Einstein and the Laws of physics - by Friedel Weinert 2015 - Article review

This document contains article review "Einstein and the Laws of physics" by Friedel Weinert written in 2015
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Contents

Reflection

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1. Introduction.

"The great power possessed by the general principle of relativity lies in the comprehensive limitation which is imposed on the laws of nature (...)".
Physics is the description and explanation of the kinematic and dynamic behavior of physical systems. Einstein agreed with this characterization when he wrote:

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"Physics is the attempt at the conceptual construction of a model of the real world, as well as its lawful structure". In his writings, Einstein often speaks of the laws of nature. When he does so, it is always in connection with the way the laws of nature are symbolically formulated in physics. In accordance with philosophical custom we should distinguish between the laws of nature and the laws of physics. The laws of nature are the regularities, which exist in nature, irrespective of human awareness.
The laws of nature are not something that exists. What exists are physical objects. The laws of nature are the results of human observations, human thoughts, that many of the observations are identical. For example, human observations show that many stars have planets. But human thought is more, they also realize that the apparent conditions that created these planets are closely identical.
The laws of physics are symbolic expressions of the laws of nature. In Einstein's understanding the laws of physics refer to the laws of nature.
The difference between the concept "laws of nature" and "laws of physics" is not clear. A much clearer definition is that the "laws of nature" are a description of identical physical, chemical and biological processes, with the emphasis on being identical, in words and sentences, which should be clear.
A different way is to describe these processes is in a mathematical notation for example in a differential equation or a difference equation. Difference relations are used to simulate the evolution of these processes with a computer. These difference equations represent the situation that the universe is not static but dynamic.
This basic distinction between the lawful regularities, which exist in nature, and their symbolic formulations in the language of mathematics, reflects Einstein's realist attitude of his later years.
The fact that (some of) the laws of nature can be described in a natural language and in mathematics does not mean that you are a realist.
Einstein was a realist in the sense that he believed in the existence of an external world.
The concepts physical world and the universe are synoniems. The universe exist. You can also define a mathematical world. The emphasis should be that a mathematical world does not exist.
This external world consists of objectively given objects and fields and their lawlike regularities. Einstein also says that physics deals with space-time events. But he also believed that scientific theories, including the laws of physics, were at all times subject to possible modifications. The empirical world provides the raw material, the rational mind imposes a structure on the empirical material. Not any structure will do, for the empirical world will resist the imposition of order that does not fit. How is this fit to be achieved? How can physics capture the "lawful structure" in nature? In a nutshell, Einstein's answer is: For the laws of physics to be expressions of the lawful regularities in nature, they have to satisfy certain constraints. These constraints must be imposed on the laws of physics, as the symbolic expressions of the laws of nature. The constraints are needed to ensure an acceptable degree of fit between the laws of physics and the laws of nature.
The descriptions of the physical processes include measurements and parameters. The scientific process requires that the result of simulations should match actual observations.
The connection between scientific constraints and Einstein's views on physical theories and laws has not been explored in the literature. The purpose of this paper is to highlight this connection between physics and philosophy. In this process it will be possible to construct an account of the laws of physics out of the toolkit of Einstein's physics. To spell out this connection, we have to consider (a) Einstein's employment of constraints in the theory of relativity (Sections 2 and 3); (b) Einstein's view on structure laws, which lead to a structural view of laws (Subsection 4); (c) Einstein's version of realism (Section 5).

2. Physical constraints

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2.1 Einstein's Constraints

In his work Einstein appeals to a number of constraints. Constraints can be understood as restrictive conditions, which symbolic constructs must satisfy in order to qualify as admissible scientific statements about the natural world. If theories are free inventions of the human mind, as Einstein insists, there is a need for constraints to make them relevant to the external world.
IMO it is impossible to have any theory without the natural world (a certain physical process) in your mind.

