“Unthinking respect for authority is the greatest enemy of truth”
“Science is and never will be a closed book”
Albert Einstein (1879-1955)
INTERVIEW BY GEORGE SYLVESTER VIERECK (1929)
“The meaning of relativity has been widely misunderstood. Philosophers play with the word like a child with a doll. Relativity, as I see it, merely denotes that certain physical and mechanical facts, which have been regarded as positive and permanent, are relative with regard to certain other facts in the sphere of physics and mechanics. It does not mean that everything in life is relative and that we have the right to turn the whole world mischievously topsy-turvy”.
“I am a determinist. As such, I do not believe in free will…human beings, vegetables or cosmic dust, we all dance to a mysterious tune, intone in the distance by an invisible player”
“I am enough of the artist to draw freely upon my imagination. Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world”
“Nationalism is an infantile disease. It is the measles of mankind”.
In the interview, Einstein adamantly states that he believes in Jesus’ existence and that he admires his teachings.
ON THE NATURE OF REALITY Albert Einstein in Conversation with Rabindranath Tagore (1930)
-“I believe in the Pythagorean argument, that the truth is independent of human beings….The mind acknowledges realities outside of it, independent of it… Our natural point of view in regard to the existence of truth apart from humanity cannot be explained or proved, but it is a belief which nobody can lack…We attribute to truth a superhuman objectivity. It is indispensable for us—this reality which is independent of our existence and our experience and our mind—though we cannot say what it means.”
THE EVOLUTION OF PHYSICS (1938) 
The attempt of this book is to record the “attempts of the human mind to find a connection between the world of ideas and the world of phenomena”. At page 9 the authors say that “human thought creates an ever-changing picture of the universe”. Indeed our view of the universe has changed much since the times of Aristotle, Ptolemy, Newton and so forth.
Essentially, for the authors the ‘law of inertia’ by Galileo and Newton is the beginning of modern physics.
Einstein and Infeld suggest that the difference between Aristotelian physics and Galileo-Newtonian physics is that in Aristotelian physics motion is understood as the connection between force and velocity itself, while in Galileo-Newtonian physics motion is understood as the connection between force and the change of velocity.
If we imagine a uniformly moving cart, we can say that a push in the direction of the cart’s motion will increase its speed while a push in the opposite direction will decrease its speed: hence it is “the action of an external force [that] changes the velocity”.
Velocity itself does not tell us if external forces are acting or not on the cart: for that we need the rate of change (which needs the use of calculus for accurate mathematical presentation).
The authors suggest that understanding the universe is like a man trying to understand the mechanism of a closed watch. The man can hear the ticking but he cannot open the case. After observation, the man may be able to create a picture of what is going on though he will not be able to compare his picture with the real mechanism. The man also acknowledges that his picture may not be the only right one to explain the mechanism. The man may also not know the meaning of this mechanism. The man may also think that there is an ‘ideal limit’ that human knowledge can reach. Perhaps the ‘ideal limit’ is the ‘objective truth’.
The authors have a good explanation of Galileo’s experiment of falling objects from a tower:
“the acceleration of a falling body increases in proportion to its gravitational mass and decreases in proportion to its inertial mass. Since all falling bodies have the same constant acceleration, the two masses must be equal”
Rumford, Mayer and Joule provided insights on the fact that heat is a form of energy.
For the authors, science is about “attempts to reduce the apparent complexity of natural phenomena to some simple fundamental ideas and relations” (a similar definition was made by Helmholtz). For Helmholtz all science could be reduced to the study of ‘attractive’ and ‘repulsive’ forces, “whose intensity depends wholly upon distance”.
At the end of the chapter on classical mechanics, the authors provide a summary:
-“in classical mechanics the future path of a moving body can be predicted and its past disclosed if its present condition and the forces acting upon it are known” (for instance the future paths of the planets because we know the active forces are Newton’s gravitational forces)
-“All phenomena can be explained by the action of forces representing either attraction or repulsion, depending only upon distance and acting between unchangeable particles”
The second chapter is about the decline of the mechanical view.
Experiment on optics: “in a room where the only source of light is incandescent sodium everything is either yellow or black.”
Huygens believed light could be explained as a wave (due to ‘ether’ permeating the universe). The problem for 19th century physicists was whether light, and electric and magnetic fluids could be explained mechanically. The authors credit Faraday, Hertz and Maxwell for bringing new insights on how to explain such phenomena.
Based on Oersted’s experiments, we can say that “The change of an electric field produced by the motion of a charge is always accompanied by a magnetic field”. We can also say “a changing magnetic field is accompanied by an electric field”.The authors believe that the use of the ‘field’ concept in physics has led to great progress, while the concept of ‘substance’ of classical mechanics gradually became more obsolete.
“The old mechanical view attempted to reduce all events in nature to forces acting between material particles…until substance was overshadowed by the field” [the field concept became necessary to understand new phenomena].
The authors credit Maxwell’s equation as the “most important event in physics since Newton’s time” because of the way in which they represent the structure of the fields.
