one's own soul" - for one's worldview , relationships with nature and one's neighbors.
Each of these stages also presents certain risks of errors and wandering in the way. E.g. at the last point, it sometimes happens that on the basis of only a superficial study, partial knowledge and insufficient understanding, we hastily come up with a bizarre and erroneous explanation. Some people with a lack of self-reflection persist in these misconceptions stubbornly; they call them "alternative science" (we often encounter the work of various "ingenious authors" refuting the theory of relativity or building far-reaching "unitary theories" of matter and space based on psychotronics, various "energies", subtle and gross-mass, and a similar arsenal of misunderstood concepts ...) - see also "Quackery versus science", below "New" and "old" physics - continuity of scientific knowledge ".
Interpersonal relationships are often based on emphasizing the "self", which leaves little room for understanding and listening to others, for appreciating their strengths and experiences that could enrich the "our self". The current trend dictates people to be informed . However, the overabundance of information often hinders its real understanding and use - it is actually an obstacle to achieving real education and, above all, wisdom - " less is sometimes more ".
"Alternative" science ?
Under the often used name " alternative science ", two fundamentally different approaches can be hidden :
¨ Different (alternative) ways of explaining and interpreting reliably identified phenomena and facts that are different from the usual prevailing interpretation in a given scientific discipline. This is a completely legitimate attempt for a possible better explanation of the analyzed phenomena and possibly prediction of new phenomena. If this concept does not work, its authors are "without blinking" willing to abandon it and join a more probable and proven theory.
¨ An alternative to science - diametrically opposed views of lay people, often based on an incomplete and insufficient understanding of the problem and an attempt at a " completely different " as if "original " explanation. These are mostly mistakes , pseudo-sciences , to which its proponents often cling stubbornly despite their disagreement with experimental facts (" Quackery versus science ") .
Distrust of an official scientific opinion can sometimes be quite honestly motivated. For our understanding of nature, Newtonian classical physics would certainly be more comprehensible than the theory of relativity and quantum physics. Why is nature so complicated? Unfortunately, real nature is governed by more complex lawstheories of relativity and quantum physics , with which we have no experience in everyday life. Experimental findings show this completely uncompromisingly! Physics never invents an unnecessarily complex description and explanation of objective reality, but only one that is essential for the correct explanation of experimental facts. For an intuitive understanding of relativistic and quantum laws, illustrative models have been developed to help every educated and thoughtful person at least provide a general understanding of the specific laws of the microworld and megasworld, as well as their role in the functioning of our nature, life and the Universe.
Nevertheless, some contemplators (or rather "smart alecks", "rocket scientists") do not follow the proven Chinese proverb "Thinking without study is dangerous! ", without proper study and understanding, they do not hesitate to reject all the knowledge gained through the hard work of generations of erudite experts and seek at all costs to promote some own" ingenious solution " (see the already mentioned discussion" Quackery versus science ") . In the physical sciences, these deformations are less common, physicists immediately recognize delusional concepts, and the general public usually does not address them. Frequent pseudo-scientific distortions are in the biological and especially in the medical fields, where so-called alternative medicine receives promotion and great financial support from companies that profit from the sale of often ineffective medicines ( eg homeopathic). In the field of biology and medicine, there are complex "tangled" and little reproducible phenomena and processes, so possibly mistakes and frauds are difficult to prove here.
Division of nature
You can divide nature into categories using various criteria. The oldest division of nature , which we each encountered at the earliest childhood during the first steps of knowledge, is the division of nature into living and inanimate nature. From a human point of view, we approach living nature with greater sympathy for belonging to the "living to the living" than to the inanimate. From a physical point of view, however, the division into living and inanimate nature is pointless *): the same basic laws of nature apply to both inanimate and inanimate nature.
*) We disregard here the fact that it is sometimes difficult to decide whether to classify some simple organic systems as living or non-living; this is a narrower problem of molecular biology and organic biochemistry.
Also, another simple division of nature into terrestrial and cosmic is obsolete and physically unjustified : we now know that the natural processes taking place here on Earth, even in the farthest reaches of the universe, are governed by the same universal laws of physics .
The really substantiated and objective division of nature according to the prevailing and determining physical laws is as follows (Fig. 1.0.1 below) :
These three categories of nature have far from sharp boundaries and often intersect . Even distant regions such as the megasworld and microworld - such as thermonuclear reactions inside the Sun or distant stars (" The role of gravity in the formation and evolution of stars ") , and even the processes of the universe itself ("Big Bang" - Standard Cosmological Model The Big Bang The Formation of the Structure of the Universe. ) , are governed by the quantum laws of nuclear physics and the interactions of the elementary particles of the microworld.