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A methodological constraint is the appeal to logical simplicity and unification in the choice of scientific theories. An empirical constraint is the demand that a scientific statement must conform to well-confirmed facts about the physical world. The empirical facts comprise Einstein's famous predictions: the redshift of light as a function of gravitationalfield strengths and the bending of light rays in the vicinity of strong gravitationalfields.
It is very difficult to predict that apples can fall from a three without ever observing that.
It is also very difficult to explain why some apples fall from a three and others not. The issue is size which is related to weight.
He also explains the perihelion advance of Mercury and other planets.
First of all the perihelion advance of Mercury is caused by all the other planets.
Secondly Newton's Law assumes that gravity acts instantaneously, which is wrong.
A theoretical constraint is the demand that a scientific statement must be compatible with well-established mathematical theorems and physical principles.
Proper science starts with performing observations and performing experiments. The next step can be to clasify that many observations are identical or almost identical. If they are almost identical it is important to investigate what the differences are. The champion of this is Charles Darwin. (?)
Einstein introduces relativity, symmetry and covariance principles as theoretical constraints. For a discussion of Einstein's views on the laws of physics, the methodological constraints are less important than the constraints associated with the theory of relativity. The insistence on constraints, which the physical laws must satisfy, is due to the enhanced importance of inertial frames in the Special theory of relativity. Inertial frames can be understood as idealized systems, which in the Special theory of relativity are constructed from measuring rods and synchronized clocks. Many physical properties, which were erstwhile regarded as absolute, become perspectival in this theory.
Perspectival means that particular values of parameters can only be determined by taking the coordinate values of individual inertial frames into account.
The physical properties of each object, for example its actual position, are created by taking the physical properties of all the other objects into account.
These coordinate values are read of synchronized clocks and rigid rods. These elements are allowed to vary from inertial frame to inertial frame. They lead, as we shall see, to a perspectival notion of reality. The prime examples are temporal and spatial measurements. These result in different coordinate systems, which describe the motion of the reference frames through space-time. The inertial frames are also related through the Lorentz transformation rules, which leave certain elements invariant. The prime example is the velocity of light. Also the general laws, on which the edifice of theoretical physics is based, claim to be valid for every natural event. We have, on the one hand, a large number of frames, between which only some properties remain invariant. On the other hand, the general laws of physics claim validity for every inertial and non-inertial system. To satisfy these demands, constraints come to hand. As the theory of relativity developed, Einstein imposed three constraints on the laws of physics; first relativity and symmetry principles, later his covariance principles.

2.2 Relativity Principles

In his famous 1905 paper Einstein used an explanatory asymmetry in classical accounts of induced currents to motivate his relativity principle. He complained that the then current view offered two different explanations for an observationally indistinguishable phenomenon. If a conductor is in motion with respect to a magnet at rest (in the ether), the electrons in the conductor experience a Lorentz force, which pushes them around the conductor, inducing a current. If the magnet is in motion with respect to the conductor at rest, the Lorentz force is no longer the cause of the current, for no Lorentz force applies to charges at rest. The time-dependent magnetic field now produces an electric field inside and outside

