SCIENTIFIC DEVELOPMENTS

Otago Daily Times, Issue 22270, 24 May 1934, Page 6

SCIENTIFIC DEVELOPMENTS

LECTURE BY DR JACK On Tuesday evening Dr K. Jack, chairman of the Astronomical Branch of the Otago Institute, delivered a lecture on the subject, " Recent Scientific Developments of Interest to Astronomers,' before a very attentive audience. Numerous experiments with some very up-to-date apparatus, together with epidiascope pictures, served to illustrate the talk and make it one of absorbing interest to students of physics. Dr Jack .stated at the outset that he intended to cover more particularly " various particles associated with the world of physios." The first of these dealt with was the " photon." A fact not generally known, said the lecturer, was that in all electromagnetic waves spreading out from n source, —e.g.. light waves' —the energy of the wave was carried along in little bundles which were scattered throughout the wave-front. These bundle* (or quanta) of energy were. j n the case of light waves, known as "photons." The second type of particle dealt with was the "electron,'' and the lecturer said that a very important property of photons was their ability to eject electrons from some materials. This wns illustrated dv placing some colourless powders in a strong beam of light from an arc for some time. On removing the light the powders were seen to give out light of different colours. due to the return of electrons which had been forced out of their normal positions by the light photons. The electron, Dr Jack said, was really a very small particle possessing a negative charge, and in the normal atom'of a substance, many of these rotated at great speeds around the positively charged core or nucleus. Plence if some 'electrons could be got rid of permanently by means of photons, they would take away their

negative charge with them. This was demonstrated experimentally using photons of ultra-violet light. The metal foil of an electroscope, projected on to the screen, when.charged negatively, was seen gradually to lose its charge. The great importance of electrons in the earth's atmosphere and above it, in connection with wireless reception, was dwelt upon at length by Dr Jack. These electrons formed, in the main, two iayers; the Kennelly Hcaviside layer at about 70 miles from the surface of the earth, and the Appleton layer at about twice that distance. The effect of these layers in reflecting wireless waves back to the earth was carefully explained, and mention was also made of the researches being carried out at present by Professor Appleton in regard to other ionised layers which had been thought to exist even beyond the moon's orbit, and which would then be the cause of the " echoes " that have frequently been obtained in the reception of siguals. A very important application of the electron particle was then demonstrated in the, use of a modern cathode ray oscillograph. This most useful instrument, it was explained, employed a stream of electrons to cause a spot of light on a screen, and this stream could be deflected by electric and magnetic fields, as Dr Jack illustrated by means of luminous electron streams through glass tubes. By moans of the oscillograph the lecturer showed how his voice could be analysed into the fundamental wave-forms of the notes used, and by the use of a receiving set, an analysis was also made of 4YA's musical programme at the time. Signals broadcast in the same room were also recorded by the instrument. The next type of particle dealt with was the " proton." a positively charged particle, much heavier than the electron, which was really the nucleus of a hydrogen atom. Even more interesting was the "positrou," which had been discovered only recently. It was a particle of the same mass as- the electron, but with an equal positive charge. Great emphasis was laid by the speaker on the tre-

mendous importance of these last two types of particle as high-speed projectiles. It was shown how, by bombarding certain substances with these projectiles, it was possible actually to change one element into a totally different one. The final particle mentioned was the "cTiplon." This was the nucleus of a new type of hydrogen that had been discovered to exist within the last year. The " diplon " had the same amount of positive charge as the "proton," but was twice as heavy. The great importance of the discovery of this " heavy hydrogen " as it was called, was emphasised by the lecturer, for, from it, it was possible to make a new kind of water which acted entirelv differently from ordinary water. The effect of these particles on astronomical considerations was observed, for some of them were known to exist in space, and others, it was considered, might exist there. Some of particles, indeed, were hurled out in millions from the sun, and hence probably also from the stars.