How does physics and science study our world ?
A huge variety of sizes, shapes and composition of objects in nature, as well as the processes occurring in them, requires a number of very different research methods and tools - often very cleverly designed instruments. In middle row Fig.1.0.1 are symbolically shows the typical objects in nature - from particles, nuclei, atoms, molecules, through cells with their organelles and DNA, organisms, planets, stars, galaxies, to the whole universe. The line below it shows the tools with which we examine the relevant objects. The upper part of Fig.1.0.1 lists the fields of science that deal with the study of relevant objects and the basic physical categories that relate to them. Below is the picturescale of object dimensions (from the smallest so-called Planck-Wheeler length 10 -33 cm [is derived and discussed in §B.4 " Quantum geometrodynamics " in the monograph " Gravity, black holes and space-time physics "] , through particle and atom pictometers , micrometers cells , millimeters and meters of organisms , kilometers of forests, mountains, seas and other objects of terrestrial nature, thousands and millions of kilometers of the planetary system , billions of kilometers, light years to billions of light years of distant space ; to infinity of open universe...) .
Fig.1.0.1. A wide range of sizes of objects in our world, explored by various fields of physics and science using various tools.
Let's start with the usual macro
world in the middle part of Fig.1.0.1 and we will first
continue towards smaller scales. We carry the most important
observation tool with us: it is our eye - an
optical system that projects light through a lens on the retina,
where an image is transmitted to the neural network in the brain.
Using visual vision, we observe and examine all common
macroscopic objects from a fraction of a millimeter (where we can help with a magnifying glass) to tens of kilometers (here we
help with binoculars) .
We use a microscope to identify tiny objects and structures the size of hundredths and thousandths of millimeters, such as cells and organelles inside- the optical system of the lens and eyepiece, which can achieve a magnification of up to about 3000 times. The invention of the microscope played a huge role in biology and medicine, which, from the originally "charlatan" disciplines, with a number of errors and unfounded assumptions, thus became exact natural sciences . The realization that all living organisms are composed of cells with a complex internal structure was followed by an investigation of the complex biochemical and molecular genetic processes that are the essence of life . This research is still ongoing.
For the study of even smaller structures in the field of molecules and atoms, in the sphere of the microworld, the most perfect optical microscope is already powerless: the wavelength of visible light is many times larger than the dimensions of atoms and molecules *). We cannot observe something as subtle as atoms with something as coarse as light! No man can ever see the structures of molecules and atoms with his eyes. To study them, indirect laboratory methods of atomic and nuclear physics must be used . The most important method here is spectrometry (especially electromagnetic radiation): we excite atoms or nuclei by a suitable supply of energy; during subsequent deexcitation, radiation is emitted, the energy distribution of which - the spectrum - is measured. From the results of these measurements we deduce the internal structure of the molecule, atom or nucleus. ........
*) An electron microscope may be used in the "intermediate stage" of the micro - dimensionswhich is able to achieve a magnification of 100,000 times or higher. We can display small intracellular structures, viruses, larger macromolecules.
Scattering experiments are another important method of studying atoms, nuclei and particles . Examined atoms or their nuclei bombarding suitable particles (electrons, protons, alpha particles, ...) on the appropriate energy and investigate at what angle to "reflect", respectively scatter. At lower energies there is usually elastic scattering , at high energies inelastic or " deep" inelastic scattering . Using Rutheford's scattering experiment with alpha particles, it was possible to reveal the internal structure of the atom - the atomic nucleus and the electron shell(§1.2, part " Structure of atoms ", Fig.1.1.4) .
To know the structure of elementary particles and the nature of the forces acting between them, it is necessary to implement particle collisions at the highest possible energies on accelerators (§1.5, section " Accelerated particle accelerators ") - to achieve deeply inelastic scattering or "breaking" of particles; in the assortment of "research tools" in Fig. 1.0.1 lies on the left margin. In such collisions, the particles penetrate each other "deep into their interiors" and the result of the interaction can tell something about their structure. Due to quantum processes in the fields of strong, weak and electromagnetic interactions, new secondary particles are formed during high-energy collisions, which are both interesting in themselves and carry important information about the nature of the fundamental forces of nature, including the possibility of their unified understanding within the unitary theory of the field . Particle collisions at high energies are a kind of "probe" into the deepest interior of matter - and at the same time into the processes of universe formation (see §5.5 " Microphysics and Cosmology. Inflation Universe. " Books "Gravity, Black Holes and the Physics of Spacetime ") . It can be said that large accelerators are the most powerful "microscopes" into the interior of matter and, with a bit of exaggeration, also the largest "virtual telescopes" in space, which make it possible to "see" up to the very early stages of the evolution of the universe, where no other astronomical telescopes can see anymore. It is of course no the direct observation of physical phenomena in the early universe, but their faithful if possible experimental simulation : Processes that investigate interactions at accelerators at high-energy particles, probably took place in the first microseconds after the universe - just after the " big bang ". We can help us understand the origin and evolution of the universe .