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the conductor, resulting in the same current. To avoid this kind of asymmetry of explanation - an asymmetry not present in the phenomena - Einstein required the physical equivalence of all inertial frames and the Lorentz invariance of Maxwell's equations. No inertial frame must serve as a preferred basis for the description of natural events.
What Einstein should have done, at least not discussed, why not use one reference frame. The removes the problem of "a preferred basis".
For this reason Einstein abandoned Newton's absolute space and time and 19th century ether theories.
What he should have done is to remove the 19th century ether theory.
Later he found that even his Special theory (STR) conferred an unjustifiable preference on inertial frames and Euclidean geometry. What he should have done is to remove the non-Euclidean geometry.
The General theory (GTR) extends the principle of relativity to all - inertial and non-inertial - systems. In its general form the principle states that all frames must be equivalent from the physical point of view. This extension is required if the theory of relativity is to include accelerated frames.
Important point.
Generally, relativity principles stipulate the physical equivalence of frames or the indistinguishability of their state of motion. In particular, Einstein referred equivalence to the laws of motion. The laws which govern the changes that happen to physical systems in motion with respect to each other are independent of the particular system, to which these changes are referred. In the General theory, the inertial frame no longer plays any particular part, having been replaced by general coordinate systems. The general principle of relativity reads: "All Gaussian co-ordinates are essentially equivalent for the formulation of the general laws of nature".
As was pointed out, an inertial frame can be understood as an idealized in which only certain parameters are of interest, in particular parameters, which concern the state of motion of the system.
All of this is rather strange, because reference frames have nothing to do with the behaviour (including any motion) of physical processes.
In his 1905 paper Einstein defined inertial frames by a network of measuring rods and synchronized clocks. Within a particular inertial frame they are all at rest with respect to each other. To construct an inertial frame - "a mechanical scaffold" - we need a system of finite rigid rods to indicate the three spatial dimensions. We then attach a number of synchronized clocks to the rods of the "scaffold". According to the Special theory of relativity, the clocks and rods will behave in distinct ways, depending on the state of motion of the frame.
Why use the term behave?
The point is, that all the clocks which behave in the same way, implying that the distances between these clocks does not change, and which are physical identical, will tick in tick in the same way i.e. with the same rate.
Rods will undergo length contraction and clocks will register time dilation effects in a frame that moves at high speed with respect to a stationary frame. This relativistic behavior of the clocks and rods will give us the spatial and temporal coordinates of a particular inertial frame (at rest or in motion).
In the GTR inertial frames are replaced by general coordinate systems because this theory is based on non-Euclidean geometry and accepts the non-uniform motion of the frames. Einstein illustrates the assignment of coordinates with a rotating disc thought experiment.
Thought experiments are tricky.
We want to measure the ratio of circumference to diameter, C/D, on two discs, which are arranged in such a way that one disc is at rest and the other rotates uniformly with respect to it. In a Euclidean world we would predict that C/D = pi on both discs.
C = 2 Pi R
But relativity demands that we introduce two frames.
In the system at rest, K, C/D = pi. But measured from this system, K, the ratio in the rotating system, K', will measure C/D > pi.
How is this measurement of rotating object actualy performed in the frame at rest?
The physical problem is when a large rotation disc is replaced by a large ring, or track. A train on that track will not undergo any length contraction. The point is if you want to measure the length of a partition of a ring you have to do that instantaneous. This requires clocks near the track which should run synchroneous. From an observer point, when he she observes the clocks, they don't run synchroneous, which imply that the observer can not measure the length of a partition, or the total length of the ring.
This inequality is due to the length contraction of the tangential rods placed along the circumference of K'.

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This inequality is due to the length contraction of the tangential rods placed along circumference of K'.
That means the length contraction of these rods is caused by the rotation of the disc, as observed by an observer at rest. The final result is that the circumference is shortend.
For a discussion See: Reflection 2.1 - Pi
There is therefore a need for more general coordinate systems to discuss the behavior of clocks and rods in accelerated systems or gravitational fields.
In short there is a more general coordinate systems required when accelerated objects are involved.
But what if you want to study all the stars in the universe or all the stars in our galaxy? Why not use one coordinate system?
Because the rigid measuring rods and synchronized clocks can no longer be used in gravitational fields, arbitrary coordinate systems take the place of the inertial frames of the STR. Coordinate systems can be characterized as the "smooth, invertible assignment of four numbers to events in space-time neighborhoods". The use of more general coordinate systems will play a role in considerations of covariance. In a letter to Ehrenfest, dated December 26, 1915, Einstein declares that "the inertial frame signifies nothing real". As in the STR the inertial frames were used to take temporal and spatial measurements, Einstein concluded that in the GTR space and time had lost "the last vestiges of reality"
It should be mentioned that a theory like GTR or STR is not something that physical exists. GTR uses space-time, which is a mathematical construct, and also does not exist. In the real world the only thing that exists are large and small objects. In between these objects there exists space, which is not empty.
Regarding time the only thing that exists is the present.

2.3 Invariance and Symmetries

Whether we consider inertial frames or arbitrary coordinate systems, there must be transformation rules between them.
That is correct. But how do you do that in practice.? The normal strategy is that you declare one at rest and the other one moving.
In the STR the transformation rules are expressed in the Poincaré group; in the GTR there are more general transformation groups, which no longer favor inertial frames.
The reality is that when you want to understand a star cluster, there are always accelerations involved, implying that you cannot use inertial frames.
As they allow only dynamic objects, Einstein's desire to move beyond Minkowski space-time, with its fixed pseudo-Euclidean background, is satisfied. Every gravitational field represents a change of the spatio-temporal metric, which is determined by the functions gik. These functions determine the metric properties in curved coordinate systems. Einstein was one of the first physicists to appreciate the importance of symmetry principles in physics.
The symmetry principles of the relativity theory are related to invariance. Compared with the many types of symmetries, which are recognized today (global, local, external, internal, continuous and discrete symmetries, See ), Einstein only deals with space-time symmetries of a global (STR) or local (GTR) kind. The Lorentz transformations are global transformations: they are constant throughout space and time.
The Lorentz rules show how to transform coordinates x and t into x' and t'. However, in Minkowski space-time, the space-time interval, ds^2, remains the same in transitions between two inertial frames and is expressed by the invariant line element:
ds^2 = c^2 dt^2 - dx^2 - dy^2 - dz^2.
(1)
Equation (1) captures Einstein's desire to call his theory "theory of invariants" rather than "relativity theory". The point about symmetries is that in a transition between inertial frames they return certain invariant parameters. But clock readings change between inertial frames in constant motion with respect to each other.
What about the laws of nature? If the laws of nature are to be the same in all coordinate systems, they must govern the invariants of the transformation groups.

