100 YEARS AGO

In the more or less popular accounts which have recently been given of Prof. Arrhenius' theory of cometary tails and the auroræ, it is generally stated that the smaller the diameter of the corpuscle upon which the light is falling the greater the excess of light-pressure over gravitational force. This explanation, however, holds only so long as the diameter is greater than the wave-length of light. If the diameter becomes of the same order as the wave-length, the ratio between light-pressure and gravitation follows an entirely different law. This has recently been demonstrated by Prof. Schwarzschild by an exhaustive mathematical treatment of the question... Prof. Schwarzschild's profound mathematical investigation makes it absolutely clear that the idea of minute electrically-charged corpuscles — of about one-thousandth the size of a hydrogen atom — being propelled by the sun's light towards the earth and causing the various phenomena of auroræ, Gegenschein, &c., receives no support from the mathematical point of view. But, even apart from these difficulties, it can hardly be said that the ingenious theory of Arrhenius settles the question as to the nature of the force acting on the cometary matter.

From Nature 6 March 1902.

50 YEARS AGO

In two previous papers, the quantum theoretical hit theory, which has been applied so successfully, for example, to gene mutations, has been applied to the problem of spontaneous cancer and cancer induced by carcinogenic hydrocarbons. The fundamental assumption of the hit hypothesis is that most, if not all, biological processes are ultimately governed by certain control centres, which are situated in the cell nuclei and are thought of as giant molecules making quantum jumps when acted upon by different agents such as chemical substances ... and ionizing radiations. In the case of mutations, these centres are now generally believed to be genes. Analogously, we have assumed in the papers referred to above that there is in each cell a certain control centre which controls the velocity of the chemical chain reactions which in turn control the velocity of growth and thus the rate of proliferation of the cells. We have now applied our theory to cancer produced by viruses, and here also the agreement with experimental findings has been very satisfactory.

From Nature 8 March 1952.