If we go the other way now - from the macroworld towards large scales to space , to observe planets, stars and their systems, nebulae, galaxies, we use large astronomical telescopes (§1.1, part "Electromagnetic radiation - the basic source of information about the universe "in the book Gravity, black holes ...) . These telescopes often have spectrometers installed in their focus , analyzing the wavelength of incoming light. This astronomical spectrometry is a powerful tool for understanding chemical composition, temperature, speed of motion of objects located at distances of thousands, millions or billions of light years, where no one ever has a chance to physically look! Astronomical telescopes (optical and infrared) are sometimes sent outside the Earth's atmosphere, into orbits around the Earth. In addition to optical telescopes, radio telescopes are also used, whose antennas capture electromagnetic radiation of longer wavelengths (units or tens of centimeters). Important information about the formation of the universe is provided by the measurement of relic microwave radiation ( §5.4, passage " Microwave relic radiation - messenger of reports about the early universe " in the book "Gravity, black holes ..." ).
Important "windows" into space is gradually becoming the detection of cosmic rays ( §1.6 , part " Cosmic rays " ) , neutrinos (§1.2, part " Neutrinos - "ghosts" between particles ") , recently and especially in the future also gravitational waves (§2.7 "Gravitational waves" in the monograph" Gravity, black holes ... ").
In the distant past (antiquity and the Middle Ages) there was only one science called philosophy , which covered all areas of human knowledge at the time - society, nature, medicine, religion, history, etc. There was little real knowledge, speculations and guesswors prevailed, conventional traditional views and religious dogmas.
A brief overview of the development of knowledge about nature , especially about space, space, time, electricity and gravity, from antiquity to the present, is given in §1.1 " Historical development of knowledge about nature, space, gravity " book " Gravity, black holes and physics spacetime ").
With the growing knowledge of nature, it was no longer possible to encompass everything within the framework of philosophy, from which the natural sciences were therefore gradually separated and earmarked . The basic division of natural sciences is based on the main areas of natural phenomena and objects they deal with :
The mentioned methodological
procedure, in which biological processes are explained by
chemical reactions and chemical reactions in turn by physical
electrical interactions of atoms, is called reductionism
- we try to reduce and explain more complex phenomena by
means of simpler phenomena. In general, this approach is very
fruitful and successful in science. However, a permanent subject
of discussion between scientists and philosophers is the question
of whether this reductionist scheme of biology Ü chemistry
Ü physics can or cannot be (at least in
principle) applied to higher nervous activity - mental and mental
processes in the human mind ..?..
In the past, around the end of the 19th century, the individual disciplines developed largely independently and closedly, and the progress of knowledge was relatively slow. The later impressive development of knowledge was caused mainly by two factors :
¨ Technical progress in observational and experimental techniques, which provided an insight into the previously unrecognizable scales of the microworld and the megaworld;
¨ Interdisciplinarity - overlap of individual special disciplines into other disciplines (neighboring and distant) , cooperation of various disciplines in solving issues of knowledge of complex phenomena. E.g. application of knowledge of nuclear physics to processes in stars - nuclear astrophysics (§4.1 " The role of gravity in the formation and evolution of stars" books" Gravity, black holes and space-time physics ") , or chemistry and physics on processes in cells - molecular biology and genetics, biochemistry and biophysics (§5.2, part" Cells - basic units of living organisms ") , led to fundamental qualitative progress of our knowledge.
According to the method and style of work in the study of natural laws, physics can be divided into three areas :
division of physics
According to specific groups of studied natural phenomena, physics is divided into a large number of disciplines and specializations (there are more than a hundred), of which we list only a few of the most basic (each has a number of subfields and specializations, including interdisciplinary) :
In addition to specialized physics disciplines, dealing with specific groups of phenomena, the structure of physics also includes two important theoretical concepts of modern physics, which have a more general character and go "across disciplines" :
Can we understand relativistic and quantum physics?
We humans and previously life here on Earth have evolved over millions of years in an environment of sunlit seas, lakes and rivers, mountains, minerals, the atmosphere. Along with our entire biological bodies, our brains are completely fixed on a "moderate" macroscopic environment with low speeds, short distances, weak gravity and small other forces, low temperatures in the range of several hundred to thousands of degrees. From this natural environment we have long ago "learned" the laws of classical mechanics, later thermals, hydrodynamics, solid state physics, electricity and magnetism, chemistry, biology, etc. Only here "we are at home" ..!..