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2.4 Perspectival Reality

Is it true that only the "invariant is real"? What happens, say in the STR, to the clock and meter readings in particular inertial frames? Should we conclude that these events are "unreal!" in the respective inertial frames? This would be unwise because the situation does not depend on perceptual relativity. Different systems in motion with respect to each other measure different values for rod lengths and clock times.
This sentence should be divided in smaller parts and each part should be clear.
These measurements do not depend on what observers perceive. Rather for the observers in the respective systems, these measurements have perspectival reality. Observers in time-like related frames, moving at a constant velocity with respect to each other, can observe that their clocks ticks at different rates and their measuring rods do not measure the same lengths. The ticking rate of the clocks and the behavior of measuring rods show that perspectivalism is not observer-dependent but frame-dependent. It depends on the behavior of rods and clocks in particular frames. For instance, in the famous Maryland experiment (1975-76), atomic clocks were put on 15-hour-flights. When they were compared to earth-bound, synchronized clocks, it was found that the air-born clocks had experienced time dilation - they had slowed down by 53ns. The perspectival realities of physics are the result of a combination of frame-dependent and frame independent parameters of inertial frames. For the different inertial frames are held together by four-dimensional Minkowski space-time.
If we adopt perspectival realities, what becomes of the physicist's criterion that only the invariant is to be regarded as real? The adoption of perspectival, framedependent realities does not contradict the invariance criterion of reality. The Minkowski space-time structure has both invariant and perspectival aspects. In Minkowski space-time, the non-tilting light cones, emanating from every space-time

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space-time event, are invariant for every observer. The space-time interval, ds, is invariant across inertially moving frames. The particular perspectives then result from attaching clocks and rods to the "scaffolds". That is, they result from the particular "slicing" of space-time by the world lines of inertial systems in relative, constant motions with respect to each other. The symmetries tell us what remains invariant across inertial frames, and what is variable. Once we know that the laws remain invariant across different inertial frames, we can derive the perspectival aspects, which attach to different inertial frames, as a function of velocity. Such a modified view of physical reality can be derived from the Minkowski presentation of the theory of relativity. Max Born compared the perspectival realities to projections, which must be connected by transformation rules to determine what remains invariant. The projections are reflections of frame-dependent properties. But there are also frame-independent properties, which are invariant in a number of "equivalent systems of reference".

"In every physical theory there is a rule which connects projections of the same object on different systems of reference, called a law of transformation, and all these transformations have the property of forming a group, i.e. the sequence of two consecutive transformations is a transformation of the same kind.
Invariants are quantities having the same value for any system of reference, hence they are independent of the transformations".

The Lorentz transformations show, Born adds, that perspectival quantities "like distances in rigid systems, time intervals shown by clocks in different positions, masses of bodies, are now found to be projections, components of invariant quantities not directly accessible". We can therefore see that perspectivalism and invariance are two faces of symmetries.

2.5 Active and Passive Transformations

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3. Mathematical Constraints

3.1 Covariance

Covariance is prima facie a mathematical constraint.
That makes it prima facie difficult to use to describe physical behaviour.
The modern use is quite different from the way Einstein uses the notion of covariance.
That does not make things simple.
Einstein associates covariance with the transformation rules of the theory of relativity.
He imposes on the laws of physics the condition that they must be covariant (a) with respect to the Lorentz transformations (Lorentz covariance in the Special theory of relativity) and (b) to general transformations of the coordinate systems (general covariance in the General theory).
These constraints are difficult to understand.
The theory of relativity will only permit laws of physics, which will remain covariant with respect to these coordinate transformations. This means that the laws must retain their form ("Gestalt") "for coordinate systems of any kind of states of motion". They must be formulated in such a manner that their expressions are equivalent in coordinate systems of any state of motion. A change from coordinate system, K, to coordinate system, K', by permissible transformations, must not change the form of the physical laws. This leads to the characterization of covariance as form invariance.
Einstein often illustrates covariance