Maxwell equations allow us to predict electromagnetic waves.
The authors add that what is missing in the writings of the early physicists is the fact that in any experiment or model the position of a body should be described with respect to some ‘frame of reference’. Physicists of classical mechanics took a general co-ordinate system as a given.
“when we wrote a body moves uniformly….” we should really have written,”a body moves uniformly, relative to a chosen c.s [coordinate system]…” If two c.s. rotate with respect to each other, then the laws of mechanics cannot be valid in both.When formulating the principal clues of mechanics we omitted one important point. We did not state for which c.s. they are valid. For this reason, the whole of classica mechanics hangs in mid-air since we do not know to which frame it refers”.
The laws of mechanics for one c.s are not valid in different c.s such as a train turning a curve or any body accelerating abruptly.
C.s where the law of mechanics are valid are inertial systems, but when we have two “c.s moving non-uniformly relative to each other, then the laws of mechanics cannot be valid in both”. Copernicus’ revolution was in transferring the c.s from the earth to the sun- though in reality the motion of two planets like the earth and the sun is relative depending on the frame of reference. However it is preferable to use the sun as a c.s because it resembles an inertial system more than the earth would.
In classical mechanics an inertial system is “a c.s. in which the laws of mechanics are valid.A body on which no external forces are acting moves uniformly in such a c.s. This property thus enables us to distinguish an inertial c.s. from any other ”
The authors introduce the concept of relative time in a c.s to further develop the argument of the downfall of classical mechanics. [classical mechanics only works if a c.s is taken as inertial’].
Classical mechanics works when dealing with object moving at much slower speeds than that of light.
Contrary to classical mechanics where mass (possessing weight) and energy (weightless),”According to the theory of relativity, there is no essential distinction between mass and energy. Energy has mass and mass represents energy. Instead of two conservation laws we have only one, that of mass-energy.”
Since the field concept showed contradictions with the old theories, a time-space continuum was introduced.
General relativity theory tries to solve the problem of “formulating physical laws for every c.s” [“The two frightening ghosts, absolute time and an inertial system, have disappeared”], while special relativity theory only applies to inertial systems (in which Newton’s inertial law is valid). Special relativity theory assumes that the laws of physics are equivalent in all the co-ordinate systems that move uniformly relative to each-other; in addition the velocity of light has the same speed.
However the laws of mechanics do not work when the velocity of a body approaches that of light.
The new law of relativity is the conservation law of mass-energy (since the two are the same).
In general relativity theory there are modifications on how the gravitational field works and also a new geometry.
In 2-d Euclidean geometry the sum of the angles of a triangle is 180, while the ratio of the diameter to the circumference in a circle is pi. However relativistic physics is not based on Euclidean geometry.
The authors on quantum mechanics: “If we had to characterize the principal idea of the quantum theory in one sentence, we could say: it must be assumed that some physical quantities so far regarded as continuous are composed of elementary quanta.”
Electricity can be explained in a granular way because of electrons.
In classical mechanics, once having known velocity and position of a particle, it is possible to make accurate predictions of the future path. In the 19th century physicists tried to reduce all physics to an easily predictable deterministic system. However it is difficult with classical mechanics to calculate both initial position and velocity of all the particles in a gas; therefore statistics is used (which “dispenses with any exact knowledge of initial states”). With statistics rather than measuring individual particles we try to understand the overall behaviour and find average values; hence rather than knowing the motion of a particle with 100% accuracy we can only “foretell the chance, the probability”
“Statistical laws can be applied only to big aggregations, but not to their individual members…..Quantum physics deals only with aggregations, and its laws are for crowds and not for individuals.” So only repeated measurements can give us greater degree of confidence about the behaviour of particles.
For instance radioactive disintegration is one example where we do not have a law explaining us why certain atoms are doomed, hence we have to use probability.
Rather than talking about initial position and velocities, in quantum physics we now talk about a ‘probability wave’ in a three-dimensional continuum.
“Without the belief that it is possible to grasp the reality with our theoretical constructions, without the belief in the inner harmony of our world, there could be no science. This belief is and always will remain the fundamental motive for all scientific creation.”
The book was full of thought experiments.
ON THE METHOD OF THEORETICAL PHYSICS The Herbert Spencer lecture, delivered at Oxford, June 10, 1933. Published in Mein Weltbild, Amsterdam: Querida Verlag, 1934
-“To him who is a discoverer in this field [theoretical physics], the products of his imagination appear so necessary and natural that he regards them, and would like to have them regarded by others, not as creations of thought but as .given realities. ”
-Euclid’s logical system in his geometry is a triumph of reason.
-“Experience remains, of course, the sole criterion of the physical utility of a mathematical construction. But the creative principle resides in mathematics. In a certain sense, therefore, I hold it true that pure thought can grasp reality”
 ‘The Evolution of Physics’ by A.Einstein and L.Infeld (CAMBRIDGE UNIVERSITY PRESS BENTLEY HOUSE, EUSTON ROAD LONDON, N.W. I)