XXth century_physics
XXth century_physics XXth century_physics
”The fact that the variables used for describing a dynamical system do not satisfy the commutative law means, of course, that they are not numbers in the sense of the word previously used in mathematics. To distinguish the two kinds of numbers, we shall call the quantum variables q-numbers and the numbers of classical methematics which satisfy the commutative law c-numbers, while the word number alone will be used to denote either a q-number or a c-number. When xy = yx we shall say that x commutes with y. At present one can form no picture of what a q-number is like. One cannot say that one q-number is greater or less than another. All one knows about q-numbers is that if z 1 and z 2 are two q-numbers, or one q number and one c-number, there exist the numbers z 1 + z 2 , z 1 z 2 , z 2 z 1 , which will in general be q-numbers, but may be c-numbers. One knows nothing of the processes by which the numbers are formed except that they satisfy all the ordinary laws of algebra, excluding the commutative law of multiplication...” Dirac (1926) [Measurements always give c numbers]
Solvay Conference 1927
- Page 32 and 33: Spectral lines were seen as manifes
- Page 34 and 35: In the Bohr’s model spectral line
- Page 36 and 37: Bohr found excellent description of
- Page 38 and 39: Periodic system of elements accordi
- Page 40 and 41: Periodic system of elements accordi
- Page 42 and 43: Intra-atomic Charge ”Now, accordi
- Page 44 and 45: H. G. J. Moseley, Phil. Mag. 26, 10
- Page 46 and 47: ”We have here a proof that there
- Page 48 and 49: James Franck Gustav Hertz Franck-He
- Page 50 and 51: James Franck Gustav Hertz ”...it
- Page 52 and 53: Wojciech (Adalbert) Rubinowicz (188
- Page 54 and 55: Solvay Conference 1921
- Page 56 and 57: Arthur Holly Compton (1892-1962) Co
- Page 58 and 59: Compton’s data [(Phys. Rev.19, 26
- Page 60 and 61: Compton effect
- Page 62 and 63: The crisis of the quantum theory
- Page 64 and 65: Louis de Broglie
- Page 66 and 67: Clinton Davisson and Lester Germer
- Page 68 and 69: George P. Thomson Electron diffract
- Page 70 and 71: Important dates in the development
- Page 72 and 73: Heisenberg to Pauli (July 9, 1925)
- Page 74 and 75: ”It is well known that the formal
- Page 76 and 77: ”In this communication I wish fir
- Page 78 and 79: The uncertainty principle
- Page 80 and 81: ”I used to take long walks on Sun
- Page 84 and 85: ”A recent paper by the author may
- Page 86 and 87: "It thus appears that we must aband
- Page 88: Solvay Conference 1930
”The fact that the variables used for describing a dynamical system<br />
do not satisfy the commutative law means, of course, that they are<br />
not numbers in the sense of the word previously used in<br />
mathematics. To distinguish the two kinds of numbers, we shall call<br />
the quantum variables q-numbers and the numbers of classical<br />
methematics which satisfy the commutative law c-numbers, while<br />
the word number alone will be used to denote either a q-number or<br />
a c-number. When xy = yx we shall say that x commutes with y.<br />
At present one can form no picture of what a q-number is like. One<br />
cannot say that one q-number is greater or less than another. All<br />
one knows about q-numbers is that if z 1 and z 2 are two q-numbers,<br />
or one q number and one c-number, there exist the numbers<br />
z 1 + z 2 , z 1 z 2 , z 2 z 1 , which will in general be q-numbers, but may be<br />
c-numbers. One knows nothing of the processes by which the<br />
numbers are formed except that they satisfy all the ordinary laws of<br />
algebra, excluding the commutative law of multiplication...”<br />
Dirac (1926)<br />
[Measurements always give c numbers]
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