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3.2 Complications

Einstein himself was not always clear about the precise status of the covariance principle.
That makes a proper discussion difficult.
Confusingly, Einstein associates general covariance both with invariance under non-linear transformations and the general principle of relativity.
When Einstein can not clear, a proper discussion is difficult.
For instance, he characterizes the principle of relativity as a covariance principle: the laws of nature are statements about space-time coincidences; they find their natural expression only in covariant equations.
Same comment as above.
When he turns to the General theory he considers that from a formal point of view the "admission of non-linear coordinate transformations" is a "mighty enlargement of the idea of invariance, i.e. the principle of relativity".
In these formulations Einstein runs together several constraints on laws, which more recent scholarship has kept apart. Einstein thought of relativity principles as requiring the physical equivalence of all frames.
This sentence is not clear.
Wigner described the Lorentz transformations as geometric symmetry transformations, which carry one inertial frame into another. A Lorentz transformation of a inertial frame K into K' returns some invariant properties. In Minkowski four-dimensional space-time the Lorentz transformations become rotations of the coordinate axes, from t to t0 and from x to x0 through some angle, alpha. The tangent of alpha indicates the speed of the x'-t'-system with respect to the x-t-system.
But if covariance is understood as form invariance, then it should be distinguished from both relativity principles and symmetry invariance.
Also a very difficult sentence

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3.3 Complications

Covariance is not tied to transformations between inertial frames; it is quite general. On the modern understanding, the laws of nature can be expressed in different mathematical languages. We can express geometric properties in Cartesian and polar coordinates.

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4. Laws of Physics

We have encountered several constraints on the laws of physics: covariance, invariance and relativity principles. Under Einstein's realist assumptions, the laws of physics are at least approximate expressions of the laws of nature, if they satisfy these constraints.

4.1 Einstein's Structure Laws

When Einstein says that the laws of physics express the lawful regularities in nature, what exactly does he mean?
It should be clear what he means with the laws of physics, but he is not.
Einstein does not directly address this question. But an answer is embedded in the constraints, which Einstein imposes on the laws.
Physical laws are descriptions of regularities in nature.
The laws of relativistic physics generally express the behavior of physical systems.
First you must describe this behaviour,
In the STR they can be represented as idealized inertial systems. A consideration of the STR strongly suggests that science deals with physical systems, not individual happenings. Science is interested in physical events represented as the interaction of idealized systems.
What is meant with: the interaction between idealized systems.
But physical systems are manifestations of structure. Physical systems display structure: they consist of relata and relations, the constituents of a system and how they are related. The relations between the constituents are often expressed in the laws of physics.
Why using such difficult language?
The laws play an essential part in determining the behavior of physical systems.
No. The behaviour of physical systems is a fact.
The idealized systems model only certain structural aspects of the natural system. For instance, the inertial frames of the STR concentrate on kinematic relations. So we should expect the laws of physics to express structural properties of physical systems. The laws express the (invariant) relations between the constituents of the structure. In his philosophical writings Einstein usually emphasizes the importance of a tight fit between the laws and experience: the world of experience practically determines the theoretical system.
We need a fit between the laws and the physical reality i.e. measurements.
He also appeals to notions like simplicity. In the development of the theory of relativity he imposes further constraints on the laws of physics. They must satisfy the light postulate, relativity

