Albert Einstein

“ Nobody doubts the "reality" of kinetic energy, otherwise the very reality of energy would have to be denied. But it is clear that the kinetic energy of a body is dependent on the state of motion of the coordinate system, with a suitable choice of the latter one can arrange for the kinetic energy of the continuous motion of a body to assume a given positive value or the value of zero. In the special case where all the masses have a velocity in the same direction and of the same magnitude, a suitable choice of coordinate system can adjust the collective kinetic energy to zero. ”

“ There are several reasons that compel us to willingly accept the complications that the theory leads us to. In the first place, it means for a man who maintains consistency of thought a great satisfaction to see that the concept of absolute motion, to which kinematically no meaning can be attributed, does not have to enter physics; it cannot be denied that by avoiding this concept the foundation of physics has gained in consistency. ”

“ Apart from that, physics needs a method to attain an action-by-contact-theory of gravitation. Without an effective confining principle the theorists could hardly attempt the problem, because ever so many theories could be formulated, that satisfy the limited experiences in this area. Embarras de richesse is one of the most malicious opponents to make the theoretician's life miserable. ”

“ Before we depart, one more question, that does not concern an objection, but that I ask out of pure curiosity: how does the diseased man of theoretical physics fare, the Aether, that many of you have declared to be definitely dead? ”

“ Ever since the special theory of relativity has been formulated, the outcome concerning the slowing influence of motion on the rate of clocks has continuously elicited opposition, and - it seems to me - with good reasons. ”

“ For example, strictly speaking one cannot say that the Earth moves in an ellipse around the Sun, because that statement presupposes a coordinate system in which the Sun is at rest, while classical mechanics also allows systems relative to which the Sun rectilinearly and uniformly moves. ”

“ Approximate integration of the gravitational equations has in fact yielded the result that induction effects must occur when masses are in accelerated motion. This consideration makes it clear that a complete clarification of the questions you have raised can only be attained if one envisions for the geometric-mechanical constitution of the Universe a representation that complies with the theory. ”

“ The situation, that the fixed stars are circling with tremendous velocities, when one bases an examination on such a coordinate system, does not constitute an argument against the admissibility, but merely against the efficiency of this choice of coordinates, nor does the complicated form of the relative to this coordinate system acting gravitational field, which for example would also have the components that correspond to the centrifugal force. ”

“ On the contrary, I talk as a human being, since I am aware that it is not rare for criticism to originate from lack of own thoughts. Also I have no wish to - as was lately done by one of my colleagues - jump on you like a district-attorney and accuse you of theft of intellectual property, or accuse you of equally dishounorable acts. ”

“ Lenard himself says that so far no objections could be raised against the validity of the special principle of relativity (that is the principle of relativity of uniform translational motion of coordinate systems) . The uniformly riding train can equally well be regarded as "at rest", the rails together with the entire surroundings can be regarded as "uniformly moving". ”

“ He will point out that it is not the surroundings that he needs to continuously heat and lubricate, it is the locomotive, and consequently it must be in the latter that the result of his labour shows itself. ”