## Comments about the book "The Evolution of Scientific thought from Newton to Einstein" by A. d'Abro

### Conclusion

There are general speaking two basic viewpoints about studying the laws of nature: starting from (1) multiple objects and their interrelations, or (2) from single objects and how each functions.
General Relativity and Newton's Law study multiple objects and their interrelations. GR studies the movement of the stars.
Special Relativity studies single objects and how each functions. SR studies the processes on earth, on the Sun or inside a Black Hole.

The subject of excellent book "The Evolution of Scientific thought from Newton to Einstein" is almost complete related to multiple objects. There is nothing wrong with that. However there are great differences how Newton solves this subject versus Einstein.
Newton's approach starts from an almost complete universal viewpoint, incasu from our solar system.
Newton's approach can be summarised in three steps: (1) Observations (2) Calculations (3) Predictions. This is one cycle. This cylcle can be repeated as many times as you like.
The purpose of this strategy has basical two reasons: (1) To calculate the initial conditions at a specific moment (2) to calculate the masses of the objects involved.
This approach can be summarised as simple, usefull and effective

Einstein's approach is completely different. He starts with a critical evaluation of the basic concepts of Newton's approach. That is correct, however the reader should keep in mind what the benefits are if you want to understand the movement of the stars.

• The first issue that Einstein discusses is the importance of the observer. He mentions that all what any observer observes is relatif and observer dependent (in space and in time). That is completely correct.
• The first step is to solve this by introducing space-time and distances which are absolute.
• The next step is to define a whole structure of equations based on space-time these absolute values. This are the so called gik parameters.
• The final step is transform the results to observables which can be tested which the results of each observer in space and in time.
This whole approach is much more complex as Newton's approach.

Are the comments, my thoughts, expressed in this bookreview, true?
Of course I try to do my best. One of the biggest problems is that not all the words and concepts used, are clearly defined. Also often the context is not clear. All from my point of view.
Why claiming that a concept like acceleration is absolute. What is the purpose? The problem is that the speed of an object, through space, is constantly changing, implying that its acceleration is also constantly changing.
Why using a concept like density? Such a concept can not be used to explain the behaviour of a single object, because density defines an average of mass in a certain region. For example the planet Mercury, any single star or a Black Hole.
Why stressing concepts like absolute and relatif? The problem is that if you want to predict in the future the trajectory of the planet Mercury this starts with observations and finally finishes with observations to demonstrate that the mathematics (theory) describing the physical processes involved are correct. Specific these observations, with all their limitations are the same if you use Newton's Law or Einstein's theory.
Why calling the speed of light a (in a vacuum) constant? I do not think that anywhere in the universe there is a vacuum, so what is the point?
Closely related to this issue is the use of the concept clock. Clocks are used to measure time, more specific to measure change. Clocks are oscillators and their innerworkings can be based on lightsignals. That is why the physical behaviour of lightsignals is so important. To define the speed of light constant as such solves this issue, in some sense, but leaves the philosophical question (How do you do science) unanswered.

Created: 17 April 2019

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