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principles and the covariance principles. The constraints Einstein imposes on the laws of physics are necessary to keep a relatively close fit between the rational and the empirical, between the symbolic expressions and what they express. In this way Einstein hopes to satisfy the objectivity criterion, which is attached to the laws of physics.
What does "fit" mean? Our consideration of constraints suggests that "fit" should be explicated in terms of constraints. A scientific model or law "fits" its domain, if it satisfies a number of constraints. The most obvious requirement is that the theoretical system should be compatible with the empirical constraints. But as the development of the theory of relativity has shown, Einstein felt compelled to introduce further constraints, in particular, the constraints associated with the theory of relativity. We can think of the idea of "fit" - understood as satisfaction of constraints - as an extension of the "best matching" of graphs to empirical data. A set of data may satisfy, say, a quadratic equation. If we go beyond empirical constraints, as the theory of relativity does, we say that a scientific theory "fits" an empirical domain if it satisfies a number of constraints. Einstein's view was that the one theory, which best copes with all the constraints - the restrictive conditions imposed on scientific constructs - was the theory of relativity. By contrast, Lorentz's account of time dilation and length contraction postulates an absolute rest frame and therefore violates the constraint of relativity.
What is wrong by using only one reference frame for our Galaxy? For our local Galaxies?
This view will be important in our consideration of Einstein's realism (Section 5).
According to Einstein and Infeld, the equations of the theory of relativity and electrodynamics can be characterized as structure laws. In the authors' view structure laws apply to fields. Structure laws express the changes which happen to electromagnetic and gravitational fields.
This slightly like playing with words.
These structure laws are local in the sense that they exclude action-at-a-distance.
Why is that necessary. It seems that we make certain aspects more complicated than they really are.
"They connect events, which happen now and here with events which will happen a little later in the immediate vicinity".
The sentence is not clear.
The Maxwell equations determine mathematical correlations between events in them electromagnetic field; the gravitational equations express mathematical correlations between events in the gravitational field. The equations of quantum mechanics determine the probability wave. "Quantum physics deals only with aggregates, and its laws are for crowds and not for individuals". Einstein submits that structure laws have the form "required of all physical laws". Einstein derives his view of structure laws from the problem situation, into which the theory of relativity had led him. Wigner was similarly aware of the importance of structure "in the events around us,"

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"that is correlations between the events of which we take cognizance. It is this structure, these correlations, which science wishes to discover, or at least the precise and sharply defined correlations"
Wigner emphasizes that the correlations between events can be mathematically determined; it is the mathematical determination, which provides the structure of the correlation.
Generalizing the Einstein-Infeld-Wigner view we can therefore say that structure laws express how the components (or relata) of physical systems are mathematically related to each other. Apart from space-time events, the relata may refer to objects like planets (as in Kepler's laws), electromagnetic or gravitational fields or the wave function, psi (as in the Schrödinger equation). Einstein declares that "the concepts of physics refer to a real external world, i.e., ideas are posited of things that claim a "real existence" independent of the perceiving subject (bodies, fields etc.)".
Through the insistence on constraints, imposed on scientific constructions to improve their "fit" with reality, and the views on structure laws Einstein's work hints at a structural view of laws. His views on structure laws agree quite closely with similar views expressed by Karl Popper.
All the text is not very clear.

4.2 A Structural View of Laws

Popper's view on laws of nature was influenced by his falsification criterion.
That is completely different issue. This is much more phylosophical discussion.
If we conjecture that a certain statement `a' expresses a natural law, Popper writes, "we conjecture that `a' expresses a structural property of the world; a property which prevents the occurrence of certain logically possible singular events". According to Popper, natural laws express certain structural properties about the physical world, and forbid others. The laws forbid perpetual motion machines and superluminary velocities.
The real way to solve this issue is to try to demonstrate a perpetual motion machine. If you cannot than a law which describes such a process should prohibit that. It is not the other way around.
Popper puts particular emphasis on the prohibitive nature of the laws because of his concern with falsification procedures. Theoretical statements in science are for Popper falsifiable conjectures. For Popper a universal law asserts impossibility. The converse of Popper's view is that laws not only forbid, they also enable physical events. As Einstein put it, the laws express the structure of physical systems, like electromagnetic and gravitational fields, as well as probability waves. The structural aspects of natural systems, quite generally

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5 Einstein and Realism

Running through the discussion of Einstein and the laws of physics is the question of Einstein's realism. It is generally agreed that Einstein's position shifted from an early sympathy for positivism to a later commitment to realism. But which form of realism? Many different versions of realism have been proposed in philosophy. The discussion so far suggests that