We have no personal experience with speeds of hundreds of thousands of kilometers per second, thousands of times greater than those of any ordinary macroscopic object, or with sub-tiny particles of the size of a millionth of a millimeter, invisible even by the best microscopes. The laws of relativistic and quantum physics are therefore not close to us and we do not understand them, they have only recently been discovered through complex experiments , precise measurements, sophisticated analyzes ...
So that we "ordinary mortals" ( relativistic or quantum "non-specialists" *) understand at least some of the quantum laws of the microworld and the relativistic laws of the megaworld, we must necessarily use approximate models based on classical mechanics. These are " ball models " for atoms and interactions (collisions) of particles (see note in §1.5, passage " Are there any elementary particles at all? Ball model. ") , or motions according to classical mechanics and Newton's law of gravitation - with additional necessary quantum and relativistic corrections .
*) Truth be told, even these specialists, if they dare to descend from the " throne of their superiority " and honestly realize that they are also just ordinary people , they admit that they also use these models ...
Significant scientific discoveries - chance
or method ?
The continuity of scientific knowledge of nature, the origins of which can be traced back to the 16th century, was from time to time disrupted - in a positive sense - by fundamental discoveries that significantly accelerated knowledge of the studied phenomena, revealed new phenomena or changed the methodology and direction of research. Let us briefly consider the role played by chance in these discoveries and what a systematic methodological approach . From this point of view, we notice three cases :
¨ The discovery of the magnetic effect of an electric current made by H.Ch.Oersted in 1820.
Were it not for the compass magnet to be placed accidentally on the desk, Oersted would continue to do a number of experiments with electrical circuits, but he would not notice the connection between electric current and magnetism.
¨ Discovery of X-rays made by WCRöntgen in 1895.
It is briefly described in §3.2 " X-ray diagnostics ". Without covering the discharge tube with black paper and lighting up a randomly placed screen, ..... Roentgen might not have inserted various objects (including his hand) between the tube and the screen . He would continue to do interesting experiments with cathode ray tubes as well as dozens of other experimenters at the time, but he probably wouldn't find new penetrating radiation (after all, this X-ray was independently discovered by H.Jackson and AACampbell-Swinton at the same time), nor its cardinal significance in medical diagnosis.
¨ The discovery of radioactivity made in 1896 by H. Becquerel.
It is briefly described in §1.2 " Radioactivity ". Were it not for the accidental deposition of minerals intended for the study of (light) luminescence on a light-tight photographic plate and the accidental development of this (supposedly "clean", unexposed) plate, Becquerel would continue to examine luminescence excited by sunlight and invisible radioactive radiation emanating from certain substances, he would have no idea...
Is it possible to judge from the history of these and many other cases that significant discoveries are perhaps the result of mere chance ? Definitely not ! The well-known saying " coincidence wishes the prepared " applies here. These researchers were experienced experimenters and carried out their experiments systematically with a well-thought-out methodological approach . Coincidence only directed this methodological approach so that it resulted in the final discovery of a new natural phenomenon. An inexperienced experimenter might rule out some observed phenomena (if he noticed them at all). ), which do not fall within the scope of the current assumptions, he would consider them as accidental errors, for example, he would throw away a photographic plate that is blackened, even though it should not be ...
Moreover, even if the aforementioned "coincidences" did not occur and Oersted, Röntgen , Becquerel and other well-known researchers from the textbooks would not make their discoveries, someone else would soon do so. There were a number of experienced researchers diligently conducting top experiments at the time, the unresolved problems were mostly "matured" and it was only a matter of time before the experiments were carried out, which would bring new "light" and direction. At present, basic scientific (especially physical) research has clearly reached the level of a systematic methodological procedure, in which entire teams composed of experts from various specializations participate, using mostly very complex and expensive (often very large) experimental equipment. But even the opposite statement that " chance has no place here " can not be considered justified ...
"New" and "old" physics
- the continuity of scientific knowledge
With the advancement of scientific knowledge, it naturally happens that earlier ideas and theories are no longer sufficient to explain newly discovered phenomena and facts - they are replaced by new theories . In the lay public and popularization literature, we often come across the claim that "a new theory has refuted or demolished the existing theory, " or even "a new physics has refuted old physics ." This opinion is completely wrong ! This was partly the case in the past in the transition from the pre-scientific period , when some unverified and erroneous views and speculations would be refuted and replaced by theories of already real science, based on facts . The current natural science - especially physics - however, in such a way elready does not proceed .
