100 YEARS AGO

We are glad to learn that the gliding experiments with which Lilienthal and Pilcher sought to investigate the balance and stability of machines supported by aëroplanes and aërocurves have not been discontinued since the death of these two investigators. A great deal of valuable work has already been done in America by Mr. Octave Chanute, and in conjunction with him by Mr. Herring, both of whom have attained results in advance of those previously achieved, by the use of machines provided with movable wings. Still more recently, i.e. from October 1900 onwards, two other workers have attacked the problem, namely, Mr. Wilbur Wright and Mr. Orville Wright, of Dayton, Ohio. Mr. Wilbur Wright adopts a two-surfaced machine and assumes a horizontal position when gliding, with the view of diminishing head resistance. He has successfully worked with a surface area of double that used by previous experimenters, and has on several occasions extricated himself from the dangerous position in which Lilienthal and other observers have found themselves when suddenly brought to rest in a high wind.

From Nature 23 January 1902.

50 YEARS AGO

Is there an æther? In his recent communication Prof. Dirac has said that in his new formulation of electrodynamics a preferred motion exists at each point of space. A preferred motion is also given at each point of space by cosmological observations (apparent isotropy of distant red-shift effects). It is of interest whether any local physical effects are associated with this cosmologically preferred state of motion, and the analogous question can be asked with respect to Dirac's formulation. We have argued that the first question may be answered in terms of the theory of continual creation (the steady-state theory of the universe), where the cosmologically preferred motion is identified with the velocity of newly created particles. Dirac answers the second question by saying that a small charge placed in a vacuum would possess the particular velocity associated with the potentials in his theory. The concept of introducing a charge into a vacuum, without fields destroying the vacuum character of the region, is given physical reality in a theory of continual creation.

H. Bondi & T. Gold

From Nature 26 January 1952.