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Einstein embraced some form of critical realism. This position simply regards scientific theories as hypothetical constructs, free inventions of the human mind. But there is also an external world, irrespective of human awareness. To be scientific, theories are required to represent reality.
A theory or a law should describe the physical reality.
They represent reality by satisfying a number of empirical and theoretical constraints. The critical realist need not claim that the theories and its laws are true mirror reflections of the world and its regularities. There only needs to be the objectivity assumption that laws of physics are good approximations and idealizations of nature's regularities. The laws express invariant, not perspectival aspects. But if the laws are projected into particular inertial systems, perspectival aspects of the kinematics of reference frames result. Physical laws are symbolic, idealized representations of nature's laws. Einstein's critical realism is to be understood in a broad sense of a synthesis of the rational and the empirical, not in the specific sense in which this term was used by some philosophers in the 1920s. Nevertheless some philosophers have recently stressed that it is more accurate to see Einstein as a holist.
It is interesting to know which physicists are holist and which are not.
For the purpose of assessing this view, it is appropriate to distinguish two versions of holism:
(a) a weaker version holds that a scientific theory is like a coherent conceptual web and that it is not possible for empirical evidence to target specific elements in this theory; Einstein had sympathies for this view. There is also a stronger version
(b) according to which there exist logically incompatible theories, which nevertheless are equally compatible with the evidence. Such a holist attitude towards scientific theories leads to a softer form of realism in the sense of empirical adequacy. Einstein accepts that, from a logical point of view, arbitrarily many "equivalent systems of theoretical physics are possible". Yet, he insists that from a practical point of view, history has shown that one system usually proves to be superior.
The best mathematical theory is the one which predictions are the best, the most accurate, based on observations in the past and future.
At the same time the underlying physical theory should be simpel, logical and 'easy' to understand based on clear definitions.
Einstein employs the analogy of a crossword puzzle to make his point. The liberty of conceptual choice, which the physicist enjoys, is that of "a man engaged in solving a well designed word puzzle. He may, it is true, propose any word as the solution; but there is only one word which really solves the puzzle in all its forms". Given Einstein's insistence on the "rigidity" or coherence of physical theories, despite the freedom to invent theoretical concepts, it is doubtful that Einstein was sympathetic to the stronger version of holism.

A problem with the holist interpretation (b) is that it neglects the importance of constraints in Einstein's work. The presence of constraints and the concern for "fit" point in the direction of a stronger form of realism. Einstein is fond of the view that theoretical constructions are not inductive generalizations from experience but free inventions of the human mind. Nevertheless there must be a fit between the theoretical expressions and the external world. This compatibility is achieved, we suggested, through the introduction of constraints. If there is indeed a fit between what the theory says and what the material world presents, the question of realism returns. What counterbalances the strong holist interpretation of Einstein's views is Einstein's repeated insistence that out of many rival theories there is one with the best fit. Einstein did not believe that many

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Index

Absolute rest frame page 15
Absolute space page 4
Determine page 3, page 5, page 15
Dimension page 4
Euclidean page 4
external world page 4
four-dimensional page 6, page 11
general coordinate system page 4, page 5
Gravitational fields page 3, page 5, page 15
GTR page 4, page 5
inertial frame page 7, page 95
Laws of motion page 4
Laws of nature page 2, page 4, page 5, page 10, page 12, page 16
Laws of physics page 2, page 3, page 8, page 14, page 15, page 19
Laws of relativistic physics page 14
Length contraction page 4, page 15, ref 2.1
Length expansion ref 2
Lorentz force page 3
Lorentz transformations page 3, page 5, page 7, page 8, page 10
Newton's Law page 3, page 4
non-Euclidian page 4
perpetual motion machines page 16
perspectival page 3, page 6, page 7
Philosophy page 2, page 14, page 19
Popper (Karl) page 16
pseudo-Euclidian page 5
Quantum mechanics page 15
Real world page 2, page 5
Space-time page 2, page 3, page 5, page 6, page 7, page 10, page 16
space and time page 4, page 5
STR page 5, page 14, ref 1
synchroneous page 4
synchronised clock page 5, page 14
Time dilation page 4, page 6, page 15

Reflection 1 - Proper Science

The article "Einstein and the Laws of physics" raises the question: "What are the Laws of physics".
A search with Google shows this link: https://www.allenoverseas.com/blog/12-fundamental-laws-of-physics-everyone-should-know/" This is a proper overview.
At item 4 "Einstein's Theory of Relativity is discussed". Here we can read the following text:
It posits that the laws of physics are the same for all non-accelerating observers.
What I want is to understand is the movement of the stars in our Galaxy. All these stars are subject of acceleration, implying that STR is not the right strategy to follow.
To get an idea select this link: https://www.nicvroom.be/VB2019%20Sagittarius.program.htm. This URL shows a simulation of 10 stars in the neighbourhood of Sagittarius A, created using Newton's Law. In order to understand select Display 9b and Display 3b
Display 9b shows the 2 trajectories of the stars S62 and S2 and (the position of) the Black Hole. This is the point in the center of the screen. From a physical point of view this means that the 2 stars influence each other. The most important star is S62.
Display 3b shows the 10 trajectories of the stars S62, S2, the trajectories of 8 stars and (the position of) the Black Hole. This is the point in the center of the screen. From a physical point of view this means that each star is influenced by 9 other stars. The most important star is S62.
Display 2 shows the detailed information of the same 10 trajectories, but only when display 2 is selected. In that case the bottom part at the right side shows more detailed information of S62.