In natural science (and in physics in particular) the continuity of scientific knowledge applies . New discoveries and new theories do not refute the experimentally verified findings of the previous theory, but supplement, refine and generalize these theories to newly discovered phenomena which the previous conception is no longer able to fully explain; it contains an earlier theory as a limit case . It also allows for a deeper understanding of phenomena in a broader perspective - what is "behind it".
We can approach this with the example of the theory of relativity and quantum physics . Einstein's special theory of relativity does not refute the classical Newtonian mechanics, which is its limit case for small velocities compared to the speed of light. However, it specifies the laws of motion so that they apply exactly even to high speeds. Similarly, the general theory of relativity does not refute the classical Newton's law of gravitation, which remains valid as a limit case of weak gravitational fields. Einstein's equations of the gravitational field are generalizations, valid even for extremely strong gravity. What is fundamental and new to the theory of relativity is a new look at the properties of space and time (see " Gravity, black holes and the physics of spacetime").") - but again it manifests itself only under" extreme "conditions; in the ordinary macro world, the classical conception of space and time in the spirit of Euclid and Newton will suffice.
Similarly, the relationship between classical and quantum physics is formulated as the so-called correspondence principle : In the limit of large quantum numbers, the difference between quantum and classical physics is blurred, quantum physics becomes classical. Or for large quantum numbers, quantum physics gives the same results as classical physics.
This relationship of continuity and correspondence will undoubtedly apply to future theories. If it is possible to successfully build unitary field theories, it will not disrupt the functioning of the laws of the existing theories of individual separate "partial" fields (electromagnetic, gravitational, nuclear forces) in conditions where they are experimentally verified. However, it predicts and explains new phenomena at extremely high energies of interactions, perhaps including phenomena in the formation of the universe, for which the existing theory is not enough.
The direction of scientific deduction
Scientific interpretation is based on deriving one knowledge from another. However, it is not just a simple deduction. For real knowledge and understanding of the context, the formal logic of deduction is not enough, but from the heuristic point of view, the direction of deduction is also important - from more fundamental laws or theories to more special ones. An example is Newton's law of gravitation, derived by its author from Kepler's earlier laws describing the orbit of planets in the solar system. However, from the point of view of scientific knowledge and explanation of the essence, the law of gravitation (along with Newton's three laws of mechanics) is undoubtedly far more fundamental. a law that explains Kepler's laws (and much more ...) - and not the other way around! Or another example: The laws of special relativity (STR) were derived by Lorentz and Einstein based on the electrodynamics of moving charged bodies. Now, however, STR is a general concept going "across" the fields of physics, which is no longer logical to explain and derive from electrodynamics, but rather to analyze the movements of charges in electric and magnetic fields with the help of STR.
Simplicity and logical economy
Another important principle in building physical (and in general natural-scientific) theories is simplicity and logical economy in terms of the number of concepts, reasons, causes introduced; these entities should not multiply more than necessary. This principle of the so-called Occam's razor *) - the principle of the simplest explanation of things - solves the problem of an infinite number of diverse, in principle admissible alternative theories, which lead to the same results in explaining a certain natural phenomenon. Occam's razor "cuts off" superfluous concepts, assumptions, and theories, leaving only the plausible, logically necessary, and rational ones; if there is more than one explanation for a phenomenon, it is reasonable to prefer the least complicated one.
*) It is not a "tool", but a principle of decision-making between different theories that have similar practical results. It is named after the English medieval philosopher William Occam (or Ockham, 1287-1347), which dealt with the logical structure of knowledge. The principle of logical economy ( "it is useless to do something with more tools when it can be done with less" ) used against an excessive number of scholastic principles, properties, essences, forms, and other imaginary starting points, as was the custom at the time.
In the theories of classical and relativistic physics, this principle is strictly observed. However, in some newer physical theories, the situation is more complicated. In quantum field theory and unitary theories, auxiliary so-called calibration fields are introduced , to which new hypothetical particles correspond (see " Unification of fundamental interactions. Supergravity. Superstrings. "). The most difficult situation is then insuperstring theory , where, in the opinion of some physicists, the principle of Occam's razor is violated ..?..
Refutable of theories
We can never prove the theory with absolute and definitive validity, but we can only test it empirically . Although the theory has been experimentally confirmed many times, we can never be sure that inconsistencies will occur in further experiments or measurements - the theory can be refuted *) by even a single experiment or observation, the results of which contradict its predictions. A valuable theory is therefore one that not only agrees with existing knowledge, but which can be empirically refuted - falsified . Until that happens, we consider the theory to be correct , or more precisely adequate . The "irrefutable" theory is scientifically empty, it has a metaphysical character. This criterion of the value of the theory is sometimes referred to as Popper's (according to the Austrian philosopher K. Popper, who was left with the theory of knowledge in terms of critical and skeptical realism ), "Popper's razor" . The refutability of theories understood in this way enables further progress of knowledge - the creation of new, more perfect theories.
