Quotes
Wheeler's First Moral Principle: Never make a calculation until you know the answer. Make an estimate before every calculation, try a simple physical argument (symmetry! invariance! conservation!) before every derivation, guess the answer to every puzzle and paradox. Courage: No one else needs to know what the guess is. Therefore make it quickly, by instinct. A right guess reinforces this instinct. A wrong guess brings the refreshment of surprise. In either case life as a spacetime expert, however long, is more fun! - John A. Wheeler [1]
I do not agree with the idea that general theory relativity is geometerizing physics or the gravitational field. The concepts of Physics have always been geometrical concepts and I cannot see why the gik field would be called more geometrical than f.i. the electro-magnetic field or the distance between bodies in Newtonian Mechanics. The notion probably comes from the fact that the mathematical origin of the is the Gaussian-Riemann theory of the metrical continuum which we are wont to look at as part of a geometry. I am convinced, however, that the distinction between geometrical and other kinds of fields is not logically founded. - Albert Einstein to Lincoln Barnett, June 19, 1948
The purpose of Einstein's new theory has often been misunderstood, and it is criticized as a attempt to explain gravity. The theory does not offer any explanation of gravitation; that lies outside its scope, and does not even hint at a possible mechanism. It is true that we have introduced a definite hypothesis as to the relation between gravity and a distortion in space; but if that explains anything, it explains not gravitation, but space, i.e. the scaffolding constructed from our measures. - A.S. Eddington, Nature, March 14, 1918, page 36
As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality - Albert Einstein - 1921
There is no exaggeration in what you told said about the German Professors. I have got to know another sad specimen of this kind -- one of the foremost physicists in Germany. To two pertinent objections I raised against one of his theories and which demonstrate a direct defect in his conclusions, he responds by pointing out that another (infallible) of his shares his opinion. I'll sure make it hot for the man with a skillful publication. Authority gone to ones head is the greatest enemy of truth. - Letter from Albert Einstein to Jost Winteler (1901)
If there is an instant, at a "big bang," when our universe started expanding, it is not in the cosmology as now accepted, because no one has thought of a way to adduce objective physical evidence that such an event really happened. - Peebles (1993) [2]
Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world. - Albert Einstein
The value of my time does not weigh heavily these days; there aren't always subjects that are ripe for rumination... A consequence of the study on electrodynamics did cross my mind. Namely, the relativity principle requires that the mass be a direct measure of the energy contained in a body. Light carries mass with it. - Letter from Albert Einstein to Conrad Habicht (1905)
Are not gross Bodies and Light convertible into one another, and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition? - Sir Isaac Newton, Optics (4th ed., 1730)
"The physical world is real." This is supposed to be the basic hypothesis. What does "hypothesis" mean here? For me, a hypothesis is a statement whose truth is temporarily assumed, whose meaning, however, is beyond all doubt. The above statement seems intrinsically senseless though, like someone saying "The physical world is a cock-a-doodle-do." It appears to me that "real" is an empty, meaningless category (draw) whose immense importance lies only in that I place certain things inside it and not certain others. It is true that this classification is not a random one ....... now I see you grinning and expecting me to fall into pragmatism so that you can bury me alive. However, I prefer to do as Mark Twain, by suggesting that you end the horror story yourself.
<Real and unreal seem to me like right and left.> I admit that science deals with the "real" and am nonetheless a "realist." - Letter from Albert Einstein to Eduard Study (Sept. 25, 1918)
If our civilization is to survive, we must break with the habit of deference to great men. Great men may make great mistakes - Karl Popper [3]
You ought not to discuss with everybody or exercise yourself against any causal person: for against some people argument is sure to deteriorate... and this can only result in a debased kind of discussion - Aristotle. [4]
A man should make up his own mind with emphasis as to what he rationally believes, and should never allow contrary irrational beliefs to pass unchallenged or obtain to hold over him however brief - Bertrand Russell [5]
A man who has committed a mistake and doesn't correct it is committing another mistake. - Confucius [6]
No number of experiments can prove me right; a single experiment can prove me wrong. Albert Einstein [7]
References:
[1] Spacetime Physics: Introduction to Special
Relativity - Second Ed., Edwin F. Taylor, John Archibald Wheeler, W.H.
Freedman and Co., (1991), page 20.
[2] Principles of Physical Cosmology, Peebles, Princeton University Press
(1993), page 6.
[3] Improving Your Reasoning, by Alex C. Michalos, page 50
[4] Ref 3, page 50
[5] Ref 3, page 70
[6] Ref 3, page 86
[7] Fundamentals of Physics - Extended Third Edition. Haliday and
Resnick, John Wiley and Sons, (1988). page 526.