Display 3b shows the results of a simulation of the movement of 10 stars around a Blackhole in time increments. That means at every moment tn the 10 positions x,y,z of the stars are calculated, and shown as 10 points px and py on the display. Those 10 points are considered simultaneous events. At tn = tn+1 the same proces is repeated.

Reflection 1.1 - Proper Science in 10 steps

  1. Proper science is the accepted methodology used to explain and understand the processes and events in the universe.
  2. Proper science starts with performing observations. Without observations there is reason to explain something.
  3. The next step is to perform experiments. Experiments are the only way to understand in detail.
  4. The next step is to describe mutual accepted concepts.
    Its like in mathematics that the shortest line between to points is a straight line.
    Its like in physics that the speed of light in vacuum is constant.
  5. Concept 1: There exist an universe, which consists of objects and space. Space is the area between the objects and is not empty.
  6. Concept 2: The universe exist now. That means at every moment all the objects in the universe have a certain position (and 3D direction) in space.
  7. Concept 3: All the objects in the universe are constantly changing. We humans have the capability to observe these changes using our eyes.
  8. Concept 4: We humans have the capability to define concepts like the present, the past and the future. But that does not mean that the past and the future actual exist. Only the present exists.
  9. Concept 5: An event is a specific action or change happening somewhere at a specific moment in the universe. This can also be an explosion, a collision between two objects, performing an observation or measurement.
  10. Concept 6: All the events happening now are happening simulataneous.
    This is an important concept because it implies that two simultaneous events, any where in the universe, can't influence each other.
    This also means that for two events, to influence each other, one must have happened in the past and the other one at present or in the future. This is true for all events happening here on earth or any where in the universe.
  11. Concept 7: To measure a distance or the length of an object can only be done between two simultaneous events. This is 'always' the case between two fixed positions on earth, because the distance is fixed, but complicated if you want to measure the distance between a fixed point on the (surface of the) moon and a fixed point on earth, because the distance varies and depents about 'the time of the day'.
  12. Concept 8: To measure a length of a moving object (a train) passing below you, from a fixed observer, will either result in length contraction or length expansion.
  13. Concept 9: Physical clocks should not be used in science. In fact clocks are not required to understand the physical processes that take place in the universe.
  14. Concept 10: A velocity is considered as calculated value based on two events i.e the position and virtual time of each event.
  15. Concept 11: In order to understand the movement of the planets around the Sun and the Sun in our Galaxy electromagnetics (the behaviour of photons) is not required, except if electromagnetic processes are studied (Northern Light).
  16. Concept 12: The most important concepts to study are gravitation, the force of gravity and the speed of gravity.
  17. Concept 13: If you want to understand the universe only one coordination system should be used. This coordination system should reflect a 3D grid, with a virtual clock at each cross section, to measure the position and time of each event.
  18. Concept 14: This grid is the bassis to calculate the mass of the objects involved (using Newton's Law as a start), based on observations.
  19. Concept 15: It does not make much sense to devide objects in vissible an invissible objects including darkmatter and blackholes. What is important to include all forms of matter including all small objects including dust particles.
  20. Concept 16: Understanding the Universe should not include thought experiments.
  21. Concept 17: Understanding the Universe requires a proper definition of the task of an observer.

Reflection 2 - Length Contraction, Pi and The Voyage around the Earth in eighty days

All these issues have some thing common. The back ground is the idea that there exist one Universe, that all the events happening at this moment are happening simultaneous. That in order to explain or understand the evolution of processes throughout the universe, you should use a grid, a 3D grid connected with virtual rods of equal length. That there should be a virtual clock at each cross section of this 3D grid and that specific you should not use moving physical clocks.

Reflection 2.1 - Pi

Reflection 2.2 - Around the world in eighty days

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Created: 6 June 2024

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