*) The word "refute" here does not mean to completely negate and demolish, but rather to define areas where it no longer applies - cf. with the continuity of scientific knowledge discussed above. Physicists understand this constructively - it is clear to them that when such a situation arises, it is a challenge to find a new, more perfect theory. However, for some people who are not sufficiently erudite and prejudiced, Popper's criterion of rebuttal may be a pretext for purposeful attacks on well-established, adequate scientific theories; mostly for the purpose of promoting theories of biased and erroneous ...
Some other philosophical and gnoseological aspects of revealing natural laws, creating their models and formulating physical theories are discussed in §1.1, passage " Natural laws, models and physical theories " monographs Gravity, black holes and the physics of spacetime ".
Rationality - intuition - fantasy in science
The basis of scientific knowledge is undoubtedly a rational analysis of phenomena in nature, observed either directly or through experiments. Using this analysis, we conclude on the common laws that govern natural processes and finally formulate the relevant laws of nature . However, in addition to a rational approach, two specific aspects of human thinking are applied in certain stages of scientific research - intuition and imagination.
Intuition it represents the ability to know directly without consciously involving reason and rational reasoning. It is a kind of "instant insight," a quick immediate understanding and knowledge; intuition has the character of "sudden enlightenment", the "sixth sense". From the point of view of the neurology of the central nervous system, it turns out that rationality and intuition are a manifestation of the activity of two different but closely cooperating large neural networks in the brain. The neural network in which intuition takes place is developmentally older, its germs are already manifested in the instincts of animals. The rational network is developmentally younger, it is specifically human. The cooperation of both networks can be compared in computer terminology to a coprocessor, which quickly exchanges the information written in the neural maps of individual networks. In a senseis intuition a shortened and accelerated subconscious running of many possibilities, which results in choosing the "right" variant ... Unlike ordinary "guessing", in science it is a subconscious operation of "trained" reason, which can "guess the right solution" . And fantasy is the ability to imagine things and events differently than we commonly see and know - modifying some of the maps written in neural networks.
Intuition is of great importance in the turning points of scientific knowledge. New generalizing and unifying natural laws often cannot be discovered in a logical way- they cannot be derived rationally, perhaps mathematically, from existing laws, because they are not contained in them (at least not directly). Here, intuition helps, which provides a "feeling" for understanding the implicit laws that are hidden behind certain phenomena. And it reveals previously underappreciated similarities, sometimes even between seemingly distant areas. The rational elaboration of intuitive ideas then creates scientific theories .
An example is the great intuition of A. Einstein, who, with the help of an imaginary experiment, noticed the similarity of long-known mechanical phenomena: the dynamics of motions of bodies in non-inertial (accelerated) systems and the dynamics of motions of bodies in the gravitational field. And by adding to this the laws of his special theory of relativity, he deduced from it a new view of gravity and curved spacetime -general theory of relativity (discussed in detail in §2.2 " Universality - a basic property and key to understanding the nature of gravity " in the book "Gravity, Black Holes and the Physics of Spacetime." )
Fantasy gives us a number of diverse possibilities "how it might work" - and it turns out that some of these possibilities (sometimes even those that originally appear as "crazy ideas") are actually realized in nature ..! .. - but others are not , it is not good to overestimate unsubstantiated innovations at all costs ...
For in order to achieve objective and true knowledge, intuition, as well as a rational method, must be based on positively ascertained facts and verified data. The usual mistake of "amateur thinkers" is that they are based on insufficient, unreliable or distorted data, moreover, insufficiently understood and not included in the context of other knowledge. Intuitively, they derive peculiar ideas from them, whose divisions (even rational and exact ones) lead to completely wrong conclusions and concepts, often without feedback and self-reflection ...
Mistakes and errors in scientific knowledge
In such a complex activity as scientific knowledge, errors and mistakes also naturally occur . These errors can be of several types, two of which are basic:
¨ Unsuccessful experiments and observations that fail to detect or confirm the phenomenon under study, or measure the correct results. The well-known saying "A negative result is also a result " in scientific knowledge is profoundly true. A negative result may have two reasons: the first is either wrong initial assumption or hypothesis and examined the phenomenon does not exist or does not occur under these conditions, eventually values of physical quantities are outside the measurable range. 2 . in the experiment or statistical monitoring we made mistakes or inaccuracies, failed to eliminate interference which "drowned" observed subtle phenomenon. A failed experiment or measure should not lead to resignation, but to rethink the methodology and improvement of experimental techniques - perhaps next time or in the future will succeed ..?..
¨ False positive experiments and observations , in which the investigated phenomenon (seemingly) manages to prove or measures seemingly demonstrable exact values of certain quantities. However, these results can sometimes be the result of experimental errors, interferences, misinterpretation. In order to be able to consider a phenomenon as proven and the values of the measured quantities to be accurate , an independent verification in another laboratory and another group of researchers is necessary , preferably several independent verifications.
Unfortunately, there are sometimes (fortunately not very often) deliberate manipulations, even falsification, of measured results. The motives are different, mostly prestigious or economic - obtaining funds (from grants and subsidies) either for your own needs or to finance the activities of the institute and the project. These disorders are more common in the biological and medical sciences, where complex "tangled" and poorly reproducible phenomena and processes are investigated, so that eventually fraud is difficult to prove here. In addition, there are often large funds, profits and particular interests of private companies (eg pharmaceuticals) "at stake" ...
The basis of scientific thinking and knowledge is unification : in the great diversity of phenomena and events, to seek general regularities and a common essence , to try to explain the diversity of phenomena on the basis of as few basic laws as possible. Thoughtful people have always longed for a concept or theory that would describe and understand all the observed complexity and diversity of nature. The ultimate (monistic) ideal is to explain all the laws of nature using a single universal principle - to create a definitive final theory or a unified " theory of everything " ( TOE - Theory Of Everything ). And it is physics, which examines the most basic laws of nature, that has the main unifying role among all the natural sciences.
A characteristic feature of the physical view of nature is the already mentioned reductionist approach and the effort to uniformly understand the widest possible class of phenomena - unitarization . This effort runs like a "red thread" throughout the history of physics - see §B.1 " The Process of Unification in Physics " of the book " Gravity, Black Holes and the Physics of Spacetime " .
The first stage of unitarization actually took place in the very beginnings of physics as a science: it was a unification of the "terrestrial" and "celestial " mechanics . Thanks to Galileo, Copernicus, Kepler and Newton was becoming clear that the laws of nature observed here on earth is true elsewhere in the universe . Newton's law of universal gravitation showed that the force of gravity causing the falling body is identical with the force holding the planets orbiting orbits, i.e. with cosmic gravity.
In the "classical" period unitarizace physics can also include unification mechanics and thermodynamics in the kinetic theory of heat, according to which the essence of thermal phenomena is the kinetic energy of the disordered and oscillating motion of molecules and atoms in matter.
An important stage of unitarization in physics was the unification of electrical and magnetic forces , which previously appeared to
be different forces of nature. The consequence of the unity of
electricity and magnetism in Faraday-Maxwell electrodynamics is
the existence of electromagnetic
which are emitted during the accelerated motion of electric
charges. The properties of these electromagnetic waves turned out
to be identical to the properties of light: in addition, optical
and electromagnetic phenomena were unified . Radio
waves, heat radiation, light, X-rays and gamma rays, together
with the classical and relativistic effects of electricity and
magnetism, are therefore just different manifestations of electromagnetic interaction .
The development of atomistics and quantum mechanics in the first third of the 20th century showed that all the diversity of chemical phenomena can be explained by electromagnetic interactions and quantum laws in the electron shells of atoms of individual elements; the same applies to the physical properties of solids (elasticity, strength, dislocation), liquids and gases. Thus, chemistry was in fact "absorbed" by physics, at least in terms of foundations.
The other two stages of unitarization are related to the theory of relativity . In his special theory of relativity, Einstein unified space and time into a single space-time continuum , in general theory of relativity then showed that Newtonian gravity and inertia are a common manifestation of the geometric properties (curvature) of spacetime, which has a dynamic character - there was a unification of gravity and spacetime .
The last stage of unitarization takes place in the area of "elementary" particles . A huge amount of experimental knowledge about the properties and interactions of elementary particles, obtained in the 50s-80s, processed and unified in the spirit of a number of quantum-theoretical concepts, resulted in the so-called Standard model of elementary particles and their interactions (discussed in more detail in §1.5) " Elementary particles and accelerators ", passage "Standard model - uniform understanding of elementary particles "). All matter in nature in its deepest interior consists of only 2 "families" of basic (elementary) particles - 6 leptons and 6 quarks , between which 4 fundamental forces (interactions) act: strong, electromagnetic , weak and gravitational. The first three of these interactions are described by exchanges of intermediate bosons with spin 1: strong interaction is mediated by gluons , electromagnetic interaction by photons , weak interaction by heavy intermediate bosons charged (W +, - ) and neutral (Z o). Quantum theory for the gravitational interaction has not yet been completed, but can be described by intermediate gravitons (spin 2).
of fundamental interactions - unitary field theory
The result of the mentioned stages of unitarization was the finding that all natural events are controlled by only four types of interactions : gravitational, electromagnetic, strong and weak interactions. Each interaction is expressed in physics using the appropriate physical field *). The unification of interactions thus consists in the creation of the so-called unitary field theory . The pioneer of unitary field theory was A. Einstein, who, after creating a general theory of relativity, worked (though not very successfully) until the last days of his life on theories of unification of the electromagnetic and gravitational fields.
*) Concept of physical field shows that even though two bodies do not physically touch, they "touch" or even intersect their fields. And that causes them to interact with each other.
The idea of unitary field theory is extremely deep and beautiful : according to it, there should be a single , completely basic and all-encompassing physical field , the manifestation of which would then be all observed fields in nature - gravitational, electromagnetic, fields of strong and weak interactions and possibly even another field, for example in subnuclear physics. Then there is nothing in the world but this field, from which everything is composed - even material formations (eg particles) are a kind of local "condensation" of this field ...
Modern unitarization efforts take place on the ground of quantum field theory and their goal is to unify the fundamental interactions between elementary particles - the interaction of strong, weak, electromagnetic and gravitational .
The first significant success on this path was recorded in the unification of the electromagnetic interaction and the weak interaction in the so-called electroweak interaction - this is the Weinberg-Salam-Glashow theory. Next unitarizace stage is referred to as a unification GUT - ( Grand Unification Theory) - here we try to unite the strong interaction, described by quark chromodynamics, with the electroweak interaction. These stages of unitarization have achieved considerable success, leading to the creation of a standard model of elementary particles (§1.3, section " Standard model - unified understanding of elementary particles ") .
The completion of the unitarization of interactions in quantum field theory would consist in the inclusion of the gravitational interaction, in its unification with the other three types of interactions. This ambitious unitarization program is called superunification or supergravity ; at present, work in the field of so-called superstring theory is being intensified in this direction, especially in its latest version, the so-called M-theory .
The concept of unitarization and specific unitary field theory are described in more detail in Chapter B " Unitary Field Theory and Quantum Gravity " of the book " Gravity, Black Holes and the Physics of Spacetime", especially in §B.6 " Unification of Fundamental Interactions. Supergravity. Superstrings. ". The question of where the specific values of the basic natural constants came from is briefly discussed in §5.5, passage " Origin of natural constants " of the mentioned monograph.
Our current physical theories are undoubtedly of limited validity, they are "preliminary" and temporary, sooner or later they will be modified and improved. However, some of their aspects already hide the seeds of the future more perfect theory, perhaps even the final "theory of everything" ..?..
Physics - beauty and adventure of
The beautiful and admirable structure of physics, which was only briefly outlined here, with the progress of knowledge allows us to better understand the structure and functioning of our world - from microscales of elementary particles, through the structure of atomic nuclei and atoms, functioning of living cells, organisms , stars and planets, galaxies, to the construction and evolution of the entire universe. He gradually answers the basic question :
" How the world around us and in us works ? ".
The scientific knowledge of new, often previously unsuspected phenomena and the beauty of the architecture of their mutual relations expressed in the laws of nature, gives the thoughtful person the infinite joy of knowledge - "how our world works", what is the essence things and events. This inner feeling is spiritual in nature, not unlike "religious ecstasy" or samadhi in meditation. This leads us to a deep respect for the grandeur of the hidden order and the "reason" that is immanently embodied in being. Through internally understood scientific knowledge, we can achieve liberation from the shackles of pettiness of pride and selfishness, spiritualization of our understanding of the world, and the refinement of our interrelationships with each other and with living and inanimate nature.
Physically, we humans are just a paltry powder in the universe. Spiritually, however, we go far beyond this insignificance of ourselves: the vast universe its structure, its functioning, its evolution we are able to know and understand him .
However, there is still a lot we do not yet know and may we have no idea about are... More adventures of knowledge await us !
|Back: Nuclear physics and physics of ionizing radiation|
|Nuclear and radiation physics||Radiation detection and spectrometry||Radiation applications|
|With cintigraphy||Computer evaluation of scintigraphy||Radiation protection|
|Gravity, black holes and space - time physics Anthropic principle or cosmic God|
|AstroNuclPhysics ® Nuclear Physics - Astrophysics - Cosmology - Philosophy|